A Basic Approach to Common Upper Extremity Mononeuropathies and Brachial Plexopathies

Paul E. Barkhaus, MD Aiesha Ahmed, MD Kerry H. Levin, MD Zachary Simmons, MD

AANEM 60th Annual Meeting San Antonio, Texas

Copyright © October 2013 American Association of Neuromuscular & Electrodiagnostic Medicine 2621 Superior Drive NW Rochester, MN 55901

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22 A Basic Approach to Common Upper Extremity Mononeuropathies and Brachial Plexopathies

Table of Contents

3URJUDP&RPPLWWHH &RXUVH2EMHFWLYHV 

Faculty 5

The Median Nerve: A Schematic Approach With Clinical Neurophsyiological Pitfalls and Myths 7 Paul E. Barkhaus, MD

Ulnar Nerve 17 Aiesha Ahmed, MD

The Radial Nerve 23 Kerry H. Levin, MD

Brachial Plexopathies: The Basics 27 Zachary Simmons, MD

CME Questions 33

1RRQHLQYROYHGLQWKHSODQQLQJRIWKLV&0(DFWLYLW\KDGDQ\UHOHYDQW¿QDQFLDOUHODWLRQVKLSVWRGLVFORVH Authors/faculty have nothing to disclose

Chair: Zachary Simmons, MD

7KHLGHDVDQGRSLQLRQVH[SUHVVHGLQWKLVSXEOLFDWLRQDUHVROHO\WKRVHRIWKHVSHFL¿FDXWKRUV DQGGRQRWQHFHVVDULO\UHSUHVHQWWKRVHRIWKH$$1(0

33 Objectives

Objectives - Participants will acquire skills to (1) Identify and distinguish the anatomical and clinical features of upper extremity mononeuropathies and brachial plexopathies, (2) design and perform EDX studies for assessment of median, ulnar, and radial neuropathies and brachial plexopathies, and  FRUUHFWO\LQWHUSUHWWKH(';¿QGLQJVZKHQVWXG\LQJPHGLDQXOQDUDQGUDGLDOQHXURSDWKLHVDQGEUDFKLDOSOH[RSDWKLHV Target Audience: ‡ Neurologists, physical medicine and rehabilitation and other physicians interested in neuromuscular and electrodiagnostic medicine ‡ Health care professionals involved in the diagnosis and management of patients with neuromuscular diseases ‡ Researchers who are actively involved in the neuromuscular and/or electrodiagnostic research Accreditation Statement - The AANEM is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing PHGLFDOHGXFDWLRQ &0( IRUSK\VLFLDQV CME Credit - 7KH$$1(0GHVLJQDWHVWKLVOLYHDFWLYLW\IRUDPD[LPXPRISXWLQAMA PRA Category 1 Credits™,ISXUFKDVHGWKH$$1(0 GHVLJQDWHVWKLVHQGXULQJPDWHULDOIRUDPD[LPXPRIAMA PRA Category 1 Credits™7KLVHGXFDWLRQDOHYHQWLVDSSURYHGDVDQ$FFUHGLWHG*URXS /HDUQLQJ$FWLYLW\XQGHU6HFWLRQRIWKH)UDPHZRUNRI&RQWLQXLQJ3URIHVVLRQDO'HYHORSPHQW &3' RSWLRQVIRUWKH0DLQWHQDQFHRI&HUWL¿FDWLRQ 3URJUDPRIWKH5R\DO&ROOHJHRI3K\VLFLDQVDQG6XUJHRQVRI&DQDGD3K\VLFLDQVVKRXOGFODLPRQWKHFUHGLWFRPPHQVXUDWHZLWKWKHH[WHQWRIWKHLU SDUWLFLSDWLRQLQWKHDFWLYLW\&0(IRUWKLVFRXUVHLVDYDLODEOH± CEUs Credit -7KH$$1(0KDVGHVLJQDWHGWKLVOLYHDFWLYLW\IRUDPD[LPXPRI$$1(0&(8¶V,ISXUFKDVHGWKH$$1(0GHVLJQDWHVWKLV HQGXULQJPDWHULDOIRUDPD[LPXPRI&(8¶V

2012-2013 Program Committee

Vincent Tranchitella, MD, Chair Robert W. Irwin, MD David B. Shuster, MD York, PA Miami, FL Dayton, OH

Thomas Bohr, MD, FRCPC Shawn Jorgensen, MD Zachary Simmons, MD Loma Linda, CA Queensbury, NY Hershey, PA

Jasvinder P. Chawla, MBBS, MD, MBA A. Atruro Leis, MD Jeffrey A. Strommen, MD Atlanta, GA Jackson, MS Rochester, MN

Maxim Moradian, MD T. Darrell Thomas, MD New Orleans, LA Knoxville, TN

2012-2013 AANEM President

Peter A. Grant, MD Medford, OR

 A Basic Approach to Common Upper Extremity Mononeuropathies and Brachial Plexopathies Faculty

Paul E. Barkhaus, MD Kerry H. Levin, MD Professor of Neurology and Physical Medicine & Chairman, Department of Neurology Rehabilitation, Medical College of Wisconsin Director, Neuromuscular Center 0LOZDXNHH:, Cleveland Clinic Cleveland, OH 'U %DUNKDXV UHFHLYHG KLV PHGLFDO GHJUHH IURP :D\QH 6WDWH 8QLYHUVLW\LQ'HWURLW0,+HFRPSOHWHGHOHFWURP\RJUDSK\ (0*  'U /HYLQ UHFHLYHG KLV PHGLFDO GHJUHH IURP -RKQV +RSNLQV IHOORZVKLSVDWWKH8QLYHUVLW\RI0LQQHVRWDDQG'XNH8QLYHUVLW\ 8QLYHUVLW\ 6FKRRO RI 0HGLFLQH +H FRPSOHWHG KLV QHXURORJ\ as well as a fellowship in clinical neuromuscular diseases at the UHVLGHQF\ DW 8QLYHUVLW\ RI &KLFDJR +RVSLWDOV DQG DQ 8QLYHUVLW\RI$UL]RQD+HLVDSURIHVVRURIQHXURORJ\DQGSK\VLFDO HOHFWURP\RJUDSK\ (0* IHOORZVKLSDW0D\R&OLQLFLQ5RFKHVWHU PHGLFLQH UHKDELOLWDWLRQDWWKH0HGLFDO&ROOHJHRI:LVFRQVLQ 01+HLVFXUUHQWO\WKHFKDLUPDQRIWKH'HSDUWPHQWRI1HXURORJ\ He is also head of the Neuromuscular Disease and Autonomic DQGWKHGLUHFWRURIWKH1HXURPXVFXODU&HQWHUDW&OHYHODQG&OLQLF Section in the Department of Neurology and director of the ALS +HDOVRVHUYHVDVWKHQHXURORJ\GLUHFWRUIRUWKH$PHULFDQ%RDUG 3URJUDP +H KDV QXPHURXV SXEOLFDWLRQV RQ TXDQWLWDWLYH (0* RI3V\FKLDWU\DQG1HXURORJ\ motor nerve conductions, motor unit estimation as well as multi- PHGLDHGXFDWLRQDOPDWHULDOV Zachary Simmons, MD Professor of Neurology Aiesha Ahmed, MD Director, Neuromuscular Program and EMG Laboratory Program Director, Clinical Neurophysiology and Pennsylvania State University Hershey Medical Center Neuromuscular Medicine Fellowships Hershey, PA Assistant Professor of Neurology Pennsylvania State University Hershey Medical Center 'U 6LPPRQV UHFHLYHG KLV PHGLFDO GHJUHH IURP WKH 8QLYHUVLW\ Hershey, PA RI )ORULGD DQG WKHQ WUDLQHG LQ QHXURORJ\ DW WKH 8QLYHUVLW\ RI Iowa and in neuromuscular diseases and electromyography at the 'U$KPHG UHFHLYHG KHU PHGLFDO GHJUHH IURP %DTXDL 0HGLFDO 8QLYHUVLW\RI0LFKLJDQ+HQRZVHUYHVDVSURIHVVRURIQHXURORJ\ College in Karachi, Pakistan, and an internship in internal DW3HQQV\OYDQLD6WDWH8QLYHUVLW\+HUVKH\0HGLFDO&HQWHUZKHUH PHGLFLQHDW6W-RVHSK+RVSLWDOLQ&KLFDJR6KHFRPSOHWHGKHU KHLVWKHGLUHFWRURIWKH1HXURPXVFXODU3URJUDPDQGWKH(0* QHXURORJ\UHVLGHQF\IURPWKH8QLYHUVLW\RI,OOLQRLVDW&KLFDJR /DERUDWRU\+HIRXQGHGDQGGLUHFWVWKH+HUVKH\0HGLFDO&HQWHU and a clinical neurophysiology fellowship and neuromuscular $/6 &OLQLF $FWLYH UHVHDUFK SURJUDPV XQGHU KLV VXSHUYLVLRQ PHGLFLQH IHOORZVKLS ERWK IURP 3HQQ 6WDWH 8QLYHUVLW\ 'U include studies of quality of life, the development of evidence- Ahmed is the program director of Clinical Neurophysiology and based practice protocols, the use of brain-computer interfaces, Neuromuscular medicine fellowships and an assistant professor DQGJHQRPLFVRI$/6'U6LPPRQVKDVVHUYHGRQWKH$PHULFDQ RIQHXURORJ\DW3HQQV\OYDQLD6WDWH8QLYHUVLW\+HUVKH\0HGLFDO Association of Neuromuscular and Electrodiagnostic Medicine &HQWHU6KHLVFHUWL¿HGE\WKH$PHULFDQ%RDUGRI3V\FKLDWU\DQG 7UDLQLQJ 3URJUDP :RUNVKRS DQG 3URJUDP &RPPLWWHHV KDV 1HXURORJ\ $PHULFDQ %RDUG RI &OLQLFDO 1HXURSK\VLRORJ\ DQG EHHQFKDLURIWKH$PHULFDQ%RDUGRI(OHFWURGLDJQRVWLF0HGLFLQH $PHULFDQ ERDUG RI 1HXURPXVFXODU 0HGLFLQH 6KH LV FXUUHQWO\ $%(0 0DLQWHQDQFHRI&HUWL¿FDWLRQ&RPPLWWHH+HLVFXUUHQWO\ D *0( FRPPLWWHH PHPEHU IRU $PHULFDQ $VVRFLDWLRQ RI co-chair of the Program Committee and serves on the AANEM 1HXURPXVFXODUDQG(OHFWURGLDJQRVWLF0HGLFLQH %RDUGRI'LUHFWRUV'U6LPPRQVLVDQ$%(0'LSORPDWH

55 66 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

The Median Nerve: A Schematic Approach With Clinical Neurophysiologic Pitfalls and Myths

Paul E. Barkhaus, MD Professor of Neurology and Physical Medicine & Rehabilitation, Medical College of Wisconsin 0LOZDXNHH:,

INTRODUCTION

A traditional choice for discussing the median nerve (MN) is the Forearm FRQYHQWLRQDO³URRWWR¿QJHUQDLO´DQDWRPLFFRXUVHRIWKH01ZLWK The MN descends through the forearm, deep and adherent to the D OLWWOH HVRWHULFD WKURZQ LQ IRU JRRG PHDVXUH +HUH D GLIIHUHQW ÀH[RU GLJLWRUXP VXSHU¿FLDOLV$ERXW  FP SUR[LPDO WR WKH ÀH[RU DSSURDFK LV WDNHQ JLYHQ WKH OLPLWHG WLPH IRU WKLV SUHVHQWDWLRQ UHWLQDFXOXPLWHPHUJHVIURPEHKLQGWKHODWHUDOHGJHRIWKH)'67KXV %HJLQQLQJZLWKWKHWUDGLWLRQDODQDWRP\SURSHUKRPDJHLVSDLG LWEHFRPHVPRUHVXSHU¿FLDOMXVWSUR[LPDOWRWKHZULVWO\LQJEHWZHHQ WR WKH PDQ\ SRWHQWLDO DQDWRPLF YDULDQWV 7KLV LV IROORZHG E\ WKHWHQGRQVRIWKHÀH[RUFDUSLUDGLDOLV )&5 DQG)'6:KHQSUHVHQW sections on functional anatomy, focal lesions, and MN mimic LWPD\EHFRYHUHGE\WKHWHQGRQRIWKHSDOPDULVORQJXV V\QGURPHV7KHODVWVHFWLRQVRQHOHFWURGLDJQRVLVFRYHUWKHPRWRU and sensory study of the MN with emphasis on electrodiagnostic The branches of the MN in the forearm include an articular (';  SLWIDOOV DQG P\WKV 0DQ\ RI WKH ODWWHU DSSO\ WR FOLQLFDO EUDQFK LHHOERZDQGSUR[LPDOUDGLRXOQDUMRLQWV DQGPXVFXODU QHXURSK\VLRORJ\LQJHQHUDOEXWLQWKLVDXWKRU¶VRSLQLRQWKH\DUH EUDQFKHV WR WKH IRUHDUP ÀH[RUV SURQDWRU WHUHV )&5 SDOPDULV SDUWLFXODUO\LPSRUWDQWLQVWXG\LQJWKH017KHXOWLPDWHJRDOLV ORQJXVDQG)'6 7KHEUDQFK HV WRWKHSURQDWRUWHUHVPD\DULVH IRUWKHUHDGHUWREHDEOHWRXWLOL]HWKHVHSUDFWLFDOWHDFKLQJSRLQWV MXVW DERYH DW RU LPPHGLDWHO\ EHORZ WKH PHGLDO HSLFRQG\OH WREHQH¿WWKHLUSDWLHQWV The muscular branches to the FCR are almost always distal to the medial epicondyle and may occur as separate branches or ANATOMY EUDQFKHVLQFRPPRQZLWKWKRVHVXSSO\LQJWKH)'6$QH[FHSWLRQ LVWKHEUDQFKRIWKH)'6WKDWVXSSOLHVWKHLQGH[¿QJHU7KLVEUDQFK The typical course of the MN is described below, followed by a DULVHVGLVWDOO\LQWKHPLGGOHRIWKHIRUHDUP EULHIGHVFULSWLRQRIDQDWRPLFYDULDQWV+HUHHPSKDVLVLVRQWKH PXVFXODUDQGFXWDQHRXVEUDQFKHV 7KHDQWHULRULQWHURVVHRXVQHUYH $,1 LVDGLVWLQFWPDMRUEUDQFK RIWKH01WKDWDULVHVIURPWKHSRVWHULRUVXUIDFHRIWKH01MXVW Origin and Upper Arm GLVWDO WR WKH VSHFL¿F PXVFOH EUDQFKHV PHQWLRQHG DERYH ZKHUH 7KH¿EHUVRIWKH01RULJLQDWHIURPIRXUPDLQURRWV&DQG WKH01SDVVHVEHWZHHQWKHWZRKHDGVRIWKHSURQDWRUWHUHV7KLV &7ZKLFKWUDYHOWKURXJKWKHEUDFKLDOSOH[XVLQWKHODWHUDODQG FDQEHFPEHORZWKHPHGLDOHSLFRQG\OH:LWKWKHDQWHULRU PHGLDOFRUGVUHVSHFWLYHO\7KH\FRPELQHWRIRUPWKH01DWWKH interosseous artery, the AIN courses distally in the forearm anterior SUR[LPDOSRUWLRQRIWKHEUDFKLDODUWHU\7KH01WUDYHOVODWHUDOWR WRWKHLQWHURVVHRXVPHPEUDQH,WJHQHUDWHVPXOWLSOHEUDQFKHVWR WKHEUDFKLDODUWHU\LQWKHXSSHUDUP,WFURVVHVPHGLDOWRWKHDUWHU\ WKHÀH[RUSROOLFLVORQJXV )3/ WKHODWHUDOWZRKHDGVRIWKHÀH[RU close to the level of the insertion of the coracobrachialis, then GLJLWRUXPSURIXQGXV )'3 DQGWKHSURQDWRUTXDGUDWXV passes deep to the tendinous bridge that connects the humeroulnar WRWKHUDGLDOKHDGRIWKHÀH[RUGLJLWRUXPVXSHU¿FLDOLV )'6 7KH The only cutaneous branch of the MN arising in the forearm is QHUYHFRXUVHVWKURXJKWKLVVHJPHQWLQWDFW LHWKH01W\SLFDOO\ WKH SDOPDU FXWDQHRXV EUDQFK 7KLV DULVHV MXVW SUR[LPDO WR RU GRHVQRWJHQHUDWHDQ\EUDQFKHV  7 THE MEDIAN NERVE: A SCHEMATIC APPROACH WITH CLINICAL NEUROPHYSIOLOGIC PITFALLS AND MYTHS

VRPHWLPHVDWWKHÀH[RUUHWLQDFXOXP7KHODWWHULVDQLPSRUWDQW +HUU'RNWRU0DUWLQDQG+HUU'RNWRU*UXEHUFRXOGQRWKDYH anatomic point that allows differentiation of MN lesions distal foreseen the legacy they would create among EDX physicians DQGSUR[LPDOWRWKHZULVWEDVHGRQWKHVHQVRU\GH¿FLW when they made their original anatomic observations in DQGUHVSHFWLYHO\5HFDOOWKDW/XLJL*DOYDQLZDV Wrist and Hand SHUIRUPLQJ KLV IDPRXV IURJ OHJ H[SHULPHQWV LQ WKH V The MN then courses lateral to the tendons of the FDS in the They could not tell whether these communications were GLVWDOIRUHDUP$VLWGHVFHQGVXQGHUWKHÀH[RUUHWLQDFXOXPWKH VHQVRU\ RU PRWRU 7KHUH DUH IRXU UHFRJQL]HG SDWWHUQV WKDW QHUYHEHFRPHVVRPHZKDW³ÀDWWHQHG´DQGOLHVLPPHGLDWHO\XQGHU KDYH EHHQ GH¿QHG DQDWRPLFDOO\ 7KHVH ³DQDVWRPRVHV´ RU WKHUHWLQDFXOXP LHWKH³URRI´RIWKHFDUSDOWXQQHO DQGDQWHULRU FRPPXQLFDWLQJEUDQFKHVDUHYDULDEOHLQWKHQXPEHURI¿EHUV WR RU RYHU WKH WHQGRQV 7KH QDUURZHVW SRUWLRQ RI WKH FDUSDO they contain, which are predominantly, if not exclusively, WXQQHOLVDERXWFPGLVWDOWRWKHSUR[LPDOHGJHRIWKHÀH[RU PRWRU )LJ 2WKHUFODVVL¿FDWLRQVUHO\RQHOHFWURSK\VLRORJLF UHWLQDFXOXP VWXGLHV

The MN terminates distal to the carpal tunnel in one main ‡ 7KHGLVWDOEUDQFKWRWKH)'6VXSSO\LQJWKHLQGH[¿QJHUWKDW PXVFXODUDQGIRXUWR¿YHWHUPLQDOPXVFXODU WRWKHODWHUDOWZR arises distally in the middle of the forearm may sometimes OXPEULFDOV DQGVHQVRU\EUDQFKHV7KHPDLQPXVFXODUEUDQFKLV DULVHIURPWKH$,1DQGQRWWKHPDLQWUXQNRIWKH01 typically lateral, underlying the palmar aponeurosis, and usually LVWKH¿UVWEUDQFKRIIWKH01LQWKLVVHJPHQW RULWPD\DULVHDVD ‡ 7KHGLVWDOEUDQFKRIWKH01PD\HQWHUWKHKDQGVXSHU¿FLDOWR WHUPLQDOEUDQFKZLWKWKHRWKHUGLJLWDOEUDQFKHV 7KH¿UVWPXVFOH WKHÀH[RUUHWLQDFXOXP VXSSOLHG LV WKH VXSHU¿FLDO SRUWLRQ RI WKH ÀH[RU SROOLFLV EUHYLV )3%  ZKHUHLWKDVVKDUHGLQQHUYDWLRQZLWKWKHXOQDUQHUYH 7KLV ‡ The thenar muscular branch may occasionally arise more EUDQFKWKHQFRXUVHVODWHUDODQGPRUHVXSHU¿FLDOWRSHQHWUDWHWKH SUR[LPDOLQWKHFDUSDOWXQQHODQGSLHUFHWKHÀH[RUUHWLQDFXOXP PHGLDOHGJHRIWKHDEGXFWRUSROOLFLVEUHYLV $3% WKHQFRXUVHV GHHSWRSHQHWUDWHWKHPHGLDOHGJHRIWKHRSSRQHQVPXVFOH7KH ‡ The thenar muscular branch may have a terminal branch that terminal sensory branches are highly variable in number and VXSSOLHVDSRUWLRQRUDOORIWKH¿UVWGRUVDOLQWHURVVHRXV )',  PD\UDQJHIURPWZRPDLQEUDQFKHVWRPXOWLSOHEUDQFKHV7KXV PXVFOH YDULDEOHWHUPLQDOEUDQFKLQJSDWWHUQVDUHFRPPRQO\HQFRXQWHUHG ‡ 7KHUH PD\ EH PHGLDQ±XOQDU FRPPXQLFDWLRQV LQ WKH KDQG Anatomic Variants between the deep branch of the ulnar nerve and the distal It is important to appreciate when reading about anatomy or WHUPLQDOEUDQFKHVRIWKH017KHVHDUHFRQVLGHUHGWRLQYROYH anatomic variants whether the studies are anatomic, physiologic, ERWKPRWRUDQGVHQVRU\¿EHUV&ROOHFWLYHO\WKHVHDUHWHUPHG RU ERWK 7KH IROORZLQJ UHSUHVHQWV PDQ\ EXW QRW DOO YDULDQWV 5LFKH±&DQQLHXDQDVWRPRVHV UHSRUWHG ‡ There may be congenital absence of the intrinsic hand ‡ $ SUH¿[HG EUDFKLDO SOH[XV LV LQ UHODWLRQ WR WKH YHUWHEUDO PXVFOHV7KLVPD\DIIHFWWKHWKHQDUPXVFOHV LH$3%)3%  FROXPQ LH D ODUJH FRQWULEXWLRQ IURP & DQG D VPDOO alone, or may also involve the FPL, and be either unilateral FRQWULEXWLRQ IURP 7  &RQYHUVHO\ D SRVW¿[HG EUDFKLDO RUELODWHUDO SOH[XVKDVDODUJHFRQWULEXWLRQIURP7DQG7$OWHUDWLRQV LQSURSRUWLRQVRIURRWFRQWULEXWLRQVDUHUHODWLYHDQGFRPPRQ ,WZRXOGEHUDUHWRKDYHDFRPSOHWHVKLIWLQURRWOHYHOV

‡ In the upper arm, communicating branches between the PXVFXORFXWDQHRXVDQG01DUHFRPPRQ7KH\YDU\LQVL]H DQGOHYHODQGPD\UHSUHVHQWSDVVDJHRI¿EHUVIURPWKH01WR WKHPXVFXORFXWDQHRXVQHUYHRUYLFHYHUVD&RPPXQLFDWLRQV from the musculocutaneous nerve to the MN have included PRWRU¿EHUVWRWKHSURQDWRUWHUHV)&5DQGHYHQWKHWKHQDU PXVFOHV7KHVHDUHFRQVLGHUHGWREHDGLVWDOPDQLIHVWDWLRQRI the more common proximal communications in the brachial SOH[XV

‡ In the forearm, the MN may be penetrated by the ulnar artery RURQHRILWVEUDQFKHV

‡ ,QWKHXSSHUIRUHDUPWKH01PD\SDVVVXSHU¿FLDOWRWKHWZR heads of the pronator teres rather than passing between its WZRKHDGV

‡ Regarding the forearm communicating branch between the 01DQGXOQDUQHUYH LH0DUWLQ±*UXEHUDQDVWRPRVHV), Figure 1. Varying patterns of Martin–Gruber anastomosis.  A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

FUNCTIONAL ANATOMY AND MUSCLE KDQG´RU³RUDWRU¶VKDQG´ 2WKHUVKDYHWHUPHGLWWKH³SDSDOKDQG´ TESTING, AND SIGNS OF MEDIAN NERVE DVLWUHVHPEOHVWKHSRSH¶VEOHVVLQJ :KHQDVNHGWRDFWLYDWHWKHVH PATHOLOGY PXVFOHVWKHSRVWXULQJVKRZVZKDWKDVEHHQFDOOHGWKH³2.´VLJQ The recognition of weakness in median-innervated muscle This can also be appreciated by a maneuver called the “bottle in addition to the appropriate pattern of sensory loss is key to VLJQ´ )LJ  LGHQWL¿FDWLRQRIPHGLDQQHXURSDWKLHV6ORZO\SURJUHVVLYHOHVLRQV PD\EHGLI¿FXOWWRDSSUHFLDWHJLYHQWKHLULQGROHQWQDWXUH/HVLRQV 3KDOHQ¶V VLJQ ZDV RULJLQDOO\ GHVFULEHG E\ RUWKRSHGLF KDQG ZLWKPLQLPDOVHYHULW\PD\DOVREHGLI¿FXOWWRORFDOL]H$¿QDO VXUJHRQ*HRUJH3KDOHQLQ7KHKDQGVDUHÀH[HGDQGWKH often underappreciated point in peripheral nerve lesions: not every GRUVDOVXUIDFHVRIWKHKDQGVDUHDSSRVHGWRHDFKRWKHUIRUV IDVFLFOH LV DIIHFWHG HTXDOO\ +HQFH FDUHIXO FOLQLFDO DVVHVVPHQW E\ZKLFKWLPHWLQJOLQJRUSDUHVWKHVLDVVKRXOGRFFXULISRVLWLYH LV FULWLFDO 7KH 7DEOH VXPPDUL]HV WKH DQDWRP\ RI WKH PHGLDQ 7KHIRUHDUPVIRUPDKRUL]RQWDOVWUDLJKWOLQH$YDULDQWFDOOHGWKH LQQHUYDWHGPXVFOHV ³UHYHUVH´3KDOHQ¶VVLJQKDVDOVREHHQDGYRFDWHG )LJ 

Table.7KHDQDWRP\RIPHGLDQQHUYHLQQHUYDWHGPXVFOHV

Muscle Origin Insertion Fixation Activation Pronator teres Two heads: humeral and ulnar Mid-lateral aspect of (OERZDJDLQVWSDWLHQW¶VVLGH Patient pronates against resistance; radius ZLWKHOERZLQSDUWLDOÀH[LRQ H[DPLQHUKROGVIRUHDUPMXVWSUR[LPDO WRZULVWWRDYRLGWZLVWLQJZULVWMRLQW Flexor carpi radialis Medial epicondyle humerus %DVHRI,,DQG,,, Forearm resting on examination :ULVWÀH[LRQLQUDGLDOGHYLDWLRQ metacarpal bones table with elbow extended, almost fully supinated Flexor digitorum sublimis Via four tendons to the :ULVWH[WHQGHGLQQHXWUDO )OH[SUR[LPDOLQWHUSKDODQJHDOMRLQW Heads of humerus, radius, middle phalanges of the against resistance and ulna index through the little ¿QJHU Flexor digitorum profundus Proximal half of ulna and Via two tendons to distal :ULVWH[WHQGHGLQQHXWUDO )OH[GLVWDOLQWHUSKDODQJHDOMRLQW LQGH[DQGPLGGOH¿QJHUV interosseous membrane LQWHUSKDODQJHDOMRLQWV against resistance Flexor pollicis longus Distal half medial radius and %DVHGLVWDOSKDODQ[RI Hand resting on table, thumb Flexion of distal thumb against interosseous membrane thumb VWUDLJKWH[FHSWIRUÀH[LRQGLVWDO resistance phalanx

Pronator quadratus Medial distal ulna Lateral distal radius Same as for pronator teres but Patient pronates against resistance; HOERZÀH[HGIXOO\HOLPLQDWHV H[DPLQHUKROGVIRUHDUPMXVWSUR[LPDO most action of the larger humeral WRZULVWWRDYRLGWZLVWLQJZULVWMRLQW portion of pronator teres Abductor pollicis brevis Flexor retinaculum, %DVHSUR[LPDOSKDODQ[ +DQGVWDELOL]HGRQWDEOHVXUIDFH Abduction held against resistance WUDSH]LXPDQGVFDSKRLG of thumb thumb abducted and distal LQWHUSKDODQJHDOMRLQWÀH[HG 2SSRQHQVSROOLFLV Flexor retinaculum and (QWLUHOHQJWKRI¿UVW +DQGVWDELOL]HGRQWDEOH 5HVLVWDQFHDJDLQVWÀH[LRQDEGXFWLRQ WUDSH]LXP metacarpal of thumb in medial rotation Flexor pollicis brevis Flexor retinaculum %DVHRISUR[LPDOSKDODQ[ +DQGVWDELOL]HGRQWDEOH )OH[LRQRIPHWDFDUSRSKDODQJHDOMRLQW VXSHU¿FLDOKHDG of thumb with distal thumb in extension

A more common scenario is when the thenar muscles are VHOHFWLYHO\DIIHFWHGVXFKDVLQFDUSDOWXQQHOV\QGURPH &76 ,Q DQDWRP\WKHSDOPLVGLJQL¿HGZLWKLWVRZQSODQH7KHYDULRXV GLUHFWLRQVRIWKXPEPRYHPHQWDUHGH¿QHGE\WKLVSODQH,QWKLV DXWKRU¶VH[SHULHQFHWKHPXVFOHPRVWFRPPRQO\³PLVWHVWHG´LV WKH$3%0DQ\H[DPLQHUVVLPSO\KDYHWKHSDWLHQWDEGXFWWKHLU WKXPEDJDLQVWUHVLVWDQFHLQWKHQHXWUDOSRVLWLRQ7KHEHVWZD\RI detecting weakness is to position the thumb in abduction with the GLVWDOSKDODQ[ÀH[HGVRDVWRLQDFWLYDWHWKHORQJH[WHQVRUVRIWKH WKXPEZKLFKFDQFRQWULEXWHWRWKXPEDEGXFWLRQ3UHVVXUHVKRXOG EHSODFHGRQWKHPHWDFDUSDO±SKDODQJHDOMRLQWRIWKHWKXPEZKHUH WKH$3%LQVHUWV$VWKLVLVWKHPRVW³ODWHUDO´DQGVXSHU¿FLDOWKXPE muscle, it is also least likely to be affected by anomalous branches IURPWKHXOQDUQHUYH

Lesions distal to the elbow where the AIN arises are perhaps WKH HDVLHU WR LGHQWLI\ :KHQ WKLV EUDQFK LV LQYROYHG WKH impairment in the FDP (II and III) and FPL have a characteristic Figure 2. Clinical signs of pathology of the median nerve: anterior SRVWXULQJRIWKHKDQGDQG¿QJHUVDQGLVUHIHUUHGWRDVWKH³RDWK interosseous nerve impairment. 9 THE MEDIAN NERVE: A SCHEMATIC APPROACH WITH CLINICAL NEUROPHYSIOLOGIC PITFALLS AND MYTHS COMMON AND UNCOMMON FOCAL MEDIAN NERVE LESIONS

7KH IROORZLQJ DUH FRPPRQ DQG XQFRPPRQ IRFDO 01 OHVLRQV A number of other rare causes of median entrapment and FRPSUHVVLRQKDYHEHHQGHVFULEHG7KHVHKDYHEHHQVXPPDUL]HG HOVHZKHUH

‡ A band of muscle originating between the subscapularis and latissimus dorsi muscles can compress the MN as it courses WRWKHDQWHULRUVXUIDFHRIWKHKXPHUXV

‡ Proximal median neuropathy of the upper arm: This is rare and usually due to a focal lesion such as a Schwannoma or DWUDXPDWLFOHVLRQ2WKHUFDXVHVRIKLJKPHGLDQQHXURSDWK\ may be pseudo-aneurysm after angiography where the Figure 3. Clinical signs of pathology of the median nerve: the Tinel and EUDFKLDODUWHU\LVSHQHWUDWHG Phalen signs. ‡ Ligament of Struthers: The medial supracondylar ridge ,Q&76WKHPRVWIDPRXVVLJQLVWKDWRI7LQHO%\WDSSLQJWKH RIWKHKXPHUXVLVMXVWSUR[LPDOWRWKHPHGLDOHSLFRQG\OH,Q volar wrist at approximately the level of the distal wrist crease, then about 1-2% of the population there may be a spur or spicule distally through the carpal tunnel, one may elicit paresthesias by RI ERQH ,Q HYHQ IHZHU FDVHV WKLV VSXU RU VSLFXOH PD\ EH JHQWOH HPSKDVLV RQ JHQWOH  SHUFXVVLRQ ZLWK WKH H[DPLQHU¶V ¿QJHU fairly prominent and give rise to a ligamentous process that RU D UHÀH[ KDPPHU 7KH SDUHVWKHVLDV DUH D UHVXOW RI WKH JUHDWHU H[WHQGV LQIHULRUO\ DQG LQVHUWV RQ WKH PHGLDO HSLFRQG\OH VXVFHSWLELOLW\WRSK\VLFDOFRQWDFWSHUFXVVLRQRIWKHQHUYH¿EHUVGXH This canal may contain the medial branch of the brachial WRGDPDJHIURPFKURQLFFRPSUHVVLRQ7RDYRLGIDOVH±SRVLWLYHVWKH DUWHU\WKHXOQDUDUWHU\DQGWKH015DUHO\WKLVLVDVRXUFH author prefers to initially percuss the lateral and medial wrists for of entrapment resulting in pain and dysfunction of some or FRPSDULVRQUDWKHUWKDQGLUHFWSHUFXVVLRQRYHUWKHFDUSDOWXQQHO$ DOORIWKHPHGLDQLQQHUYDWHGVWUXFWXUHVGLVWDOO\'LDJQRVLVLV ³WUXH´7LQHO¶VVLJQLVQRWGLVFRPIRUWDWWKHSRLQWRISHUFXVVLRQEXWWKH UHDGLO\VXVSHFWZLWKDSODLQ;UD\¿OPRIWKHGLVWDOKXPHUXV HOLFLWLQJRISDUHVWKHVLDVIURPWKHSRLQWRISHUFXVVLRQGLVWDOO\3DWLHQWV should be asked if the sensation is somewhat similar to when they ‡ Pronator teres syndrome: This is another rare ³KLWWKHLUIXQQ\ERQH´ LHDFFLGHQWDOO\VWULNHWKHLUXOQDUQHUYHDWWKH syndrome resulting from compression of the MN as it goes HOERZ  )LJ  deep at the antecubital fossa between the two heads of the SURQDWRUWHUHV 7KLV DXWKRU ¿QGV WKH ³ÀLFN VLJQ´ PRVW KHOSIXO ,Q &76 KDQG SDUHVWKHVLDVIUHTXHQWO\DZDNHQSDWLHQWVIURPVOHHS7KHÀLFNVLJQLV ‡ Anterior interosseous syndrome: Aside from trauma, WKHÀLFNLQJPRWLRQD&76SDWLHQWPDNHVZLWKWKHLUZULVWVDQGKDQGV WKLVIRFDOQHXURSDWK\PD\EHDUHVXOWRI¿EURXVEDQGVIURP ZKHQGHVFULELQJKRZWKH\³ZDNHWKHLUKDQGVXSIURPEHLQJDVOHHS´ WKHSURQDWRUWHUHVRU)'6PXVFOHV7UDXPDDWYDU\LQJOHYHOV HJHLWKHUVLGHWRVLGHRULQÀH[LRQ±H[WHQVLRQ  )LJ 6RPHPD\ of the upper arm may also show this pattern of pure motor DFWXDOO\JHWRXWRIEHGDQGZDONDERXWÀLFNLQJWKHLUKDQGV,WLVRIWHQ ZHDNQHVVRIWKHWKUHHPXVFOHVLWVXSSOLHV$¿QDOFDYHDWLV DQHDUO\VLJQ,IWKHSDWLHQWLVVHHQZKHQWKHOHVLRQLVPRUHDGYDQFHG that it may be selectively involved as part of the syndrome SDUHVWKHVLDVPD\EHOHVVLQWHQVH7KHH[DPLQHUPD\PLVVWKLVNH\ RIDFXWHEUDFKLDOQHXULWLV LH3DUVRQDJH±7XUQHUV\QGURPH  KLVWRU\XQOHVVWKH\VSHFL¿FDOO\DVNZKHWKHUWKLVKDGRFFXUUHGHDUOLHU 7KLVLVSDUWLFXODUO\WUXHZKHQ&76LVSUHVHQWLQWKHHOGHUO\ ‡ CTS is a focal distal median neuropathy and undoubtedly WKH FRPPRQHVW IRFDO QHXURSDWK\ It arises from compression of the distal MN where it travels under the ÀH[RUUHWLQDFXOXPWKURXJKWKHFDUSDOWXQQHO,WZDVGHVFULEHG DQDWRPLFDOO\ LQ  EXW LW ZDV QRW DFWXDOO\ UHFRJQL]HG FOLQLFDOO\XQWLODOPRVW\HDUVODWHU$QH[WHQVLYHGLVFXVVLRQ is beyond the scope of this review and the reader is referred WRRWKHUUHYLHZV

‡ 7KH FRUH LVVXH LQ &76 LV LWV GH¿QLWLRQ )URP D FOLQLFDO QHXURSK\VLRORJ\ VWDQGSRLQW LW LV GH¿QHG DV DQ LGLRSDWKLF GLVWDO PHGLDQ QHXURSDWK\ DW WKH ZULVW DV UHÀHFWHG LQ WKH SURORQJDWLRQLQWKHGLVWDO01¶VVHQVRU\DQGPRWRUODWHQFLHV In addition, other structural abnormalities can produce CTS, such as aberrant muscle tissue in the carpal tunnel, leprosy, RVVHRXVDEQRUPDOLWLHVDQGVRIRUWK6RPHFRQVLGHUDQ\SDLQ Figure 4. &OLQLFDOVLJQVRISDWKRORJ\RIWKHPHGLDQQHUYHWKH)OLFNVLJQ DWWKHZULVWWREH&76VXFKDVLQDVLPSOHRYHUXVHV\QGURPH 1010 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

7KLV DXWKRU¶V SUHIHUHQFH LV WR GHVFULEH &76 DV D GLVWDO ‡ Hereditary neuropathy with liability to pressure palsies: This median neuropathy at the wrist due to chronic compression LVDIDLUO\FRPPRQIRUPRIKHUHGLWDU\QHXURSDWK\$KLVWRU\RI so as not to bias the referring physician from looking into SULRUSUHVVXUHSDOVLHVWKDWKDYHUHFRYHUHGLVKHOSIXOWRHOLFLW RWKHU FDXVDWLRQV The advent of ultrasound has given an (';WHVWLQJVKRZVJHQHUDOL]HGVORZLQJRIQHUYHFRQGXFWLRQ DSSUHFLDWLRQRIDOWHUQDWHGLDJQRVWLFSRVVLELOLWLHV11 velocities in addition to regions of focal slowing, usually at SRLQWVRIW\SLFDOHQWUDSPHQWFRPSUHVVLRQ ‡ Acute CTS is far less common and may represent a FRPSDUWPHQWV\QGURPHIURPDFXWHVZHOOLQJ7KHDXWKRUKDV ‡ Amyotrophic lateral sclerosis (split hand syndrome): This is seen a case of bilateral acute CTS secondary to an individual D'U$VD:LOERXUQ appellation and refers to the selective who was electrocuted while holding a metal ladder that vulnerability of the lateral hand muscles (thenar and FDI) in WRXFKHGDSRZHUOLQH WKLVGLVHDVH7KHUHLVYDULDELOLW\LQLQYROYHPHQWEXWDSDWLHQW with isolated thenar denervation, often with involvement of the FDI muscle, should be considered as highly suspect for MEDIAN NERVE MIMIC CONDITIONS PRWRUQHXURQGLVHDVHXQWLOSURYHQRWKHUZLVH

Conditions that can mimic those of the MN can be broadly ‡ Diabetes mellitus: The distal symmetric sensorimotor RUJDQL]HG LQWR GLIIHUHQW FDWHJRULHV FHQWUDO QHUYRXV V\VWHP polyneuropathy of diabetes is a predominantly axonal diffuse processes, focal neurologic lesions (in which the MN or QHXURSDWK\ )RU UHDVRQV XQFOHDU DV\PSWRPDWLF PLOG LWV¿EHUVDUHLQYROYHG RUQRQQHXURORJLFSURFHVVHVWKDWPD\ORRN prolongation of the median distal motor and sensory OLNHLVRODWHGPHGLDQQHXURSDWKLHV latencies may occur in such patients with an otherwise PLQLPDO SRO\QHXURSDWK\ Some practitioners comment on Central Nervous System/Diffuse Processes WKLVUHSUHVHQWLQJ&767KLVDXWKRUSUHIHUVWRPDNHQRWHRILW and to counsel the patient regarding possible development of ‡ Pseudo-thoracic outlet syndrome: A patient with ipsilateral V\PSWRPVVXJJHVWLQJ&76 VXEFODYLDQ VWHQRVLV DQG DWULDO ¿EULOODWLRQ ZDV UHSRUWHG resulting in a mixed clinical picture of peripheral and central Focal Neurologic Lesions (In Which the QHUYRXVV\VWHP¿QGLQJV Median Nerve or Fibers are Involved)

‡ High cervical lesions: Lesions causing narrowing of the ‡ +LUD\DPD¶V GLVHDVH DOVR FDOOHG MXYHQLOH VHJPHQWDO VSLQDO cervical spinal canal in the mid to upper levels can be muscular atrophy, benign focal amyotrophy): This is an associated with patterns of hand numbness suggesting LQVLGLRXV XQLODWHUDO SURJUHVVLYH ZHDNQHVV RI WKH &7 SHULSKHUDOOHVLRQVRIWKH01 The author had a recent case PXVFXODWXUH ,Q VRPH FDVHV WKH FRQWUDODWHUDO VLGH PD\ EH of profound right side wasting of all intrinsic hand muscles LQYROYHGDVZHOO,WLVQRWFRPPRQLQ:HVWHUQSRSXODWLRQV DQGWRDOHVVHUGHJUHH&LQQHUYDWHGPXVFOHV ZLWKQRUPDO 6RPH DUJXH WKDW UHSHDWHG FHUYLFDO ÀH[LRQ LQ LQGLYLGXDOV VHQVRU\IXQFWLRQ&HUYLFDOVSLQHPDJQHWLFUHVRQDQFHLPDJLQJ with a tight dural sac results in compression of the lower revealed marked multi-level spondylotic changes with a FHUYLFDO FRUG 7KH SUHGLVSRVLWLRQ RI WKH DQWHULRU JUD\ WR VPDOOULJKWK\SRGHQVHOHVLRQDWWKH&YHUWHEUDOOHYHOLQWKH microcirculatory changes could explain the appearance of a UHJLRQRIWKHYHQWUDOJUH\DORQJZLWKFRUGGHIRUPLW\ ORZHUPRWRUQHXURQV\QGURPH

‡ Syrinx: In the lower cervical cord a syrinx lesion can result ‡ 5DGLFXORSDWK\&LVRQHRIWKHOHDVWIUHTXHQWURRWVDIIHFWHG LQKDQGZDVWLQJDQGQXPEQHVV+RZHYHUVLQFHWKHOHVLRQLV E\VSRQG\ORVLVEHWZHHQ&WR&+HUHWKHGLIIHUHQWLDWLQJ preganglionic, the sensory nerve conduction studies (NCSs) SRLQW LV WKDW RWKHU QRQPHGLDQ &LQQHUYDWHG PXVFOHV DUH ZLOOEHQRUPDOGHVSLWHFOLQLFDOVHQVRU\ORVV DIIHFWHG HJH[WHQVRULQGLFLV  ‡ 7UXH QHXURJHQLF WKRUDFLF RXWOHW V\QGURPH 726 : Multifocal motor neuropathy: The lesion is primarily one ‡ 'HSHQGLQJRQWKHDXWKRUFRQVXOWHG726YDULHVLQIUHTXHQF\ of demyelination; hence, there is dissociation between the It is traditionally a more common diagnosis made by surgeons PRWRULQYROYHPHQWDQGVHQVRU\VSDULQJ,QDGGLWLRQSDWLHQWV DQG UDUHU DPRQJ QHXURORJLVWV 7KLV ZDV ZHOO GHVFULEHG typically have fairly well-preserved muscle bulk despite LQFOXGLQJWKHVXUJLFDOULVNVE\'U:LOERXUQ The classic ZHDNQHVV SDWWHUQRI726LVWKHUHGXFHGDPSOLWXGHRIWKHHYRNHGWKHQDU (median) compound muscle action potential (CMAP) with Sporadic inclusion body myositis: This is the most common ‡ UHODWLYH SUHVHUYDWLRQ RI WKH K\SRWKHQDU XOQDU  UHVSRQVH DFTXLUHG P\RSDWK\ LQ WKH PLGGOH DJHG WR HOGHUO\ 6RPH Conversely, the median sensory response is preserved FRQVLGHULWDGHJHQHUDWLYHSURFHVV,WDIIHFWVPDOHVPRUHWKDQ ZKHUHDVWKHXOQDUUHVSRQVHLVUHGXFHG)ZDYHODWHQFLHVDUH IHPDOHV DQG LV SDUWLFXODUO\ PRUH FRPPRQ LQ &DXFDVLDQV not useful and this author would be remiss in not mentioning ,WV SURSHQVLW\ WR DIIHFW WKH ¿QJHU DQG ZULVW ÀH[RUV RXW RI RQHRI'U:LOERXUQ¶V¿QHUPRPHQWVLQPHGLFDOZULWLQJ+H proportion to their extensor counterparts is a hallmark of the FRUUHFWO\LGHQWL¿HG³IXGJHG´HOHFWURSK\VLRORJLFZDYHIRUPV GLVHDVHVSXULRXVO\VXJJHVWLQJDPHGLDQQHXURSDWK\ LQD¿JXUHDOOHJHGO\VKRZLQJ)ZDYHODWHQF\GHOD\LQ726  \HDUV IROORZLQJ WKH DUWLFOH¶V SXEOLFDWLRQ The author refers you to the original source material for the pleasure and REOLJDWLRQRIUHDGLQJDERXWUHVSRQVLELOLW\LQDXWKRUVKLS 11 THE MEDIAN NERVE: A SCHEMATIC APPROACH WITH CLINICAL NEUROPHYSIOLOGIC PITFALLS AND MYTHS

:KLOH D ¿UVW ULE OLJDPHQWRXV EDQG KDV WUDGLWLRQDOO\ EHHQ considered the culprit, advanced imaging has shown that any of the three components of the thoracic outlet region may be UHVSRQVLEOH LH LQWHUVFDOHQH WULDQJOH FRVWRFODYLFXODU VSDFH DQGUHWURSHFWRUDOLVPLQRUVSDFH 13 A recent case seen by the DXWKRUVKRZHGWKHFRQYHQWLRQDO(';¿QGLQJVDORQJZLWKIRFDO QDUURZLQJRIWKHVXEFODYLDQDUWHU\LQWKHLQWHUVFDOHQHWULDQJOH

‡ 1HXUDOJLFDP\RWURSK\ RUDFXWHEUDFKLDOQHXULWLV3DUVRQDJH± 7XUQHUV\QGURPH 7KLVFRQGLWLRQLVFKDUDFWHUL]HGE\DFXWH pain in the shoulder, rapidly followed by weakness in the XSSHU SUR[LPDO PXVFOHV RI WKH EUDFKLDO SOH[XV 9DULDQWV have been described, such as when the AIN is selectively LQYROYHG Non-Neurologic Processes Figure 5. Electrodiagnostic testing of the median nerve: motor conduction ‡ 9RONPDQQ¶V LVFKHPLF FRQWUDFWXUH 7KLV PD\ DULVH IURP D montage. supracondylar fracture of the humerus where the brachial DUWHU\PD\EHLQMXUHGEXWWKH01VSDUHG7KHUHVXOWDQWGDPDJH WKHVLJQDO7KH&0$3LVDOVRLQÀXHQFHGE\RWKHUIDFWRUVVXFKDV WRWKHGLVWDOPXVFOHLVLVFKHPLFUDWKHUWKDQQHXURJHQLF HOHFWURGHVL]HDQGJHRPHWU\,WFDQEHUHFRUGHGRQO\IURPDOLPLWHG GLVWDQFHIURPWKHVXUIDFHRIWKHPXVFOH ‡ Arthritis: Severe arthritis may result in thenar atrophy because of lack of movement of the thumb with consequent The most common median sensory NCSs performed are GLVXVHDWURSK\ WKH DQWLGURPLF LQGH[ ¿QJHU )LJ   DQG PL[HG SDOPDU UHFRUGLQJV Although the latter has some motor contribution ‡ 'H4XHUYDLQ¶VV\QGURPH7KLVLVDQLQÀDPPDWLRQRIWKHORQJ IURP WKH OXPEULFDO PXVFOH WKLV DXWKRU¶V VWXGLHV VKRZ WKDW H[WHQVRUWHQGRQVRIWKHWKXPEDQGZULVW3DLQRQSHUFXVVLRQ WKH RYHUZKHOPLQJ FRPSRVLWLRQ RI WKLV VLJQDO LV VHQVRU\ The of the distal extensor tendons or a positive Finkelstein protocol is to make sure that the segment of sensory nerve to be PDQHXYHULVKLJKO\VXJJHVWLYHRIWKHGLDJQRVLV,WPD\DOVR studied is warmed, that the montage is correct with respect to E1 RFFXULQDVVRFLDWLRQZLWK&76 DQG(LQWHUHOHFWURGHGLVWDQFH PP DQGWKDWWKHDQRGH of the stimulator is moved so as to reduce stimulation artifact ‡ 9LEUDWLRQZKLWH¿QJHURUKDQG±DUPYLEUDWLRQV\QGURPH7KLV LH³ZDONLQJWKHDQRGH´ $OOUHVSRQVHVDUHDYHUDJHGHVSHFLDOO\ is usually an occupational syndrome resulting in secondary WKRVH —9 )LJ $IWHUDYHUDJLQJWKHVLJQDOFDQEHIXUWKHU 5D\QDXG¶V V\QGURPH &76 PD\ RFFXU LQ VXFK LQGLYLGXDOV RSWLPL]HG E\ XVLQJ WKH ³HQKDQFHPHQW´ IXQFWLRQ DV ZHOO DV WKH DVZHOO&DUHIXOZRUNDQGRWKHUDFWLYLW\ KREELHV KLVWRU\LV VPRRWKLQJ IXQFWLRQ RQ WKH (0* PDFKLQH )LJ  7KH IRUPHU LPSRUWDQW DGMXVWVIRUWKHVWLPXODWLRQDUWLIDFWDQGWKHODWWHUDFWVDVDORZSDVV ¿OWHULQJPDQHXYHUE\IXUWKHUUHGXFLQJQRLVHLQWKHEDVHOLQH0RVW ELECTRODIAGNOSTIC EVALUATION OF THE FRQWHPSRUDU\(0*V\VWHPVKDYHWKHVHIXQFWLRQV MEDIAN NERVE8,14,23

The median motor and sensory NCSs are among the most commonly performed (but not necessarily performed well) in WKH HOHFWURP\RJUDSK\ (0*  ODERUDWRU\ )RU WKH PRWRU 1&6 D VWDQGDUGPRQWDJH )LJ LVXVHGWRUHFRUGWKH&0$3VGLVWDODQG )ZDYH ODWHQFLHV DQG FRQGXFWLRQ YHORFLWLHV7KH WKHQDU PXVFOHV VSHFL¿FDOO\WKH$3% DUHWKHPRVWFRPPRQO\VWXGLHGKRZHYHU some investigators also record from the lateral lumbrical muscle ZKHQWHVWLQJIRU&767KLVGLVFXVVLRQIRFXVHVRQWKHWKHQDUPXVFOH

To ensure quality in the laboratory, the following steps should be observed: (1) ensure the area to be studied is adequately warmed; (2) when starting to stimulate, look at the muscle being studied for a response (twitch) to the stimulus; and (3) move the active recording electrode (E1) to ensure a location yielding the highest amplitude, WKHQPHDVXUHFRQGXFWLRQGLVWDQFHDQGPDNHD¿QDOUHFRUGLQJ,WLV LPSRUWDQWWRRSWLPL]H&0$3DPSOLWXGHVRDVWRUHGXFHYDULDELOLW\ Figure 6. Electrodiagnostic testing of the median nerve: sensory DVLWLVFRPPRQIRUUHSHDWVWXGLHVWREHSHUIRUPHG7KHUHIHUHQFH conduction montage. HOHFWURGH ( LVQRWDQ³LQHUW´HOHFWURGHDQGDOVRFRQWULEXWHVWR

1212 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

Figure 9. Electrodiagnostic testing of the median nerve: demonstration of Figure 7. Electrodiagnostic testing of the median nerve: averaging and 0DUWLQ±*UXEHUDQDVWRPRVLV W\SH$  VPRRWKLQJ WHFKQLTXHV 7HFKQLTXHV FRPSDUHG ³%LQV´ DUH WKH XQLWV WKH GLJLWL]HGVLJQDOLVEURNHQGRZQLQWREDVHGRQVDPSOLQJUDWH7KHIDVWHUWKH ELECTRODIAGNOSTIC MEDIAN NERVE sampling rate, the smaller the bin size, and therefore the better the signal PITFALLS can be digitized and reconstructed from the analogue signal. The pitfalls encountered during EDX testing of the MN are GHVFULEHGEHORZ

‡ Hand temperature too cool: Limb temperature is important WR UHFRUGLQJ DFFXUDWH 1&6V ,I ZDUPLQJ LV QHHGHG WKHQ one must choose a method of warming that is safe and H[SHGLHQW6XSHU¿FLDOZDUPLQJRIDOLPEPD\EHLQVXI¿FLHQW 0HWKRGV XWLOL]HG LQFOXGH OLPE LPPHUVLRQ LQ ZDUP QRW KRW ZDWHU2WKHUWHFKQLTXHVLQFOXGHXVHRIZDUPLQJODPSV DQGK\GURFROODWRUSDFNV0LFURZDYHGKHDWLQJSDGVDUHQRW recommended as they may heat very unevenly, resulting in EXUQV6RPHOLPEVFRROTXLFNO\KHQFHKDYLQJWKHOLPEUHVW RQDK\GURFROODWRUSDFNKHOSVPDLQWDLQZDUPWK &DYHDW,Q patients with polyneuropathies who may have associated skin changes, warming should be conducted with utmost care so DVWRDYRLGVNLQEUHDNGRZQ$OVREHDZDUHWKDWVXFKSDWLHQWV may not sense temperatures which are hot enough to burn Figure 8. Electrodiagnostic testing of the median nerve: the effect of smoothing and enhancing on averaged traces. VNLQDQGVRWKH\PXVWEHFDUHIXOO\PRQLWRUHG

:KHQ HQFRXQWHUHG WKH PHGLDQ±XOQDU FRPPXQLFDWLQJ ‡ )DLOXUHWRRSWLPL]H&0$3DPSOLWXGH LQDGHTXDWHVWLPXOXV  branches in the forearm require special attention so as to not This is less a problem in most instances as opposed to excess PLVLQWHUSUHW DEQRUPDO ¿QGLQJV VXFK DV LQ &76 $Q H[DPSOH VWLPXODWLRQ ,Q WKH PDMRULW\ RI FDVHV D PRWRU UHVSRQVH RI D 0DUWLQ±*UXEHU DQDVWRPRVLV LV VKRZQ LQ )LJXUH  VKRXOGVWDUWWREHDSSDUHQWE\P$DWPVGXUDWLRQ VWLPXOXV([FHSWLRQVRFFXULQODUJHOLPEVDQGKDQGV2QFHDQ Each laboratory needs to determine its own reference values, apparent maximal response is reached, the stimulus should GHSHQGLQJ RQ WKHLU VSHFL¿F WHFKQLTXHV 7KXV UHIHUHQFH YDOXHV EHLQFUHDVHGE\DERXWWRHQVXUHWKDWLWLVVXSUDPD[LPDO DUHQRWSURYLGHGKHUH7KHUHDUHRWKHUPHWKRGVWRHVWDEOLVKWKH GLDJQRVLVRI&76DVUHYLHZHGE\6WHYHQV ‡ )DLOXUHWRRSWLPL]H&0$3DPSOLWXGH (SODFHPHQW 2QFH WKH VWLPXOXV LQWHQVLW\ LV RSWLPL]HG WKHQ WKH ( VKRXOG EH moved around the original recording site to make certain that WKH &0$3 DPSOLWXGH LV WUXO\ PD[LPDO 6WLPXOXV LQWHQVLW\ and E1 placement are two important, but different, variables LQDFKLHYLQJUHSURGXFLEOH&0$3V

‡ )DLOXUH WR UHFRJQL]H KDQG SRVLWLRQ FKDQJH 3DWLHQWV PD\ LQDGYHUWHQWO\ PRYH WKHLU ¿QJHUV DQG WKXPE GXULQJ D 1&6 resulting in the EDX physician chasing CMAPs with YDU\LQJDPSOLWXGHVIURPGLVWDOWRSUR[LPDOVWLPXODWLRQV%H REVHUYDQWIRUVXFKSRVLWLRQFKDQJHV 13 THE MEDIAN NERVE: A SCHEMATIC APPROACH WITH CLINICAL NEUROPHYSIOLOGIC PITFALLS AND MYTHS

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‡ ,QFRUUHFWODWHQF\PHDVXUHPHQWE\QRWLQFUHDVLQJWKHDPSOL¿HU ‡ Two recent techniques that allow better measurement of VHQVLWLYLW\(';SK\VLFLDQVUHO\WRRKHDYLO\RQWKHLU(0* 61$3V DUH ³HQKDQFLQJ´ DQG ³VPRRWKLQJ´ (QKDQFLQJ LV D V\VWHP WR PDNH GHFLVLRQV IRU WKHP 7KH\ DFFHSW ZLWKRXW IXQFWLRQ DYDLODEOH LQ PDQ\ (0* V\VWHPV WKDW FRUUHFWV IRU TXHVWLRQWKHDXWRPDWHGODWHQF\PDUNLQJV2QHPXVWUHDOL]H WKHVWLPXODWLRQDUWLIDFW7KLVFDQKDYHDFRQVLGHUDEOHHIIHFW WKDW WKHVH V\VWHPV ZRUN RQ DOJRULWKPV WR VHW WKH FXUVRUV on SNAP amplitudes with short latencies (see “walking the 6ORSHFULWHULDDUHXVXDOO\XVHG7KHVKDUSHUWKHULVHWLPHRI DQRGH´EHORZ 6PRRWKLQJLVDTXDVLDYHUDJLQJIXQFWLRQRI WKH&0$3¶VLQLWLDOGHÀHFWLRQWKHPRUHDFFXUDWHO\LWLVVHWDW WKHEDVHOLQH,QFRQWUDVWWRWUXHDYHUDJLQJDGDWDSRLQWDORQJ DQ\VHQVLWLYLW\VHWWLQJ7KHSUREOHPLVZKHQWKHULVHWLPHLV the baseline is averaged by adding its value to the data points VORZHU,QWKLVVLWXDWLRQWKHFXUVRUWHQGVWREHVHWDWDORQJHU RQWKHEDVHOLQHQH[WWRLW SRLQWVWRHDFKVLGH 7KLVUHVXOWV ODWHQF\WKDQWKHWUXHLQLWLDOGHYLDWLRQIURPWKHEDVHOLQH,WLV LQIXUWKHU³VPRRWKLQJ´RIWKHEDVHOLQHVLPLODUWRORZHULQJ important to appreciate this problem, otherwise one will be WKHKLJKIUHTXHQF\ RUORZSDVV ¿OWHU )LJV  UHFRUGLQJ DUWL¿FLDOO\ VORZHU YHORFLWLHV LQ RWKHUZLVH QRUPDO QHUYHV ,Q WKH DXWKRU¶V ODERUDWRU\ ODWHQFLHV W\SLFDOO\ DUH ‡ An absent median SNAP when a response might be PHDVXUHGZLWKWKHJDLQVHWDWRU—9 expected in CTS: The EDX physician failed to interact with WKH UHFRUGLQJ V\VWHP WR ¿QG WKH VLJQDO7\SLFDOO\ WKLV WKLV ‡ Incorrect latency measurement due to reinnervation and accomplished by slowing the sweep speed, increasing the spread of the end plate: In normal muscle, particularly smaller VHQVLWLYLW\VHWWLQJDQGDYHUDJLQJ,IQHFHVVDU\FRQ¿UPWKH GLVWDO PXVFOHV WKH HQG SODWH UHJLRQ LV ZHOO FLUFXPVFULEHG ¿QGLQJVZLWKDQRUWKRGURPLFUHFRUGLQJ The E1 electrode easily overlies it and a biphasic CMAP with DVKDUSXSWDNHLVUHFRUGHG:KHQWKHUHLVSDUWLDOGHQHUYDWLRQ ‡ 6XERSWLPDO ³PL[HG SDOPDU´ UHVSRQVH DPSOLWXGHV GXH WR ZLWK UHLQQHUYDWLRQ WKH $3% DQG RWKHU WKHQDU PXVFOHV H[FHVV VWLPXODWLRQ DUWLIDFW E\ QRW ³ZDONLQJ WKH DQRGH´ may become smaller (resulting in a-= change in anatomic 7KH HOHFWULFDO ¿HOGV JHQHUDWHG E\ WKH FDWKRGH DQG DQRGH boundaries) and the endplate region may become enlarged FDQEHDOWHUHGZLWKUHIHUHQFHDVWRKRZWKH\DUH³VHHQ´E\ RUPRUHGLIIXVH,QVXFKLQVWDQFHVLWPD\EHLPSRVVLEOHWR WKH(HOHFWURGH7KLVLVHDVLO\DFFRPSOLVKHGE\URWDWLQJRU REWDLQDELSKDVLF&0$3ZLWKDVKDUSXSWDNH,QWKLVFDVHRQH ³ZDONLQJ´WKHDQRGH7KLVLVRISDUWLFXODULPSRUWDQFHZKHQ PD\XVHWKHLQLWLDOGHYLDWLRQIURPWKHEDVHOLQH6XFK&0$3V the latency is short, such as when performing short segment DUHDOPRVWDOZD\VUHGXFHGLQDPSOLWXGH,IVXFKDUHVSRQVH WUDQVFDUSDOUHFRUGLQJV$OWKRXJKWKHHQKDQFHPHQWIXQFWLRQ LVUHFRUGHGZLWKQRUPDODPSOLWXGHORRNIRUWHFKQLFDOHUURU may help correct for this, it is better for the EDX physician WRWU\WKH³ZDONLQJ´PDQHXYHU¿UVWWRPLQLPL]HWKLVDUWLIDFW ‡ Misinterpretation of all drops in CMAP amplitude as due to FRQGXFWLRQEORFN1RWKLVLVQRWDOZD\VWKHFDVH$EQRUPDO ‡ ,PSURSHU YHUWLFDO QHHGOHHOHFWURGHLQVHUWLRQLQWRWKH$3% temporal dispersion may also cause drops in CMAP It is common to see needle electrode insertions into the DPSOLWXGH 7R YHULI\ ZKHWKHU FRQGXFWLRQ EORFN LV SUHVHQW $3%SHUIRUPHGYHUWLFDOO\WKURXJKWKHJODEURXVVNLQRIWKH versus abnormal temporal dispersion, it is important to look SDOP )LJ +HUHDUHWKHDXWKRU¶VDUJXPHQWVDJDLQVWWKLV at the area and duration of the initial negative portion of the SUDFWLFH7KHJODEURXVVNLQLVPRUHVHQVLWLYHDQGSDLQIXOWKDQ &0$3:KHUHWKHUHLVDODUJHGHJUHHRIDEQRUPDOWHPSRUDO WKH QRQJODEURXV VNLQ 7KH $3% DQG RWKHU WKHQDU PXVFOHV dispersion, such measurements may be problematic due to DUH UHODWLYHO\ EURDG DQG ÀDW DQG OLH LQ D ³VWDFN´ LQ WKH SKDVHFDQFHOODWLRQ WKHQDUHPLQHQFH,IRQHZLVKHVWRUHFRUGIURPWKH$3%LW makes more anatomic sense to insert laterally and move the ‡ Misinterpretation of sensory responses recorded from the electrode medially along its width, which is greater than its thumb when stimulating and comparing responses of the WKLFNQHVV,WDOVRDOORZVIRUJUHDWHUFRQWUROLQDFWLYDWLRQDQG radial nerve and the MN: Some EDX physicians like to use the LVOHVVSDLQIXO differences between the radial and median sensory nerve action potential (SNAP) latencies recorded from the thumb to detect

 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

‡ Slowed distal median motor and sensory response in a GLDEHWLF ZLWKRXW V\PSWRPV RI &76 UHDOO\ UHSUHVHQWV &76 Diabetic patients with distal symmetric polyneuropathy often PD\ VKRZ PLOG GLVWDO PRWRU RU VHQVRU\ VORZLQJ 8QOHVV V\PSWRPDWLFWKLVDXWKRUUHSRUWVWKLVDVD¿QGLQJRIXQFHUWDLQ VLJQL¿FDQFHZLWKUHFRPPHQGDWLRQIRUFDUHIXOPRQLWRULQJRI V\PSWRPV2WKHUQRQGLDEHWLFLQGLYLGXDOVPD\VKRZWKLVDV ZHOO

‡ 2QH FDQ PHDVXUH FRQGXFWLRQ EORFN LQ 61$3V 7KLV LV QRW SRVVLEOH XQOHVV UHFRUGLQJ IURP YHU\ VKRUW GLVWDO VHJPHQWV 7KH61$3LVFRPSULVHGRIVHQVRU\¿EHUVRIYDU\LQJGLDPHWHU DQGWKXVYDU\LQJFRQGXFWLRQYHORFLWLHV$VRQHVWLPXODWHV further from the recording electrodes, the amplitude drops more precipitously than the analogous CMAPs recorded at WKHVDPHGLVWDQFH Figure 10. Proper needle electrode examination of the abductor pollicis EUHYLVPXVFOH SDSHUFOLSXVHGIRUGHPRQVWUDWLRQIRUHDVLHUYLVXDOL]DWLRQ  ‡ A slowed forearm median motor conduction velocity in an RWKHUZLVH QRUPDO LQGLYLGXDO ZLWK &76 LH QR XQGHUO\LQJ ELECTRODIAGNOSTIC MEDIAN NERVE polyneuropathy) means there is compression proximal to MYTHS WKHFDUSDOWXQQHO1R)RUHDUPPRWRUFRQGXFWLRQYHORFLWLHV in CTS may show mild slowing for at least two different A number of myths regarding the EDX assessment of the MN are UHDVRQV,IWKHFRPSUHVVLRQDWWKHFDUSDOWXQQHOLVPRGHUDWH DGGUHVVHGEHORZ to-severe, then it is likely that the faster conducting motor axons have been compromised to a greater degree than the ‡ 7LQHO  GHVFULEHGKLVVLJQZKHQKHGHVFULEHG&76 VORZHUFRQGXFWLQJD[RQV$QRWKHUH[SODQDWLRQLVWKDWWKHUH LQ)DOVH-XOHV7LQHOZDVDQHXURORJLVWZKRZDVFDOOHG are axonal changes proximal to the point of compression that XSWRVHUYHDVDPHGLFDORI¿FHULQWKH)UHQFKDUP\LQ:RUOG PD\UHVXOWLQVORZLQJ :DU,DQGVHUYHGDWWKH1HXURORJLFDO&HQWHULQ/H0DQV+LV RULJLQDO GHVFULSWLRQ RI ³/H VLJQH GX µIRXUPLOOHPHQW¶ GDQV ‡ 7KH H[LVWHQFH RI 'RXEOH FUXVK V\QGURPH The basic OHVOpVLRQVGHVQHUIVSpULSKpULTXHV´GHVFULEHGWKH³WLQJOLQJ´ concept is that in a lower cervical radiculopathy, there is IURPSODFLQJSUHVVXUHRQDQHUYHDVDVLJQRIUHJHQHUDWLRQ DSURSHQVLW\IRUDGLVWDOHQWUDSPHQWVXFKDV&76WRRFFXU ,URQLFDOO\ KLV FRXQWHUSDUW LQ WKH ,PSHULDO *HUPDQ $UP\ 7KLVKDV\HWWREHXOWLPDWHO\UHVROYHG7KLVKDUNHQVEDFNWR Paul Hoffmann, simultaneously described the same sign whether one should do a needle electrode examination in IURPREVHUYLQJZRXQGHG*HUPDQVROGLHUVDWKLVIDFLOLW\LQ FDVHVRI&767KLVFDQEHOHIWWRWKHMXGJPHQWRIWKH(0&,Q :XU]EXUJ %RWK RULJLQDOO\ XVHG VLPSOH ¿QJHU SHUFXVVLRQ favor of doing a needle electrode examination would be the ZKLFKKDVHYROYHGWRXVLQJDUHÀH[KDPPHULQFXUUHQWXVH ability to ascertain the presence of motor axonal involvement 7KLV DXWKRU XVHV ERWK +LVWRU\ KDV DZDUGHG WKH YLFWRU WKH LQ WKH $3% QRW DSSDUHQW ZKHQ &0$3 DPSOLWXGH LV VWLOO VSRLOVRIWKHHSRQ\PZKLFKKDVORVWLWVRULJLQDOLQWHQW'U QRUPDOGXHWRZHOOFRPSHQVDWHGUHLQQHUYDWLRQ$VVHVVPHQW +RIIPDQQKDVKRZHYHUUHFHLYHGVRPHKLVWRULFDOMXVWLFH)RU RI QRQPHGLDQ &LQQHUYDWHG PXVFOHV SHUPLWV GHWHFWLRQ KLVZRUNRQUHÀH[HV(';SK\VLFLDQVUHPHPEHUKLPEHVWE\ RI LQYROYHPHQW RI WKDW URRW $VVHVVPHQW RI &LQQHUYDWHG WKH¿UVWOHWWHURIKLVQDPH³+´ LHWKH+UHÀH[  PXVFOH LV XVHIXO EHFDXVH WKH & GHUPDWRPH DSSUR[LPDWHV WKDWRIWKH01¶VWHUPLQDOVHQVRU\EUDQFKHV,QOLHXRIP\WK ‡ 7KH(HOHFWURGHLVQRWUHFRUGLQJDQ\VLJQDOH[FHSW³QRLVH´ SHUKDSVGRXEOHFUXVK\HWUHPDLQVWREHSURYHQ The E2 varies in its contribution to the CMAP depending on WKHQHUYHEHLQJVWXGLHG,QWKH01WKH(FRQWULEXWHVDERXW RIWKHWRWDO&0$3

‡ $ ORZ &0$3  P9  FRQ¿UPV WKH SUHVHQFH RI YLDEOH PRWRU ¿EHUV 9HU\ RIWHQ VXFK ORZ DPSOLWXGH &0$3V DUH the result of volume conduction from other (non-median) PXVFOH ,W LV UHFRPPHQGHG WKDW DQ\ &0$3  P9 EH FRQ¿UPHGZLWKDQLQWUDPXVFXODUQHHGOHUHFRUGLQJWRFRQ¿UP that the surface response is accurate, especially if no visible ³WZLWFK´ UHVSRQVHLVREVHUYHGZLWKVWLPXODWLRQ

15 THE MEDIAN NERVE: A SCHEMATIC APPROACH WITH CLINICAL NEUROPHYSIOLOGIC PITFALLS AND MYTHS REFERENCES

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16 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

Ulnar Nerve

Aiesha Ahmed, MD Program Director, Clinical Neurophysiology and Neuromuscular Medicine Fellowships Assistant Professor of Neurology Pennsylvania State University Hershey Medical Center Hershey, PA

INTRODUCTION 7KHXOQDUQHUYHWKHQHQWHUV*X\RQ¶VFDQDODWWKHZULVW*X\RQ¶V canal, also known as the ulnar canal, is a small anatomical space 8QGHUVWDQGLQJ WKH DQDWRP\ DQG HOHFWURGLDJQRVWLF (';  IRUPHGE\WKHSLVLIRUPDQGKDPDWHERQHV7KHXOQDUDUWHU\WUDYHOV assessment of the ulnar nerve is important for physicians and with the ulnar nerve through this space on their way into the technologists to accurately identify ulnar neuropathy as well as KDQG +HUH GLJLWDO EUDQFKHV DULVH WKDW SURYLGH VHQVDWLRQ WR WKH ORFDOL]HWKHOHVLRQ,QDGGLWLRQLWFDQDOVRKHOSZLWKGLIIHUHQWLDWLQJ SDOPDU DVSHFW RI WKH PHGLDO ULQJ DQG OLWWOH ¿QJHUV ,Q DGGLWLRQ XOQDU QHXURSDWK\ IURP &7 UDGLFXORSDWK\ DQG EUDFKLDO PRWRUEUDQFKHVDULVHWRLQQHUYDWHWKHK\SRWKHQDUPXVFOHV LH SOH[RSDWK\ opponens digiti minimi, abductor digiti minimi [ADM], and ÀH[RU GLJLWL PLQLPL  SDOPDU DQG GRUVDO LQWHURVVHL WKLUG DQG ANATOMY IRXUWKOXPEULFDOVDGGXFWRUSROOLFLVDQGGHHSKHDGRIWKHÀH[RU SROOLFLVEUHYLVPXVFOHV2 7KHXOQDUQHUYHLVGHULYHGIURPWKH&7QHUYHURRWV1HDUO\DOO XOQDUQHUYH¿EHUVWUDYHOWKURXJKWKHORZHUWUXQNDQGPHGLDOFRUG CLINICAL AND ELECTRODIAGNOSTIC RIWKHEUDFKLDOSOH[XV1 During its descent through the medial arm, FEATURES OF ULNAR NERVE DYSFUNCTION the ulnar nerve does not give off any branches until it reaches the HOERZ$WWKHHOERZWKHXOQDUQHUYHWUDYHOVWKURXJKWKHJURRYH Ulnar Neuropathy at the Elbow formed by the medial epicondyle and olecranon process of the 8OQDU QHXURSDWK\ DW WKH HOERZ LV WKH VHFRQG PRVW FRPPRQ ulna bone, and it passes deep to the humeroulnar aponeurotic HQWUDSPHQW QHXURSDWK\ DIWHU FDUSDO WXQQHO V\QGURPH 6RPH DUFDGH +8$ EHWWHUNQRZQDVWKHFXELWDOWXQQHO+HUHPXVFXODU common causes of ulnar neuropathy at the elbow are listed in EUDQFKHVWRWKHÀH[RUFDUSLXOQDULV )&8 DQGÀH[RUGLJLWRUXP 7DEOH1 SURIXQGXV )'3  ULQJ DQG OLWWOH ¿QJHUV  DULVH ZKLOH WKH PDLQ WUXQNRIWKHXOQDUQHUYHFRQWLQXHVLWVGHVFHQWWRWKHZULVW2 Typical symptoms include numbness and tingling in the distribution of the ulnar nerve along with elbow pain that radiates $SSUR[LPDWHO\FPSUR[LPDOWRWKHZULVWWKHPDLQXOQDUQHUYH LQWR WKH XOQDU DVSHFW RI WKH KDQG ,Q VRPH FDVHV RQO\ VHQVRU\ JLYHVULVHWRWZRVHQVRU\EUDQFKHV7KHGRUVDOXOQDUFXWDQHRXV V\PSWRPVDUHSUHVHQW3,PSDLUHGVHQVDWLRQLQWKH¿QJHUWLSVLVWKH VHQVRU\EUDQFKWUDYHOVEHQHDWKWKH)&8WRSURYLGHVHQVDWLRQRYHU PRVWFRPPRQVHQVRU\GH¿FLW6HQVRU\ORVVLQWKHXOQDUSDOPLV WKHGRUVRPHGLDODVSHFWRIWKHKDQG7KHSDOPDUFXWDQHRXVVHQVRU\ OHVVIUHTXHQW3 An early sign may be inability to adduct the little branch provides sensation over the hypothenar area of the hand ¿QJHU,QPRUHVHYHUHFDVHVWKHUHZLOOEHZHDNQHVVRIKDQGJULS DQGQDLOV2 DQGDWURSK\RIWKHLQWULQVLFKDQGPXVFOHV:HDNQHVVRIWKH¿UVW GRUVDO LQWHURVVHRXV PXVFOH )',  LV PRUH IUHTXHQW   WKDQ ZHDNQHVVRIWKH$'0PXVFOH  :HDNQHVVRIWKH)'3DQG 17 ULNAR NERVE

)&8 PXVFOHV RFFXU LQ  DQG  UHVSHFWLYHO\ In severe FDVHV FODZLQJ RI WKH ULQJ DQG OLWWOH ¿QJHUV FDQ GHYHORS 'HHS WHQGRQUHÀH[HVXVXDOO\DUHSUHVHUYHGLQWKLVW\SHRIQHXURSDWK\ Various provocative maneuvers have been described that may LQFUHDVH WKH GLDJQRVWLF \LHOG 7KHVH LQFOXGH VXVWDLQHG PDQXDO SUHVVXUH RYHU WKH FXELWDO WXQQHO VXVWDLQHG HOERZ ÀH[LRQ DQG ÀH[LRQFRPELQHGZLWKPDQXDOSUHVVXUH&RPELQHGÀH[LRQZLWK manual pressure over the cubital tunnel has been reported to have WKHKLJKHVWVHQVLWLYLW\  

Table 1. Common causes of ulnar neuropathy1

At the elbow 2OGIUDFWXUHZLWKMRLQWGHIRUPLW\ Recent elbow trauma without fracture Habitual leaning on elbow Figure 1.8OQDUVHQVRU\FRQGXFWLRQVWXG\ DQWLGURPLF  2FFXSDWLRQDOUHSHWLWLYHÀH[LRQH[WHQVLRQ &RQJHQLWDOYDULDWLRQVRI+8$DUFKLWHFWXUH Dorsal ulnar cutaneous sensory study: 7KLV 1&6 LV XWLOL]HG Diabetes mellitus LI WKHUH LV WKH FRQIRXQGLQJ SRVVLELOLW\ RI ZULVW SDWKRORJ\ ,W LV Hereditary neuropathy with liability to pressure palsies SHUIRUPHGXVLQJVWDQGDUGGLVFHOHFWURGHV )LJ *LVSODFHG Rheumatoid arthritis RYHUWKHZHEVSDFHEHWZHHQWKHULQJDQGOLWWOH¿QJHUVZKLOH*LV Iatrogenic SODFHGFPGLVWDORYHUWKHOLWWOH¿QJHU1 The nerve is stimulated Malpositioning during surgery FPSUR[LPDOO\7KHVWLPXODWLRQVLWHOLHVMXVWSUR[LPDOWRDQG Nerve infarction during transposition VOLJKWO\EHORZWKHXOQDUVW\ORLG1 Since this nerve arises proximal to the wrist, it may be involved in ulnar neuropathies at the elbow, At the wrist EXWZLOOEHQRUPDOZKHQWKHXOQDUQHUYHLVHQWUDSSHGDWWKHZULVW :ULVWIUDFWXUH *DQJOLRQF\VWZLWKLQ*X\RQ¶VFDQDO Frequent pressure on hypothenar eminence 5HSHWLWLYHPRYHPHQWVDJDLQVWWKHXOQDUZULVW HJELNHUVDQG laborers) HUA=humeroulnar aponeurotic arcade

Differential Diagnosis The differential diagnosis of ulnar neuropathy at the elbow includes the following:

‡ Lower trunk brachial plexopathy

‡ Medial cord brachial plexopathy

‡ &7UDGLFXORSDWK\

‡ 8OQDUQHXURSDWK\DWVRPHORFDWLRQRWKHUWKDQWKHHOERZ Figure 2. Dorsal ulnar cutaneous sensory study.

Electrodiagnostic Testing Ulnar motor study::KHQSHUIRUPLQJWKHXOQDUPRWRU1&6LWLV LPSRUWDQWWRXQGHUVWDQGWKDWHOERZSRVLWLRQLVFUXFLDO7KHÀH[HG As with all nerve conduction studies (NCSs), limb temperatures DWGHJUHHV HOERZSRVLWLRQVKRXOGEHXWLOL]HGEHFDXVHLW should be maintained within the reference range (>32°C) and has been shown to be more sensitive than testing with the elbow GRFXPHQWHG H[WHQGHG

Ulnar sensory study:7KHDQWLGURPLFXOQDUVHQVRU\1&6 )LJ  The ulnar motor NCS can be recorded from either the ADM is performed using ring electrodes to record from the little )LJV DQGRU)',PXVFOHV )LJ 5HFRUGLQJRYHUWKH)', ¿QJHU5LQJHOHFWURGHVDUHSODFHGZLWK*RYHUWKHPHWDFDUSDO± PXVFOH PD\ EH PRUH VHQVLWLYH WKDQ WKH$'0 PXVFOH 8VLQJ SKDODQJHDOMRLQW 0&3 DQG*SODFHGFPGLVWDOO\1 The ulnar VWDQGDUGGLVFHOHFWURGHV*LVSODFHGRYHUWKHEHOO\RIWKHPXVFOH QHUYHLVWKHQVWLPXODWHGSUR[LPDOWRWKHZULVWDGMDFHQWWRWKH)&8 EHLQJUHFRUGHGZKLOH*LVSODFHGFPGLVWDORYHUWKH0&3 WHQGRQ1 7KH GLVWDQFH EHWZHHQ WKH VWLPXODWLRQ VLWH DQG WKH * MRLQW1 The ulnar nerve is then stimulated at up to four sites: (1) electrode will be dependent on the normative values used in each :ULVW : ZKLFKLVMXVWSUR[LPDOWRWKHZULVWDGMDFHQWWRWKH)&8 ODERUDWRU\7\SLFDOO\WKLVGLVWDQFHLVLQWKHUDQJHRIFP WHQGRQ )LJ   %HORZHOERZ %( ZKLFKOLHVFPGLVWDO WRWKHPHGLDOHSLFRQG\OH )LJ   $ERYHHOERZ $( ZKLFK  A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

OLHVDSSUR[LPDWHO\FPSUR[LPDOWRWKH%(VLWHLQWKHVSDFH EHWZHHQWKHELFHSVDQGWULFHSVPXVFOHVDQGOHVVFRPPRQO\   Axilla (A): which lies in the proximal axilla, medial to the biceps PXVFOHDQGRYHUWKHD[LOODU\SXOVH1 The measurement across the HOERZVHJPHQWPXVWIROORZWKHFXUYHGSDWKRIWKHXOQDUQHUYH

Figure 5. Ulnar motor nerve conduction study, recording from the abductor digiti minimi muscle, stimulating above the elbow.

Figure 3. Ulnar motor nerve conduction study, recording from the abductor digiti minimi muscle, stimulating at the wrist.

Figure 6.8OQDU0RWRU&RQGXFWLRQ6WXG\UHFRUGLQJ¿UVWGRUVDOLQWHURVVHRXV muscle.

Evaluation of the ulnar nerve with NCSs should include the URXWLQH VWXGLHV VKRZQ LQ 7DEOH  6KRXOG URXWLQH 1&6V QRW ORFDOL]H WKH OHVLRQ DGGLWLRQDO WHFKQLTXHV PD\ EH KHOSIXO WR FRQVLGHU7KHVHPD\LQFOXGH  UHSHDWLQJWKHXOQDUPRWRU1&6 while recording from the FDI muscle; (2) ulnar motor NCS using inching techniques across the elbow segment; (3) mixed-nerve FRPSDUDWLYH 1&6V DFURVV WKH HOERZ   FRPSDULQJ WKH GRUVDO ulnar cutaneous sensory responses between the affected and DV\PSWRPDWLFOLPE DQG   FRPSDULQJ WKH PHGLDO DQWHEUDFKLDO cutaneous sensory response between affected and asymptomatic VLGHVLIWKHUHLVUHDVRQWRVXVSHFWDEUDFKLDOSOH[RSDWK\,QPRVW cases the lesion is at the elbow; however, lesions at the wrist or more proximal locations (brachial plexus or root) should be H[FOXGHGE\WKHHOHFWURGLDJQRVWLF ('; VWXG\

Figure 4. Ulnar motor conduction study, recording from the abductor digiti minimi muscle, stimulating below the elbow.

In certain cases, inching across the elbow can be performed to GHPRQVWUDWH IRFDO GHP\HOLQDWLRQ The setup is identical to XOQDUPRWRUVWXGLHVUHFRUGLQJIURPWKH$'0DQG)',PXVFOHV 5HFRUGLQJLVSHUIRUPHGDWWKH:DQG%(VLWHVDVGHVFULEHGDERYH 7KH %(±$( VHFWLRQ LV WKHQ GLYLGHG LQWR  FP VHJPHQWV DQG LQGLYLGXDOPRWRUUHVSRQVHVDUHREWDLQHGDWHDFKLQFUHPHQW1 The most convincing abnormality would be a change in latency and/or DFKDQJHLQFRPSRXQGPXVFOHDFWLRQSRWHQWLDODPSOLWXGH !  PRUSKRORJ\RUDUHDDFURVVWKH%(±$(VHJPHQW 19 ULNAR NERVE

Table 2. Electrodiagnostic evaluation of ulnar neuropathy at the elbow1 Table 3. Clinical syndromes produced by ulnar nerve compression within the canal of Guyon1,9 A. Nerve conduction studies (Figs. 1-6) 8OQDUQHUYHVWXGLHV A. Combined motor and sensory syndrome (type 1) D8OQDUPRWRUVWXG\VWLPXODWLQJDWWKHZULVWEHORZHOERZ A lesion at the proximal portion of the canal may involve both and above elbow sites, while recording from the abductor PRWRUDQGVHQVRU\GLYLVLRQV:HDNQHVVRIDOOXOQDULQQHUYDWHG digiti minimi muscle KDQGPXVFOHVDQGORVVRIVHQVDWLRQRYHUWKHSDOPDUOLWWOH¿QJHU E8OQDU)UHVSRQVHV DQG PHGLDO ULQJ ¿QJHU RFFXUV &XWDQHRXV VHQVDWLRQ RYHU WKH F8OQDUVHQVRU\VWXG\VWLPXODWLQJDWWKHZULVWZKLOHUHFRUGLQJ hypothenar and dorsomedial surfaces of the hand should be IURPWKHOLWWOH¿QJHU VSDUHG 0HGLDQQHUYHVWXGLHV D 0HGLDQ PRWRU VWXG\ VWLPXODWLQJ DW WKH ZULVW DQG HOERZ B. Pure sensory syndrome (type 2) sites while recording from the abductor pollicis brevis muscle Clinically, there is loss of sensation over the palmar surface of E0HGLDQ)UHVSRQVHV WKHOLWWOH¿QJHUDQGPHGLDOULQJ¿QJHU6HQVDWLRQLVVSDUHGRYHU F 0HGLDQ VHQVRU\ VWXG\ VWLPXODWLQJ DW WKH ZULVW ZKLOH WKHK\SRWKHQDUHPLQHQFH0RWRU¿EHUVDUHQRWDIIHFWHG7KHUH recording from the thumb LVQRZHDNQHVVDVVRFLDWHGZLWKWKLVOHVLRQ B. Needle electromyography 5RXWLQH C. Pure motor syndromes D$W OHDVW RQH XOQDULQQHUYDWHG PXVFOH GLVWDO WR WKH ZULVW  Lesion affecting the deep palmar and hypothenar motor HJ¿UVWGRUVDOLQWHURVVHRXVRUDEGXFWRUGLJLWLPLQLPL branches (type 3) E7ZRXOQDULQQHUYDWHGPXVFOHVRIWKHIRUHDUP HJÀH[RU This lesion affects the motor trunk proximal to the takeoff GLJLWRUXP SURIXQGXV >PLGGOH DQG ULQJ ¿QJHUV@ DQG ÀH[RU RIWKHK\SRWKHQDUEUDQFKHV$VDUHVXOWDOOXOQDLQQHUYDWHG carpi ulnaris) PXVFOHV RI WKH KDQG DUH LQYROYHG %HFDXVH WKH VHQVRU\  ,I WHVWLQJ RI DQ\ RI WKH URXWLQH PXVFOHV LV DEQRUPDO WKHQ EUDQFKLVQRWDIIHFWHGVHQVDWLRQLVVSDUHG additional needle examination should include: D$WOHDVWWZRQRQXOQDUORZHUWUXQN&7PXVFOHV HJ  /HVLRQDIIHFWLQJWKHGHHSSDOPDUPRWRUEUDQFKRQO\ W\SH DEGXFWRU SROOLFLV EUHYLV ÀH[RU SROOLFLV ORQJXV H[WHQVRU &OLQLFDOO\WKHUHLVZHDNQHVVRI¿UVWDQGVHFRQGOXPEULFDOV indicis proprius) DVZHOODVXOQDULQQHUYDWHGPXVFOHVRIWKHWKHQDUHPLQHQFH E&DQG7SDUDVSLQDOPXVFOHV This type of lesion spares the muscles of the hypothenar HPLQHQFH Management  Lesion affecting only the distal deep palmar motor branch The treatment of patients with ulnar neuropathy at the elbow W\SH PD\FRQVLVWRIFRQVHUYDWLYHRUVXUJLFDOPHDVXUHV1RQRSHUDWLYH 7KLV W\SH RI OHVLRQ RFFXUV MXVW SUR[LPDO WR WKH EUDQFKHV management should include avoidance of pressure on the elbow LQQHUYDWLQJWKHDGGXFWRUSROOLFLVDQG¿UVWGRUVDOLQWHURVVHRXV DQGRUSURORQJHGHOERZÀH[LRQDVZHOODVXWLOL]DWLRQRIDQHOERZ PXVFOHVUHVXOWLQJLQZHDNQHVVRIWKHVHPXVFOHV VSOLQW,QFHUWDLQFDVHVVWHURLGLQMHFWLRQVLQWRWKHFXELWDOWXQQHO PD\EHKHOSIXO)RUSDWLHQWVZKRKDYHVLJQL¿FDQWRUSURJUHVVLYH Differential Diagnosis QHXURORJLFDOGH¿FLWVVXUJLFDOGHFRPSUHVVLRQLVUHFRPPHQGHG3 The differential diagnosis of ulnar neuropathy at the wrist includes Ulnar Neuropathy at the Wrist the following:

Entrapment of the ulnar nerve at the wrist is rare relative to ‡ Lower trunk brachial plexopathy FRPSUHVVLRQ DW WKH HOERZ 7KH FRPPRQ VLWH RI HQWUDSPHQW LV ZLWKLQ*X\RQ¶VFDQDO6RPHFRPPRQFDXVHVRIXOQDUQHXURSDWK\ ‡ Medial cord brachial plexopathy DWWKHZULVWDUHOLVWHGLQ7DEOH)LYHGLIIHUHQWV\QGURPHVKDYH EHHQGHVFULEHGVHFRQGDU\WRHQWUDSPHQWLQWKLVUHJLRQ 7DEOH  ‡ &±7UDGLFXORSDWK\ Patients may present with sensory and/or motor involvement FRQ¿QHG WR WKH GLVWDO XOQDU QHUYH GLVWULEXWLRQ 7KH\ PD\ KDYH ‡ 8OQDUQHXURSDWK\DWVRPHORFDWLRQRWKHUWKDQWKHHOERZ sensory loss, paresthesias, or pain in the region supplied by the GLVWDO XOQDU VHQVRU\ EUDQFK 7KH UHJLRQ VXSSOLHG E\ WKH GRUVDO ‡ Early motor neuron disease1 XOQDU FXWDQHRXV VHQVRU\ EUDQFK LV VSDUHG 0RWRU GH¿FLWV DUH limited to the muscles of the hand with sparing of the proximal Electrodiagnostic Testing XOQDULQQHUYDWHG PXVFOHV ([DPLQDWLRQ PD\ GHPRQVWUDWH weakness with atrophy or fasciculations of the intrinsic hand 7DEOH  RXWOLQHV D WHVWLQJ SURWRFRO IRU SRVVLEOH XOQDU QHUYH PXVFOHV7LQHO¶VVLJQPD\EHSUHVHQWRYHU*X\RQ¶VFDQDO OHVLRQVDWWKHZULVW7KHVHWXSIRUWKHVHVWXGLHVDUHWKHVDPHDV IRU HYDOXDWLRQV DW WKH HOERZ ZLWK WKH DGGLWLRQ RI OXPEULFDO± LQWHURVVHRXV )LJ FRPSDULVRQV7KLVVWXG\DOORZVVFRPSDULVRQ of ulnar to median nerve conduction across the wrist due to the fact that the second lumbrical muscle (median innervated) 2020 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

RYHUOLHVWKH¿UVWSDOPDULQWHURVVHRXVPXVFOH XOQDULQQHUYDWHG  Management :LWK WKLV VWXG\ GLVF HOHFWURGHV DUH SODFHG ZLWK * MXVW ODWHUDO WRWKHPLGGOHRIWKHWKLUGPHWDFDUSDODQG*RYHUWKH0&3MRLQW Magnetic resonance imaging (MRI) may be useful in detecting RI WKH LQGH[ ¿QJHU 7KH PHGLDQ QHUYH DQG WKH XOQDU QHUYH DUH VWUXFWXUDODEQRUPDOLWLHVDIIHFWLQJWKHXOQDUQHUYHLQ*X\RQ¶VFDQDO stimulated supramaximally at their usual wrist locations using $JDQJOLRQF\VWRUWUDXPDWLFZULVWLQMXU\DFFRXQWIRUWKHPDMRULW\ LGHQWLFDOGLVWDQFHV17DEOHVXPPDUL]HVW\SLFDO(';¿QGLQJVLQ RIFDVHV11,QFDVHVZKHUHDVWUXFWXUDOOHVLRQLVLGHQWL¿HGVXUJLFDO HDFKRIWKHYDULRXVV\QGURPHV UHPRYDOLVUHFRPPHQGHG,QFHUWDLQFDVHVVXUJLFDOH[SORUDWLRQ PD\EHFRQVLGHUHGHYHQZKHQ05,IDLOVWRLGHQWLI\DOHVLRQ Table 4. Electrodiagnostic evaluation of ulnar neuropathy at the wrist1 Table 5.1HUYHFRQGXFWLRQVWXG\¿QGLQJVLQXOQDUQHXURSDWK\DWWKHZULVW10 A. Nerve conduction studies (Figs. 1-6) 8OQDUQHUYHVWXGLHV A. Combined motor and sensory syndrome (type 1) D8OQDUPRWRUVWXG\VWLPXODWLQJDWWKHZULVWEHORZHOERZ 'HFUHDVHGXOQDUVHQVRU\DPSOLWXGH8OQDUPRWRUDPSOLWXGHLV and above elbow sites, while recording from the abductor GHFUHDVHGZLWKSURORQJHGGLVWDOODWHQF\1HHGOH(0*VKRZV digiti minimi muscle GHQHUYDWLRQRIDOOLQWULQVLFKDQGPXVFOHV E8OQDUPRWRUVWXG\ ELODWHUDO VWLPXODWLQJDWWKHZULVWZKLOH UHFRUGLQJIURPWKH¿UVWGRUVDOLQWHURVVHRXVPXVFOH B. Pure sensory syndrome (type 2) F8OQDU)UHVSRQVHV 'HFUHDVHG XOQDU VHQVRU\ DPSOLWXGH 8OQDU PRWRU VWXG\ LV G 8OQDU VHQVRU\ VWXG\ VWLPXODWLQJ DW WKH ZULVW UHFRUGLQJ QRUPDO1HHGOH(0*LVQRUPDO IURPWKHOLWWOH¿QJHU H'RUVDOXOQDUFXWDQHRXVVHQVRU\VWXG\VWLPXODWLQJIRUHDUP C. Pure motor syndromes while recording from the dorsolateral hand 8OQDU±PHGLDQFRPSDULVRQVWXGLHV  Lesion affecting the deep palmar and hypothenar motor D/XPEULFDO VHFRQG ±LQWHURVVHRXV ¿UVWSDOPDU FRPSDULVRQ branches (type 3) study 8OQDUVHQVRU\UHVSRQVHLVQRUPDO8OQDUPRWRUDPSOLWXGH LVGHFUHDVHGZLWKSURORQJHGGLVWDOODWHQF\1HHGOH(0* B. Needle electromyography VKRZVGHQHUYDWLRQRIDOOLQWULQVLFKDQGPXVFOHV 5RXWLQH D 2QH GHHS SDOPDU PRWRU PXVFOH HJ ¿UVW GRUVDO  Lesion affecting the deep palmar motor branch only interosseous) W\SH E 2QH K\SRWKHQDU EUDQFK PXVFOH HJ DEGXFWRU GLJLWL 8OQDUVHQVRU\UHVSRQVHLVQRUPDO8OQDUPRWRUDPSOLWXGH minimi) is decreased with prolonged distal latency when recording F7ZRIRUHDUPPXVFOHV HJÀH[RUFDUSLXOQDULVDQGÀH[RU IURPWKH¿UVWGRUVDOLQWHURVVHRXVPXVFOH1HHGOH(0* GLJLWRUXPSURIXQGXV>PLGGOHDQGULQJ¿QJHUV@ VKRZVGHQHUYDWLRQRIWKH¿UVWGRUVDOLQWHURVVHRXV¿UVW  ,I WHVWLQJ RI DQ\ RI WKH URXWLQH PXVFOHV LV DEQRUPDO WKHQ and second lumbricals, and thenar muscles with sparing additional needle examination should include: RIWKHK\SRWKHQDUPXVFOHV D$WOHDVWWZRQRQXOQDUORZHUWUXQN&7PXVFOHV HJ DEGXFWRUSROOLFLVEUHYLVÀH[RUSROOLFLVORQJXVDQGH[WHQVRU  Lesion affecting only the distal deep palmar motor indicis proprius) EUDQFK W\SH E&DQG7SDUDVSLQDOPXVFOHV 8OQDUVHQVRU\UHVSRQVHLVQRUPDO8OQDUPRWRUDPSOLWXGH is decreased with prolonged distal latency when recording IURPWKH¿UVWGRUVDOLQWHURVVHRXVPXVFOH1HHGOH(0* VKRZV GHQHUYDWLRQ RI WKH ¿UVW GRUVDO LQWHURVVHRXV DQG adductor pollicis muscles with sparing of the hypothenar PXVFOHV EMG=electromyography

Figure 7. Lumbrical–interosseous motor study. Top: Stimulating the median nerve recording at the 2nd lumbrical muscle. Bottom: Stimulating the ulnar nerve recording at the interosseous muscle.

21 ULNAR NERVE REFERENCES

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2222 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

The Radial Nerve

Kerry H. Levin, MD Chairman, Department of Neurology Director, Neuromuscular Center Cleveland Clinic Cleveland, OH

DERIVATION AND MAJOR ELEMENTS OF THE RADIAL NERVE

7KHUDGLDOQHUYHLVFRQVWLWXWHGIURPQHUYH¿EHUVLQWKH&URRW VHJPHQWV )LJV 1HUYH¿EHUVVHJUHJDWHLQWKHSRVWHULRUFRUG and become the radial nerve after the branch points of the axillary DQG WKRUDFRGRUVDO QHUYHV$URXQG WKH HOERZ RU MXVW EHORZ WKH radial nerve separates into the posterior interosseous nerve (PIN) DQGVXSHU¿FLDOUDGLDOQHUYH 651 

Figure 2. Radial nerve anatomy in the forearm. Reproduced with permission.5

RADIAL NERVE ABOVE THE ELBOW

The radial nerve courses along the lateral wall of the axilla and the Figure 1. Radial nerve anatomy in the upper arm. PHGLDOVLGHRIWKHKXPHUXV,WZLQGVREOLTXHO\EHKLQGDQGDURXQG Reproduced with permission of the author.10 the humerus in the spiral groove, between the two triceps heads, DQGWKURXJKD¿EURXVDUFKIRUPHGE\WKHERQ\DWWDFKPHQWRIWKH ODWHUDOKHDGRIWKHWULFHSV,WUHDFKHVWKHDQWHULRUDUPWKURXJKDQ intermuscular septum below the insertion of the deltoid muscle and enters the forearm by going between the distal biceps and SUR[LPDOEUDFKLRUDGLDOLVPXVFOHV 23 THE RADIAL NERVE

0RWRUEUDQFKHVWRWKHWULFHSVDULVHDORQJWKHVSLUDOJURRYH7KH ÀH[LRQRUWZLVWLQJFDXVLQJDUDGLDOOHVLRQGLVWDOWRWKHEUDQFKWR EUDQFKWREUDFKLRUDGLDOLVDULVHVMXVWEHORZWKHGHOWRLGLQVHUWLRQ WULFHSV Compression with a tourniquet (usually during surgery) %UDQFKHVWRH[WHQVRUFDUSLUDGLDOLV (&5 ORQJXVDQGEUHYLVDULVH FDQLQMXUHWKHUDGLDOQHUYHDORQHEXWLWPD\DIIHFWWKHXOQDUDQG LQWKHGLVWDODUPDQGQHDUWKHHOERZUHVSHFWLYHO\7KHVHQVRU\ PHGLDQQHUYHVDVZHOOEXWWRDOHVVHUGHJUHH7KHUDGLDOQHUYH branch to the posterior cutaneous nerve of the arm arises in may be affected by masses such as tumors and perineurial sheath WKH D[LOOD 7KH SRVWHULRU FXWDQHRXV QHUYH RI WKH IRUHDUP DULVHV SUROLIHUDWLRQ SUR[LPDOWRWKHVSLUDOJURRYH In the Forearm RADIAL NERVE BELOW THE ELBOW 8SSHU IRUHDUP UDGLXV IUDFWXUHV XQFRPPRQO\ FDXVH QHXURSDWK\ PIN damage can occur from mid forearm fractures of the radius Division into the PIN and SRN occurs at about the level of the DQG XOQD /DFHUDWLRQV GR QRW XVXDOO\ FDXVH 3,1 LQMXU\ EHFDXVH HOERZ7KH3,1ZLQGVGRUVRODWHUDOO\DURXQGWKHQHFNRIWKHUDGLXV WKH QHUYH OLHV GHHS WR WKH H[WHQVRU PXVFOHV The PIN can be WRWKHH[WHQVRUFRPSDUWPHQWRIWKHIRUHDUP,WHQWHUVWKHVXSLQDWRU HQWUDSSHGDWWKHDUFDGHRI)URKVHZLWKLQWKHVXSLQDWRUPXVFOH PXVFOHWKURXJKWKH$UFDGHRI)URKVHLQQHUYDWLQJWKHVXSLQDWRU ,W FDQ EH HQWUDSSHG GXH WR DQJXODWLRQ RYHU GHIRUPHG MRLQWV RU SRVWIUDFWXUHFDOOXVIRUPDWLRQORQJDIWHUWUDXPD Motor branches to extensor digitorum communis (EDC), extensor FDUSL XOQDULV (&8  H[WHQVRU SROOLFLV ORQJXV H[WHQVRU SROOLFLV Compression can occur from soft tissue masses and tumors brevis, abductor pollicis longus, extensor indicis proprius (EIP), HVSHFLDOO\ OLSRPDV  RU IURP D EUDFKLRFHSKDOLF ¿VWXOD IRU DQGH[WHQVRUGLJLWLPLQLPLIROORZLQWKHPLGIRUHDUP7KHQHUYH KHPRGLDO\VLV ([WHUQDO FRPSUHVVLRQ XQFRPPRQO\ RFFXUV IURP HQGVLQVHQVRU\DQGSURSULRFHSWLYH¿EHUVLQSRVWHULRUFDSVXOHRI &DQDGLDQFUXWFKHV7KHSRVWHULRUFXWDQHRXVQHUYHRIWKHIRUHDUPLV ZULVWMRLQW XQFRPPRQO\LQMXUHGE\EOXQWWUDXPDRUWRXUQLTXHWFRPSUHVVLRQ

7KHVXSHU¿FLDOUDGLDOQHUYHSDVVHVRYHUWKHVXSLQDWRUDQGSURQDWRU 6XSHU¿FLDO5DGLDO1HXURSDWK\ WHUHV PXVFOHV GHHS WR EUDFKLRUDGLDOLV ,Q WKH GLVWDO IRUHDUP LW Distal Lesions passes over the dorsolateral aspect of the wrist and divides into 7KH651LVPRVWYXOQHUDEOHWRLQMXU\DWWKHZULVWO\LQJFORVHWR terminal branches to supply the dorsolateral hand and the thumb WKHGLVWDOUDGLXV WKURXJKWKHPLGGOH¿QJHU ,WLVVXEMHFWWRFRPSUHVVLRQIURPZDWFKVWUDSVKDQGFXIIVUXEEHU STRUCTURAL DISORDERS OF THE RADIAL JORYHV DQG RUWKRSHGLF FDVWV &RLQFLGHQW XOQDU DQG PHGLDQ NERVE QHUYH GDPDJH KDV EHHQ UHSRUWHG ZLWK KDQGFXIIV  ,QMXU\ FDQ also occur as the result of blunt trauma, distal radial fractures, In the Axilla DQGZULVWODFHUDWLRQV7KH651FDQEHDIIHFWHGE\LQÀDPPDWLRQ Crutch palsy develops when a crutch compresses the radial nerve FRQWLJXRXVZLWKGH4XHUYDLQ¶VWHQRV\QRYLWLV,DWURJHQLFOHVLRQV against the humerus or muscles of the axilla (median and ulnar RFFXUDVDUHVXOWRIVXUJHU\IRUGH4XHUYDLQ¶VWHQRV\QRYLWLV DERXW QHUYHV PD\ DOVR EH DIIHFWHG  3HUFXWDQHRXV D[LOODU\ DQHVWKHWLF DULVN  and during harvest of the radial artery for coronary nerve block and axillary arteriography can lead to hematoma, DUWHU\E\SDVVJUDIWLQJ ! GXULQJFDQQXODWLRQRIWKHDGMDFHQW producing a medial brachial fascial compartment syndrome that FHSKDOLFYHLQ1 DIIHFWVWKHUDGLDOQHUYHEXWDOZD\VLQFRQMXQFWLRQZLWKPHGLDQ QHUYHLQYROYHPHQW12 Radial neuropathy can occur with anterior Proximal Lesions shoulder dislocation, although axillary and suprascapular nerve ,QMXU\ WR WKH 651 FDQ RFFXU GXH WR PXVFOH FRPSUHVVLRQ ZKHQ LQMXULHV DUH PRUH FRPPRQ2 Proximal humeral fracture causes LWWDNHVDQDEHUUDQWFRXUVHWKURXJKWKH(&5PXVFOH It can be UDGLDOQHXURSDWK\LQDERXWRIFDVHVDOWKRXJKXVXDOO\ZLWK compressed at the elbow near its branch point from the main RWKHUQHUYHLQYROYHPHQW13 UDGLDOQHUYHWUXQN(QWUDSPHQWFDQRFFXUDWVLWHVLQWKHIRUHDUP ZKHUH WKH IDVFLD MRLQV WHQGRQV RI WKH EUDFKLRUDGLDOLV DQG (&5 In the Upper Arm ORQJXVPXVFOHV Radial neuropathy occurs in about 12% of cases of humeral IUDFWXUH3 Spiral fractures can occur from strenuous throwing NONFOCAL, NONSTRUCTURAL CAUSES OF HJ EDVHEDOOV KDQG JUHQDGHV  RU DUP ZUHVWOLQJ XVXDOO\ WKH RADIAL AND POSTERIOR INTEROSSEOUS radial nerve alone, but can be with median and/or ulnar nerve NERVE LESIONS LQYROYHPHQW 2WKHUWUDXPDFDQLQMXUHWKHUDGLDOQHUYHLQFOXGLQJ JXQVKRWZRXQGVODFHUDWLRQEOXQWLQMXU\DQGFRPSUHVVLRQ HJ $QXPEHURIDXWRLPPXQHDQGLQÀDPPDWRU\GLVRUGHUVFDQDIIHFW WRXUQLTXHWVOHHSSRVLWLRQPXVFXODUH[HUWLRQ &RPSUHVVLRQDORQJ WKHUDGLDOQHUYHDORQHRULQFRPELQDWLRQZLWKRWKHUQHUYHWUXQNV WKHPHGLDOXSSHUDUP LHRYHUWKHHGJHRIDFKDLU LVWKHFODVVLF These would include neuralgic amyotrophy (acute brachial VFHQDULRIRUWKHFRPPRQO\GHVFULEHG³6DWXUGD\QLJKWSDOV\´7KH neuropathy), hereditary neuropathy with tendency to pressure nerve can also be compressed along the lateral upper arm when palsy (HNPP), multifocal mononeuropathy with conduction block the arm is pinned between the body and a hard surface such as the 001 DQGPRQRQHXURSDWK\PXOWLSOH[ ÀRRURURSHUDWLQJWDEOH&RPSUHVVLRQZLWKLQWKHWULFHSVFDQRFFXU from strenuous muscle contraction with or without forceful elbow

 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES CLINICAL FINDINGS IN RADIAL NEUROPATHIES

Lesions above the spiral groove produce main trunk radial neuropathy manifested by weakness of all radial-innervated muscles, including the triceps, as well as sensory loss in the SRN GLVWULEXWLRQ:LWKVSLUDOJURRYHOHVLRQVWKHWULFHSVLVVSDUHGDQG WKHUHLVYDULDEOHZHDNQHVVLQWKHEUDFKLRUDGLDOLVZULVWDQG¿QJHU H[WHQVRUVDQGYDULDEOHLQYROYHPHQWRIWKH651,QRQHUHSRUW FDVHVKDGVSDULQJRIWKHEUDFKLRUDGLDOLVDQGKDGQR VHQVRU\ LQYROYHPHQW11 :LWK 3,1 OHVLRQV WKHUH LV ZHDNQHVV RI WKH¿QJHUH[WHQVRUVDQGWKH(&8,QYROYHPHQWRIWKH('&DORQH Figure 4. Radial motor conduction study recording from the extensor indicis leads to weakness limited to the extension of the index through proprius and stimulating at the forearm. The recording electrodes are placed WKHULQJ¿QJHU over the extensor indicis muscle with the active electrode over the belly of the muscle and the reference electrode at least 3 cm distal to the active DIFFERENTIAL DIAGNOSIS electrode, over the tendon. The ground is placed between the recording electrodes and the stimulation site on the forearm. The nerve is stimulated & UDGLFXORSDWK\ FDQ PLPLF D SUR[LPDO UDGLDO QHXURSDWK\ distally over the lateral forearm, with the cathode distal to the anode. There especially when there is prominent involvement of the triceps LVQR¿[HGGLVWDQFH7KHUDGLDOQHUYHLVVWLPXODWHGPRUHSUR[LPDOO\DWWKH DQGZULVWH[WHQVRUV$&UDGLFXORSDWK\FDQEHFRQIXVHGZLWKD elbow, lateral to the biceps tendon, beneath the brachioradialis muscle. It PIN lesion, especially when there is prominent involvement of can be stimulated more proximally over the lateral aspect of the arm at the WKH ¿QJHU H[WHQVRUV $ SRVWHULRU FRUG EUDFKLDO SOH[RSDWK\ FDQ VSLUDOJURRYHDQGDOVRLQWKHVXSUDFODYLFXODUIRVVD (UE¶VSRLQW 3UR[LPDO be mistaken for a radial neuropathy, especially in the setting of VWLPXODWLRQ PD\ EH DVVRFLDWHG ZLWK DQ LQLWLDO SRVLWLYH GHÀHFWLRQ RI WKH shoulder pain that can mask the assessment of true weakness in compound muscle action potential because of activation of other muscles the deltoid (involvement in the axillary nerve distribution) and innervated by the radial nerve. WKHODWLVVLPXVGRUVLPXVFOHV5XSWXUHRIWKHWHQGRQVWRWKHWKXPE Reproduced with permission of the American Association of Neuromuscular DQG¿QJHUH[WHQVRUVIURPUKHXPDWRLGDUWKULWLVFDQPLPLFD3,1 & Electrodiagnostic Medicine. OHVLRQ ELECTRODIAGNOSIS Workup Nerve Conduction Studies The radial motor nerve conduction study (NCS) is performed by recording over the EIP and/or EDC, stimulating at the forearm, elbow, below the spiral groove, above spiral groove, and axilla, with appropriate comparison studies on the opposite side )LJV 6FUHHQLQJPRWRU1&6VVKRXOGEHSHUIRUPHGRQWKH PHGLDQ DQG XOQDU QHUYHV RQ WKH V\PSWRPDWLF VLGH 7KH 651 sensory NCS is performed by recording over the SRN at the Figure 5. Radial motor conduction study recording from the extensor indicis snuffbox, stimulating above the wrist, with comparison on the proprius stimulating at elbow. RSSRVLWHVLGHLIZDUUDQWHG )LJ 6FUHHQLQJPHGLDQDQGXOQDU Reproduced with permission of the American Association of Neuromuscular VHQVRU\1&6VVKRXOGEHSHUIRUPHGRQWKHV\PSWRPDWLFVLGH & Electrodiagnostic Medicine.

Figure 6. Radial motor conduction study recording from the extensor indicis proprius stimulating below spiral groove. Figure 3. Radial sensory conduction study. The active recording electrode Reproduced with permission of the American Association of Neuromuscular LVSODFHGRYHUWKHSDOSDEOHSRUWLRQRIWKHVXSHU¿FLDOUDGLDOQHUYH7KHQHUYH & Electrodiagnostic Medicine. can be palpated over the extensor pollicis longus tendon. The inactive or UHIHUHQFHHOHFWURGHLVSODFHGFPGLVWDOO\RQWKHWKXPE7KHJURXQGLV placed over the dorsum of the wrist between the stimulating and recording electrodes. The nerve is stimulated along the dorsal edge of the radius, 10 cm from the active recording electrode, with the cathode distal to the anode. Reproduced with permission of the American Association of Neuromuscular 25 & Electrodiagnostic Medicine. THE RADIAL NERVE REFERENCES

 %OHL]LIIHU6+HWWLFK,(LVHQKDXHU%HWDO1HXURORJLFVHTXHODHRI the donor arm after endoscopic versus conventional radial artery KDUYHVWLQJ-7KRUDF&DUGLRYDVF6XUJ  GH/DDW($9LVVHU&3&RHQH/13DKOSODW]397DY\'/1HUYH lesions in primary shoulder dislocations and humeral neck fractures: D SURVSHFWLYH FOLQLFDO DQG (0* VWXG\ - %RQH -RLQW 6XUJ %U   'H)UDQFR 0- /DZWRQ -1 5DGLDO QHUYH LQMXULHV DVVRFLDWHG ZLWK Figure 7. Radial motor conduction study recording at the extensor indicis KXPHUDOIUDFWXUHV-+DQG6XUJ $P  proprius stimulating above spiral groove.  'HOORQ$/0DFNLQQRQ6(5DGLDOVHQVRU\QHUYHHQWUDSPHQWLQWKH Reproduced with permission of the American Association of Neuromuscular IRUHDUP-+DQG6XUJHU\ $P  & Electrodiagnostic Medicine.  .LP '+ 5DGLDO QHUYH ,Q .LP '+ 0LGKD 5 0XURYLF -$ HW Needle Electromyography DOHGV.OLQHDQG+XGVRQ¶VQHUYHLQMXULHVQGHG3KLODGHOSKLD 7KHQHHGOHHOHFWURP\RJUDSK\ (0* VKRXOGLQFOXGHH[DPLQDWLRQ 6DXQGHUV(OVHYLHUS of muscles innervated by the proximal radial nerve as well as  .RSHOO +3 7KRPSVRQ :$ 3HULSKHUDO HQWUDSPHQW QHXURSDWKLHV the PIN, including the EIP, EDC, brachioradialis, ECR, and QGHG+XQWLQJWRQ1<.ULHJHU WULFHSV $GGLWLRQDO PXVFOHV LQFOXGH WKH VXSLQDWRU DQFRQHXV  0HOORU 6- )HUULV %' &RPSOLFDWLRQV RI D VLPSOH SURFHGXUH GH DQG(&8LIQHFHVVDU\EDVHGRQWKHURXWLQHVWXG\7RH[FOXGHD 4XHUYDLQ¶VGLVHDVHUHYLVLWHG,QW-&OLQ3UDFW PRUHZLGHVSUHDGGLVRUGHULWLVQHFHVVDU\WRVDPSOHQRQUDGLDO±  6FRWW .5 8OQDU DQG UDGLDO QHUYHV ,Q$$1(0$QQXDO 0HHWLQJ LQQHUYDWHG PXVFOHV HVSHFLDOO\ WKH GHOWRLG 7KH PHGLDQ DQG &RXUVH6\OODEXV1HXURDQDWRP\RI1&65RFKHVWHU01$PHULFDQ ulnar-innervated muscles should be sampled, especially muscles $VVRFLDWLRQRI1HXURPXVFXODU (OHFWURGLDJQRVWLF0HGLFLQH LQP\RWRPDOGLVWULEXWLRQVVLPLODUWRWKRVHDIIHFWHG  6LQVRQ*=DJHU(/.OLQH'*:LQGPLOOSLWFKHU¶VUDGLDOQHXURSDWK\ 1HXURVXUJHU\ (OHFWURGLDJQRVWLF)LQGLQJVLQ6SHFL¿F'LVRUGHUV  6WHZDUW-'7KHUDGLDOQHUYH,Q)RFDOSHULSKHUDOQHXURSDWKLHV&K 3XUH&RQGXFWLRQ%ORFN5DGLDO1HXURSDWK\DWWKH6SLUDO*URRYH 9DQFRXYHU-%-3XEOLVKHUV In a pure conduction block radial neuropathy at the spiral  7URMDERUJ:5DWHRIUHFRYHU\LQPRWRUDQGVHQVRU\¿EHUVRIWKH groove, there is motor conduction block across the spiral groove UDGLDO QHUYH FOLQLFDO DQG HOHFWURSK\VLRORJLFDO DVSHFWV - 1HXURO ZLWK SUHVHUYHG 651 1&6V 2Q QHHGOH (0* WKHUH LV UHGXFHG 1HXURVXUJ3V\FKLDWU\ recruitment without axon loss changes in radial muscles, sparing  7VDR %(:LOERXUQ$-7KH PHGLDO EUDFKLDO IDVFLDO FRPSDUWPHQW WKHWULFHSVDQGDQFRQHXV V\QGURPH IROORZLQJ D[LOODU\ DUWHULRJUDSK\ 1HXURORJ\  Axon Loss Radial Neuropathy at the Spiral Groove  9LVVHU &3&RHQH /1 %UDQG 5 HW DO 1HUYH OHVLRQV LQ SUR[LPDO In an axon loss radial neuropathy at the spiral groove, there KXPHUDOIUDFWXUHV-6KRXOGHU(OERZ6XUJ are low amplitude radial compound muscle action potentials &0$3V DQG651VHQVRU\QHUYHDFWLRQSRWHQWLDOV 61$3V 2Q QHHGOH (0* WKHUH DUH IHDWXUHV RI DFWLYH DQGRU FKURQLF PRWRU D[RQORVVLQWKHUDGLDOPXVFOHVVSDULQJWKHWULFHSVDQGDQFRQHXV

Posterior Interosseous Nerve Lesion in the Forearm In a PIN lesion in the forearm, there are low amplitude radial &0$3VZLWKQRUPDO65161$3V2QQHHGOH(0*WKHUHDUH features of active and/or chronic motor axon loss in the EIP, EDC, (&8DQGVXSLQDWRU

26 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

Brachial Plexopathies: The Basics

Zachary Simmons, MD Professor of Neurology Director, Neuromuscular Program and EMG Laboratory Pennsylvania State University Hershey Medical Center Hershey, PA

INTRODUCTION

Patients commonly are referred to the neuromuscular specialist or electrodiagnostic (EDX) physician because of weakness, pain, RU QXPEQHVV RI DQ XSSHU OLPE %UDFKLDO SOH[RSDWK\ PD\ EH D FRQVLGHUDWLRQ\HWIHZDQDWRPLFDOVWUXFWXUHVDUHVRGDXQWLQJ7KH goal of this brief review is to provide information which will aid WKHFOLQLFLDQDQG(';SK\VLFLDQLQVXFKDQDVVHVVPHQW ANATOMY OF THE BRACHIAL PLEXUS AND ITS MAJOR BRANCHES

7KHEUDFKLDOSOH[XVKDV¿YHFRPSRQHQWVURRWVWUXQNVGLYLVLRQV FRUGVDQGWHUPLQDOEUDQFKHV )LJ ,WUXQVEHKLQGWKHVFDOHQH muscles proximally and then behind the clavicle and pectoral muscles more distally as it courses from the neck into the shoulder JLUGOHDQGDUP3UR[LPDOWRWKHFODYLFOHDUHWKHURRWVDQGWUXQNV %HQHDWKLWDUHWKHGLYLVLRQV'LVWDOWRLWDUHWKHFRUGVDQGWHUPLQDO Figure 1. The brachial plexus: the components shown are the roots, QHUYHEUDQFKHV,QDGGLWLRQWRSURYLGLQJWKHPRWRUQHUYHVXSSO\ WUXQNVGLYLVLRQVFRUGVDQGWKHPDMRUWHUPLQDOEUDQFKHV to all muscles of the upper extremities and shoulder girdle, the brachial plexus supplies upper extremity cutaneous sensation YDULDWLRQ 7KH WHUP ³SUH¿[HG SOH[XV´ LV XVHG ZKHQ WKHUH LV D )LJ $NQRZOHGJHRISOH[XVDQDWRP\LVKHOSIXO FRQWULEXWLRQIURP&DQGWKH7FRQWULEXWLRQLVPLQLPDO,QVXFK cases, all the nerve contributions to the brachial plexus are shifted Roots RQHOHYHOVXSHULRUO\,QD³SRVW¿[HGSOH[XV´WKHUHLVDPLQLPDO 7KHEUDFKLDOSOH[XVDULVHVIURPWKHVSLQDOFRUGDWWKH&WKURXJK FRQWULEXWLRQ IURP & DQG D PRUH VXEVWDQWLDO FRQWULEXWLRQ IURP 7OHYHOV(DFKRIWKHVHOHYHOVJLYHVULVHWRGRUVDO VHQVRU\ DQG 7UHVXOWLQJLQWKHSOH[XVEHLQJVKLIWHGRQHURRWOHYHOLQIHULRUO\ ventral (motor) rootlets which then merge to form a short spinal At times, the plexus may be expanded, with contributions from QHUYH 7KLV LQ WXUQ GLYLGHV LQWR DQWHULRU DQG SRVWHULRU SULPDU\ & WKURXJK 7 7ZR EUDQFKHV RULJLQDWH GLUHFWO\ DW WKH URRW UDPL )LJ 7KHDQWHULRUSULPDU\UDPLDUHRIWHQUHIHUUHGWRDV OHYHO  7KHGRUVDOVFDSXODUQHUYHLVGHULYHGIURPWKH&URRW the roots of the brachial plexus, and they are located immediately VRPHWLPHVZLWKDFRQWULEXWLRQIURP&DQGSURYLGHVLQQHUYDWLRQ H[WHUQDOWRWKHLQWHUYHUWHEUDOIRUDPLQD7KHUHLVDQDWRPLF WRWKHPDMRUDQGPLQRUUKRPERLGPXVFOHV  7KHORQJWKRUDFLF 27 BRACHIAL PLEXOPATHIES: THE BASICS

Figure 3. Details of the anatomy at a cervical spinal cord level. The dorsal and ventral rootlets combine to form a spinal nerve, which then divides into anterior and posterior primary rami.

Trunks 7KHUHDUHWKUHHWUXQNV7KHXSSHUWUXQNLVIRUPHGE\WKHPHUJHU RIWKH&DQG&URRWV7KHPLGGOHWUXQNLVWKHFRQWLQXDWLRQRI WKH&URRW7KH&DQG7URRWVPHUJHWRIRUPWKHORZHUWUXQN 2QHPDMRUEUDQFKDQGRQHPLQRURQHDULVHIURPWKHXSSHUWUXQN  7KHVXSUDVFDSXODUQHUYHGHULYHGIURPWKH&DQG&URRWVLV WKHPDMRUWHUPLQDOEUDQFKRULJLQDWLQJDWWKHWUXQNOHYHOFRPLQJ off the upper trunk to provide innervation to the supraspinatus DQG LQIUDVSLQDWXV PXVFOHV ,W SDVVHV WKURXJK WKH VXSUDVFDSXODU notch of the scapula, an area covered by the transverse scapular ligament, and supplies motor branches to the supraspinatus PXVFOH7KHQLWFRQWLQXHVDURXQGWKHVSLQRJOHQRLGQRWFKRIWKH scapular spine (bounded by the scapula spine medially and the spinoglenoid ligament [inferior transverse scapular ligament] ODWHUDOO\ WRVXSSO\PRWRUEUDQFKHVWRWKHLQIUDVSLQDWXVPXVFOH (2) The nerve to the subclavius is a minor branch of the upper trunk which cannot be tested easily by physical examination or (';WHVWLQJ7KHUHDUHQRVLJQL¿FDQWWHUPLQDOEUDQFKHVDULVLQJ GLUHFWO\IURPWKHPLGGOHRUORZHUWUXQN Divisions Each of the three trunks divides into an anterior and a posterior GLYLVLRQVLWXDWHGEHKLQGWKHFODYLFOH1RWHUPLQDOEUDQFKHVDULVH GLUHFWO\IURPWKHGLYLVLRQV Cords 7KHWKUHHFRUGVDUHIRUPHGIURPWKHVL[GLYLVLRQV7KHDQWHULRU divisions of the upper and middle trunks form the lateral cord, whereas the anterior division of the lower trunk continues as WKHPHGLDOFRUG$OOWKUHHSRVWHULRUGLYLVLRQVPHUJHWRIRUPWKH SRVWHULRUFRUG6HYHUDOWHUPLQDOEUDQFKHVDULVHDWWKHFRUGOHYHO Figure 2.&XWDQHRXVLQQHUYDWLRQRIWKHXSSHUH[WUHPLWLHV $ ULJKWXSSHU H[WUHPLW\DQWHULRUDVSHFWDQG % ULJKWXSSHUH[WUHPLW\SRVWHULRUDVSHFW

QHUYH FRPHV GLUHFWO\ RII WKH & & DQG VRPHWLPHV WKH & DQWHULRU SULPDU\ UDPL LQQHUYDWLQJ WKH VHUUDWXV DQWHULRU PXVFOH EDX physicians should bear in mind that the cervical paraspinal muscles are innervated by the posterior primary rami, and therefore they can also be considered to have their innervation DULVHGLUHFWO\DWWKHURRWOHYHO

 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES Branches of the Lateral Cord CAUSES OF BRACHIAL PLEXOPATHY 7KHUHDUHWZREUDQFKHVRIWKHODWHUDOFRUG  7KHODWHUDOSHFWRUDO QHUYHLVGHULYHGIURPWKH&VSLQDOQHUYHOHYHOVDQGLQQHUYDWHV A listing of the most common causes of brachial plexopathy is WKHSHFWRUDOLVPDMRUPXVFOH  7KHPXVFXORFXWDQHRXVQHUYHLV SURYLGHGLQ7DEOH$IHZRIWKHVHPHULWPRUHGHWDLOHGGLVFXVVLRQ GHULYHGIURPWKH&VSLQDOOHYHOVVRPHWLPHVZLWKDFRQWULEXWLRQ IURP&,WLQQHUYDWHVWKHFRUDFREUDFKLDOLVELFHSVEUDFKLLDQG Table 1. Common causes of brachial plexopathy brachialis muscles, and it gives rise to the lateral antebrachial cutaneous nerve (lateral cutaneous nerve of the forearm), which Traction provides cutaneous sensation to the lateral forearm from wrist to Fall from a height, particularly onto shoulder HOERZ Trauma in which the arm is pulled down, damaging the upper plexus Branches of the Medial Cord Trauma in which the arm is pulled up, damaging the lower 7KHUHDUHIRXUEUDQFKHVRIWKHPHGLDOFRUG  7KHPHGLDOSHFWRUDO plexus QHUYHLVIRUPHGIURP&DQG7VSLQDOQHUYHV,WLQQHUYDWHVWKH 6SRUWVLQMXULHVHVSHFLDOO\IRRWEDOO pectoralis minor muscle and the inferior portions of the pectoralis Motor vehicle accidents and other trauma PDMRUPXVFOH  7KHPHGLDOEUDFKLDOFXWDQHRXVQHUYH PHGLDO 2EVWHWULFSDUDO\VLV cutaneous nerve of the arm) provides cutaneous sensation to the Surgery, particularly during median sternotomy PHGLDODUPSUR[LPDOWRWKHHOERZ  7KHPHGLDQDQWHEUDFKLDO Compression cutaneous nerve (medial cutaneous nerve of the forearm) provides Supraclavicular from pack straps cutaneous sensation to the medial forearm between the wrist Infraclavicular from crutches DQGHOERZ  7KHXOQDUQHUYHDULVHVIURPVSLQDOOHYHOV&7 Hematoma, aneurysm, and arteriovenous malformations SULPDULO\XVXDOO\ZLWKDFRQWULEXWLRQIURP&,WVXSSOLHVPDQ\ /DFHUDWLRQVIURPSHQHWUDWLQJLQMXULHV forearm and hand muscles, and it provides cutaneous sensation Ischemia RYHUWKHPHGLDOKDQGSDUWRIWKHULQJ¿QJHUDQGDOORIWKHOLWWOH 1HRSODVWLFLQ¿OWUDWLRQ ¿QJHU Radiation-induced Thoracic outlet syndrome Branch of Both the Lateral and Medial Cords 1HXUDOJLFDP\RWURSK\ 3DUVRQDJH±7XUQHUV\QGURPH 7KHPHGLDQQHUYHLVGHULYHGIURPVSLQDOOHYHOV&77KHPRWRU Iatrogenic ¿EHUV DUH GHULYHG IURP DOO WKHVH OHYHOV ZKHUHDV VHQVRU\ ¿EHUV 'LUHFWLQMXU\GXULQJVXUJHU\ DUH GHULYHG SULPDULO\ IURP & 2FFDVLRQDOO\ & FRQWULEXWHV 6HQVRU\¿EHUVWUDYHOWKURXJKWKHXSSHUDQGPLGGOHWUXQNVWRWKH Traction ODWHUDOFRUG0RWRU¿EHUVWUDYHOWKURXJKDOOWUXQNVWRWKHODWHUDODQG 7UDFWLRQ LQMXULHV DUH YHU\ FRPPRQ 7KHUH DUH PDQ\ FDXVHV PHGLDOFRUGV7KLVKDVPHDQLQJIXOFOLQLFDODQG(';LPSOLFDWLRQV including a fall onto the shoulder from a height, traction to a limb IRU ORFDOL]DWLRQ 7KH PHGLDQ QHUYH VXSSOLHV IRUHDUP DQG KDQG ZKHQLWLVSXOOHGVHYHUHO\VSRUWVLQMXULHV SDUWLFXODUO\LQIRRWEDOO  PXVFOHVDQGFXWDQHRXVVHQVDWLRQRYHUSDUWRIWKHKDQG DQG FORVHG WUDFWLRQ GXULQJ PRWRU YHKLFOH DFFLGHQWV1 Traction GXULQJVXUJHU\PD\UHVXOWLQSRVWRSHUDWLYHEUDFKLDOSOH[RSDWK\ Branches of the Posterior Cord This most commonly occurs after chest surgeries due to stretch 7KHUH DUH ¿YH EUDQFKHV RI WKH SRVWHULRU FRUG   7KH XSSHU LQMXULHVWRWKHSOH[XVIURPFKHVWZDOOUHWUDFWLRQ7KHORZHUWUXQN VXEVFDSXODU QHUYH LV GHULYHG IURP WKH & VSLQDO OHYHOV DQG or medial cord usually are involved, with the expected clinical LQQHUYDWHVWKHXSSHUSRUWLRQRIWKHVXEVFDSXODULVPXVFOH  7KH SUHVHQWDWLRQDVGHVFULEHGODWHU5HFRYHU\GHSHQGVRQWKHVHYHULW\ ORZHUVXEVFDSXODUQHUYHLVGHULYHGIURPWKH&VSLQDOOHYHOV RID[RQDOLQMXU\2EVWHWULFSDUDO\VLVXVXDOO\KDVEHHQDWWULEXWHG and innervates the lower portion of the subscapularis muscle to traction on the neck by the clinician during passage in the DQG WKH WHUHV PDMRU PXVFOH  7KH WKRUDFRGRUVDO QHUYH DULVHV ELUWKFDQDO2 However, it now appears that some of these develop between the upper and lower subscapular nerves, derives from prenatally or are due to propulsive forces over which the birth WKH&VSLQDOOHYHOVDQGLQQHUYDWHVWKHODWLVVLPXVGRUVLPXVFOH DWWHQGDQW GRHV QRW KDYH FRQWURO1,3 8SSHU RU XSSHU DQG PLGGOH   7KH D[LOODU\ QHUYH LV GHULYHG IURP VSLQDO OHYHOV & ,W plexus involvement are most common, although about 23% of supplies the teres minor muscle, then terminates by innervating LQIDQWVVXVWDLQSDQSOH[XVLQMXULHV WKH GHOWRLG PXVFOH ,W DOVR VXSSOLHV FXWDQHRXV VHQVDWLRQ WR WKH ODWHUDO DVSHFW RI WKH XSSHU DUP RYHUO\LQJ WKH GHOWRLG PXVFOH Neoplastic and Radiation-Induced Brachial Plexopathy  7KHUDGLDOQHUYHDULVHVIURPVSLQDOOHYHOV&RFFDVLRQDOO\ Radiation-induced brachial plexopathy is most commonly a ZLWKD7FRQWULEXWLRQ,WVXSSOLHVWKHWULFHSVPXVFOHDQFRQHXV delayed syndrome, occurring from a few weeks to many years PXVFOH DQG PXVFOHV RI WKH IRUHDUP DQG KDQG ,W DOVR SURYLGHV DIWHUUDGLDWLRQ7KHKLJKHUWKHUDGLDWLRQGRVHWKHKLJKHUWKHULVN cutaneous sensation to the arm, forearm, and hand as the posterior RIGHYHORSLQJDUDGLDWLRQLQGXFHGEUDFKLDOSOH[RSDWK\ The EDX cutaneous nerve of the arm, lower lateral cutaneous nerve of the physician is most often called upon to distinguish a radiation- DUP SRVWHULRU FXWDQHRXV QHUYH RI WKH IRUHDUP DQG VXSHU¿FLDO LQGXFHG SOH[RSDWK\ IURP RQH GXH WR QHRSODVWLF LQ¿OWUDWLRQ UDGLDOVHQVRU\QHUYH Radiation-induced plexopathy is less likely to be painful and PRUHOLNHO\WREHFKDUDFWHUL]HGE\SURJUHVVLYHO\HYROYLQJVHQVRU\ GLVWXUEDQFHV (OHFWURGLDJQRVWLFDOO\ P\RN\PLF GLVFKDUJHV DQG fasciculation potentials are more likely to be present in radiation- LQGXFHG SOH[RSDWK\ ,Q FRQWUDVW QHRSODVWLF EUDFKLDO SOH[RSDWK\ 29 BRACHIAL PLEXOPATHIES: THE BASICS

XVXDOO\LVFKDUDFWHUL]HGE\SURPLQHQWSDLQPRUHUDSLGO\GHYHORSLQJ DUHGHFUHDVHGRUDEVHQW6HQVRU\ORVVLVH[SHFWHGWREHRYHUWKH V\PSWRPVRIWHQDFFRPSDQLHGE\D+RUQHU¶VV\QGURPHDQGUDUHO\ lateral upper arm in the distribution of the axillary nerve, in the DVVRFLDWHGZLWKIDVFLFXODWLRQSRWHQWLDOVRUP\RN\PLD Tumors at ODWHUDO KDQG DQG WKH WKXPE WKURXJK WKH PLGGOH ¿QJHU PHGLDQ WKHOXQJDSH[ LH3DQFRDVWWXPRUV PRVWFRPPRQO\LQYDGHWKH and radial sensory branches), and in the distribution of the lateral lower portion of the plexus, but metastases from other types of DQWHEUDFKLDOFXWDQHRXVQHUYHRYHUWKHODWHUDOIRUHDUP PDOLJQDQFLHVRUGLUHFWLQ¿OWUDWLRQRIWKHQHUYHVRUQHUYHVKHDWKV DOVRFDQRFFXUDWDQ\OHYHORIWKHSOH[XV Middle Trunk Plexopathy Isolated lesions of the middle trunk are rare, and they usually Thoracic Outlet Syndrome RFFXU LQ FRQMXQFWLRQ ZLWK PRUH ZLGHVSUHDG EUDFKLDO SOH[XV 7KRUDFLFRXWOHWV\QGURPHKDVEHHQWKHVXEMHFWRIH[WHQVLYHUHYLHZ OHVLRQV7KHPLGGOHWUXQNLVIRUPHGIURPWKH&DQWHULRUSULPDU\ WR ZKLFK WKH LQWHUHVWHG UHDGHU LV UHIHUUHG True neurogenic UDPXVDQGVRKDVWKHVDPHFOLQLFDOIHDWXUHVDVD&UDGLFXORSDWK\ WKRUDFLF RXWOHW V\QGURPH LV UDUH 0RVW FDVHV DUH FDXVHG E\ D ZLWKZHDNQHVVRIHOERZZULVWDQG¿QJHUH[WHQVLRQDVZHOODV ¿EURXVEDQGIURPDUXGLPHQWDU\FHUYLFDOULEWRWKH¿UVWWKRUDFLF ZHDNQHVVRIWKHÀH[RUFDUSLUDGLDOLV ZULVWÀH[LRQ DQGSURQDWRU ULEZKLFKHQWUDSVWKHORZHUWUXQNRIWKHEUDFKLDOSOH[XV7KXVWKH WHUHV IRUHDUPSURQDWLRQ PXVFOHV7KHWULFHSVUHÀH[LVGHFUHDVHG FOLQLFDOSUHVHQWDWLRQDQGWKH(';¿QGLQJVDUHWKRVHRIDORZHU RU DEVHQW 6HQVRU\ ORVV LV RYHU WKHGLVWULEXWLRQRI WKHSRVWHULRU WUXQNEUDFKLDOSOH[RSDWK\WKHH[FHSWLRQEHLQJWKDWWKH7¿EHUV cutaneous nerve of the forearm and in the hand over the middle usually are preferentially affected, resulting in greater atrophy of ¿QJHUDQGWRDOHVVHUGHJUHHWKHLQGH[DQGULQJ¿QJHUV WKHWKHQDUWKDQK\SRWKHQDUPXVFOHV Sensory loss parallels that VHHQLQORZHUWUXQNSOH[RSDWKLHV Lower Trunk Plexopathy 7KHORZHUWUXQNLVIRUPHGIURPWKH&7VSLQDOOHYHOV/HVLRQV Neuralgic Amyotrophy (Parsonage–Turner Syndrome) LQYROYH DOO XOQDULQQHUYDWHG PXVFOHV DQG DOVR &7 PHGLDQ Also termed immune brachial plexus neuropathy, neuralgic LQQHUYDWHG PXVFOHV VXFK DV WKH ÀH[RU SROOLFLV ORQJXV SURQDWRU amyotrophy is most commonly sporadic, although it may be TXDGUDWXVDQGLQWULQVLFKDQGPXVFOHVDQG&LQQHUYDWHGUDGLDO IDPLOLDO)LUVWGHVFULEHGLQGHWDLOLQWKHPRGHUQHUDE\3DUVRQDJH muscles such as the extensor indicis, extensor digitorum, and DQG7XUQHU LQ  and then described in detail with respect extensor carpi ulnaris, resulting in weakness of grip due to WR LWV QDWXUDO KLVWRU\ PRUH WKDQ  \HDUV ODWHU11 it is now well ZHDNQHVV RI KDQG PXVFOHV LQDELOLW\ WR IXOO\ ÀH[ WKH ¿QJHUV UHFRJQL]HG E\ PRVW QHXURORJLVWV EXW RIWHQ XQNQRZQ WR QRQ DQGWKXPEDQGSDUWLDOZHDNQHVVRI¿QJHUDQGZULVWH[WHQVLRQ QHXURORJLVWVDQGFRQIXVHGZLWKFHUYLFDOUDGLFXORSDWK\,QGLYLGXDOV 1R XSSHU H[WUHPLW\ UHÀH[ DEQRUPDOLWLHV DUH SUHVHQW 6HQVRU\ RIDOODJHVPD\EHDIIHFWHGDQGWKHUHLVDPDOHSUHGRPLQDQFH abnormalities occur in the medial arm, medial forearm, medial 7KHV\PSWRPVDUHZLGHO\YDULHGDVKDVEHHQZHOOGHVFULEHG12,13 KDQGDQGWKHULQJDQGOLWWOH¿QJHUV Most commonly, the initial symptom is pain of abrupt onset, RIWHQVHYHUHXVXDOO\LQWKHVKRXOGHURUSHULVFDSXODUUHJLRQ3DLQ Lateral Cord Plexopathy generally begins to improve in 2-3 weeks, in association with /HVLRQVDWWKHODWHUDOFRUGUHVXOWLQZHDNQHVVRI&±LQQHUYDWHG WKH GHYHORSPHQW RI ZHDNQHVV 7KH ZHDNQHVV PD\ LQYROYH WKH PHGLDQ PXVFOHV VXFK DV WKH SURQDWRU WHUHV DQG ÀH[RU FDUSL brachial plexus in a patchy fashion, for example affecting one or UDGLDOLV ZULVWÀH[LRQ DQGLQZHDNQHVVRIHOERZÀH[LRQGXHWR more trunks or single peripheral nerves, most commonly the long LQYROYHPHQW RI WKH ELFHSV EUDFKLL PXVFOH 7KH ELFHSV UHÀH[ LV WKRUDFLFVXSUDVFDSXODURUD[LOODU\QHUYHV%LODWHUDOLQYROYHPHQW GHFUHDVHGRUDEVHQWEXWWKHEUDFKLRUDGLDOLVDQGWULFHSVUHÀH[HV RFFXUVLQDERXWRQHWKLUGRISDWLHQWVXVXDOO\DV\PPHWULFDOO\,W DUHQRUPDO6HQVRU\ORVVRFFXUVRYHUWKHODWHUDOIRUHDUPDQGKDQG PD\EHSUHFHGHGE\DÀXOLNHV\QGURPHRURWKHUIHEULOHLOOQHVV DQGWKHWKXPEWKURXJKWKHPLGGOH¿QJHU and reports of this syndrome following a variety of conditions HJLPPXQHLQIHFWLRXVQHRSODVWLFWUDXPDWLFHWF KDYHEHHQ Posterior Cord Plexopathy reported, suggesting that a variety of events can trigger an :HDNQHVVRFFXUVLQDOOPXVFOHVLQQHUYDWHGE\WKHUDGLDOQHUYH LPPXQHPHGLDWHGDWWDFNRQWKHEUDFKLDOSOH[XV EDX studies UHVXOWLQJ LQ ¿QJHU H[WHQVLRQ ZHDNQHVV ZULVW GURS DQG DUP may reveal a pattern of brachial plexus involvement not readily H[WHQVLRQZHDNQHVVDWWKHHOERZ7KHUHLVZHDNQHVVRIVKRXOGHU ORFDOL]DEOH WR RQH RU PRUH VSHFL¿F WUXQNV GLYLVLRQV FRUGV RU DEGXFWLRQ GHOWRLG DQGDGGXFWLRQ ODWLVVLPXVGRUVL 7KHWULFHSV SHULSKHUDO QHUYHV 7KLV SDWFK\ RU PXOWLIRFDO LQYROYHPHQW LV DQGEUDFKLRUDGLDOLVUHÀH[HVDUHGHFUHDVHGRUDEVHQWDOWKRXJKWKH FRPPRQ DQG LV D KDOOPDUN RI WKLV V\QGURPH 3DWKRJHQHWLFDOO\ ELFHSVUHÀH[LVSUHVHUYHG7KHUHLVVHQVRU\ORVVLQWKHGLVWULEXWLRQV WKLVDSSHDUVWREHDQLQÀDPPDWRU\LPPXQHPHGLDWHGSURFHVV of the axillary nerve, posterior cutaneous nerve of the arm, and VXSHU¿FLDOUDGLDOQHUYH CLINICAL PRESENTATIONS OF BRACHIAL PLEXOPATHY Medial Cord Plexopathy 0HGLDOFRUGSOH[RSDWK\UHVXOWVLQWKHVDPHFOLQLFDOGH¿FLWVDVD Upper Trunk Plexopathy lower trunk lesion, except for preservation of radial-innervated In upper trunk plexopathy, weakness will be seen in muscles &¿EHUV3DWLHQWVGHPRQVWUDWHZHDNQHVVRIDOOXOQDULQQHUYDWHG LQQHUYDWHG DW WKH & OHYHOV VXFK DV WKH VSLQDWL DUP H[WHUQDO PXVFOHV DQG &7±LQQHUYDWHG PHGLDQ PXVFOHV OHDGLQJ WR rotation), deltoid (arm abduction), biceps, and brachioradialis weakness of grip due to weakness of hand muscles, and to HOERZÀH[LRQ 6RPHPXVFOHVDUHSDUWLDOO\LQQHUYDWHGIURPWKH LQDELOLW\ WR IXOO\ ÀH[ WKH ¿QJHUV DQG WKXPE +RZHYHU ¿QJHU upper trunk and may be partially affected, such as the pronator DQG ZULVW H[WHQVRUV DUH VSDUHG 7KHUH LV VHQVRU\ ORVV LQ WKH WHUHV IRUHDUPSURQDWLRQ ÀH[RUFDUSLUDGLDOLV ZULVWÀH[LRQ DQG same distribution as for lower trunk lesions: medial arm, medial WULFHSV HOERZH[WHQVLRQ 7KHELFHSVDQGEUDFKLRUDGLDOLVUHÀH[HV IRUHDUPPHGLDOKDQGDQGWKHULQJDQGOLWWOH¿QJHUV7KHUHDUHQR 3030 UHÀH[DEQRUPDOLWLHV A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

Pan-Plexopathy Table 3. Guidelines for the needle examination in brachial plexopathy :LGHVSUHDG OHVLRQV RI WKH EUDFKLDO SOH[XV FDXVH ZHDNQHVV RI the entire upper extremity except for remaining function of  2IWHQZLOOQHHGWREHH[WHQVLYH WKH UKRPERLGV DQG VHUUDWXV DQWHULRU PXVFOHV 5HÀH[HV DUH DOO ‡ Presence or absence of axonal continuity often is of GHFUHDVHGRUDEVHQW7KHUHLVZLGHVSUHDGVHQVRU\ORVV JUHDWYDOXHWRWKHVXUJHRQ ‡ Search carefully for voluntary motor unit action ELECTRODIAGNOSIS OF BRACHIAL SRWHQWLDO¿ULQJLQZHDNPXVFOHV PLEXOPATHY  Keep in mind those muscles which are innervated at the URRWOHYHOSUR[LPDOWRWKHEUDFKLDOSOH[XV 7KH(';SK\VLFLDQ¶VUROHLVRQHRIORFDOL]DWLRQDQGDVVHVVPHQWRI ‡ Those muscles will be abnormal in some radiculopathies, VHYHULW\UDWKHUWKDQGHWHUPLQDWLRQRIHWLRORJ\(';HYDOXDWLRQVRI EXWQRUPDOLQEUDFKLDOSOH[RSDWKLHV brachial plexopathies generally are complex, involving the study  Anatomic variations occur, and studies may not be “black RIPXOWLSOHQHUYHVDQGPXVFOHVWRSHUPLWDFFXUDWHORFDOL]DWLRQ DQGZKLWH´ *HQHUDO SULQFLSOHV ZKLFK VKRXOG JXLGH WKH SHUIRUPDQFH RI WKH EDX evaluation of brachial plexopathies are provided in Tables Middle Trunk Plexopathy DQG The median sensory response is expected to be abnormal ZKHQ UHFRUGLQJ IURP WKH PLGGOH ¿QJHU 5RXWLQH VWXGLHV RI WKH Upper Trunk Plexopathy PHGLDQDQGXOQDUPRWRUQHUYHVDUHQRUPDO1HHGOHH[DPLQDWLRQ Sensory studies will reveal abnormalities in the lateral antebrachial JHQHUDOO\ UHYHDOV DEQRUPDOLWLHV LQ &LQQHUYDWHG PXVFOHV VXFK cutaneous, median sensory (particularly to the thumb), and radial DVWKHSURQDWRUWHUHVÀH[RUFDUSLUDGLDOLVWULFHSVH[WHQVRUFDUSL VHQVRU\ SDUWLFXODUO\ WR WKH WKXPE  QHUYHV 5RXWLQH VWXGLHV RI UDGLDOLVDQGH[WHQVRUGLJLWRUXPFRPPXQLVPXVFOHV&PXVFOHV the median and ulnar motor nerves are normal, but studies of innervated at the root level will be spared, such as the cervical the suprascapular, axillary, and musculocutaneous nerves, if SDUDVSLQDODQGVHUUDWXVDQWHULRUPXVFOHV SHUIRUPHG PD\ EH DEQRUPDO 1HHGOH H[DPLQDWLRQ LV H[SHFWHG to demonstrate abnormalities in the supraspinatus, infraspinatus, Lower Trunk Plexopathy GHOWRLGELFHSVEUDFKLLDQGEUDFKLRUDGLDOLVPXVFOHV7KHSURQDWRU In a lower trunk plexopathy, several sensory studies will be WHUHV ÀH[RU FDUSL UDGLDOLV WULFHSV DQG H[WHQVRU FDUSL UDGLDOLV abnormal, including the medial antebrachial cutaneous, the PXVFOHV PD\ VKRZ DEQRUPDOLWLHV & PXVFOHV LQQHUYDWHG DW PHGLDQVHQVRU\WRWKHULQJ¿QJHUWKHXOQDUVHQVRU\WRWKHOLWWOH the root level will be spared, including the cervical paraspinal, ¿QJHUDQGWKHGRUVDOXOQDUFXWDQHRXVVHQVRU\QHUYH,IWKHUHLV VHUUDWXVDQWHULRUDQGUKRPERLGPXVFOHV VXI¿FLHQWD[RQORVVWKHPHGLDQDQGXOQDUPRWRUVWXGLHVPD\EH abnormal, with the degree of abnormality being determined by Table 2. Guidelines for sensory nerve conduction studies in brachial WKHVHYHULW\RIWKHD[RQORVV3DUWLDOD[RQORVVPD\UHYHDOORZ plexopathy compound muscle action potential (CMAP) amplitudes, mildly to moderately prolonged distal latencies, and mildly to moderately ‡ 'LVWLQJXLVKEUDFKLDOSOH[RSDWKLHVIURPUDGLFXORSDWKLHV VORZHG FRQGXFWLRQ YHORFLWLHV &9V  6HYHUH D[RQ ORVV FRXOG ‡ Radiculopathy = lesion proximal to the dorsal root UHVXOWLQDEVHQWUHVSRQVHV2QQHHGOHH[DPLQDWLRQDEQRUPDOLWLHV JDQJOLRQ DUHH[SHFWHGLQ&7±LQQHUYDWHGPXVFOHVLQFOXGLQJDOOXOQDU ‡ 6HQVRU\ QHUYH FRQGXFWLRQ VWXGLHV DUH 1250$/ LQQHUYDWHGPXVFOHVDQGVHOHFWHGPHGLDQDQGUDGLDOPXVFOHV2I because the sensory nerve is intact from the level of the radial-innervated muscles, the extensor indicis is a particularly its cell body (the dorsal root ganglion) to the level of XVHIXOPXVFOHWRWHVW0HGLDQLQQHUYDWHGPXVFOHVZKLFKDUHOLNHO\ WKHVNLQ WREHDEQRUPDODUHWKHÀH[RUSROOLFLVORQJXVSURQDWRUTXDGUDWXV ‡ 3OH[RSDWKLHV OHVLRQDWRUGLVWDOWRWKHGRUVDOURRWJDQJOLRQ DQGLQWULQVLFKDQGPXVFOHV2IFRXUVHFHUYLFDOSDUDVSLQDOPXVFOHV ‡ 6HQVRU\ QHUYH FRQGXFWLRQ VWXGLHV DUH $%1250$/ ZLOOEHVSDUHG because of axon loss from the level of the cell body to WKHVNLQ Lateral Cord Plexopathy ‡ 3HUIRUPH[WHQVLYHVHQVRU\QHUYHFRQGXFWLRQVWXGLHV In a lateral cord plexopathy, abnormalities are expected in the ‡ Medial and lateral antebrachial cutaneous nerve conduction lateral antebrachial cutaneous nerve and the median sensory studies are particularly useful for distinguishing plexopathy QHUYHUHFRUGLQJIURPWKHWKXPELQGH[RUPLGGOH¿QJHU5RXWLQH IURPUDGLFXORSDWK\ VWXGLHVRIWKHPHGLDQDQGXOQDUPRWRUQHUYHVDUHQRUPDO1HHGOH ‡ 3HUIRUPVLGHWRVLGHFRPSDULVRQVRIVHQVRU\DPSOLWXGHV examination reveals abnormalities in the biceps brachii and ‡ A sensory nerve action potential amplitude on the PHGLDQLQQHUYDWHG IRUHDUP PXVFOHV LH SURQDWRU WHUHV ÀH[RU symptomatic side which is less than half of that on the carpi radialis), with sparing of the more distal median-innervated asymptomatic side is considered to be abnormal, even if PXVFOHVVXFKDVWKHÀH[RUSROOLFLVORQJXVDQGPHGLDQLQQHUYDWHG the absolute value of the amplitude falls within the normal KDQG PXVFOHV &HUYLFDO SDUDVSLQDO PXVFOHV DQG RWKHU PXVFOHV UDQJH LQQHUYDWHGDWWKHURRWOHYHODUHVSDUHG

31 BRACHIAL PLEXOPATHIES: THE BASICS Posterior Cord Plexopathy REFERENCES ,QDSRVWHULRUFRUGSOH[RSDWK\WKHUDGLDOVHQVRU\VWXG\LVDEQRUPDO 5RXWLQHVWXGLHVRIWKHPHGLDQDQGXOQDUPRWRUQHUYHVDUHQRUPDO  :LOERXUQ$- %UDFKLDO SOH[XV OHVLRQV ,Q '\FN 3- 7KRPDV 3. ,IWKHUHLVVXI¿FLHQWD[RQORVVWKHUDGLDOPRWRUVWXGLHVPD\EH HGV3HULSKHUDOQHXURSDWK\WKHG3KLODGHOSKLD(OVHYLHU6DXQGHUV abnormal, with the degree of abnormality being determined by the SS VHYHULW\RIWKHD[RQORVV3DUWLDOD[RQORVVPD\UHYHDOORZ&0$3  'RGGV6':ROIH6:3HULQDWDOEUDFKLDOSOH[XVSDOV\&XUU2SLQ amplitudes, mildly to moderately prolonged distal latencies, and 3HGLDWU PLOGO\WRPRGHUDWHO\VORZHG&9V6HYHUHD[RQORVVFRXOGUHVXOW  6DQGPLUH +) 'H0RWW 5. (UE¶V SDOV\ FRQFHSWV RI FDXVDWLRQ LQ DEVHQW UHVSRQVHV 1HHGOH H[DPLQDWLRQ LV H[SHFWHG WR VKRZ 2EVWHW*\QHFRO abnormalities in all radial-innervated muscles and in the deltoid,  *LOEHUW $ /RQJWHUP HYDOXDWLRQ RI EUDFKLDO SOH[XV VXUJHU\ LQ WHUHVPLQRUDQGODWLVVLPXVGRUVLPXVFOHV REVWHWULFDOSDOV\+DQG&OLQ  -RKDQVVRQ66YHQVVRQ+/DUVVRQ/*HWDO%UDFKLDOSOH[RSDWK\ Medial Cord Plexopathy DIWHU SRVWRSHUDWLYH UDGLRWKHUDS\ RI EUHDVW FDQFHU SDWLHQWV $FWD EDX testing in a medial cord plexopathy is expected to produce 2QFRO WKHVDPH¿QGLQJVDVIRUDORZHUWUXQNOHVLRQEXWZLWKVSDULQJ  2OVHQ1.3IHLIIHU3-RKDQQVHQ/HWDO5DGLDWLRQLQGXFHGEUDFKLDO RI&PXVFOHVLQQHUYDWHGE\WKHUDGLDOQHUYH$EQRUPDOLWLHVDUH SOH[RSDWK\ QHXURORJLFDO IROORZXS LQ  UHFXUUHQFHIUHH EUHDVW expected on testing of the medial antebrachial cutaneous, the FDQFHUSDWLHQWV,QW-5DGLDW2QFRO PHGLDQVHQVRU\WRWKHULQJ¿QJHUWKHXOQDUVHQVRU\WRWKHOLWWOH  /HYLQ .+ :LOERXUQ$- 0DJJLDQR +- &HUYLFDO ULE DQG PHGLDQ ¿QJHUDQGWKHGRUVDOXOQDUFXWDQHRXVVHQVRU\QHUYH,IWKHUHLV VWHUQRWRP\UHODWHGEUDFKLDOSOH[RSDWKLHV1HXURORJ\ VXI¿FLHQWD[RQORVVWKHPHGLDQDQGXOQDUPRWRUVWXGLHVPD\EH  abnormal, with the degree of abnormality being determined by the  6DQGHUV5-+DPPRQG6/5DR107KRUDFLFRXWOHWV\QGURPHD VHYHULW\RIWKHD[RQORVV3DUWLDOD[RQORVVPD\UHYHDOORZ&0$3 UHYLHZ1HXURORJLVW amplitudes, mildly to moderately prolonged distal latencies,  2]RD*$OYHV')LVK'(7KRUDFLFRXWOHWV\QGURPH3K\V0HG DQG PLOGO\ WR PRGHUDWHO\ VORZHG &9V 6HYHUH D[RQ ORVV FRXOG 5HKDELO&OLQ1RUWK$P UHVXOW LQ DEVHQW UHVSRQVHV 1HHGOH H[DPLQDWLRQ VKRXOG UHYHDO  3DUVRQDJH07XUQHU-1HXUDOJLFDP\RWURSK\WKHVKRXOGHUJLUGOH DEQRUPDOLWLHVLQ&7±LQQHUYDWHGPXVFOHVVXSSOLHGE\WKHXOQDU V\QGURPH/DQFHW and median nerves, including all ulnar-innervated muscles and  7VDLULV3'\FN3-0XOGHU':1DWXUDOKLVWRU\RIEUDFKLDOSOH[XV VHOHFWHG PHGLDQLQQHUYDWHG PXVFOHV VXFK DV WKH ÀH[RU SROOLFLV QHXURSDWK\$UFK1HXURO ORQJXVSURQDWRUTXDGUDWXVDQGLQWULQVLFKDQGPXVFOHV$VQRWHG  (QJODQG -' 6XPQHU$- 1HXUDOJLF DP\RWURSK\ DQ LQFUHDVLQJO\ DERYH UDGLDOLQQHUYDWHG & PXVFOHV DUH VSDUHG 7KH H[WHQVRU GLYHUVHHQWLW\0XVFOH1HUYH LQGLFLVLVDSDUWLFXODUO\XVHIXOPXVFOHWRWHVW2QFHDJDLQFHUYLFDO  (QJODQG-'7KHYDULDWLRQVRIQHXUDOJLFDP\RWURSK\0XVFOH1HUYH SDUDVSLQDOPXVFOHVDUHVSDUHGDVZLWKDOOSOH[XVOHVLRQV   6XDUH] *$ ,PPXQH EUDFKLDO SOH[XV QHXURSDWK\ ,Q '\FN 3- Pan-Plexopathy 7KRPDV 3. HGV 3HULSKHUDO QHXURSDWK\ WK HG 3KLODGHOSKLD $VH[SHFWHGWKHDEQRUPDOLWLHVLQDSDQSOH[RSDWK\DUHZLGHVSUHDG (OVHYLHU6DXQGHUVSS Median, ulnar, and radial sensory responses are abnormal, as  6XDUH]*$*LDQQLQL&%RVFK(3HWDO,PPXQHEUDFKLDOSOH[XV DUH WKH PHGLDO DQG ODWHUDO DQWHEUDFKLDO FXWDQHRXV VWXGLHV ,I QHXURSDWK\ VXJJHVWLYH HYLGHQFH IRU DQ LQÀDPPDWRU\LPPXQH WKHUHLVVXI¿FLHQWD[RQORVVWKHPHGLDQXOQDUDQGUDGLDOPRWRU SDWKRJHQHVLV1HXURORJ\ studies may be abnormal, as may the suprascapular, axillary, and musculocutaneous studies, with the degree of abnormality being GHWHUPLQHGE\WKHVHYHULW\RIWKHD[RQORVV3DUWLDOD[RQORVVPD\ reveal low CMAP amplitudes, mildly to moderately prolonged GLVWDO ODWHQFLHV DQG PLOGO\ WR PRGHUDWHO\ VORZHG &9V 6HYHUH D[RQORVVFRXOGUHVXOWLQDEVHQWUHVSRQVHV2QQHHGOHH[DPLQDWLRQ abnormalities are expected in all muscles of the upper extremity and shoulder girdle except for those innervated directly at the root OHYHOVSHFL¿FDOO\WKHFHUYLFDOSDUDVSLQDOUKRPERLGDQGVHUUDWXV DQWHULRUPXVFOHV

32 A BASIC APPROACH TO COMMON UPPER EXTREMITY MONONEUROPATHIES AND BRACHIAL PLEXOPATHIES

A Basic Approach to Common Upper Extremity Mononeuropathies and Brachial Plexopathies CME Questions:

 7KHVHQVRU\QHUYHDFWLRQSRWHQWLDOFDQEHHQKDQFHGE\DOORI  )LQGLQJVRUFRPSODLQWVWKDW\RXUSDWLHQWGHVFULEHVWKDWDUH the following except: suggestive of an ulnar nerve entrapment at the elbow include $ 6PRRWKLQJ all of the following except: % :DONLQJWKHDQRGH $ 1XPEQHVVLQYROYLQJWKHWKDQGWK¿QJHUVRIWKHKDQG & $YHUDJLQJ % :HDNQHVVRIWKHKDQG ' 6FDQQLQJ & Pain at the elbow which radiates along the medial ( (QKDQFLQJ DVSHFWRIWKHIRUHDUP ' Loss of sensation over the web space between the  $SDWLHQWSUHVHQWVZLWKZHDNQHVVRIWKHPHGLDQLQQHUYDWHG WKXPEDQGIRUH¿QJHU WKHQDUPXVFOHVDQGVHQVRU\ORVVLQWKHGLJLWVDQGSDOP7KLV ( 3DLQZLWKSHUFXVVLRQRIWKHDUHDRYHUWKHFXELWDOWXQQHO lesion cannot be at the: $ )OH[RUUHWLQDFXOXP  2QHFOLQLFDO¿QGLQJWKDWFDQKHOSWRVHSDUDWHXOQDUQHUYH % )OH[RUGLJLWRUXPVXEOLPLV compression at the wrist from a more proximal lesion would be: & 3URQDWRU7HUHV $ 6HQVRU\GH¿FLWVLQYROYLQJWKHSDOPDUDVSHFWRIWKHWK ' $QWHFXELWDOIRVVD DQGWK¿QJHUV ( /LJDPHQWRI6WUXWKHUV % $WURSK\RIWKHK\SRWKHQDUDQGLQWULQVLFKDQGPXVFOHV & 6HQVRU\GH¿FLWLQYROYLQJWKHGRUVRPHGLDODVSHFWRIWKH  7KHVHQVRU\URRWRULJLQVIRUWKHPHGLDQQHUYHLV KDQG $ & ' :HDNQHVVRIZULVWÀH[LRQ % & ( :HDNQHVVRIZULVWH[WHQVLRQ & & ' &7  ,PSRUWDQWWHFKQLFDOIDFWRUVWRFRQVLGHUZKHQHYDOXDWLQJIRU DQXOQDUQHXURSDWK\DWWKHHOERZLQRUGHUWRPLQLPL]HWKH  7KH PHGLDQ FRPSRXQG PXVFOH DFWLRQ SRWHQWLDO FDQ EH chance of artifactual slowing of conduction velocity, include altered by all of the following except: all of the following except: $ 6XEPD[LPDOVWLPXODWLRQ $ Achieving supramaximal stimulation levels at the % 7KXPESRVLWLRQ DERYHHOERZVLWHV & ([FHVVVWLPXODWLRQ % Performing nerve conduction studies with the elbow ' 6XERSWLPDOSODFHPHQWRI( H[WHQGHG ( )ZDYHVXSHULPSRVLWLRQ & Performing an additional ulnar motor study recording IURPWKHVWGRUVDOLQWHURVVHRXVPXVFOH  7KRUDFLF RXWOHW V\QGURPH PD\ EH FDXVHG E\ DQDWRPLF ' Performing a dorsal ulnar cutaneous sensory study (and disruption of neural elements passing through all of the FRPSDULQJWRWKHDV\PSWRPDWLFVLGH  following except: ( 8VLQJ PHDVXUHPHQW WHFKQLTXHV WKDW DFFRXQW IRU WKH $ ,QWHUVFDOHQHWULDQJOH FXUYHGWUDMHFWRU\RIWKHXOQDUQHUYH % &RVWRFODYLFXODUVSDFH & /LJDPHQWRXVEDQGIURP¿UVWULE ' 3RVW¿[HGSOH[XV ( 5HWURSHFWRUDOLVPLQRUVSDFH

33 CME QUESTIONS

 :KHQ ZH DUH HYDOXDWLQJ WKH XOQDU QHUYH ZKDW W\SHV RI  $VDQRUPDOYDULDQWWKHVXSHU¿FLDOUDGLDOQHUYHFDQSURYLGH information would support the diagnosis of a focal lesion at innervation to a territory usually served by which of the WKHHOERZ" following nerves: $ $FRQGXFWLRQYHORFLW\RI PHWHUVVHFRQG $ 0HGLDQVHQVRU\QHUYHWRGLJLW % A decrease in compound muscle action potential % 'RUVDOXOQDUVHQVRU\QHUYH DPSOLWXGH &0$3  RI ! DFURVV WKH LQYROYHG & 8OQDUVHQVRU\QHUYHWRGLJLW VHJPHQW ' /DWHUDODQWHEUDFKLDOFXWDQHRXVQHUYH & A change in compound muscle action potential (CMAP) PRUSKRORJ\  3URFHHGLQJ IURP PRVW SUR[LPDO WR PRVW GLVWDO WKH ¿YH ' $FRQGXFWLRQYHORFLW\WKDWLV!PHWHUVVHFRQGVORZHU components of the brachial plexus are: DFURVVWKHHOERZ $ 5RRWVWUXQNVGLYLVLRQVFRUGVEUDQFKHV ( $OORIWKHDERYH % 5RRWVWUXQNVFRUGVEUDQFKHVGLYLVLRQV & 5RRWVGLYLVLRQVWUXQNVFRUGVEUDQFKHV  8OQDU QHUYH HQWUDSPHQW ZLWKLQ WKH *X\RQ¶V FDQDO FDQ ' 5RRWVFRUGVWUXQNVGLYLVLRQVEUDQFKHV include all of the following except: $ Sensory impairment over the hypothenar area of the  7KHSRVWHULRUFRUGRIWKHEUDFKLDOSOH[XVJLYHVULVHWR KDQGDQGQDLOV $ 7KHXSSHUVXEVFDSXODUDQGPHGLDQQHUYHV % Sensory impairment over the palmar little and medial % 7KHORZHUVXEVFDSXODUDQGUDGLDOQHUYHV ULQJ¿QJHUV & 7KHD[LOODU\DQGPHGLDQQHUYHV & :HDNQHVVRIOXPEULFDOVDQG ' 7KHPHGLDODQWHEUDFKLDOFXWDQHRXVDQGUDGLDOQHUYHV ' :HDNQHVVRIXOQDULQQHUYDWHGWKHQDUPXVFOHV ( $WURSK\RILQWULQVLFKDQGPXVFOHV  :KLFKRIWKHIROORZLQJIHDWXUHVLVOLNHO\WREHFKDUDFWHULVWLF RIUDGLDWLRQLQGXFHGEUDFKLDOSOH[RSDWK\"  :KLFK RI WKH IROORZLQJ PXVFOHV LV ZHDN LQ D SRVWHULRU $ 3DLQ LQWHURVVHRXVQHUYHOHVLRQ" % 6XGGHQRQVHW $ ([WHQVRUFDUSLXOQDULV & 0\RN\PLFGLVFKDUJHV % ([WHQVRUFDUSLUDGLDOLV ' +RUQHU¶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¿QJHU WKHUDGLDOQHUYHDWZKDWSRLQW" & 'RUVDOFXWDQHRXVXOQDU $ 3UR[LPDOWRWKHVSLUDOJURRYH ' 0HGLDQUHFRUGLQJLQGH[¿QJHU % -XVWGLVWDOWRWKHVSLUDOJURRYH & &ORVHWRWKHHOERZ ' %HORZWKHHOERZ