Upper Extremity NCS Lesion Localization and Characterization 2019 Annual AANEM Meeting Austin, Texas Mark A. Ferrante, MD Professor, Department of Neurology Co-Director, Neurophysiology Fellowship Associate Director, Residency Training Program University of Tennessee Health Science Center Chief of Neurology Section Chief of Neurophysiology, Director of ALS Clinic VA Medical Center Memphis, Tennessee Disclosures • Gator fan • Publishing royalties – AANEM • What We Measure and What It Means – Ferrante, 2012 – Cambridge University Press • Comprehensive Electromyography – Ferrante, 2018 – Demos Publishing • EMG Lesion Localization and Characterization – Ferrante and Tsao, 2020 Introduction • Lesion localization and characterization – The major skills of the EDX provider – Lesion localization – Lesion characterization • Fiber type involved: sensory or motor • Pathology: Axon loss or demyelination • Severity • Temporal characteristics (needle EMG) – Acute, subacute, or chronic – Rate of progression – Introductory material cases • Mechanisms of nerve injury – Large number • Pathology and pathophysiology – Limited • Myelin disruption (demyelination) – Conduction slowing (DMCS) – Conduction block (DMCB) • Axon disruption (Wallerian degeneration) – Conduction failure – Prior to Wallerian degeneration » Transient “conduction block” pattern Nerve Fiber Disruption • Focal demyelination – Focal effects • Focal axon disruption – Initially: Focal effects – Later: Distal effects – Wallerian degeneration Ferrante MA, Tsao B. EMG Lesion Localization and Characterization, 2020 DMCS, uniform The pathophysiologies associated with DMCS, non-uniform demyelination DMCB Motor NCS are able to assess long segments of nerve Forearm Elbow Below SG Above SG – Timing of Wallerian degeneration • Motor axon terminals and endplates degenerate first – NMJ transmission failure occurs before nerve fiber conduction failure – CMAP abnormalities precede SNAP abnormalities » CMAPs: day 3 to day 7 » SNAPs: day 6 to day 10 Ferrante MA. Comprehensive Electromyography 9 • NCS identify – Focal DM and early axon disruption • Between the stimulating and recording sites – Screens for Wallerian degeneration proximal to these sites • All the way to the cell bodes of origin Ferrante. Muscle and Nerve 2004;30:547-568. ANTERIOR PRIIMARY RAMI C5 C6 C7 C8 T1 Proximal Nerve Innervation For the motor NCS Rhomboids (dorsal scapular) Spinati (suprascapular) Deltoid (axillary) Myotomal charts indicate: Biceps (musculocutaneous) Brachialis (musculocutaneous) Radial Nerve Innervation • the root innervation Brachioradialis Triceps • the nerve innervation Anconeus Extensor carpi radialis Extensor pollicis brevis Example: Biceps Extensor indicis Median Nerve Innervation Pronator teres Flexor carpi radialis Flexor pollicis longus Pronator quadratus Abductor pollicis brevis Ulnar Nerve Innervation Flexor carpi ulnaris Flexor digitorum profundus (D4,D5) Abductor digiti minimi Adductor polllicis First dorsal interosseous POSTERIOR PRIMARY RAMI Cervical paraspinal muscles High thoracic paraspinal muscles predominant contribution sometimes significant contribution minor contribution Ferrante MA, Tsao B. EMG Lesion Localization and Characterization, 2020 LABC SNAP Ferrante and Wilbourn, Muscle and Nerve, 1995 Med-D1 SNAP Ferrante and Wilbourn, Muscle and Nerve, 1995 Superficial Radial SNAP Ferrante and Wilbourn, Muscle and Nerve, 1995 Med-D2 SNAP Ferrante and Wilbourn, Muscle and Nerve, 1995 Med-D3 SNAP Ferrante and Wilbourn, Muscle and Nerve, 1995 Uln-D5 SNAP Ferrante and Wilbourn, Muscle and Nerve, 1995 MABC SNAP Ferrante and Wilbourn, Muscle and Nerve, 1995 C6 C6>7 C7>6 C6 C7 T1 C8 Ferrante and Wilbourn, Muscle and Nerve, 1995 Routine Screening NCS of Upper Extremity (Only weakly assesses upper plexus) Radial C5 Med-D2 Uln-D5 C6 C7 C8 T1 Ulnar-ADM Median-APB NCS Assessment of Upper Plexus LABC (100%) Med-D1 (100%) Radial (60%)* C5 C6 C7 C8 T1 Musculocutaneous-BC Axillary-Deltoid NCS Assessment of Middle Plexus Med-D2 (80%)* Med-D3 (70%) C5 Radial (40%)* C6 C7 C8 T1 NCS Assessment of Lower Plexus Uln-D5 (100%)* C5 MABC (100%) C6 C7 C8 T1 Radial – distal forearm Ulnar – ADM or FDI* Median – APB* NCS Assessment of Lateral Cord LABC (100%) Med-D1 (100%) Med-D2 (100%)* C5 Med-D3 (80%) C6 C7 C8 T1 Musculocutaneous - BC NCS Assessment of Posterior Cord Radial (100%)* C5 C6 C7 C8 T1 Axillary – Deltoid Radial – Proximal FA Radial – Distal FA NCS Assessment of Medial Cord Uln-D5 (100%)* C5 MABC (100%) C6 C7 C8 T1 Ulnar – ADM/FDI* Median – APB* • Which sensory NCS should be done first? – Perform “routine” sensory NCS + NCS to address the referral diagnosis + NCS to address the clinical features – Based on identified abnormalities, add others • For C6,7 abnormalities (Med-D2; SRN) – Add LABC and Med-D1 • For C8 abnormalities (Uln-D5) – Add MABC • Add contralateral studies when indicated EDX CASE STUDIES Localization Pathophysiology Severity Temporal Case 1A • 67yo RH male – Episodic hand numbness and tingling x 5 years, R > L – Present upon awakening – Precipitated by driving – Occur spontaneously while seated at rest • No neck pain • Examination normal – Hand sensation – Thenar eminence strength and bulk • Clinical features – Suggest bilateral CTS, right > left – Dominant limb first and worst • Exceptions – Profession and hobbies » Ferrante, Federal Practitioner, 2016;33:10-15 • Start NCS Median-D2 – Screening sensory NCS Ulnar-D5 • Start with RUE Superficial radial – More symptomatic side – If Median-D2 is normal, add palmar NCS » More sensitive to CTS CASE 1A UPPER EXTREMITY NERVE CONDUCTION STUDY WORKSHEET LEFT RIGHT NCS PERFORMED LAT AMP CV nAUC LAT AMP CV nAUC SENSORY DRG Median-D2 C6,7 4.2 6.4 Ulnar-D5 C8 2.9 6.2 Superficial radial C6,7 2.4 13.5 Perform Contralateral NCS Median-D2 CASE 1A UPPER EXTREMITY NERVE CONDUCTION STUDY WORKSHEET LEFT RIGHT NCS PERFORMED LAT AMP CV nAUC LAT AMP CV nAUC SENSORY DRG Median-D2 C6,7 3.6 12.0 4.2 6.4 Ulnar-D5 C8 2.9 6.2 Superficial radial C6,7 2.4 13.5 Median Palmar 2.4 18.2 Ulnar Palmar 1.9 12.5 Localization Bilateral Median: distal to the wrist stimulation sites Pathophysiology Demyelinating and axon loss on the right; demyelinating on the left Severity Mild to mild-moderate on the right and mild on the left Temporal Chronic by history (this is determined by the needle EMG findings) Which Motor NCS? Routine motor NCS x RUE Median-APB x LUE UPPER EXTREMITY NERVE CONDUCTION STUDY CASE 1A WORKSHEET LEFT RIGHT NCS PERFORMED LAT AMP CV nAUC LAT AMP CV nAUC SENSORY DRG Median-D2 C6,7 3.6 12.0 4.2 6.4 Ulnar-D5 C8 2.9 6.2 Spfcl radial C6,7 2.4 13.5 Median Palmar 2.4 18.2 Ulnar Palmar 1.9 12.5 Stim MOTOR Site Median-APB Wrist 3.4 7.6 4.1 5.8 Elbow 5.5 51 Ulnar-ADM Wrist 2.4 11.4 28.8 BE 9.6 52 26.8 AE 8.8 53 26.7 Localization Distal to the wrist stimulation site on both sides Pathophysiology DMCS and axon loss on the right, involving the sensory and motor nerve fibers DMCS on the left, involving the sensory nerve fibers Severity At least moderate on the right and mild on the left Temporal Chronic by history UPPER EXTREMITY NEEDLE EMG WORKSHEET Insertional activity Spontaneous Activity MUAP Analysis CASE 1A MUAP MUAP Normal IPSWs SCP Other None Fibs Fascs Other Recruitment Morphology RIGHT APB X X Normal Normal FDI X X Normal Normal Pron teres X X Normal Normal LEFT APB X X Normal Normal Case 1A Impression 1. Bilateral Median Neuropathies (e.g., carpal tunnel syndrome) • The above are demyelinating and axon loss in nature on the right and demyelinating in nature on the left, involve the sensory and motor nerve fibers on the right and the sensory nerve fibers on the left, and are located at or distal to the wrist on both sides. • Electrically, the abnormalities are moderate in severity on the right and mild in severity on the left. Case 1B • 56yo RH male – Episodic hand numbness and tingling x 2 years, R > L – Present upon awakening – Precipitated by driving – Occur spontaneously while seated at rest • No neck pain • Examination normal – Hand sensation decreased • Median distribution – Thenar eminence muscles • Normal strength • Thenar eminence – Wasting, mild in degree CASE 1B UPPER EXTREMITY NERVE CONDUCTION STUDY WORKSHEET LEFT RIGHT NCS PERFORMED LAT AMP CV nAUC LAT AMP CV nAUC SENSORY DRG Median-D2 C6,7 NR Ulnar-D5 C8 2.7 12.2 Superficial radial C6,7 2.4 17.8 Median Palmar NR Localization Median nerve, lateral cord, upper plexus, C6/7 DRG Pathophysiology Axon loss, sensory nerve fibers Severity Unclear (at least moderate) Temporal Chronic by history • Due to time constraints, we will only discuss the ipsilateral findings • Hx s/o CTS CASE 1A UPPER EXTREMITY NERVE CONDUCTION STUDY WORKSHEET LEFT RIGHT NCS PERFORMED LAT AMP CV nAUC LAT AMP CV nAUC SENSORY DRG Median-D2 C6,7 NR Ulnar-D5 C8 2.7 12.2 Superficial radial C6,7 2.4 17.8 Median Palmar NR Stim MOTOR Site Median-APB Wrist 4.6 4.8 Elbow 4.5 51 Ulnar-ADM Wrist 2.3 10.9 BE 10.3 57 AE 10.3 58 Localization Median nerve, distal to the stimulation site Pathophysiology Demyelination and axon loss; involves the sensory and motor nerve fibers Severity Unclear (at least moderate) Temporal Chronic by history Case 1C • 43yo RH male – Episodic hand numbness and tingling x 10 years, R > L – Present upon awakening – Precipitated by driving – Occur spontaneously while seated at rest • No neck pain • Examination normal – Hand sensation decreased • Median distribution – Thenar eminence muscles • Normal strength • Severe thenar eminence wasting CASE 1C UPPER EXTREMITY NERVE CONDUCTION STUDY WORKSHEET LEFT RIGHT NCS PERFORMED