SCIENTIFIC ARTICLE Outcomes of Microneurolysis of Hourglass Constrictions in Chronic Neuralgic Amyotrophy Karthik R. Krishnan, MS,*‡ Darryl B. Sneag, MD,*†‡ Joseph H. Feinberg, MD,* Ogonna K. Nwawka, MD,*†‡ Steve K. Lee, MD,*‡ Zsuzsanna Arányi, MD, PhD,§ Scott W. Wolfe, MD*‡ Purpose Wide variability in the recovery of patients affected by neuralgic amyotrophy (NA) is recognized, with up to 30% experiencing residual motor deficits. Using magnetic resonance imaging and ultrasound (US), we identified hourglass constrictions (HGCs) in all affected nerves of patients with chronic motor paralysis from NA. We hypothesized that chronic NA patients undergoing microsurgical epineurolysis and perineurolysis of constrictions would experience greater recovery compared with patients managed nonsurgically. Methods We treated 24 patients with chronic motor palsy from NA and HGCs identified on magnetic resonance imaging and US either with microsurgical epineurolysis and perineur- olysis of HGCs (11 of 24) or nonsurgically (13 of 24). Muscle strength (both groups) and electrodiagnostic testing (EDX) (operative group) was performed before and after surgery. Preoperative EDX confirmed muscle denervation in the distribution of affected nerve(s). All patients met criteria for microneurolysis: 12 months without improvement since onset or failure of clinical and EDX improvement after 6 months documented by 3 successive ex- aminations, each at least 6 weeks apart. Results Mean time from onset to surgery was 12.5 Æ 4.0 months. Average time to most recent post-onset follow-up occurred at 27.3 months (range, 18e42 months; 15 nerves). Average time to latest follow-up among nonsurgical patients was 33.6 months (range, 18e108 months; 16 nerves). Constrictions involved individual fascicular groups (FCs) of the median nerve and the suprascapular, axillary and radial nerves proper (HGCs). Nine of 11 operative patients experienced clinical recovery compared with 3 of 13 nonsurgical patients. EMG revealed significant motor unit recovery from axonal regeneration in the operative group. Conclusions Microsurgical epineurolysis and perineurolysis of FCs and HGCs was associated with significantly improved clinical and nerve regeneration at an average follow-up of 14.8 months compared with nonsurgical management. We recommend microneurolysis of HGCs and FCs as a treatment option for patients with chronic NA who have failed to improve with nonsurgical treatment. (J Hand Surg Am. 2020;-(-):1.e1-e11. Copyright Ó 2020 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic IV. Key words Brachial plexus, neuralgic amyotrophy, neurolysis, Parsonage Turner. From the *Center for Brachial Plexus and Traumatic Nerve Injury and †Department of Corresponding author: Scott W. Wolfe, MD, Center for Brachial Plexus and Traumatic Radiology and Imaging, Hospital for Special Surgery; and the ‡Weill Medical College of Cornell Nerve Injury, Hospital for Special Surgery, 523 East 72nd Street, New York, NY 10021; University, New York, NY; and the §Department of Neurology, Semmelweis University, e-mail: [email protected]. Budapest, Hungary. 0363-5023/20/---0001$36.00/0 Received for publication December 17, 2019; accepted in revised form July 24, 2020. https://doi.org/10.1016/j.jhsa.2020.07.015 No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Ó 2020 ASSH r Published by Elsevier, Inc. All rights reserved. r 1.e1 1.e2 NEUROLYSIS IN NEURALGIC AMYOTROPHY EURALGIC AMYOTROPHY (NA), also known as MATERIALS AND METHODS Parsonage Turner syndrome, is an idiopathic This 2-center retrospective cohort study was N peripheral axonopathy that most frequently approved by both institutional review boards. Patients presents with a prodrome of severe upper-extremity with a diagnosis of NA presented to our centers pain, followed by profound muscle weakness in the because of failure to improve with nonsurgical care distribution of one or more upper-extremity nerves.1,2 (Table 1). A diagnosis of NA was defined as the Although its etiology is debated, there is evidence to spontaneous, acute onset of muscle palsy in the dis- support an immune-mediated cause.1,3,4 Reported tribution of one or more upper limb nerves, usually triggers include viral infections, vaccination, stren- heralded by severe shoulder, periscapular or upper- uous exercise, surgery, pregnancy, and traumatic in- limb pain, and confirmed by electrodiagnostic e jury.5 8 Patients exhibit substantial variability in testing (EDX) that documented total or subtotal presentation, including affected nerve(s), laterality, muscle denervation in the nerve(s) or nerve fasci- the number of muscles involved, the extent of recov- cle(s) distribution. Muscle denervation was defined as ery, and recurrence. The variation in recovery re- low discrete or no motor unit recruitment during mains unexplained; some patients recover maximal volitional activation, the presence of diffuse spontaneously, whereas up to 30% have residual mo- positive sharp waves and fibrillation potentials, and tor deficits years after onset.5 absent axonal regeneration. Recruitment categories, The presence of hourglass constrictions (HGCs) of in order of ascending activity, were graded as none, individual nerves or nerve fascicles (fascicular con- low discrete (1 or 2 motor units with maximum strictions [FCs]) has been reported in peripheral recruitment), high discrete (3þ motor units), nerves of the upper extremity for decades, but only decreased, or full.19 Motor unit configuration cate- e recent reports suggest a correlation with NA.9 17 In gories included none, nascents (representing regen- 2011, Pan et al11 documented HGCs in 5 cases of NA eration), increased polyphasics (representing terminal and proposed the HGC as an explanation for failure collateral sprouting), and di/triphasics. Electro- to recover from this syndrome. Their subsequent diagnostic testing of all operative patients was con- report described surgical treatment of HGCs or FCs ducted by a board-certified electrodiagnostic in 47 spontaneous nerve palsies in 42 patients using specialist with extensive experience in the treatment neurolysis, repair, or grafting.10 Using US, Arányi of brachial plexus injuries and NA to verify whether et al. found that 74% of affected nerves in NA pa- recovery occurred as a result of axonal regeneration tients (52 of 70) exhibited abnormalities ranging from or terminal collateral sprouting. fascicular swelling to varying degrees of nerve We reviewed records of 96 patients evaluated for constriction. In their study, an increased degree of NA. Patients were eligible for inclusion if they had at constriction correlated with lower rates of reinner- least one FC or HGC on diagnostic imaging and met vation after 6 months.18 Sneag et al2 studied 27 pa- either of the criteria for chronic NA: (1) lack of re- tients with clinically confirmed NA and found covery at greater than 12 months from onset, constrictions in 84% of affected nerves on MRI. A demonstrating complete or near-complete denerva- recent 2-center report on anterior interosseous nerve tion; or (2) lack of recovery at 6 months after onset syndrome demonstrated FCs in the median nerve with 3 successive clinical and electrodiagnostic above the elbow using high-resolution MRI in all exams at least 6 weeks apart that demonstrated cases, and in 83% of cases using US.9 Given the complete denervation and no clinical recovery of strong association of this pathological feature with function. A total of 24 patients met inclusion criteria. NA and its prognostic importance, nerve or FCs may All patients who met inclusion criteria at site 1 were represent a therapeutic target, particularly in patients offered surgery or continued nonsurgical treatment; who have not recovered spontaneously. 11 of 15 opted to proceed with surgery whereas 4 The purpose of our study was to report outcomes opted for continued nonsurgical management. All of focused epineurolysis and perineurolysis of FCs patients at site 2 were offered nonsurgical manage- and HGCs in a cohort of patients with chronic NA ment because the site lacked a microsurgical protocol who did not improve with nonsurgical care. We hy- or experience in the operative treatment of NA. Eight pothesized that patients with chronic NA would operative patients had confirmed NA for greater than regain increased electrical and clinically important 12 months (average of 63 weeks; range, 52e81 muscle function from focused microneurolysis at weeks), with complete denervation of 7 nerves and constriction sites identified on imaging compared near-complete denervation of 2 nerves. Three opera- with those managed nonsurgically. tive patients had confirmed NA for 6, 8, and 9 J Hand Surg Am. r Vol. -, - 2020 TABLE 1. Patient Characteristics and Clinical Information* Affected Nerve(s) Time From Surgery Time From Onset Time From Surgery Time From Surgery Age (y), Involved Undergoing Neurolysis or Time From Onset to Most Recent to Latest to Initial Clinical to Initial EDX Patient Gender Limb Nonsurgical Treatment to Surgery, mo Follow-Up, mo Follow-Up, mo Improvement, mo Improvement, mo 1 40 M R Axillary 8 12 19 1.3 1.3 ‡ 2 21 M R SS 19 6 25 2.0 5.9 3 50 M L SS 9 24 33 5.0 5.0 AIN PT/median radial/PIN † 4 30 F L AIN 18 6 24 2.7 2.7 ‡ 5 58 F R AIN 12 43 55 4.8 7.8 ‡ 6 60 F R AIN 13 29 42 1.6 4.2 NEUROLYSIS IN NEURALGIC AMYOTROPHY J Hand Surg Am. Radial 7 61 M L Radial 6 21 27 9.6 9.6 8 51 M L Radial 14 16 30 ee ‡ 9 52 F R AIN 13 11 24 1.8 5.9 ‡ 10 66 F L AIN 12 12 24 3.9 4.2 r 11 58 M R AIN 15 9 24 9.2 9.2 Vol. 12 37 M R Axillary ee24 - 13 53 F L SS ee18 , - 14 30 F R SS ee18 2020 AIN 84 Radial 108 15 39 M L PT/Median ee18 Radial 16 47 F R AIN ee19 17 69 F R AIN ee18 18 41 F L Radial ee24 19 42 M L Radial ee18 20 40 M L Radial ee36 21 49 M R AIN ee72 (Continued) 1.e3 1.e4 NEUROLYSIS IN NEURALGIC AMYOTROPHY months, respectively, with complete denervation of 1 to 4 nerves each.