The Role of Micro-neurolysis for Hourglass Constrictions in Neuralgic Amyotrophy
Scott W Wolfe, MD1, Karthik Kirshnan, BS2, Steve K Lee, MD3, Joseph H Feinberg, MD4, Ogonna K. Nwawka, MD4 and Darryl B Sneag, MD4, (1)Hand and Upper Extremity Service, Hospital for Special Surgery, New York, NY, (2)Weill Medical College of Cornell University, New York, NY, (3)Orthopedic Surgery, Hospital for Special Surgery, New York, NY, (4)Hospital for Special Surgery, New York, NY
Purpose: Wide variability in recovery of patients affected by Neuralgic Amyotrophy (Parsonage Turner Syndrome) is recognized, with up to 60% experiencing residual motor deficits or pain. Using high-resolution MRI and ultrasound (US), we routinely identify hourglass constrictions (HGCs) in affected nerves of patients with NA. We hypothesized that patients with chronic NA and HGCs would experience motor recovery and functional improvement following microsurgical epi- and perineurolysis of the constrictions.
Methods: Ten patients (5 F), ages 21-61 years, with chronic, persistent motor palsy from NA were treated with microsurgical epi- and peri-neurolysis of HGCs. Average time from symptom onset to surgery was 12.2 ± 4.1 months. Preoperative electrodiagnostic (EDX) testing and manual motor testing confirmed complete muscle denervation in the distribution of affected nerve(s). HGCs were identified in one or more nerves in all patients using 3.0 T MRI and US. Microneurolysis was indicated for the following: failure to improve clinical and EDX function after 6 months with 3 successive exams, each at least 6 weeks apart (n = 3), or 12 months without improvement since symptom onset (n = 7). Recovery was assessed pre-and postoperatively using the modified Medical Research Council (MRC) scale and EDX. Changes in MRC and EDX classifications were assessed using a two-tailed Wilcoxon signed-rank test.
Results: Average postoperative clinical and EDX follow-up was 13.6 months (range, 4-29). Thirty-five HGCs in 14 nerves were identified on imaging and confirmed intra-operatively, involving the pronator teres and anterior interosseous fascicles of the median nerve and suprascapular, axillary and radial nerves proper. One patient presented initially with bilateral disease. 8/10 patients experienced functional recovery and 8/9 experienced electrical recovery in the majority of affected muscles. Average MRC increased from 0.0 to 3.6 ± 1.4 (p<0.01). EDX revealed significant motor unit recovery from axonal regeneration in 25/31 muscles (p<0.01).
Conclusion: High resolution MRI and US detected HGCs of peripheral nerves and nerve fascicles in NA patients with chronic, recalcitrant motor palsy. Microsurgical epi- and peri-neurolysis of HGCs in this small patient cohort was associated with significant electrical and clinical muscle recovery at an average follow-up of 13.7 months. We conclude that the HGC is unique to NA, and recommend microsurgical epi- and perineurolysis of HGCs for patients with NA who fail to improve with non-operative treatment.
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