American Society for Peripheral Nerve

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Median Nerve Compression in The Forearm Is A Clinical Diagnosis Outcome of Step Lengthening Surgical Technique
Madi El Haj, MD MSc1; Wei Ding, MD1; J. Megan M. Patterson, MD2; Christine B Novak, PT, PhD3; Lorna Kahn, PT CHT1; Susan E. Mackinnon, MD1
1Washington University School of Medicine, St. Louis, MO; 2University of North Carolina, Chapel Hill, NC; 3University of Toronto, Toronto, ON, Canada

Median nerve entrapment in the forearm (MNEF) without motor paralysis is a challenging diagnosis. This retrospective study evaluates the clinical presentation, diagnostic studies and clinical outcomes of patients following surgical decompression of the median nerve in the forearm.

Material & Methods:
147 patients diagnosed with MNEF who underwent surgical decompression from 2007 and 2017 were reviewed. We excluded 120 patients with combined nerve entrapments (radial and ulnar), polyneuropathy, traumatic peripheral nerve injuries or median nerve motor palsy. Charts were reviewed for clinical presentation, and pre- and postoperative pain, strength, functional outcomes, and DASH scores.

27 patients were treated for isolated median nerve entrapment. Average follow-up time was 32 months. There were 16 women (59%) and 11 men (41%), most patients were overweight 29.2 (kg/m2) and in the fifth decade of life. The dominant hand was involved in 70% (19/27). Presenting symptoms included forearm pain (22/27), involving the entire median nerve distribution, including the palmar cutaneous branch of the median nerve (21/27). Pain was described as "aching" (74%), "throbbing" (48%), "shooting" (40%), and burning/cramping (30%). A Tinel's sign was present in the mid-forearm in less than 50% of patients (11/27). Most patients had pain with deep pressure over the FDS arch/pronator (24/27) and all patients had a positive scratch collapse test (SCT). Electrodiagnostic studies (EDX) were positive for CTS in 50% of patients (11/21) and positive for MNEF in only 10% (2/21). 13 patients had previous carpal tunnel release (CTR). Simultaneous primary CTR was performed in 10/27 patients and revision in 7 of the 13 patients with previous CTR. Postoperatively there were significant (p < 0.005) improvements in grip and key pinch strength, VAS pain (6.6 vs 2.2), quality of life (67 vs 31) and DASH scores (50.2 vs 32.2).

Median compression in the forearm without motor paralysis is a clinical not an electrodiagnostic diagnosis. Patients' pain drawings and pain quality provide valuable information for the diagnosis of MNEF. SCT is useful tool for localizing the nerve entrapment points. Patients with persistent forearm pain and median nerve symptoms (especially after CTR) should be considered for a diagnosis of MNEF. Surgical decompression provides satisfactory outcomes.

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