Diagnostic value of proximal cutaneous nerve biopsy in brachial and lumbosacral plexus pathologies

Background: Brachial and lumbosacral plexopathies can result from numerous non-traumatic etiologies, including those of inflammatory, autoimmune, or neoplastic origin, that often require nerve biopsy for diagnosis. The purpose of this study was to evaluate the diagnostic efficacy of medial antebrachial cutaneous nerve (MABC) and posterior femoral cutaneous nerve (PFCN) nerve biopsies in proximal brachial and lumbosacral plexus pathology. Method: Patients undergoing MABC or PFCN nerve biopsies at a single institution were reviewed. Patient demographics, clinical diagnosis, symptom duration, intraoperative findings, post-operative complications, and pathology results were recorded. Biopsy results were classified as diagnostic, inconclusive, or negative based on the final pathology. Results: Thirty patients undergoing MABC biopsies in the proximal arm or axilla and five patients with PFCN biopsies in the thigh or buttock were included. MABC biopsies were diagnostic in 70% of cases overall and 85% diagnostic in cases where pre-operative MRI also demonstrated abnormalities in the MABC. PFCN biopsies were diagnostic in 60% of cases overall and in 100% of patients with abnormal pre-operative MRIs. There were no biopsy-related post-operative complications in either group. Conclusions: In diagnosing non-traumatic etiologies of brachial and lumbosacral plexopathies, proximal biopsies of the MABC and PFCN provide high diagnostic value with low donor morbidity.