Sensory nerve abnormalities in brachial plexopathy

Sensory nerve action potential (SNAP) amplitude should be abnormal in brachial plexopathies (BP) which cause axonal degeneration in distal segments. Fifty-six patients with BP were identified. In diffuse BP. 22/25 (88%) showed low amplitude or absent median or ulnar SNAP. Three of 5 patients with upper trunk BP had low amplitude or absent SNAP (1 median. 1 radial. 1 lateral antebrachial cutaneous). Seventy-five percent of patients with lower trunk/medial cord BP had low amplitude or absent SNAP (8/24 median. 18/24 ulnar). Overall. 82.5% of patients had low amplitude or absent SNAP when a sensory nerve in the distribution of signs was studied. Testing multiple sensory nerves to include symptomatic regions enhances the diagnostic yield of SNAP in BP.