Electrophysiologic features of ulnar neuropathy in childhood and adolescence

Objective To analyze patterns of nerve injury in pediatric ulnar neuropathy (PUN). Methods Retrospective analysis of 49 children with PUN. Results Sensory loss in digit V was the prevailing complaint (89%). Predominant localization was at the elbow (55%). Diminished ulnar SNAP was the most common abnormality (71%) with median axon loss estimate (MAXE) of 62%. Dorsal ulnar cutaneous (DUC) sensory nerve action potential (SNAP) was reduced in 55% with MAXE of 43%. Abductor digiti minimi (ADM) and first dorsal interosseous (FDI) compound muscle action potential (CMAP) were reduced half of the time, with MAXE of 30% and 28% respectively. There was high correlation between ulnar sensory MAXE and ADM MAXE (r = 0.76, p < 0.0001), FDI MAXE (r = 0.81, p < 0.0001) and DUC MAXE (r = 0.60, p = 0.0048). Neurogenic changes were seen in the ADM, FDI, flexor carpi ulnaris (FCU) and flexor digitorum profundus IV (FDP IV) in 79%, 77%, 25% and 35% respectively. Pathophysiology was demyelinating in 27%, axonal in 59% and mixed in 14%. Conclusions In proximal axonal lesions, sensory fibers to digit V and motor fibers to distal muscles are predominantly affected, whereas in demyelinating lesions, slowing occurs twice as frequently as conduction block. Significance There is frequent axonal and fascicular injury in PUN.