Reduction of motor artifact in antidromic ulnar sensory studies

Motor artifact often interferes with recording of antidromic ulnar sensory responses from digit 5. In the belief that this artifact is due to a volume-conducted motor response, eight different recording electrode and finger positions were evaluated in 10 normal subjects in an attempt to reduce or eliminate it. Placement of the recording electrodes over the middle and distal phalanges of digit 5 while the fingers were extended and abducted reduced this artifact most effectively, with minimal decrease in amplitude of the sensory response. This finding has important implications for the routine performance of antidromic sensory conduction studies of the ulnar nerve.