Tremor and peripheral nerve entrapment. Case report

A patient is described in whom pain, paresthesias, weakness and resting tremor gradually developed 8 years after an ulnar nerve transposition. Electromyography revealed that the tremor occurred at 4 to 5 Hz, was abolished by voluntary muscle contraction, and was localized to ulnar-innervated muscles. Ulnar nerve conduction was focally slowed at the elbow; therefore, ulnar neurolysis was performed and a fusiform neuroma-in-continuity was found. Mechanically tapping the neuroma elicited repetitive discharges at 4 to 5 Hz in the intrinsic muscles of the hand; these discharges were abolished by anesthetic block proximal to the neuroma. Although the pain, paresthesias, and weakness were abolished by the neurolysis, the tremor persisted. Possible neurophysiological mechanisms underlying the appearance of tremor with peripheral nerve entrapment are discussed.