Electrodiagnosis in entrapment neuropathy by the arcade of Struthers.

Two cases of high ulnar nerve neuropathy are reported. Lesions were localized at the midarm level by electrophysiologic studies. In the first case, the lesion was found mainly to be a prolonged neurapraxia, and neurolysis was effective. The ulnar nerve was swollen 1 cm in length under the arcade of Struthers. After neurolysis, the palsy recovered rapidly. In the other case, the lesion seemed to be a mild injury to the myelin sheath. Delayed segmental conduction velocity and partial conduction block were found at the midarm level. The paresis improved slightly during the 11-month followup without any treatment, but the electrophysiologic studies were unchanged. In both cases, physical examination did not distinguish the lesions from cubital tunnel syndrome. Electrophysiologic examination proved to be effective as a diagnostic procedure. In the presence of ulnar neuropathy, the upper arm segment should be included in a routine nerve conduction study to screen for the rare but important entrapment neuropathy caused by the arcade of Struthers.