[Ulnar nerve lesion at the elbow. Epidemiological, clinical and electromyographical data. Apropos of 312 patients].

Four hundred and ninety-three electromyographic ulnar nerve lesions identified in 312 patients were reviewed. During the same period, 1,000 cases of median nerve entrapment were seen in the same department. Among ulnar nerve lesions, 84% were idiopathic and only 52% were responsible for clinical symptoms. In patients with symptoms, three main patterns of paresthesia were seen: exacerbation at night and/or in the morning upon awakening (39%), permanent isolated paresthesia (34%), and permanent paresthesia with exacerbation at night and/or in the morning upon awakening (27%). Objective sensory loss was found in 1/3 to 1/4 of cases. All patients with muscle wasting (11%) also had sensory loss; muscle strength was markedly decreased in 19% of patients. Pain was mild and infrequent (35%). Electromyographic studies revealed a decrease in motor and sensory conduction velocity at the elbow (mean value 36.2 m/sec). Sensory conduction velocity was the most sensitive parameter for detecting incipient or moderate forms, whereas motor conduction velocity was extremely helpful in severe forms. Eighty-three per cent of patients had alterations of both conduction velocities (sensory and motor). In the mildest forms, nerve conduction velocity was normal (13% of cases); in these patients diagnosis was established on the basis of either a partial motor conduction block (3%) or desynchronization of the sensory action potential (10%).