Repetitive nerve stimulation testing of the ulnar nerve was systematically performed on 21 normal controls and 120 patients with myasthenia gravis (MG). Diagnostic sensitivity increased from 0% in MG in remission and 17.2% in ocular MG to 100% in severe generalized MG. Six types of responses were observed in MG and could be classified into two distinct patterns based upon disease severity: ( 1 ) in mild MG, an abnormal decremental response at low rate of stimulation, normal response at high rate of stimulation, and prominent posttetanic facilitation and exhaustion phenomena; and (2) in severe MG, abnormal decremental responses at low as well as high stimulation rates and less common posttetanic facilitation and rare posttetanic exhaustion phenomena. This difference is most likely due to the severity of the neuromuscular block in MG. Oh Methods and MaterialsFor study of neuromuscular transmission we used the Harvey-Masland method with the surface-recording electrode on the abductor digiti quinti muscle and the surfacestimulating electrode on the transsulcal segment of the ulnar nerve [ 111. For the recording electrode, the active electrode was placed over the belly of the muscle and the reference electrode over the tendon. For stimulation of the nerve, we used the supramaximal 0.2 msec stimulus duration.Each subject lay on a bed with the forearm and hand fixed on a stand with a heavy base (281. The nerve was stimulated at 3isec for 2 seconds, at 5isec for 1 sec-ond, and at 50/sec for I second, using DISA 14 and 1500 EMG machines. There was at least a I-minute interval between each test. Immediately and 4 minutes after tetanic stimulation at 50isec, the nerve was stimulated at S/sec for 1 second each time.The peak-to-peak amplitude of each muscle potential was measured. The percentage of decrement or increment was calculated by comparing the first response with the lowest or highest among the first five responses at the low rate of stimulation and during t h e first second at the high rate of stimulation. When the results differed by 2 standard deviations from the mean in controls, they were considered abnormal.Posttetanic facilitation and exhaustion phenomena were defined as having occurred when the decremental response at Sisec immediately after and 4 minutes after tetanic stimulation showed improvement or aggravation, respectively, compared with the response at 5isec prior to tetanic stimulation.The present analysis is based on 2 1 normal controls a d 120 patients with MG. M G was diagnosed by a combination of clinical examination and consistent reversal of signs and symptoms upon parenteral administration of edrophonium or neostigmine. Among 103 patients with symptomatic MG, the test was performed in 79 before any medication was started (no-anticholinesterase group), in 18 after anticholinesterases had been discontinued for at least 12 hours (anticholinesterase-off group), and in 6 patients with myasthenic crisis within 6 hours after administration of anticholinesterase medication.

Tarsal tunnel syndrome (TTS) is a rare compression neuropathy of the posterior tibial nerve. Typical symptoms are burning pain and paresthesia in the toes and along the sole of the foot. The presence of Tinel's sign and objective sensory loss in the territory of any of the terminal branches of the posterior tibial nerve are diagnostically helpful. The terminal latency and sensory nerve conduction velocity in medial and lateral plantar nerves were studied in 20 normal controls and 21 cases of TTS in 17 patients. Prolonged terminal latency was observed in 11 cases, with TTS, while sensory nerve conduction abnormality (either absent nerve potential or slow sensory nerve conduction velocity) was found in 19. The sensory nerve conduction velocity in the lateral and medial plantar nerves is a superior objective diagnostic index of TTS.

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In eight patients with unilateral pontine and midbrain lesions, brainstem auditory evoked potentials (BAEPs) were studied with ipsilateral (Cz-Ai) and contralateral (Cz-Ac) recordings after monaural stimulation. In all cases, the most prominent abnormality was noted in BAEP generated by stimulating the ear ipsilateral to the lesions. The Cz-Ai and Cz-Ac patterns showed similar abnormalities in five of the patients and dissociated abnormalities in two patients. We conclude that: (1) Lateralization of BAEP is possible in unilateral pontine and midbrain lesions. (2) Monaural stimulation with Cz-Ai and Cz-Ac recordings is essential for lateralization. (3) The BAEP in monaural stimulation is predominantly generated from the auditory structures ipsilateral to the stimulated ear.

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