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This study was performed to evaluate an automatic method of motor unit action potential (MUAP) analysis developed in our laboratory. MUAPs were recorded from the biceps brachii muscle of 68 normal subjects and 122 patients with nerve or muscle disease. The values of mean MUAP durations from normal subjects obtained by automatic analysis were similar to those reported in the literature. However, the normal range of MUAP amplitude and the incidence of polyphasic MUAPs were much higher. Normal ranges of mean MUAP area, area/amplitude ratio, and the number of turns were also defined. Automatic analysis demonstrated an abnormality of at least one MUAP feature in 70% of patients. There was concordance between automated analysis and visual assessment of MUAPs in 76% of patients with neuropathy but in only 50% of patients with myopathy. The relationships between different MUAP features seen in neuropathy and myopathy are explained in physiologic terms.

We have reviewed the electromyographic (EMG) studies of 17 patients with chronic progressive external ophthalmoplegia (CPEO). In 13 of 17 patients, conventional concentric needle EMG demonstrated a "myopathic" pattern, usually predominating in the shoulder muscles. Single-fiber EMG showed increased jitter and/or blocking in at least one muscle in 13 of 16 patients. Jitter was increased in the frontalis muscle in 10 of 13 patients and in an arm muscle in 5 of 12. When both muscles were tested, jitter was greater in the frontalis muscle in 5 patients and in the arm muscle in 2. These observations demonstrate that it may be difficult to distinguish myasthenia gravis from CPEO by EMG. The frequency with which abnormal jitter is found in CPEO suggests that, in addition to a mild generalized myopathy, a primary defect in neuromuscular transmission may be present.

Epidemics of epilepsy, a form of mass hysteria, were known in Eastern and Western cultures in the 17th and 18th centuries. A unique situation in the United States during the 19th centurey was the frontier religious movement, the setting in which the "jerks" occurred. The "falling exercise," "dancing exercise," "barking exercise," "laughing exercise," and the "running exercise" centered around the excitement involved in the religious revival. During some exercises, people saw "visions," and exhibited bizarre behavior and sudden jerking motions. During the summers of 1801-1803 on the Kentucky frontier, some pioneers who attended the religious revival camp meetings had convulsions, hallucinations, tremors, jerks, compulsive dancing and "epileptic trances." Although these have been assumed to be psychological in origin, the epidemiology of the symptoms may correlate with the diagnosis of ergotism. Those affected were usually children and young adults. Symptoms of ergotism include giddiness, fatigue, depression, formications, muscle twitching, tonic spasms, convulsions, delirium, and loss of speech.

In a 61-year-old man with facial diplegia and new onset of congestive heart failure (CHF), electroneuromyography indicated diffuse axonal degeneration, but sural nerve biopsy showed mild changes and no amyloid. Four months later, after the onset of diplopia and increasing CHF, rectal biopsy demonstrated amyloid.

Five adult patients (four of them men) had episodic brachioradial pruritus associated with forearm paresthesia and hypalgesia. No cervical, shoulder, or forearm trauma was known. Onset was variable, but two had had the condition for more than ten years. In each, sensory alteration was detectable by pinprick and temperature in the distribution of the posterior cutaneous nerve of the forearm supplying the skin over the proximal portion of the brachioradial muscle. This seems to be a benign neuropathy.

We report four patients with myasthenia gravis (MG) in whom single-fiber electromyography (SFEMG) jitter measurements were normal in some muslces while they were taking pyridostigmine and became abnormal 2-14 days after the medication was discontinued. When the abnormality of neuromuscular transmission in MG is mild, cholinesterase inhibitors may mask the findings of increased jitter on SFEMG.

This study was performed to compare different techniques of analyzing the electromyographic interference pattern (IP). Recordings were made from the biceps muscle with a concentric needle electrode at different sites and at different constant levels of voluntary contraction. The number of turns per second (NT), the mean amplitude change between successive turns (MA) and NT:MA ratio were determined for epochs of 1 sec duration. Normal limits of individual epoch NT:MA ratios and the mean value of NT:MA ratio obtained from all epochs in each muscle were determined. The mean NT:MA ratio was less in normal males than in females. IP recordings were made in the biceps muscle of 69 patients with neuropathy and 54 patients with myopathy, though this muscle was not necessarily affected by the disease in all patients. The IP was abnormal by visual inspection in 82% of patients compared to 61% based on NT:MA ratio and 74% using a technique that automatically quantitates some features of the IP that are assessed subjectively by an electromyographer. All techniques demonstrated IP abnormalities in more than 80% of the muscles that were moderately to severely weak. Though measuring the NT:MA ratio without monitoring the force of contraction is not as sensitive as other IP analysis techniques, it may be useful in quantitating abnormalities when other techniques are not available.

Headache associated with intracranial venous anomalies is well described but headache associated with extracranial venous malformation previously has not been recognized. A case of extracranial venous malformation producing vascular headache is presented.