Subacute structural myopathy associated with human immunodeficiency virus infection

An unusual myopathy characterized by selective loss of thick filaments and widespread formation of rod bodies is described in two men, both seropositive for human immunodeficiency virus. We were unable to find any previous reports documenting this combination of morphological abnormalities, which we believe may be related to human immunodeficiency virus infection. Both patients responded to treatment: one, to steroid therapy; the other, to plasmapheresis.

Relative utility of different electrophysiologic techniques in the evaluation of brachial plexopathies

We report the results of detailed electrophysiologic studies in 23 patients with suspected brachial plexopathies. In five with neurogenic thoracic outlet syndrome, needle EMG and determination of size of ulnar sensory nerve action potentials (SNAPs) and thenar M waves were important in localizing the lesion; F-response and somatosensory evoked potential (SEP) studies were of more limited utility. All electrodiagnostic studies were normal in 10 patients with nonneurogenic thoracic outlet syndrome. In traumatic (three patients) or idiopathic brachial plexopathy (five patients), needle EMG was especially helpful but, in the former, SEP studies helped to guide management and, in the latter, to confirm the proximal site of the lesion when peripheral SNAPs were normal. The presence of preserved but small SNAPs but absent M waves in patients with traumatic plexopathies suggested a combined pre- and postganglionic lesion.

Magnetic resonance imaging in amyotrophic lateral sclerosis

Magnetic resonance imaging (MRI) was used in 5 patients with clinically definite amyotrophic lateral sclerosis to determine the frequency of central white matter abnormalities. Two patients had symmetrical areas of increased signal intensity seen on MRI extending from the cortex, through the corona radiata, posterior limb of the internal capsule, and cerebral peduncles into the pons. These MRI abnormalities presumably relate to the pathological changes observed by others in the central white matter of patients with amyotrophic lateral sclerosis.

The effect of temporal dispersion on compound action potential area in human peripheral nerve

In 32 ulnar nerves of healthy volunteers, the mean area of the compound muscle action potential recorded over abductor digiti minimi was reduced by 7.4% when comparing above-elbow with wrist stimulation and by 1.9% when comparing above-elbow with below-elbow stimulation. In 20 of these nerves, the mean area of the compound nerve action potential (CNAP) recorded over the fifth digit was reduced by 36% when comparing above-elbow with wrist stimulation. Area reduction of the compound action potential, especially of the CNAP, appears to be a characteristic effect of temporal dispersion in peripheral nerve when utilizing the bipolar recording technique routinely employed in clinical neurophysiology. A thorough understanding of the effects caused by temporal dispersion and of their quantitative limits in normal peripheral nerve is important for the proper interpretation of nerve conduction studies.

Ulnar nerve conduction study of the first dorsal interosseous muscle

Ulnar neuropathy at or distal to the wrist is difficult to diagnose. Sensation is normal in the majority of cases, and the interosseous muscles are usually more severely involved than are the hypothenar muscles. A technique for ulnar nerve conduction study of the first dorsal interosseous muscle is described, and normal values based upon 373 studies are presented. Using this technique the upper limit for distal motor latency (DML) to the first dorsal interosseous (FDI) muscle is 4.5 ms. More precisely, DML to the FDI should not exceed DML to the contralateral FDI by more than 1.3 ms, nor should this value exceed the DML to the ipsilateral abductor digiti minimi by more than 2.0 ms. The lower limit for amplitude of the compound muscle action potential recorded over FDI is 6mV. If motor conduction study of the first dorsal interosseous muscle is more routinely performed, earlier and more frequent recognition could be followed by improved surgical remediation of this compression neuropathy.

Conduction block in compression neuropathy: recognition and quantification

Previous reports of conduction block in compression neuropathy have used the amplitude difference of the compound muscle action potential (CMAP) comparing proximal with distal stimulation. The present study was undertaken to determine if area reduction of the proximal CMAP provides diagnostic information that is not included in amplitude reduction, particularly in distinguishing conduction block from temporal dispersion. Digitized, integrated area measurements were compared with amplitude and, as a convenient estimate of area, the calculated M-index (1/2 duration X amplitude). Amplitude reduction did not reliably distinguish conduction block from temporal dispersion in compression neuropathy. Both in the investigation of conduction block and in the management of compression neuropathy, integrated area measurement allows for the more accurate identification and quantification of conduction--a usually reversible cause for weakness in compression neuropathy.

Absence spells. Hyperventilation syndrome as a previously unrecognized cause

Absence spells in adults have been recognized in association with disorders of excessive somnolence, transient ischemia of the temporal lobes, and seizure disorders. A 66-year-old man who presented with a history of absence spells for more than 20 years is described. After diagnosis of a hyperventilation syndrome without an associated seizure disorder, educational and behavioral therapy without the use of medication has produced a long, continuing remission of these spells. The hyperventilation syndrome continues to present in many ways, often without recognition by physicians for prolonged periods. The case presented exemplifies this problem and may be the first report of absence spells caused by hyperventilation.

Peripheral neuropathy associated with disulfiram administration

Very few cases of peripheral neuropathy as a complication of disulfiram therapy have been described. The clinical and electrodiagnostic features of two patients who developed a severe peripheral neuropathy during disulfiram administration are reported. Evidence is presented which suggests that disulfiram causes a dying-back axonal neuropathy.