Erythromycin-associated ergotamine intoxication: arteriographic and electrophysiologic analysis of a rare cause of severe ischemia of the lower extremities and associated ischemic neuropathy.

Vasospasm associated with ergotamine is a well-known phenomenon. In this case report we present a rare drug interaction between erythromycin and ergotamine at normal doses causing lower extremity ischemia in a 36-year-old woman. Nitroprusside proved to be the treatment of choice. The response was dramatic and took place in a matter of hours in this patient. Ischemic monomelic neuropathy is a recently described entity in which axonal necrosis is caused by a loss of distal extremity blood flow. The association between erythromycin and ergotamine may be a dangerous pharmacologic combination; drugs that have a hepatic cycle with ergotamine derivatives must be used with caution.

Utility of short-latency evoked potentials in the classification of progressive, early onset cerebellar ataxias.

In recent years, several authors have proposed new classifications of inherited ataxias, some of them being based on systematic clinical studies of large groups of patients. This methodic approach has led to the identification of new types of ataxias and helped the development of molecular biology research in these diseases. Up to now, nerve conduction velocity and evoked potential studies have not been considered in the classification of hereditary ataxias. We have studied the results of short latency evoked potentials in 102 patients affected by a early onset, progressive cerebellar ataxia. Based on the results of this study and a review of the literature on this subject, we will evaluate the utility of nerve conduction velocity and evoked potential recordings in the classification of this group of diseases.

Transcarpal median sensory conduction: detection of latent abnormalities in mild carpal tunnel syndrome.

The major slowing of nerve conduction in the carpal tunnel syndrome is located in the palm to wrist segment. The aim of this study is to develop a reliable, sensitive and accessible approach to measure transcarpal median sensory nerve conduction. For this purpose, a fast recovery amplifier with a stimulus artifact suppressor was designed by the author. On stimulation of digits II or III, evoked orthodromic sensory nerve action potentials were simultaneously recorded at the palm and at the wrist. Distances were determined with a ruler. Median sensory nerve conduction velocity was estimated from digit to palm and from palm to wrist in 80 healthy hands and 253 hands with a presumptive diagnosis of carpal tunnel syndrome. According to conventional criteria, 131 of the 253 hands from those suspected of carpal tunnel syndrome were thought to have median nerve compression. When transcarpal median sensory conduction velocity was taken into account, the diagnostic yield increased by 18.1%. The described technique provides a simple, sensitive and reliable method of diagnosing mild or early carpal tunnel syndrome.

Pathological findings in a case of hypoxic myoclonus treated with 5-hydroxytryptophan and a decarboxylase inhibitor.

A 72-year-old woman suffered a respiratory arrest following intoxication with barbiturates. Her examination 27 months after the anoxic incident revealed involuntary jerks of trunk and limb muscles triggered by willed movements. On a regimen of 1 g L-5-HTP and 100 mg l-alpha-methyldopa hydrazine (carbidopa), action myoclonus disappeared completely. This medication had to be discontinued because of a regressive hysterical reaction. Two months later, she was found unconscious; resuscitation efforts were unsuccessful. Autopsy showed death was caused by choking on food. Coronal slices of the cerebral hemispheres and transverse section of the brainstem and cerebellum revealed no lesion. No evidence of hypoxic damage could be demonstrated in the cerebral cortex, hippocampus, striatum, pallidum, subthalamus, thalamus, or other diencephalic structures. In the caudal half of the midbrain tegmentum, a marked astrocytic reaction of some duration was encountered in the lateral parts of the supratrochlearis nucleus, the lateral subnucleus of the mesencephalic gray, and the immediately adjacent cuneiform and subcuneiform nuclei. In the former nucleus, sites of presumed nerve cell disintegration were found, but the neuronal populations of this nucleus and of the other raphe nuclei were well maintained. The other brainstem structures and the cerebellum were normal. Our neuropathological findings suggest that hypoxic myoclonus (a) does not seem to be explained by demonstrable neuronal loss in motor structures, such as cerebellum, thalamus, or basal ganglia and (b) does not appear to be causally related to a detectable reduction in the serotonin-containing neurons of the brain but rather to a functional derangement of anatomically intact serotonergic pathways originating perhaps from other, as yet unidentified, damaged neuronal structures.

Beneficial effects of serotonin precursors in postanoxic action myoclonus.

In two patients with postanoxic action myoclonus, L-tryptophan or a monoamine oxidase inhibitor induced a moderate improvement, but L-5-hydroxytryptophan had greater therapeutic effect. Methysergide, a potent blocker of serotonin receptors, consistently induced a marked deterioration in myoclonus. Pretreatment cerebrospinal fluid 5-hydroxyindoleacetic acid levels were reduced significantly in both patients. These findings suggest that postanoxic action myoclonus likely is associated with insufficient serotonergic activity in the central nervous system. Data are inadequate to determine whether this apparent insufficiency reflects structural changes in 5HT-containing raphe nuclei due to a direct anoxic damage to these structures of functional changes caused by a secondary reduction in the activity of intact serotonergic neurons.

Shy-Drager syndrome. Neuropathological correlation and response to levodopa therapy.

The post-mortem examination of the nervous system of a patient with Shy-Drager syndrome successfully treated with levodopa (Sharpe et al, 1972) revealed features of striato-nigral degeneration and amyotrophic lateral sclerosis, a cerebellar system degeneration and a loss of approximately 75% of sympathetic preganglionic neurons. Lewy bodies were not present and no detectable changes were observed in the sympathetic prevertebral ganglia. While the limited and transient beneficial effect of levodopa on the bradykinesia in our case is possibly due to the progressive loss of striatal dopaminergic receptors seen in striatonigral degeneration, we propose that in Shy-Drager syndrome, levodopa therapy benefits orthostatic hypotension because of a suppression of the central depressor action of this drug. This suppression is attributable to functional disconnection of sympathetic ganglia secondary to the loss of preganglionic neurons or to degeneration of central autonomic catecholaminergic systems.