MUSCLE CRAMP AS THE RESULT OF IMPAIRED GABA FUNCTION - AN ELECTROPHYSIOLOGICAL AND PHARMACOLOGICAL OBSERVATION

We investigated the mechanism of cramps in 2 patients: a 48-year-old m an with bulbospinal neuronopathy, and a 46-year-old man with amyotroph ic lateral sclerosis. Cramps were quite easily induced by volitional e xertion and high-frequency stimulation of the peripheral nerves. When an ulnar nerve was blocked with lidocaine at the elbow, no cramp was i nduced despite the application of high-frequency stimulation at the wr ist. Diazepam (GABA(A) agonist) was effective in the first patient and baclofen (GABA(A) agonist) in the second, with no cramps induced in s pite of increasing stimulation intensity. Impairment of interneurons m ediated by GABA as the neurotransmitter is thought to be involved in t he mechanism of the cramps. (C) 1993 John Wiley & Sons, Inc.