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Neurotonia: Impulse‐induced repetitive discharges in motor nerves in peripheral neuropathy
Author(s) -
Warmolts John R.,
Mendell Jerry R.
Publication year - 1980
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.410070307
Subject(s) - motor unit , medicine , motor nerve , peripheral neuropathy , peripheral , electromyography , anatomy , neuroscience , anesthesia , psychology , physical medicine and rehabilitation , diabetes mellitus , endocrinology
Delayed relaxation of muscle following voluntary contraction was an unusual feature of a mild chronic sensorimotor peripheral neuropathy in an adult. This abnormality resulted from rapid repetitive discharges in motor nerves occurring only in response to passing impulses; there was no spontaneous nerve discharge. Voluntary contraction of affected muscles generated involuntary high‐frequency discharges of motor unit potentials, which persisted briefly after attempted relaxation. Nerve blocks localized independent zones of hyperexcitability in distal and proximal sections of nerve from which such repetitive discharges could be triggered. Intravenous administration of phenytoin diminished the discharge. Examination of intramuscular nerve bundles revealed loss of myelinated nerve fibers with numerous sprouting and remyelinating axons. These findings, along with muscle biopsy changes of neurogenic atrophy and type grouping, strongly favor an axonal neuropathy. An explanation for the repetitive nerve discharge is slow waning of heightened excitability of a motor nerve after passage of an impulse.