F-response multiplicity in lower motor neuron disorders
Pradhan, S.
Electromyography and Clinical Neurophysiology 36(7): 441-448
1996
ISSN/ISBN: 0301-150X PMID: 8957171 Document Number: 466136
Multiple F-response following a single supramaximal distal nerve stimulation was observed in about 4% of the patients suffering from disorders of lower motor neuron. The phenomenon was observed in old poliomyelitis, entrapment neuropathies, axonopathies and demyelinating neuropathies. Thirty healthy subjects and 30 patients of upper motor neuron disorder were also studied for this purpose but none showed F-multiplicity. On repeated stimulation at sufficient intervals, some or all the components of the multiple F-response could be reproduced individually or in different combinations with similar latency and morphology. These responses had all the characteristics of F-response and were distinguishable from H-reflex or axon reflex. Increase in the number and frequency of repeater F-response and markedly increased chronodispersion were also observed consistently in association with multiple F-responses. Multiplicity in the F-response is a hitherto unknown phenomenon of relatively rare occurrence, presence of which however, is always indicative of disease of the lower motor neuron. The possible mechanisms of its generation are discussed.