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Reflex myoclonus in cortical‐basal ganglionic degeneration involves a transcortical pathway
Author(s) -
Strafella A.,
Ashby P.,
Lang A. E.
Publication year - 1997
Publication title -
movement disorders
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.352
H-Index - 198
eISSN - 1531-8257
pISSN - 0885-3185
DOI - 10.1002/mds.870120315
Subject(s) - neuroscience , motor cortex , silent period , reflex , inhibitory postsynaptic potential , stimulation , transcranial magnetic stimulation , myoclonus , stimulus (psychology) , anatomy , medicine , psychology , psychotherapist
The short‐latency reflex myoclonus that appears to be characteristic of cortical‐basal ganglionic degeneration (CBGD) was investigated in two patients. Stimulating the digital nerves of the middle finger caused exaggerated reflex activity in the first dorsal interosseus (FDI) muscle of that hand with a latency of 46–51 ms. Magnetic stimulation over the contralateral cortex, delivered 25 ms after the digital nerve stimulus, resulted in greater than expected facilitation of FDI, implying spatial summation. Poststimulus time histograms (PSTH) of individual FDI motor units indicated that this spatial summation was occurring “upstream” from the motoneurons. It is argued that this occurs at the motor cortex. Magnetic stimulation over the cortex in normal subjects results in short‐latency facilitation of the contralateral motoneurons followed by inhibition. This inhibition was less in the patients with CBGD. It is argued that this results from the loss of an intrinsic cortical or corticothalamic inhibitory mechanism.