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Spinal and cortical inhibition in huntington's chorea
Author(s) -
Priori Alberto,
Polidori Luigi,
Rona Sabine,
Manfredi Mario,
Berardelli Alfredo
Publication year - 2000
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 - 10.1002/1531-8257(200009)15:5<938::aid-mds1026>3.0.co;2-q
Subject(s) - transcranial magnetic stimulation , reciprocal inhibition , neuroscience , motor cortex , inhibitory postsynaptic potential , h reflex , spinal cord , chorea , strychnine , medicine , psychology , reflex , facilitation , silent period , withdrawal reflex , pyramidal tracts , huntington's disease , stimulation , disease
In this article we studied spinal and cortical inhibitory mechanisms in patients with Huntington's disease. To evaluate spinal cord inhibitory circuitries, we assessed reciprocal inhibition between antagonist forearm muscles and the recovery cycle of the H reflex in the flexor carpi radialis. Patients showed a significant decrease in the presynaptic phase of reciprocal inhibition reaching a minimum at the conditioning‐test interval of 20 msec and an abnormal facilitation of the test H reflex at the conditioning test interval of 40 to 60 msec. Throughout its time course (10–200 msec), the H reflex recovery cycle showed a more prominent facilitation in patients than in control subjects. To assess whether the observed pathophysiological abnormalities might have arisen from an abnormal motor cortical excitability, we examined the recovery cycle of the motor potentials evoked by paired transcranial magnetic stimuli. We found that the inhibitory mechanisms controlling motor cortical excitability were normal. An interpretation of the spinal cord abnormalities is that the intrinsically normal but deafferentated motor cortex in Huntington's disease partly loses its inhibitory control, thus disinhibiting spinal cord circuitry. Our findings from paired transcranial magnetic stimulation suggest that cortical motor areas are not hyperexcitable in Huntington's disease. Hence, the postulated thalamocortical overactivity in experimental models of Huntington's disease needs to be reappraised.