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Lack of inhibitory interaction between somatosensory afferent inputs and intracortical inhibitory interneurons in focal hand dystonia
Author(s) -
SimonettaMoreau Marion,
Lourenço George,
Sangla Sophie,
Mazieres Leonor,
Vidailhet Marie,
Meunier Sabine
Publication year - 2006
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.20821
Subject(s) - somatosensory system , wrist , transcranial magnetic stimulation , neuroscience , silent period , psychology , inhibitory postsynaptic potential , dystonia , focal dystonia , motor cortex , tonic (physiology) , stimulation , physical medicine and rehabilitation , motor control , medicine , anatomy
We looked for an impaired interaction in the primary motor cortex between intracortical inhibitory circuits and circuits fed by somatosensory inputs in patients with writer's cramp. Short‐interval intracortical inhibition (sICI) to wrist extensor carpi radialis muscle (ECR) was conditioned by stimulation of antagonist muscle afferents and sICI to first dorsal interosseus (FDI) muscle by homotopic cutaneous afferents stimulation. sICI was assessed at rest and during a tonic contraction of the target muscle. Eighteen patients with writer's cramp (10 having a wrist dystonic posture in flexion during writing and 8 in extension) were compared to 14 control subjects. Peripheral inputs decreased sICI in control subjects. This decrease was lost in patients in both FDI and ECR, regardless of the wrist dystonic posture. By contrast, contraction‐induced depression of sICI appeared dependant on the dystonic status of the muscle: depression of sICI to ECR was abolished in patients with wrist dystonic posture in flexion, but not in patients with dystonic posture in extension, sICI even giving way to motor‐evoked potential facilitation. Loss of interaction between interneurons mediating sICI and peripheral inputs probably belongs to the initial abnormalities underlying dystonia. Lack of peripherally induced sICI modulation may oppose wrist and/or hand muscles synergies. © 2006 Movement Disorder Society