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Changes in cortical inhibition during task‐specific contractions in primary writing tremor patients
Author(s) -
Ljubisavljevic Milos,
Kacar Aleksandra,
Milanovic Sladjan,
Svetel Marina,
Kostic Vladimir S.
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.20807
Subject(s) - transcranial magnetic stimulation , silent period , pathophysiology , stimulation , medicine , inhibitory postsynaptic potential , psychology , contraction (grammar) , focal dystonia , inhibitory control , neuroscience , dystonia , endocrinology , cognition
Primary writing tremor (PWT) is a rare disease of unknown pathophysiology. We studied changes in silent period (SP) duration, after transcranial magnetic stimulation (TMS), set at 20% above the motor threshold in 6 PWT patients and 7 healthy control subjects. SP duration was tested during a task‐specific act, i.e., writing that induced tremor in all patients in the affected hand (Wr); nonspecific voluntary contraction of intensity, matching that developed during writing (VCWr); and during near maximal voluntary contraction (VCNmax). There were no differences in SP duration during Wr and VCWr contraction on the right affected side or between sides in both PWT patients and control subjects, nor between the groups. However, during VCNmax, SP significantly shortened on both sides in PWT patients, whereas there were no changes in control subjects. Although it appears that inhibitory mechanism are not directly involved in the generation of the tremulous activity, the shortening of SP indicates that central inhibitory mechanisms are affected in PWT patients. Therefore, whereas the underlying pathophysiological mechanisms in PWT and writer's cramp may share common features, the results indicate that PWT is not a variant of focal task‐specific dystonia but rather a separate nosological entity. © 2006 Movement Disorder Society