title: Abnormality of motor cortex excitability in peripherally induced dystonia.
abstract: It is widely accepted that peripheral trauma such as soft tissue injuries can trigger dystonia, although little is known about the underlying mechanism. Because peripheral injury only rarely appears to elicit dystonia, a predisposing vulnerability in cortical motor areas might play a role. Using single and paired-pulse pulse transcranial magnetic stimulation, we evaluated motor cortex excitability of a hand muscle in a patient with peripherally induced foot dystonia, in her brother with craniocervical dystonia, and in her unaffected sister, and compared their results to those from a group of normal subjects. In the patient with peripherally induced dystonia, we found a paradoxical intracortical facilitation at short interstimulus intervals of 3 and 5 milliseconds, at which regular intracortical inhibition (ICI) occurred in healthy subjects. These findings suggest that the foot dystonia may have been precipitated as the result of a preexisting abnormality of motor cortex excitability. Furthermore, the abnormality of ICI in her brother and sister indicates that altered motor excitability may be a hereditary predisposition. The study demonstrates that the paired-pulse technique is a useful tool to assess individual vulnerability, which can be particularly relevant when the causal association between trauma and dystonia is less evident.
authors.affiliation: Human Motor Control Section, National Institute of Neurological Disorders and Stroke NINDS, NIH, Bethesda, MD 20892-1428, USA.
authors.forename: Stephan
authors.initials: S
authors.lastname: Bohlhalter
authors.forename: Fidias E
authors.initials: FE
authors.lastname: Leon-Sarmiento
authors.forename: Mark
authors.initials: M
authors.lastname: Hallett
mesh_terms: D001143:Arousal / Q000502:physiology*; D004421:Dystonia / Q000175:diagnosis / Q000503:physiopathology* / Q000628:therapy; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006225:Hand / Q000294:innervation / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000503:physiopathology; D050781:Transcranial Magnetic Stimulation