Corticospinal excitability in patients with secondary dystonia due to focal lesions of the basal ganglia and thalamus.

Objective: To investigate the possible correlations between clinico-radiological features and pathophysiological mechanisms in patients with dystonia secondary to focal brain lesions. Methods: Single and paired-pulse transcranial magnetic stimulation was used to assess corticospinal excitability in 10 patients (4 females; mean age 61) and a group of normal controls. Active threshold, latency and amplitude of motor evoked potentials (MEPs), silent period (SP) duration and short-interval intracortical inhibition (SICI) were evaluated. Results: Patients with lesions involving the putamen and caudate presented with dystonic postures at rest. TMS assessment in these subjects showed increased MEP amplitude on the affected side and a bilateral decrease of SP duration and SICI. When the lesion spared the putamen and caudate, mainly involving the thalamus, the clinical picture was dominated by slow repetitive involuntary movements and tremor. In the affected side of these subjects the MEP amplitude was reduced and the MEP threshold was increased. Conclusions: When putamen and caudate were lesioned, the patients presented with dystonic postures at rest; furthermore the patients showed changes of corticospinal excitability in comparison to both healthy subjects and other dystonic patients. Significance: There are correlations between type of dystonia, site of the lesion and neurophysiological findings