Hand dystonia secondary to cervical demyelinating lesion.

Dystonia is generally considered a disease of basal ganglia. We report two patients with definite MS who acutely developed hand dystonia and athetoid movements. In both patients: 1) dystonia was electrophysiologically demonstrated by lack of reciprocal inhibition between antagonistic forearm muscles; 2) SEP from median nerve stimulation showed delayed cervical N13 and absent frontal and parietal components; 3) the long latency response after stimulation of median nerve of the affected hand was absent or delayed; 4) MRI showed lesions in the posterolateral cervical spine but no involvement of basal ganglia and thalami. We think that, in these cases, dystonia and athetoid movements could be ascribed respectively to the involvement of descending pathways regulating reciprocal inhibition of motoneurons and to the involvement of large diameter afferents due to the demyelinating lesion at the cervical level.