Involvement of the motor cortex in pseudochoreoathetosis

The pathophysiological background of involuntary movements in pseudochoreoa thetosis is unclear. We therefore recorded in four patients with pseudochor eoathetosis and in six age-matched controls cortical activity with a whole- head magnetoencephalography (MEG) system and surface EMGs from hand muscles . Subjects performed the following tasks: 1) rest, and 2) constant finger s tretch during forearm elevation. controls additionally simulated pseudochor eoathetotic finger movements. During rest, the patients showed involuntary finger movements associated with excessive MEG-EMG coherence at frequencies between 6 and 20 Hz. whereas coherence in controls simulating pseudochoreo athetotic movements did not exceed noise level (P < 0.02). During finger st retch, MEG-EMG coherence in patients was similar to that of controls. Corti cal sources of MEG-EMG coherence in patients were localized in the contrala teral motor cortex. We conclude that pseudochoreoathetosis is associated wi th pathologically increased cortico-muscular coherence and thus differs, ne urophysiologically. from voluntarily simulated pseudochoreoathetotic moveme nts. The enhanced MEG-EMG coherence in pseudochoreoathetosis probably refle cts a pathologically strong motor cortical drive of spinal motorneurons aft er deafferentation. (C) 2001 Movement Disorder Society.