Supplementary motor seizures: clinical and electroencephalographic findings.

The clinical and EEG features of 11 patients with seizures arising in the supplementary motor area (SMA) were reviewed. All patients underwent prolonged EEG with simultaneous video recording. Three patients had recordings and electrical stimulation of the SMA using subdural electrode arrays. All patients had preservation of consciousness during the seizure unless it became secondarily generalized. Tonic posturing of the extremities was present in all patients, and in seven it was present bilaterally. Adversive movements were not seen unless the seizure became secondarily generalized. Interictal and/or ictal abnormalities were present at or adjacent to the midline in ten patients. Seizures arising from the supplementary motor region are clinically distinct, and the diagnosis can almost always be verified with prolonged EEG/video recording.