Epileptic seizures triggered directly by focal transcranial magnetic stimulation.

Focal, secondarily generalizing, epileptic seizures were released by magnetic stimulation in a patient with focal epilepsy. The stimulation induced seizures had a similar clinical appearance to the patient's spontaneous seizures. They were released exclusively by an angulated "figure-of-8" coil which stimulates the brain more focally as compared to the commonly used flat round coil. The epileptic focus could be located in the left frontal cortex by electroencephalographic recordings, by magnetic resonance and by positron emission tomography imaging. Functional assessment of the motor system by transcranial magnetic stimulation (TMS) disclosed markedly prolonged electrical silence of contralesional electromyographic activity following the early excitation. This is the first EMG-documented demonstration of a focal motor seizure directly triggered by magnetic brain stimulation.