Transcranial magnetic stimulation (TMS) has come to be widely used to evaluate the CNS since the first report on the use of TMS in humans by Barker et al 1 in 1985. Depending on the frequency, intensity, and duration of stimulation, trains of repetitive TMS (rTMS) can transiently block or inhibit the function of a cortical region.It has been suggested that rTMS has therapeutic potential for the treatment of Parkinson's disease2 3 and psychiatric disorders.4 To apply rTMS as a clinical tool, an evaluation of the safety margins during the stimulation is required.

A 56 year old woman was admitted to Hokkaido University Medical Hospital on 6 October 1999 for treatment of involuntary movement of the trunk and lower limbs that had persisted for 8 years. In 1991, the patient had a spinal cord injury at thoracic and lumbar levels and a shearing fracture at the level of L1/L2. At that time, neurological examination disclosed paresis of the lower limbs, and the patient underwent a posterior fixation. Involuntary movement in her left thigh began a few months after the injury. In 1997, the involuntary movement became worse and had spread from the trunk to both limbs.

Examination using a surface EMG showed that the involuntary movement consisted of an elevation of the pelvis and a flexion and rotation of the trunk via the bilateral rectus abdominis, obliquus externus abdominis, and obliquus internus abdominis. Extension of …