LEG PARESTHESIAS INDUCED BY MAGNETIC BRAIN-STIMULATION IN PATIENTS WITH THORACIC SPINAL-CORD INJURY

We studied the induction of leg paresthesias by magnetic stimulation of the brain in seven patients with thoracic T9-12 spinal cord injury and in four normal volunteers by delivering transcranial magnetic stimulation over scalp positions 1 cm apart with a Cadwell MES-10 magnetic stimulator and an 8-shaped magnetic coil at 100% stimulus intensity. We asked subjects to report sensations felt after each stimulus. In all normal subjects, magnetic stimulation evoked sensations described as tingling or a wave descending along the leg, usually accompanied by EMG responses in leg muscles. In three of the seven patients, stimulation evoked sensations of tingling, numbness, touch, or a wave descending along the leg, lasting up to 10 seconds and referred to different parts of the legs and toes. In the patients, sensations were felt more distally the closer the site of stimulation was to the midline. Patients with leg paresthesias had less motor reorganization in abdominal muscles than those without paresthesias. These findings suggest that portions of the cortical representation areas for body parts deafferented by a complete spinal cord injury can remain related to those body parts for up to several years. A central origin of these paresthesias is probable.