Transcranial magnetic stimulation of the motor cortex in cervical spondylosis and spinal canal stenosis.

Abstract

This study investigated the clinical usefulness of motor evoked potentials and a silent period after motor evoked potentials produced by transcranial magnetic stimulation of the brain. The results were correlated with the clinical state of the patients with myelopathy, whereas no abnormality of the conduction time was observed in the patients with spinal canal stenosis. Magnetic stimulation has been widely used for examination of the descending excitatory motor pathways in the central nervous system, but little attention has been paid to cervical spondylosis and spinal canal stenosis. Motor evoked potentials were examined in 35 normal subjects, 67 patients with cervical spondylotic myelopathy, and 24 patients with spinal canal stenosis. Motor evoked potentials were evoked by transcranial brain stimulation during relaxation and during maximum voluntary contraction of the target muscle. The central motor conduction time was found to correlate with the clinical state of the myelopathy patients, whereas no abnormality of the conduction time was observed in the patients with spinal canal stenosis. During maximum voluntary contraction of the target muscle, a silent period was always observed after the motor evoked potentials in the normal subjects, and its duration was markedly shortened in the myelopathy patients. In cervical myelopathy patients, the central motor conduction time was correlated with clinical evaluation and the silent period was significantly shortened. These findings about duration of the central motor conduction time and the silent period might be a useful parameter of spinal pathology.