Clinical utility of magnetic corticospinal tract stimulation at the foramen magnum level

Abstract

We applied magnetic stimulation of the corticospinal tract at the foramen magnum level to 19 patients with various neurological disorders. Results were consistent with our previous speculation that activation occurs at the foramen magnum level. This method was clinically useful for the following conditions. (1) Detection of subclinical lesion: one patient who had transient ischemic attack that caused no clinical symptoms at examination was shown to have dysfunction of the corticospinal tract. (2) Multiple lesions: our method disclosed at least one lesion above and below the foramen magnum in two patients with multiple sclerosis. (3) Unmasking of dysfunction of the corticospinal tract masked by peripheral neuropathy: magnetic stimulation showed conduction delay in the corticospinal tract in two patients in whom no pyramidal signs were evident because of muscular atrophy due to neuropathy. One patient had multiple sclerosis and chronic inflammatory demyelinating polyradiculoneuropathy, the other had degenerative ataxia and neuropathy. (4) Association of disorders: conduction delay rostral to the foramen magnum, which should not occur in patients with only cervical myelopathy, was shown in a patient with cervical myeloradiculopathy and amyotrophic lateral sclerosis. We conclude that this magnetic stimulation method which is less painful than electrical stimulation has extensive clinical usefulness.