Dissociation of early SEP components in unilateral traumatic section of the lower medulla.

Spinal and scalp early SEPs were recorded, using a noncephalic reference electrode, in a patient with a traumatic cervicomedullary lesion causing unilateral loss of position sense. Cervical N11 and N13 and scalp-recorded far-field P14 SEPs were clearly dissociated following stimulation of the affected side. The findings suggest that the P14 component is generated above the foramen magnum, whereas the cervical N13 has a spinal generator.