Evoked electrospinogram in spinal cord and peripheral nerve disorders

Abstract

Spinal cord evoked potentials were studied by means of intrathecal application in 80 patients with various spinal cord and peripheral nerve disorders. The segmental spinal cord potentials are normal in acute motor polyneuropathy, generalized anterior horn cell disease and in discrete lesions of dorso-lumbar segments. The 1st component of the segmental response is delayed, reduced and sometimes dispersed or lost in chronic sensory-motor polyneuropathy and in hereditary spinocerebellar degeneration. The reduction in amplitude is also present in multiple sclerosis with clinical signs of dorsal funiculus involvement. In compressive lesions of the cauda-conus, recordings of lower thoracic intervertebral level show that the segmental responses are delayed with marked amplitude reduction. The potentials recorded from lumbo-sacral segments show a greater amplitude of the 2nd component proportionally to the 1st as the duration of 2nd component is longer in spastic paraplegia regardless of its etiology. The cervical tractus response is markedly slowed with a reduction of amplitude or is often absent in chronic polyneuropathy, spinocerebellar degeneration and in multiple sclerosis. The primary sensory neurons lying both in periphery and in the dorsal column are probably responsible for the segmental evoked potentials especially for the 1st component. The late slow component is related to the activation of interneurons situated within the segmental gray matter and segmental collaterals of the dorsal root fibers carrying impulses to those cells. Cervical tractus responses are mostly formed by the dorsal column fibers and their physiological action on demyelination is similar to that of the peripheral nerves.