The role of upper limb somatosensory evoked potentials in the management of cervical spondylotic myelopathy: preliminary data.

We studied upper limb somatosensory evoked potentials (SEPs) in 11 patients with MRI and clinical evidence of cervical spondylotic myelopathy (CSM), before and after cervical open-door laminoplasty. SEP studies before surgery revealed two main types of abnormality, the first characterized by the isolated loss of the spinal N13 response, reflecting the dysfunction of dorsal horn cervical cells in 4 patients. The second combined abnormalities of both spinal N13 and scalp far-field P14 potential, suggesting the involvement of both dorsal horn cells and dorsal columns at the cervical level in 7 patients. After surgery, N13 recovered in 9 patients, while P14 abnormalities remained unchanged. Clinical recovery, evaluated by means of the Japanese Orthopaedic Association (JOA) disability scale, was accompanied by SEP improvement. Moreover, this improvement was more pronounced in patients with isolated loss of the N13 than in patients with combined abnormalities of the N13 and scalp P14 response. Our data strongly suggest that upper limb SEPs can be useful in monitoring the effectiveness of surgery, as well as in selecting before surgery patients who are likely to have a better postsurgical outcome.