Superior sensitivity of motor over somatosensory evoked potentials in the diagnosis of cervical spondylotic myelopathy.

Myelopathy secondary to cervical spondylosis is often a difficult clinical diagnosis. Furthermore, with the introduction of magnetic resonance imaging (MRI) an increasing number of patients are identified with spondylotic cervical spinal cord compression. We analyzed the value of functional assessment of the spinal cord by motor and sensory evoked potentials (MEP and SEP) in the detection of myelopathy, with special emphasis on the correlation of clinical and electrophysiological findings. Fifty-one patients with at least some degree of spinal cord compression because of cervical spondylosis, as shown by MRI, were included in the study, grouped according to clinical symptoms. We found that patients who had no clinical symptoms whatsoever indicating myelopathy (they were referred to MRI examination mostly because of cervical radiculopathy), had in the large majority normal MEP and SEP findings. Patients with slight, unspecific and non-confirmative symptoms without pyramidal signs had mostly abnormal MEP but normal SEP findings. This points to the superior sensitivity of MEP over SEP in detecting myelopathy in its early stages. Patients with obvious clinical signs of myelopathy, including pyramidal signs had both abnormal MEP and SEP findings. Altogether these findings may help clinicians in interpreting MRI signs of cervical spinal cord compression.