Motor and somatosensory evoked potentials in asymptomatic spondylotic cord compression.

To assess whether electrophysiological tests are of use in differentiating between patients with asymptomatic cervical stenosis and patients with clinical evidence of myelopathy, we studied motor evoked potentials (MEPs) to magnetic brain stimulation and somatosensory evoked potentials (SEPs) in patients with asymptomatic cervical cord compression and compared the results to healthy age-matched controls. The MEPs were normal in 23 of 25 patients and SEPs in 22 of 23 patients. Thus, MEPs and SEPs are normal in most cases of asymptomatic cervical stenosis. As previous studies have shown MEPs, and to a lesser extent SEPs, to be sensitive in the detection of spondylotic myelopathy, our data indicate that MEP and SEP may be clinically useful for differentiating patients with cervical stenosis who have myelopathy from those who have not.