Somatosensory evoked potentials and magnetic resonance imaging in intraspinal neoplasms

Median and posterior tibial somatosensory evoked potentials (SEPs) were studied on 25 patients with pathologically proven intraspinal neoplasms, and the results were compared and correlated with the details of clinical examination and the information derived from magnetic resonance imaging (MR). MR was abnormal in all cases and in 23 of 25 (92%) demonstrated an intraspinal expansile lesion. SEP was abnormal in 19 of 25 patients (76%). Abnormal SEPs were found in 18 of 19 patients (94%) with cervical or thoracic neoplasms but only in 1 of 6 patients (16%) with the tumor in the thoracolumbar or lumbar region. SEP-MR correlation was significant (P less than 0.05) for thoracic intraspinal neoplasms where all 9 had an abnormal SEP showing a similar pattern of normal median and abnormal posterior tibial study. Clinically, all 7 patients with posterior column sensory deficits had abnormal SEP (100%). Abnormal SEPs were seen in 7 of 11 (63%) patients with spinothalamic deficits and in 4 of 8 (50%) of those with normal sensory examinations. Four of 9 patients (44%) with a normal neurological examination or an examination disclosing ambiguous results indistinguishable from a peripheral pathology had an abnormal SEP strongly suggesting a central sensory disorder. Comparison of preoperative and postoperative SEPs did not disclose useful prognostic information pertaining to the functional recovery.