[Evaluation of cord functions in patients with cervical radiculomyelopathy using cortical and spinal somatosensory...

It is desirable for neurosurgeons to be able to evaluate cord functions. To assess electrophysiologically functional status of spinal cord, cortical and spinal somatosensory evoked potentials (SEP) were studied in 33 patients with cervical radiculomyelopathy; 11 cases of cervical spondylosis, 11 cases of OPLL, 3 cases of narrow canal, 2 cases of narrow canal with OPLL, 3 cases of intradural extramedullary tumor, 2 cases of intramedullary tumor and one case of traumatic cervical cord injury. Before the operation cortical SEP was recorded from post-Rolandic area by the median nerve stimulation. Spinal SEP was recorded from the dorsal surface of the cord after partial and complete laminectomy, or before and after tumor removal.

Cortical SEP showed abnormalities in 45% of the cases, whose abnormalities were disappearance of the early components such as P1N1 wave, P1 to P2 complex or P1 to P3 complex and delay of the peak latency. Spinal SEP showed abnormalities in 42% of the cases, and the abnormal patterns were divided into 3 groups as follows: Type 1: Slightly abnormal, P1 and N1 waves are well recorded, whereas the P2 wave is absent or markedly suppressed in the amplitude. Type 2: Moderately abnormal, the P2 wave is flat and in addition the N1 wave is diminished in the amplitude. Type 3: Severely abnormal, only the P1 wave is recorded and the N1 to P2 complex is absent. Type 1 was obtained from 3 patients, type 2 from 9 patients, and type 3 from 2 patients. Cortical and spinal SEP were closely related to deep sensations, and cortical SEP was relatively correlated with superficial sensations. There were no differences of spinal SEP in most of the cases between partial and complete laminectomy. In intradural extramedullary tumor, however, good spinal SEP was recorded in collapsed cord after the tumor removal. Clinical symptoms were improved postoperatively in 80% of patients with both normal cortical and spinal SEP. It is concluded that cortical and spinal SEP are useful for prognostic value in patients with cervical radiculomyelopathy.