Efficacy of multimodality spinal cord monitoring during surgery for neuromuscular scoliosis

Study Design. This study determinad the relative efficacy of somatosensory-evoked potentials and motor-evoked potentials in monitoring spinal cord function during surgery for patients with idiopathic versus neuromuscular scoliosis. Objectives. To determine whether patients with idiopathic versus neuromuecular scoliosis demonstrate significantly different samatosensory-evoked potentiate and motor-evoked potentials recorded during surgsry. Summary of Background Data. Ashkenaze et al (1993) end others have reported that cortical somatosensory-evoked potentials are unreliable when used to monitor spinal cord function in patients with neuromuscular scoliosis. It was recommended that other neuro-physiologic tests be used. Methods. Somatosensory-evoked potentials and motor-evoked potentials were recorded from two groups of patients: Those with idiopathic scoliosis and those with neuromuscular scoliosis. Somatosensory-evoked potentials were obtained before and during surgery. Motor-evoked potentials were obtained during surgery. Normal variability, as indicated from idiopathic scoliotic results, was compared with data obtained from patients with neuromuscular scoliosis. Motor-evoked potentials and somatosensory-evoked potentials were obtained sequuntiatly during the duration of surgery. Results. Single-channel cortical somatosensory-evoked potentials demonstrated a 27% positive rate, which was consistent with results (28%) from Ashkenaze et al. The use of multiple recording sites for the somalosorsory-evoked potentials and the addition of motor-evoked potential procedures indicated that a reliable response could be obtained in more than 96% of the patients. It also was found that cortical somatosensory-evoked potentials were more affected by anesthetic agents when recorded from patients with neuromuscular scoliosis compared with patients with idiopathic scoliosis. Conclusions. Single-channel cortical somatosensory-evoked potentials demonstrated a high level of unreliability, which reduced their clinical effectiveness. However, by using multiple recording sites with the somatosensory-evoked potentials and by administering motor-evokad potential procedures, it was possible to monitor spinal cord function in neuromuscular patients and avoid postoperative neurologic deficitis.