EFFICACY OF MULTIMODALITY SPINAL-CORD MONITORING DURING SURGERY FOR NEUROMUSCULAR SCOLIOSIS

Study Design. This study determined the relative efficacy of somatosen sory-evoked potentials and motor-evoked potentials in monitoring spina l cord function during surgery for patients with idiopathic versus neu romuscular scoliosis. Objectives. To determine whether patients with i diopathic versus neuromuscular scoliosis demonstrate significantly dif ferent somatosensory-evoked potentials and motor-evoked potentials rec orded during surgery. Summary of Background Data. Ashkenaze et al (199 3) and others have reported that cortical somatosensory-evoked potenti als are unreliable when used to monitor spinal cord function in patien ts with neuromuscular scoliosis. It was recommended that other neuroph ysiologic tests be used. Methods. Somatosensory-evoked potentials and motor-evoked potentials were recorded from two groups of patients: tho se with idiopathic scoliosis and those with neuromuscular scoliosis. S omatosensory-evoked potentials were obtained before and during surgery . Motor-evoked potentials were obtained during surgery. Normal variabi lity, as indicated from idiopathic scoliotic results, was compared wit h data obtained from patients with neuromuscular scoliosis. Motor-evok ed potentials and somatosensory-evoked potentials were obtained sequen tially during the duration of surgery. Results. Single-channel cortica l somatosensory-evoked potentials demonstrated a 27% positive rate, wh ich was consistent with results (28%) from Ashkenaze et al. The use of multiple recording sites for the somatosensory-evoked potentials and the addition of motor-evoked potential procedures indicated that a rel iable 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 neurom uscular scoliosis compared with patients with idiopathic scoliosis. Co nclusions. Single-channel cortical somatosensory-evoked potentials dem onstrated a high level of unreliability, which reduced their clinical effectiveness. However, by using multiple recording sites with the som atosensory-evoked potentials and by administering motor-evoked potenti al procedures, it was possible to monitor spinal cord function in neur omuscular patients and avoid postoperative neurologic deficits.