Sensitivity of spinal cord monitoring to intraoperative events

Intraoperative somatosensory evoked potentials in 50 patients were reviewed; each waveform was correlated with intraoperative surgical events and conditions. Twenty-two patients maintained reproducible waveforms and awoke without neurological deficit. Two patients had random waveform changes not correlated with a surgical event and awoke without deficit. Twelve patients showed waveform changes temporally related to circumstances that might endanger cord function; two of these awoke with transient neurological abnormality. Satisfactory waveforms were not obtained from 14 patients. Somatosensory evoked potential monitoring in scoliosis surgery appears to be sensitive, but may not be sufficiently specific; waveform changes do not necessarily indicate objective neurological damage.