Intraoperative neurophysiologic spinal cord monitoring in thoracolumbar burst fractures

Abstract

Study design: Clinical prospective cohort study in academic tertiary setting.

Objective: Evaluate intraoperative neurophysiologic monitoring of the spinal cord in patients with thoracolumbar burst fractures.

Summary of background data: The majority of clinical studies using intraoperative neurophysiologic monitoring in spinal trauma focus exclusively on somatosensory-evoked potentials (SSEP), and there are no specific article on the use of transcranial motor-evoked potentials (TcMEP), and stimulated electromyography (SEMG) by direct stimulation of the pedicular screws in thoracolumbar burst type fractures. In addition, controversy regarding the relation between spinal cord decompression and improvement in spinal cord function in such patients remains.

Methods: Eighteen patients with thoracolumbar burst type fractures (<3 weeks) who underwent indirect posterior spinal cord decompression was carried out from 2002 to 2006. Patients were monitored intraoperatively by SSEP, TcMEP, and SEMG. Findings that suggested worsening of spinal cord function were as follows: reduction in SSEP amplitude greater than 50% or increased latency time of 10%; and increased TcMEP of 100 V. Signs of improvement were 20% increase in SSEP amplitude and 20% decrease in TcMEP stimuli intensity. Four (22%) patients presented neurologic deficit. The mean American Spinal Injury Association (1993) score for motor function was 99+/-29 (range, 90-100). The mean American Spinal Injury Association (1993) score for sensory function was 111+/-32 (range, 107-112).

Results: There were no significant changes in the spinal cord function during the surgical procedure, although a decrease in the mean latency could be observed after spinal cord decompression (43.21x40.86; P<0.01). Two screws triggered SEMG responses and were replaced. All cases were true negatives.

Conclusion: No significant changes in spinal cord function (to better or worse) were found in the current series after indirect spinal cord decompression through a posterior approach in patients with mild or no neurologic deficits. Further studies with larger series of patients presenting severe neurologic deficits are necessary to better establish these findings.