Objective: Determine the incidence of abnormal somatosensory evoked potentials (SSEP) in patients with ‘at risk’ spinal cords undergoing anterior spinal deformity surgery.

Design: A retrospective chart and SSEP trace review of cases between 1982–2001.

Subjects: Patients undergoing elective anterior spinal deformity surgery were included. Excluded were those with inadequate SSEP monitoring or no pre-operative MRI scan.

Outcome measures: Paraparesis due to cord ischaemia based on an abnormal SSEP trace, i. e. > 50% decrease in SSEP baseline amplitude +/− > 10% increase in latency¹.

Results: Partial data was available for 1982–1990, thus analysis was based on cases between 1990–2001.871 patients underwent elective anterior spinal deformity surgery, 11% were ‘at risk cords’; 2% demonstrated intraoperative SSEP changes. Post operative paraparesis ws found in 0.6%. Intra-operative changes were significantly more common in ‘at risk cords’ (chi-squared test = 30.3, df = 2; p< 0.005). No statistical difference in the incidence of paraparesis in normal cords vs ‘at risk’ cords.

Conclusions: Post operative neurological deficit is rare in anterior spinal deformity surgery. Significant SSEP changes do occur with ligation of segmental vessels, implying cord ischaemia. Therefore, for the ‘at risk cord’, these patients should be considered for spinal cord monitoring and temporary clamping of segmental vessels prior to their division