Abstract
Introduction
Somatosensory evoked potential (SSEP) monitoring allows for assessment of the spinal cord and susceptible structures during complex spinal surgery. It is well validated for the detection of potential neurological injury but little is known of surgeon's responses to an abnormal trace and its effect on neurological outcome. We aimed to investigate this in spinal deformity patients who are particularly vulnerable during their corrective surgery.
Methods
Our institutional neurophysiology database was analysed between 1st October 2005 and 31st March 2010. Monitoring was performed by a team of trained neurophysiology technicians who were separate from the surgical team. A significant trace was defined as a 50% reduction in trace amplitude or a 10% increase in signal latency. Patients suffering a significant trace event were examined post-operatively by a Consultant Neurologist who was separate from the surgical team.
Results
2386 consecutive operations (F:1719, M:667 median age 16 yrs) were performed in the time period and 72 operations reported a significant trace event (‘red alert’). From these cases 47 (65%) had a clearly documented intervention by the surgeon and 7 patients overall suffered a lasting neurological deficit (0.3%). The most common timing events were during instrumentation (50%) and during correction/distraction (16%). Most common responses were optimisation of patient/monitoring set-up (23%) and adjustment of metalwork (22%). There were 18 wake-up tests performed. We found SSEP monitoring to have a sensitivity of 100%, specificity 97.4%, positive predictive value 14% and negative predictive value 100%. A Chi-square test (p=0.016) was significant suggesting intervention had a beneficial effect on neurological outcome.
Conclusion
We would advocate the use of SSEP monitoring in all patients undergoing spinal deformity surgery. These patients tend to be young, neurologically intact pre-operatively and are particularly vulnerable to the large corrective forces their surgery requires.
