What is the role of somatosensory evoked potentials (SEPs) in the monitoring of the spinal cord during surgery?

Updated: Aug 20, 2019
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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SEP monitoring is used widely to assess integrity of the spinal cord during surgery in which the spinal cord is manipulated. SEPs are used most often during scoliosis correction. Ischemia of ascending somatosensory pathways produces a drop in amplitude or loss of waveforms, thus warning the surgeon in time to take corrective action. Ischemic changes are usually widespread; rarely, motor function is lost when somatosensory pathways have not been affected.

The use of intraoperative neuromonitoring, especially SSEPs, MEPs and EMGs, during pediatric scoliosis repair has become commonplace to reduce the risk of potentially devastating postoperative neurologic deficits. [5]

The increased amplitude, particularly in cortical SSEPs (N20/P25), detected specifically during steady-state hypothermia seems to support the clinical use in monitoring the brain function; this is not only during cardiac surgery with cardiopulmonary bypass but also in other settings, such as therapeutic hypothermia procedures in an ICU. [6]

Other spinal procedures in which SEP monitoring is used include reduction of vertebral fractures and other vertebral injuries and spinal cord tumor surgery. Conduction abnormalities that selectively abolish the silent periods can distinguish between hydromyelia (a physiologically dilated central canal) and space-occupying syringomyelia.

Researchers evaluated the diagnostic accuracy of SSEP monitoring during scoliosis fusion and found SSEP to be a highly sensitive and specific test. Data also showed that iatrogenic spinal cord injury resulting in new neurological deficits was 340 times more likely to have changes in SSEP compared to those without any new deficits. [7]

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