J Korean Neurosurg Soc.  2021 Mar;64(2):143-150. 10.3340/jkns.2020.0124.

Intraoperative Neurophysiology Monitoring for Spinal Dysraphism

• Kim K

• KMID: 2513847
• DOI: http://doi.org/10.3340/jkns.2020.0124

Abstract

Spinal dysraphism often causes neurological impairment from direct involvement of lesions or from cord tethering. The conus medullaris and lumbosacral roots are most vulnerable. Surgical intervention such as untethering surgery is indicated to minimize or prevent further neurological deficits. Because untethering surgery itself imposes risk of neural injury, intraoperative neurophysiological monitoring (IONM) is indicated to help surgeons to be guided during surgery and to improve functional outcome. Monitoring of electromyography (EMG), motor evoked potential, and bulbocavernosus reflex (BCR) is essential modalities in IONM for untethering. Sensory evoked potential can be also employed to further interpretation. In specific, free-running EMG and triggered EMG is of most utility to identify lumbosacral roots within the field of surgery and filum terminale or non-functioning cord can be also confirmed by absence of responses at higher intensity of stimulation. The sacral nervous system should be vigilantly monitored as pathophysiology of tethered cord syndrome affects the sacral function most and earliest. BCR monitoring can be readily applicable for sacral monitoring and has been shown to be useful for prediction of postoperative sacral dysfunction. Further research is guaranteed because current IONM methodology in spinal dysraphism is still deficient of quantitative and objective evaluation and fails to directly measure the sacral autonomic nervous system.

Keyword

Monitoring, Intraoperative; Spinal dysraphism; Neural tube defect; Surgery

Figure

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  Fig. 1. Muscles selected to monitor electromyography and motor evoked potential, in front (A) and rear (B) view. Vastus medialis, tibialis anterior, abductor hallucis, gastrocnemius, and external anal sphincter was installed with subdermal needle electrodes.

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  Fig. 2. Motor evoked potentials and free-running electromyography monitored during untethering surgery.

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  Fig. 3. Sensory evoked potentials from posterior tibial nerve monitored during untethering surgery.

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  Fig. 4. Bulbocavernosus reflex monitored during untethering surgery.

Reference

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