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Surface electrode somatosensory-evoked potentials in spinal surgery: implications for indications and practice
S L Papastefanou1, L M Henderson, N J Smith
1Department of Orthopaedic Surgery, Middlesbrough General Hospital, Cleveland TS5 5AZ, UK. sotiris@doctors.org.uk
Spine
|October 3, 2000
Summary
This study on spinal cord monitoring found somatosensory-evoked potential (SEP) recording to be a reliable method for spinal surgery. Modified guidelines are suggested to improve the interpretation of intraoperative SEP changes and reduce unnecessary wake-up tests.
Area of Science:
- Neurosurgery
- Neurology
- Spinal Cord Monitoring
Background:
- Routine use of somatosensory-evoked potential (SEP) monitoring in spinal surgery is debated.
- A specific SEP recording method using scalp or high cervical electrodes was employed.
- The study aimed to evaluate this method's reliability and refine intraoperative protocols.
Purpose of the Study:
- Assess the reliability of SEP monitoring in major spinal operations.
- Establish criteria for intraoperative corrective actions based on SEP changes.
- Redefine the necessity and application of the wake-up test during surgery.
Main Methods:
- Retrospective analysis of 442 major spinal operations with spinal cord monitoring (1982-1992).
- Review of SEP recordings and patient outcomes.
- Application of American EEG Society definitions to classify SEP responses.
Main Results:
- 23 technical failures (5.2%) occurred, primarily in patients with severe preoperative neurological deficits.
- Significant intraoperative SEP changes were observed in 16.7% of procedures.
- 100% sensitivity and 85.33% specificity were achieved; no false-negatives were recorded.
- Wake-up tests were performed in only 5% of cases due to persistent SEP suppression.
Conclusions:
- Modified guidelines for intraoperative SEP monitoring in spinal surgery are necessary.
- Focus should be on causative analysis of abnormal responses rather than the term "false-positive".
- SEP monitoring effectively alerted surgeons to potential spinal cord dysfunction, guiding corrective actions in an additional 9.78% of patients.