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Quantification of lumbar nerve root decompression using somatosensory-evoked potentials
P H Castello1, H M Place, D E Hemler
1Orthopedic Service, Fitzsimons Army Medical Center, Aurora, CO 80045-5001, USA.
Journal of Spinal Disorders
|December 1, 1995
Summary
Somatosensory-evoked potentials (SSEP) monitoring during lumbar surgery for herniated nucleus pulposus (HNP) showed no significant changes overall. However, bony decompression significantly reduced latency in patients with lateral recess stenosis (LRS).
Area of Science:
- Neurosurgery
- Spinal Surgery
- Neurology
Background:
- Acute lumbar herniated nucleus pulposus (HNP) is a common cause of nerve root compression.
- Intraoperative somatosensory-evoked potentials (SSEP) are used to monitor neural function during spinal surgery.
- The effectiveness of different surgical approaches in decompressing neural structures requires further investigation.
Purpose of the Study:
- To evaluate the impact of diskectomy versus bony decompression on SSEP parameters in patients with lumbar HNP.
- To assess SSEP changes specifically in patients with co-existing lateral recess stenosis (LRS).
Main Methods:
- Prospective collection of SSEP data in patients undergoing open limited diskectomy, hemilaminotomy, and partial foraminotomy for acute HNP.
- Randomization of the surgical sequence (diskectomy first vs. bony decompression first).
- Blind interpretation of SSEP tracings, comparing post-operative data to baseline for latency and amplitude changes.
Main Results:
- No statistically significant differences in SSEP latency or amplitude changes were observed between diskectomy and bony decompression in the overall patient cohort.
- A statistically significant reduction in SSEP latency (average -2.05 ms) was noted after bony decompression compared to diskectomy (-0.62 ms) in the subgroup of six patients with LRS.
- These findings suggest that diskectomy alone may be insufficient for adequate nerve root decompression in cases of underlying LRS.
Conclusions:
- While overall SSEP changes were not significant, bony decompression provided a more pronounced latency reduction in patients with LRS.
- Minimally invasive techniques focusing solely on the disc may be inadequate for patients with both HNP and LRS.
- SSEP monitoring can help differentiate the neurophysiological effects of diskectomy versus bony decompression, particularly in complex cases involving LRS.