Intraoperative Neuro-Monitoring During Spondylolisthesis Surgery

Direct nerve root stimulation-L5

Threshold (mA)

Normal root threshold

First stimulation medial to pedicle

5–13

Lateral exposure and decompression of L5 root

3–8

Discectomy, sacral dome osteotomy

3–8

Reduction and inter-body graft placement

3–8

After compression

2–7

Fig. 27.1

After completion of L5 nerve root decompression, a stimulation probe directly stimulates nerve root to establish triggering threshold

Conclusions

IONM is extremely valuable in the prevention of neurological injury during spine procedures. It is important to understand the spectrum of modalities available for neuro-monitoring—including SSEPs, MEPs, sEMG, and tEMG—and their limitations. With spondylolisthesis, utilizing all modalities including tEMG and direct nerve root stimulation helps maximize the diagnostic value of IOM during spinal procedures and mitigating the risk for neurologic injury.

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