Multimodal Intraoperative Neurophysiological Monitoring in Spine Surgeries: The Experience at a Spine Centre through Years

Abstract

Study design: Retrospective observational study.

Purpose: To share our experience of multimodal intraoperative neurophysiological monitoring (IONM) used in Sakra World Hospital, Bengaluru in various spine surgeries.

Overview of literature: The development of new onset postoperative neurological deficits can be completely avoided. In order to avoid these, IONM has become a standard of care in recent times for early detection and manipulation of the surgical procedure to prevent postoperative neurological deficits.

Methods: This retrospective study was performed on 408 patients who had undergone spine surgeries with IONM during April 2014 to March 2020 at a single center. The operative report, anesthesia record, and IONM were reviewed. All the patients were reassessed for postoperative neurological deficits in the postoperative period and followed up based on the intraoperative findings and neurological deficits for 4 weeks. Signal changes in IONM were reviewed, and the obtained results were further categorized into true positive, true negative, false positive, or false negative. If changes were observed during the IONM, the patients were managed as per the algorithm.

Results: Of the 408 patients being monitored continuously during the intraoperative period, 38 showed changes in recordings, 28 developed postoperative neurological deficits, and one developed neurological deficit without any change in the IONM. Nine patients had transient neurological deficits, and the other 20 had permanent neurological deficits. Overall, the multimodal IONM used in our study had a sensitivity of 96.6%, specificity of 97.4%, a positive predictive value of 73.7%, and a negative predictive value of 99.7%.

Conclusions: Use of decision algorithm and multimodal neuromonitoring consisting of motor evoked potentials, somatosensory evoked potentials, and electromyography complement each other in the detection of neurological injury during the course the surgery, improve intraoperative care, and prevent further damage and morbidity in patients.

Keywords: Electromyogram; Intraoperative neurophysiological monitoring; Motor evoked potentials; Somatosensory evoked potentials; Spine.

Fig. 1

Decision algorithm during change in evoked potentials observed during the study.

Fig. 2

During a case of C3 to C7 laminectomy and lateral mass fusion, (A) a significant fall in the TcMEPs (arrows) during the surgery was noticed, following which wake-up test was performed to confirm the change in TcMEPs. (B) Laminectomy was extended after confirmation of neurological deficit. TcMEPs recovered back to normal amplitude (arrows) and patient developed transient neurological deficit which recovered within 24 hours. TcMEPs, transcranial electrical motor evoked potentials.

Fig. 3

(A, B) A case of intramedullary tumor at the level of D7. A fall in the motor evoked potentials were noticed during the surgery in the tibialis anterior and abductor hallucis longus muscle groups bilaterally (arrows pointing towards the affected waves), which required a halt in the procedure. Paraparesis was observed in the postoperative period.