Impact of multimodal intraoperative monitoring during surgery for spine deformity and potential risk factors for neurological monitoring changes

Abstract

Study design: Retrospective review.

Objective: To evaluate the efficacy of multimodal intraoperative neuromonitoring for predicting iatrogenic neurological injury during surgical correction of a spine deformity and evaluate the potential risk factors for neurological monitoring changes.

Summary of background data: Single modal intraoperative neuromonitoring is insufficient to predict neurological injury during surgical correction of spine deformity. Multimodal monitoring can provide more accuracy. Some risk factors were reported to be correlated with high rates of neurological deficits during scoliosis correction. But few studies have reported on the risk factors for neurological monitoring changes (NMCs).

Methods: The records of 176 consecutive patients who underwent surgery for the treatment of spinal deformities were reviewed. The patients were monitored using transcranial electric motor-evoked potential (MEP) and/or somatosensory-evoked potential (SEP). Alterations with the MEP wave amplitude decreasing more than 75% and SEP amplitude decreasing more than 50%, as compared with the baseline, were diagnosed as positive changes. Risk factors related to NMCs were evaluated, in light of preoperative neurological deficits, comorbidity of spinal cord deformity, procedure of osteotomy, main curve Cobb angle, and a diagnosis of kyphosis.

Results: Combined MEP/SEP monitoring was successfully achieved in 175 of 176 cases. Eleven cases were presented with true NMCs according to MEPs. One patient had an irreversible neurological deficit and 4 patients had transient neurological deficits after waking up from the operation. SEP lagged MEP for an average of 15 minutes when both were presented with positive changes. The sensitivity and specificity of MEP were 91.7% and 98.8%, respectively. Solo SEP were 50% and 95.2%. Combined MEP and SEP were 92.9% and 99.4%. The procedure of osteotomy, curve Cobb angle more than 90 degrees, and preoperative kyphosis were correlated with a higher incidence of NMCs.

Conclusions: Multimodal intraoperative monitoring provides higher sensitivity for monitoring during spine deformity surgery and can predict events of neurological injury. The detection of NMCs and adjustment of surgical strategy may prevent irreversible neurological deficits. The possible risk factors for NMCs during spine deformity surgery include an osteotomy procedure, kyphosis correction, and preoperative Cobb angle more than 90 degrees.