Amplitude-reduction alert criteria and intervention during complex paediatric cervical spine surgery.

Objective: To determine the utility of widely used intraoperative neuromonitoring (IONM) alert criteria and intervention for predicting postoperative outcome following paediatric spinal surgery.

Methods: Retrospective analysis of somatosensory evoked potentials (SSEP) and motor evoked potentials (MEP) in consecutive cervical spine fixations. An intervention protocol followed amplitude-reductions in SSEPs (≥50 %) and/or MEPs (≥80 %). Alert breaches were reversed when SSEP/MEP amplitude was restored to > 50 %/20 % of baseline. Sensorimotor function was assessed preoperatively and 3-months postoperatively via the Modified McCormick Scale score (MMS). We explored associations between postoperative outcome, demographic/surgical and IONM variables.

Results: Forty-five procedures in 38 children (mean age:9 ± 4 years;55 % female) were monitored, 42 %of which breached alert criteria. Instrumentation (6/19,32 %) and hypotension (5/19,26 %) were common causes for alert and the majority (13/19,68 %) were reversed following intervention. There was an association between pre- and post-MMS and the type of breach (p = 0.002). All children with worse postoperative MMS (3/38,8%) had irreversible breaches.

Conclusions: IONM in this small sample accurately detected neurological injury. The majority of breaches reversed following an intervention protocol. Irreversible breaches frequently led to worse postoperative sensorimotor function.

Significance: An intervention protocol which reversed IONM alerts never resulted in postoperative worsening of sensorimotor function.