Background

Progressive scoliosis often requires deformity correction. Intraoperative neuromonitoring (IONM) using motor evoked potentials (MEP) and sensory evoked potentials (SEP) is the method of standard to evaluate the integrity of the spinal cord during the procedure. Thus, IONM may detect iatrogenic spinal cord injuries with excellent sensitivity. But there are multiple factors that influence the IONM results.

Objectives

Aim of the study was to identify origins of occurring IONM alarms.

Methods

A total of 54 operative procedures from 2014 to 2017 in 34 children and 18 adults (m:w = 17:35, age 16 +/- 5) were analyzed retrospectively. All patients suffered from scoliosis, underwent spinal deformity surgery and were monitored by MEP and SEP performance intraoperatively.

Anesthesia was generated with propofol, sufentanil and remifentanil. MEP alarms were defined as an amplitudal decrement > 90%. SEP alarms were defined as any extension of latency. According to our algorithm, alarms were categorized in 3 different origins: anestetical, surgical and technical.

Results

In 48 (88,9%) out of 54 procedures reliable MEP and SEP could be generated. 17 alarms were detected. 15 alarms (88,2%) were associated with anesthetic agents. 2 alarms (11,8%) had technical causes. None could be assigned to the surgical procedure.

Conclusion

IONM is state of the art to evaluate spinal cord integrity changes during deformity correction. Dosage and selection of anesthetic agents are the major causes of IONM alarms during scoliosis surgery.