Rare true-positive outcome of spinal cord monitoring in patients under age 4 years

Background context: Intraoperative monitoring (IOM) is becoming an essential component in spinal surgery, but there are many different viewpoints about it in patients under age 4 years.

Purpose: This study aims to report some IOM features in children under age 4 years.

Design/setting: This is a retrospective cases study.

Patient sample: A total of 37 children (35.76 months±1.47) and 120 patients with adolescent idiopathic scoliosis (AIS, 14.2 years) were recruited between September 2012 and December 2014.

Outcome measures: Relevant monitoring changes were identified as transcranial motor evoked potentials (MEP) or somatosensory evoked potentials (SEP) loss associated with high-risk surgical maneuvers.

Methods: Motor evoked potential, SEP, and free-run electromyography (free-run EMG) were used for IOM. The IOM parameters (amplitude, latency, and waveform) and monitoring outcomes (signal changes, true positive, and false positive) were mainly analyzed in the patients under age 4 years.

Results: All young patients presented stable MEP (90.6 µV±20.3) and SEP (1.01 µV±0.3) baseline. The baseline success rate (100%) was the same as that in patients with AIS; however, the MEP amplitude of young patients was significantly lower than that of patients with AIS (90.6 µV±20.3 vs. 312.1 µV±25.2, n=120; **p<.01) under the same stimulus parameters. Moreover, children under age 4 years have more monitoring changes (18.9%, 7 of 37), but true-positive findings are rare (0%) in our population.

Conclusions: Intraoperative monitoring baseline can be obtained satisfactorily in children under age 4 years, but true-positive findings are rare; meanwhile, low MEP amplitude and poor waveforms are common.