Management Principles in a Case of True-positive Loss of Neuromonitoring Signals during Scoliosis Surgery: A Case...

Multimodal intraoperative neuromonitoring (IOM) is essential in scoliosis surgery. This is affected by misplaced instrumentation, cord trauma, hemodynamic instability, and anesthesia. We present an irreversible loss of IOM without identifiable intra-operative cause to highlight its occurrence and discuss post-operative investigations and management.

A 14-year-old girl with adolescent idiopathic scoliosis, no co-morbidities, and normal spinal magnetic resonance imaging (MRI) underwent posterior spinal fusion. During screw placement, bilateral motor evoked potentials (MEPs) and right somatosensory evoked potentials (SSEPs) were lost in the legs. All screws were removed with no evidence of cortical breach. Left leg responses gradually improved, but there was no recovery of right leg SSEPs or MEPs. Subsequently, the procedure was abandoned. The patient had reduced right leg strength (3/5) and sensation with the left leg was normal. Immediate post-operative spinal MRI identified no abnormality. Computed tomography (CT) showed no cortical breach with satisfactory pedicle screw tracts. Repeat MRI (day 7) showed high T2-signal within the cord at T11 indicating ischemia. Gradual neurological recovery occurred and on day 15, repeat neurophysiology found reproducible SSEPs and MagStim MEPs. The patient underwent revision posterior fusion with single rod correction without complication and IOM was maintained. By day 24, the patient had 5/5 power and normal sensation in both legs. Good scoliosis correction was achieved and maintained at 3-year follow-up.

This patient represents a vascular event affecting the lower spinal cord and highlights the role of sequential imaging and pre-operative neurophysiology including MagStim in deciding when to proceed with revision surgery while reducing risk using conservative techniques.