Intraoperative Neurophysiological Monitoring (IONM): Lessons Learned from 32 Case Events in 2069 Spine Cases


Matthew Eager, M.D.1; Adam Shimer, M.D.
University of Virginia Medical Center
Department of Orthopedic Surgery
Charlottesville, Virginia

Faisal R. Jahangiri, M.D., CNIM, DABNM
Impulse Monitoring Inc.
Columbia, Maryland

Francis Shen, M.D.1; Vincent Arlet, M.D.1
University of Virginia Medical Center
Department of Neurosurgery
Charlottesville, Virginia

Intraoperative neurophysiological monitoring (IONM) is becoming the standard of care for many spinal surgeries, especially those with deformity correction and instrumentation. We reviewed 2069 spine cases with multimodality IONM including somatosensory evoked potentials (SSEP), transcranial electrical motor evoked potentials (TCeMEP), and spontaneous and triggered electromyography (s-EMG and t-EMG) in a University setting over a period of four years to examine perioperative clinical fi ndings when an IONM event was noted and to ascertain how IONM has affected our ability to avoid potential neurological injury during spine surgery.

We performed a retrospective analysis of cases from 2006 to 2010 to study the frequency and cause of intraoperative events detected via IONM and the clinical outcome of the patient. There were 32 cases (1.5%) with possible intraoperative events. There were 17 (53%) cases where IONM changes affected the course of the surgery and prevented possible postoperative neurological defi cits. Seven cases (41%) were due to deformity correction, fi ve (29%) due to hypotension, four (24%) due to patient positioning, and one (6%) due to a screw requiring repositioning. None of the 17 patients had postoperative motor or sensory defi cits.

There were four cases with false-positive IONM fi ndings due to correctible technical issues. Three cases required surgical revision due to pedicle screw malposition. In each case, s-EMGs failed to exhibit intraoperative changes but the patient presented with postoperative radiculopathy. We believe that the use of t-EMGs may have prevented these complications.

This review reinforces the importance of multimodality IONM for spinal surgery. The incidence of possible events in our series was 1.5%, and several likely postoperative neurologic defi cits were avoided by vintraoperative intervention.

Brian De La Torre