Causes of Intraoperative Neuromonitoring Events in Adult Spine Deformity Surgery: A Systematic Review

Introduction: Corrective spinal surgery in adult spinal deformity (ASD) is a common and relatively high risk procedure. Intraoperative neuromonitoring (IOMN) has become a standard practice in the detection and prevention of nerve damage and postoperative deficit. This systematic review identifies the leading causes of IONM alerts during ASD surgeries. While multicenter studies have addressed this inquiry, there have been no systematic reviews to date.

Methods: Following PRISMA guidelines, a literature search was performed in PubMed and Embase. Sources in languages other than English were not included, nor was unpublished research. Screening was performed by two independent investigators and conflicts were resolved by a third. Data extraction was performed independently by two investigators. Alert causes were grouped by equivalent terms used across different studies and binned into larger categories. Surgeon error/maneuver included corrective forces, hardware placement, osteotomy, direct contusion, and similar events. Changes in blood pressure/temperature included most of the other alert causes, with patient position, oxygenation, and anesthesia including most others.

Results: Inclusion criteria were studies on adult patients receiving ASD correction surgery using IONM with documented alert causes. 1,544 references were included in abstract review, 128 in full text review, and 16 studies qualified for data extraction. From those studies, there was a total of 3,945 adult patients with 299 IONM alerts. Surgical maneuver led the alert causes (258 alerts/86.3%), with signal loss most commonly occurring at correction or osteotomy (101/33.8% and 95/31.8% respectively). Pedicle screw placement caused 35 alerts (11.7%). Changes in temperature and blood pressure were the third largest category (34/11.4%).

Conclusion : The most frequent causes of IONM alerts in ASD surgery were surgical maneuvers such as correction, osteotomy, and pedicle screw placement. This information provides spine surgeons with a quantitative perspective on the causes of IONM changes and show that most occur at predictable times during ASD surgery.