Surgical Nuances for Safeguarding Anomalous Vertebral Artery during Atlantoaxial/Occipital-C2 Fixation in Complex CV...

Nearly one-fifth of craniovertebral junction (CVJ) pathologies are associated with anomalous vertebral arteries (VAs), posing a significant surgical challenge. The VA can be damaged during dissection or screw placement. Eight patients with CVJ pathology and anomalous VA underwent instrumented fusion (C1-C2/O-C2). A comprehensive preoperative radiological evaluation with intraoperative biplanar fluoroscopy and Doppler was utilized for VA localization and screw placement. A postoperative computed tomography (CT) cervical spine with VA angiography was performed to assess the VA status and screw placement. Analysis revealed atlas assimilation/segmentation bony anomalies in all patients. The variations of anomalous VA included fenestrated V3 VA, C2 segmental VA, and high-riding VA, either alone or in combination. Few patients demonstrated bilateral anomalous VA. All cases had C1-C2 joints drilled and opened. C1 lateral mass-C2 pedicle fusion was performed in 6/8 and O-C2 pedicle fusion in 2/8 cases. All cases except one had spacer insertion. There was no injury to the anomalous VA. One patient required spacer revision due to malposition. Utilizing preoperative three-dimensional CT angiography to identify anomalous VA, meticulous surgical dissection on the normal side first, experienced assisting surgeon, identification of C2 nerve root ganglion, and intraoperative Doppler, we aim to enhance the safety and efficacy of CV J fixation procedures, leading to improved patient outcomes. Mobilization of the anomalous vessel is essential to facilitate the safe drilling of the facets and the accurate placement of screws and spacers under direct visualization. Strict compliance with the above techniques ensures rigid fusion in the presence of an anomalous VA.