Robot- and navigation-assisted cervical fusion and decompression for complex vertebral artery anomalies in os odontoideum with Klippel-Feil syndrome: illustrative case

BACKGROUND: Vertebral artery (VA) anomalies, particularly those associated with congenital atlantoaxial dislocations, are well documented in the literature. Typically, these anomalies are linked to persistent first intersegmental artery variants or occur in conjunction with occipitalization of the atlas. The case presented in this report is unique due to the presence of bilateral ectatic VAs with an anomalous course beneath the posterior arch of C1, in the absence of occipitalization of the atlas. This finding adds to the growing recognition of anatomical variability in patients with congenital conditions such as os odontoideum and Klippel-Feil syndrome (KFS). OBSERVATIONS: The authors present the case of a 65-year-old female patient with progressive cervical myelopathy, os odontoideum, and KFS. The preoperative imaging revealed the VA anomalies, and additional caution was exercised intraoperatively. The patient underwent C1-4 fixation and foramen magnum decompression using robot-assisted cervical fusion and neuronavigation. LESSONS: In patients with fused cervical segments, VA anomalies may be overlooked in preoperative imaging, highlighting the need for intraoperative vigilance. Robot-assisted surgery and neurophysiological monitoring significantly improve the safety and precision of the procedure, ensuring optimal outcomes in complex cases like this. https://thejns.org/doi/10.3171/CASE25493.