Imaging Evaluation of Suspected Craniovertebral Junction Anomalies Using CT, MRI and CT Vertebral Angiography

Background: Craniovertebral junction (CVJ) anomalies represent a heterogeneous group of structural deformities involving the occiput, atlas, and axis with their supporting ligamentous apparatus. These anomalies carry significant neurosurgical implications and are encountered more frequently in the Indian subcontinent than elsewhere in the world. The objective is to evaluate the incidence of congenital CVJ anomalies across age groups, assess sex prevalence, characterise radiological abnormalities on CT and MRI, and document the course of the vertebral artery in order to inform surgical planning. Material and Methods: A hospital-based descriptive study was conducted from January 2018 to June 2019. Thirty patients with confirmed congenital CVJ anomalies underwent CT and/or MRI evaluation. Standard craniometric measurements — McRae's line, Chamberlain's line, McGregor's line, bimastoid line, digastric line, Wackenheim's clivus canal line, clivus canal angle, and Welcher's basal angle — were recorded. CT angiography was performed where vertebral artery anomalies were suspected. Results: CVJ anomalies were distributed across all age groups, with the 31–40 year cohort most commonly affected (23.3%). Males constituted 76.7% of cases (p = 0.01). Bony anomalies predominated (97%), with basilar invagination being the most frequent diagnosis in 80% of patients. All six standard craniometric lines were abnormal in 80% of cases. Arnold-Chiari malformation was the principal soft tissue anomaly (6%). Abnormal vertebral artery course was identified in 30% of cases, predominantly involving the V3 segment. Conclusion: Congenital bony anomalies, particularly basilar invagination, dominate the CVJ anomaly spectrum with a significant male preponderance. Pre-operative CT angiographic evaluation of the vertebral artery is essential, given its aberrant course in nearly one-third of patients. CT and MRI together constitute the gold standard for diagnosis and surgical planning.

Keywords: Craniovertebral junction anomalies; basilar invagination; Arnold-Chiari malformation; craniometric measurements; vertebral artery; CT; MRI; occipitalisation of atlas.