Dissecting the Enigma: insights from a retrospective study from India on congenital craniovertebral junction...

Single-center retrospective observational study.

This study aimed to analyze the associated anomalies, neurological manifestations, cord signal changes, surgical outcomes, and complications of congenital atlantoaxial instability (cAAI). Additionally, we summarized the evolving treatment options and provided technical notes relevant to anatomical variations encountered, outlining a stepwise approach for diagnosis/management.

AAI is predominantly congenital (approximately 73%) and often associated with various bony and vascular anomalies. These anatomical variations complicate the restoration of craniovertebral junction (CVJ) alignment and increase the risk of progressive myelopathy. Standard treatment involves reduction with or without release, followed by instrumentation. However, the optimal correction angle, extent of fixation, implant choice, surgical approach, and role of foramen magnum decompression have remained controversial.

This single-center retrospective study from a tertiary care center analyzed data collected over 8 years (2015-2023). Patients with congenital AAI were included, whereas those with traumatic, inflammatory, or infective etiologies were excluded. Of 103 AAI patients evaluated, 25 (24.27%) had congenital etiology and 78 had acquired pathology. The primary outcome variables included radiological parameters (C1-C2 angle, posterior occipitocervical angle, atlantodens interval, space available for cord, and clivocanal angle) and clinical parameters assessing neurology and function.

Vascular (36%) and bony (92%) anomalies were frequent, with the most common being occipitoatlantal assimilation (68%). Moreover, 84% of the patients had cord signal intensity changes. An anomalous course and hypoplastic vertebral artery were observed in 16% of the patients each, while 7/25 patients (28%) had irreducible dislocations requiring anterior release. The average C1-C2 angle (C1C2A) correction was 20.6° (standard deviation [SD]=12.24; 95% confidence interval [CI], 15.812-25.408), whereas the average postoperative C1C2A was 22.36° (SD=5.68; CI, 20.133-24.587; p<0.05, paired t -test).

cAAI poses additional challenges over other forms of AAI given its corresponding abnormal bony and vascular anatomy. Thorough planning and anatomical restoration are essential for satisfactory outcomes.