Radiological Parameters of the Craniovertebral Junction in Decision Making for Type a Basilar Invagination Surgery

Introduction: This study was designed to observe the effect of bony morphology of the craniovertebral-junction on choice of a surgical approach.

Methods: Preoperative imaging of 29 new cases of basilar invagination surgically treated at Neurosurgical unit, LRH Peshawar from January 2018 to January 2022 were analyzed. These were compared with age adjusted 29 normal CT done for traumatic causes. Measurements included atlanto-dental interval (ADI), distance above chamberlain line (CL), C1-2 joint inclinations in sagittal and coronal planes, craniocervical tilt (CCT), narrowest canal diameter (NCD) and foramen magnum tilt (FMT). Anomalous path of vertebral artery was also recorded. 20 cases underwent posterior atlanto-axial manipulation and fixation while 09 cases were treated with transoral odontoidectomy (TOO).

Results: All the recorded variables had statistically significant differences with the normal population. Joint inclination in sagittal plane and foramen magnum tilt were associated with severity of CL and ADI. 21 cases had atlas assimilation while 16 had other cervical vertebral fusion. 11 cases had some type of aberrance of bony path of VA while 4 had significant anomaly to affect surgical strategy. The mean ADI and CL for posterior manipulation cases was 5.3 and 6.2mm while those for TOO cases were 6.3mm and 9.1mm. The difference in sagittal C1-2 joint inclination between the two operated groups was also significant however CCT, FMT and NCD demonstrated no statistically significant difference.

Conclusion : C1-2 joint inclination help in optimal procedure selection for type A BI. Joint inclination and FMT are associated withs severity of BI and AAD.