Surgically Relevant Bony Anatomical Variations in Paraclinoid Aneurysms-Three-Dimensional Multi-Detector Row Computed Tomography-Based Study

OBJECTIVE: To evaluate the proportion of surgically relevant anatomical variations such as caroticoclinoid foramen, interclinoid osseous bridge, and anterior clinoid pneumatization in patients with paraclinoid aneurysms based on computed tomography (CT) cerebral angiography studies. MATERIALS AND METHODS: Fifty-four CT cerebral angiography studies showing paraclinoid aneurysms involving the cavernous, clinoid, and supraclinoid internal carotid artery (ICA) were retrospectively evaluated. Source images were processed for three-dimensional reconstructions to evaluate the presence and type of caroticoclinoid foramen, interclinoid osseous bridge, and multiplanar reconstructions with bone algorithm to study the type of pneumatization. RESULTS: The study included 30 female and 24 male patients with mean age of 45.61 (10.47) years. Among the 108 sides studied in 54 patients, caroticoclinoid foramen was seen in 24 cases (22.22%), interclinoid osseous bridge was seen unilaterally in 1 case (0.9%), and pneumatization of anterior clinoid process occurred in 12 cases (11.11%). Incomplete caroticoclinoid foramen (11 cases) and Type I pneumatization (7 cases) were seen to be predominant subtypes. There was no statistically significant gender difference in the occurrence of caroticoclinoid foramen and anterior clinoid pneumatization. Seventy-four aneurysms were detected in 54 patients. Based on their location, 46 aneurysms involved supraclinoid ICA, 18 aneurysms in the clinoid segment, and 10 aneurysms in the cavernous segment. Caroticoclinoid foramen was most prevalent in clinoid aneurysms with 12 cases occurring in the clinoid segment. CONCLUSION: Notable proportions of caroticoclinoid foramen and pneumatization occur in cases of paraclinoid aneurysm. Radiological reports should emphasize on these surgically relevant bony anatomical variations.