Radiological Assessment of Clival Morphological Variants in the Thai Population Using Computed Tomography

The clivus is an important landmark in neurosurgery and radiology due to its proximity to critical neurovascular structures. Anatomical variations of the clivus are diverse and may mimic pathological lesions on imaging. However, data on their prevalence in Southeast Asian populations are limited. This study investigated the prevalence and morphology of clival anatomical variations in the Thai population using computed tomography (CT). A total of 429 cranial CT scans (233 males and 196 females; mean age 39.5 ± 15.4 years) from patients without cranial abnormalities were retrospectively analyzed. The CT images were examined for fossa navicularis magna (FNM), basilar processes (BP), canalis basilaris medianus (CBM), tubercle at the anterior margin of the foramen magnum (TFM), condylus tertius (CT), and arcus praebasiooccipitalis (AP). FNM was the most common variation, identified in 107 cases (24.9%), followed by CBM (9.6%), BP (7.2%), and TFM (4.9%). CT (1.6%) and AP (0.5%) were rare. The CBM appeared as superior recess (5.1%), channel (2.6%), and inferior recess (2.3%) types. No significant sex differences were found for any variant (p > 0.05). These findings indicate that clival variations are relatively common in the Thai population, with FNM being the most prevalent. Knowledge of these variations is essential for accurate radiological interpretation and for planning neurosurgical procedures involving the skull base. Population-specific data such as these are crucial to improve diagnostic accuracy and surgical safety among Thai individuals.