Anatomical variations of clivus: a descriptive anatomical study.

PURPOSE: The clivus is a part of the sphenoid bone. It may show some anatomical variations such as fossa navicularis magna (FNM), canalis basilaris medianus (CBM) and craniopharyngeal canal (CPC). These variations have been associated with conditions like meningitis and tumors of skull base. Inadequate information about these structures may pose a risk of inaccurate diagnosis resulting in unwarranted interventional procedures. Hence, the knowledge about the prevalence of these variations is important. Thus, the objective of this study was to determine the prevalence of fossa navicularis magna, craniopharyngeal canal and canalis basilaris medianus and its types utilizing cone-beam computed tomography (CBCT) images. METHODS: Retrospectively, a total of 350 CBCT scans were evaluated for the presence of FNM, CBM, its types and CPC. The analysis was done by two observers independently. Cohen's kappa statistics was used to determine the interobserver agreement. RESULTS: FNM was noted in 19.4% cases, CBM in 9.7% cases, whereas CPC was not identified in any case. Type 5 was the most common type of CBM. There was no significant difference (p > 0.05) between genders and age groups for the prevalence and a highly significant (p < 0.01) substantial agreement between observers for the prevalence of FNM and highly significant (p < 0.01) moderate agreement for the prevalence of CBM and its types was obtained. CONCLUSION: FNM, CBM, CPC, albeit rare anatomical variations of clivus, knowledge of these structures is important for radiologists, anatomists and surgeons to avoid misdiagnosis and provide awareness to the individual of a higher possibility of meningitis or tumors of the skull base.

Variations in the Position of Mandibular Foramen in Temporomandibular Ankylosis Patients.

Aim: To evaluate the variation in the position of the mandibular foramen and mandibular canal in patients with and without temporomandibular joint ankylosis. Materials and Methods: 100 temporomandibular joints were evaluated of which 50 joints were ankylosed joints (Group A) and the rest 50 were normal joints (Group B) without ankylosis. These groups were further divided into those with growing potential (less than 18 years) and those without growing potential (above 18 years). The position of the mandibular foramen was measured from its center to the glenoid fossa, sigmoid notch, coronoid notch, gonion and posterior border on CBCT scans. The position of the mandibular canal was measured from the outer aspect of the canal to the lower border of the mandible, buccal and lingual cortical plates and the alveolus in the region of the 1st, 2nd and 3rd molars. Results: The mean distance of the foramen from the base of the skull in Group A was 19.01 mm while the same for Group B was 31.26 mm. The mandibular foramen was found to be closer to the occlusal plane (5.43 mm) in Group A as compared to the mean distance of 6.21 mm reported in Group B. There was no significant difference in the position of the foramen from the posterior border, gonion and sigmoid notch between the groups. The mental foramen was seen more commonly posterior to the 2nd premolar and closer to the first molar region in Group A while in Group B it was seen anterior or near the 2nd premolar. In Group A, the mean distance of the canal to the buccal cortical plate in the 1st and 2nd molar regions was 3.65 mm and 5.76 mm, respectively, while in Group B it was 6.09 mm and 6.59 mm. The canal was further away from the lower border in ankylosis cases (8.79 mm) than the control group (7.41 mm). On comparing the unaffected side in unilateral cases with the normal mandible, the canal and the foramen location were similar to that of a normal mandible with the values in the lower range that is usually seen in normal mandibles. Conclusion: Ankylosis of the mandible is a debilitating condition especially when it develops in an individual prior completion of growth as it can affect the mandibular anatomy. Understanding the variations that accompany a deranged mandible can assist the surgeon in planning of surgical procedures in a manner that limits the possible complications resulting from surgery.