MATERIAL and METHODS: The FTs of 200 dry cervical vertebrae (C3?C7) from 40 spines were studied for the presence of variations in their number (single, double, or triple), size, and shape. The foramina were classified according to their shape depending upon the direction of their main diameter.

RESULTS: Accessory foramina were found in 40 cervical vertebrae. Bilateral accessory foramina were slightly more common than a unilateral accessory foramen. Accessory foramina occurred in a particular pattern, with incidence increasing with descending order of cervical vertebrae, and were most commonly found in C7. The mean values of the anteroposterior and transverse FT diameters on the right side were 4.96 ± 1.08 and 5.68 ± 1.20 mm, respectively, and on the left side were 5.07 ± 1.12 and 5.76 ± 1.29 mm, respectively. The difference was not statistically significant. FTs with very small diameter (<3.5 mm) were found mostly in C7 followed by C5 and C6. Five types of shape were noted. Type 1 was predominant on the right side, whereas type 4 was predominant on the left side.

CONCLUSION: Differences in number (duplication), size, and shape of the FTs are not uncommon phenomena. Anatomical knowledge of FT variations is surgically pertinent, as in such conditions the vertebral artery may become twisted or deformed and result in vertebrobasilar insufficiency. Morphometric measurements from this study may be useful in interpreting radiographic images of the cervical spine obtained using computed tomography or cervical angiograms. Keywords : Anatomical variation, Cervical vertebra, Foramen transversarium, Transverse process, Vertebral artery