The course of the V1 segment of the vertebral artery

Background: It has become important to know the exact origin and course of the vertebral artery as well as the percentage of the abnormalities of these variations from the point of view of surgery, angiography and in all non-invasive procedures. In decompressive procedures and for subsequent stabilization procedures of the cervical spine, thorough knowledge of the anatomy of the vertebral artery is mandatory to avoid a potentially catastrophic injury to the vertebral artery. Aims of the Study: The present study was aimed at investigating the frequency of occurrence of the variations of the pre-transverse segment of the vertebral artery especially concerning the level of its entry into the foramen transversarium, tortuosity and size in formalin fixed adult cadavers and fetuses with the view of keeping the surgeons alert regarding the frequency of occurrence of these variations in the local subjects. Materials and Methods: The pre-transverse segment of the vertebral artery (V1 segment) was studied in 19 formalin fixed cadavers (6 females and 13 males) and ten formalin fixed newborn fetuses. The total length and the diameter of the V1 segment of the vertebral artery were measured in adult cadavers to the nearest millimeter using a sliding caliper. Variations in the level of entry of the vertebral artery in to the foramen transversarium and also tortuosity of the artery were noted down. Results: The vertebral artery measured a mean length of 4.9 ± 1.24 cms and a mean diameter of 3.58 ±1.59 mms. In over 71% of the cases the vertebral artery entered the foramen transversarium at the level of C6. The next highest frequency was C7 (18.42%) and in small percentage of the cases at C5 (5.3%), C4 (2.6%) and C3 (2.6%). The vertebral artery was found to be tortuous in nine cases (23.7%). Conclusions: Data derived from gross anatomical studies serve as an indicator of prevalence of variations within a population group. But it would be safest for the surgeon to investigate each case by a computed tomographic scan before the cervical surgery.