The right vertebral artery originating from the right occipital artery and the absence of the transverse foramen: a rare anatomical variation

Variations in the origin of the vertebral artery (VA) is a congenital anomaly that occurs during embryological development. Multiple variations related to VA origin have been reported in the literature. Abnormal VA origin is usually determined as incidental findings during angiographic or postmortem anatomical studies. Although most of the cases are asymptomatic, in patients with VA anomaly symptoms such as dizziness have been described. The anomalous variation in the origin of the right VA is rare and separated into three categories: (1) originating from the aorta, (2) originating from the carotid arteries, (3) duplicated origin. In this case, we aimed to present the right VA originating from the right occipital artery and concomitant anomalies of the transverse foramen that have not been reported previously according to our knowledge in literature. In a 32-year-old female patient referred to our hospital because of dizziness, the right VA was not observed on magnetic resonance imaging and computed tomography angiography (CTA) examination was performed. CTA showed hypoplasia of the right transverse foramen at the levels of the C1, C5 and C6 vertebrae and aplasia of the right transverse foramen at the levels of the C2, C3 and C4 vertebrae. The right VA originating from the right occipital artery continues to its normal course by entering the cranium through the foramen magnum at the level of the atlantooccipital junction.