Vertebral artery variations and osseous anomaly at the C1-2 level diagnosed by 3D CT angiography in normal subjects

The craniovertebral junction is anatomically complicated. Representative vertebral artery (VA) variations include the persistent first intersegmental artery (FIA), fenestration of the VA above and below C1 (FEN), posterior inferior cerebellar artery (PICA) from C1/2, and high-riding VA (HRVA). The ponticulus posticus (PP) is a well-known osseous anomaly at C1. Although those anomalies are frequent in patients with cervical deformity, the prevalence of these in subjects with normal cervical spines is still unknown. The aim of this study is to investigate the variations and prevalence of vascular and osseous anomalies based on three-dimensional computed tomographic (3D CT) angiography in patients without any cervical diseases, such as rheumatoid arthritis, Klippel-Feil syndrome, or Down syndrome.Eligible subjects were patients who underwent 3D CT angiography by the Department of Otorhinolaryngology and Internal Medicine from January 2009 to October 2013 in our institution. The authors defined a HRVA as a C2 pedicle with a maximum diameter of 4 mm or less.Among 480 subjects with a mean age of 63.1 years, 387 patients were eligible. One hundred and eighteen subjects were female, and 269 were male. HRVA was observed in 10.1% of patients (39 out of 387 cases), FIA in 1.8% (7 cases), FEN in 1.3% (5 cases), and PICA in 1.3% (5 cases). PP was observed in 6.2% of patients (24 cases).According to past reports, many VA anomalies could be attributed to congenital or acquired conditions (e.g., rheumatoid arthritis). However, VA anomalies appear to exist even in patients without any such cervical diseases.