Anatomy of occipital artery through far lateral approach and its nuance in vessel bypass of posterior circulation

Objective To observe the anatomical course of occipital artery through far lateral approach and make preparation for posterior circulation vascular bypass operation. Methods Far lateral approach was performed to observe the 20 occipital arteries in 10 cadaveric heads with color silicon glue perfusion. The origin, course branches, adjacent structure and diameter of related segments were observed and measured. The distance from the adjacent structures and the diameter of vertebral arteries were measured at the same time. The anatomical structures were recorded by taking photos. Results The occipital artery originated from posterior wall of external carotid artery at the level of mandibular angle and raised up between medial to external carotid artery and lateral to Jugular vein. Then it coursed to posteriorlateral direction, raising up between digastric posterior belly and rectus capitis lateralis, going up digastric posterior belly and superior oblique muscle. And then, it crossed longus scapitis on or beneath its surface and coursed medially on the surface of superior oblique muscle and semispinalis capitis muscle below the superior nuchal line. The occipital artery crossed up the superior nuchal line where trapezius muscle and semispinalis capitis muscle attached, accompanied with greater occipital nerve. And then, it outgrew 1 or 2 branches distributing the distal scalp beneath the superficial fascia of scalp. The diameter of occipital artery was (2.4±0.4) mm, (2.0±0.2) mm, (1.7±0.1) mm at the original point, superior border of transverse process and superior nuchal line, respectively.The length of occipital artery from point of superior border of transverse process to the point of superior nuchal line was (93.3±2.4) mm, from the point of superior nuchal line to external occipital protuberance was (21.6±0.8) mm. Diameter of the midpoint of V3 segment of vertebral artery was (3.3±1.3) mm. Conclusions The far lateral approach focusing on the vertebral artery could expose the course of occipital artery, vertebral artery, and atlas-occipital junction widely. The occipital artery could locate the position by mastoidale, digastric posterior belly, and transverse process of atlas. Its diameter and length are suitable for vessel bypass of posterior circulation. Key words: Far lateral approach; Occipital artery; Microanatomy; Vessel bypass of posterior circulation