The vertebral artery is one of the major arteries of the neck. They branch from the subclavian artery, courses through the foramen transversanium from C6 to C2, and merge to form the single midline basilar artery in a complex called the vertebrobasilar system.
The origin of the vertebral arteries is usually from the posterior superior part of the subclavian arteries bilaterally, although the origin can be variable:
brachiocephalic artery (on the right) aortic arch: 6% of cases, most on the left The VA is normally 3-5 mm in diameter and the ostium is the most common site of stenosis.
When the origin is from the arch, then it is common for the artery to enter the foramen transversarium at a level higher than normal (C5 instead of C6).
The vertebral artery is typically divided into 4 segments:
V1 (preforaminal): origin to transverse foramen of C6
V2 (foraminal): from the transverse foramen of C6 to the transverse foramen of C2
V3 (atlantic or extradural): from C2 to the dura
V4 (intradural): from the dura to their confluence to form the basilar artery.
The first part runs upward and backward between the Longus colli and the Scalenus anterior.
In front of it are the internal jugular and vertebral veins, and it is crossed by the inferior thyroid artery; the left vertebral is crossed by the thoracic duct also.
Behind it are the transverse process of the seventh cervical vertebra, the sympathetic trunk and its inferior cervical ganglion.
The second part runs upward through the foramina in the transverse processes of the C6 to C2 vertebræ, and is surrounded by branches from the inferior cervical sympathetic ganglion and by a plexus of veins which unite to form the vertebral vein at the lower part of the neck.
It is situated in front of the trunks of the cervical nerves, and pursues an almost vertical course as far as the transverse process of the axis.
The third part issues from the C2 foramen transversarium on the medial side of the Rectus capitis lateralis. It is further subdivided into the vertical part V3v passing vertically upwards, crossing the C2 root and entering the foramen transversarium of C1, and the horizontal part V3h, curving medially and posteriorly behind the superior articular process of the atlas, the anterior ramus of the first cervical nerve being on its medial side; it then lies in the groove on the upper surface of the posterior arch of the atlas, and enters the vertebral canal by passing beneath the posterior atlantoöccipital membrane.
This part of the artery is covered by the Semispinalis capitis and is contained in the suboccipital triangle—a triangular space bounded by the Rectus capitis posterior major, the Obliquus superior, and the Obliquus inferior.
The first cervical or suboccipital nerve lies between the artery and the posterior arch of the atlas.
The fourth part pierces the dura mater and inclines medialward to the front of the medulla oblongata; it is placed between the hypoglossal nerve and the anterior root of the first cervical nerve and beneath the first digitation of the ligamentum denticulatum.
At the lower border of the pons it unites with the vessel of the opposite side to form the basilar artery.
The perforating arteries were noted to range in number from 1 to 11 (mean, 6.5) and in diameter between 100 microm and 520 microm (average, 243 microm). They arose from the vertebral artery (VA) (54.54%), 8 from the right, the left or both VAs. The anterior spinal artery (ASA), which was singular (81.82%), duplicated (13.64%), or plexiform (4.55%), always gave rise to the perforators. The vascular roots of the ASA were the source of the perforators in 95.45% of the brains. The latter vessels arose from the anterolateral arteries in 50% of the cases. The anastomoses involving the perforators, which were present in 40.91% of the brains, varied in diameter between 100 microm and 350 microm (mean, 169 microm). The perforating vessels gave rise to the side branches in 95.45% of the brains that varied in diameter from 100 microm to 300 microm (average, 161 microm). The perforators usually entered the foramen cecum and the anterior median sulcus, and then continued close and parallel to the raphe of the medulla. The perforators can be compressed by a VA aneurysm, which was found in one among the 71 examined patients with cerebral aneurysms 1).
Variability in dimensions and course of vertebral artery (VA) makes it vulnerable to injury during surgery for congenital atlantoaxial instability (AAD) with or without an occipitalized atlas.
A preoperative detailed risk assessment of anatomical variations in the size and course of VA at the CVJ significantly reduces chances of its iatrogenic injury 2).
Representative vertebral artery (VA) variations include the persistent first intersegmental artery (FIA), fenestration of the vertebral artery above and below C1 (FEN), posterior inferior cerebellar artery (PICA) from C1/2, and high riding vertebral artery (HRVA).
Occlusion of one of the vertebral arteries can cause many serious consequences, ranging from blindness to paralysis.
The ascending pharyngeal artery (APA) may, in very rare cases, supply the posterior inferior cerebellar artery (PICA). In reported cases, when such is the case, the ipsilateral vertebral artery (VA) does not supply the PICA, and most of the time it is hypoplastic.
The embryogenesis differs from that of any other vessel, and is characterized by a great variety of malformations and anomalies. Some of the malformations are truly pathological (that is symptomatic); the anomalies are either found by chance postmorten or by angiography. All of these should be kept in mind by the surgeon approaching the deep cervical and craniospinal regions as well as by the interventional radiologist.
Anomalous origin of the right vertebral artery may not be the sole reason behind a disease process. However, it can certainly lead to a misdiagnosis during diagnostic vascular studies. Detailed information is essential for any surgery or endovascular intervention in this location.
Tortuosity and kinking, course anomalies, duplication and fenestration, persistence of primitive arteries, and anomalies of collateral branches. Other pathologies of the cervical VA associated exclusively with genetic diseases, such as spontaneous aneurysms and arteriovenous fistulae in neurofibromatosis type 1 are also to be considered 3).
Its important to identify and categorize anatomical anomalies of the vertebral artery and determine the relationship of these unexpected variations to the site for transforaminal cervical epidural steroid injections (CTESI).
Vertebral artery compressing the medulla and causing intractable vomiting has only been reported in two ocasions A 69-year-old woman with intractable nausea and vomiting causing a 50 pound weight loss and who failed medical management and whose symptoms were completely reversed following microvascular decompression (MVD) 4).
The incidence of anomalous origin of a vertebral artery seems to be underestimated in recent literature. A careful review of the literature shows more than 100 such cases. The right vertebral artery can arise from the aortic arch or one of its branches. Dual origin of the vertebral artery is not uncommon. The embryologic developmental hypotheses are contradictory and complex.
Anomalous origin of the right vertebral artery may not be the sole reason behind a disease process. However, it can certainly lead to a misdiagnosis during diagnostic vascular studies. Detailed information is essential for any surgery or endovascular intervention in this location 5).
V3 Vertebral Artery to M2 Middle Cerebral Artery Bypass: 3-Dimensional Operative Video 6).
Vertebral Artery to Anterior Inferior Cerebellar Artery Bypass 7)