Vertebral ArteriesEdit
The vertebral arteries are a pair of major vessels that form the posterior circulation of the brain. Each artery arises from the respective subclavian artery, ascends through the transverse foramina of the cervical spine, and enters the skull via the foramen magnum. In the skull base, the right and left vertebral arteries unite to form the basilar artery, which then supplies a large portion of the brainstem, cerebellum, and posterior cerebral regions. Together with its branches, the vertebral-arterial system sustains critical functions such as coordination, balance, and autonomic control by feeding the brainstem, cerebellum, and portions of the occipital and temporal lobes.
The vertebral arteries contribute not only to posterior circulation but also to the perfusion of the spinal cord and surrounding structures through various medullary and meningeal branches. They are a key part of the cerebrovascular network that includes the Basilar artery and the Posterior cerebral circulation, and they interact with the Subclavian artery and the cervical spine in ways that are clinically meaningful in cases of injury, vascular disease, or surgical intervention.
Anatomy and variations
Origin and course - Each vertebral artery typically originates from the posterosuperior aspect of the corresponding Subclavian artery and ascends through the transverse foramina of the cervical vertebrae, usually starting at the level of C6. From there, the artery proceeds cephalad, curves posteriorly near the atlas (C1), and pierces the dura at the foramen magnum to enter the skull.
Branches and distribution - The vertebral arteries give off several important branches before and after entering the skull. Medullary and perforating branches supply segments of the lower brainstem and upper spinal cord. The posterior inferior cerebellar arteries (Posterior inferior cerebellar artery) are among the most clinically relevant branches, supplying the dorsolateral medulla and parts of the cerebellum. Additional smaller branches contribute to the posterior spinal arteries (often via contributions from the vertebral arteries) and to meningeal territories around the cranium. The vertebral arteries also contribute to the formation of the anterior spinal artery through anastomotic connections near the brainstem.
Anastomoses and the vertebrobasilar system - As they merge to form the basilar artery, the vertebral arteries participate in a complex network that supports the posterior circulation. The basilar artery then gives rise to several pontine and cerebellar branches and ultimately contributes to the posterior cerebral arteries and the posterior communication pathways, maintaining a durable blood supply to the brainstem and posterior cerebral cortex.
Variations - Anatomical variation is common. Some individuals have hypoplastic (underdeveloped) vertebral arteries on one side, which can affect collateral circulation. Rare variants include fenestrations, duplications, or anomalous origins (for example, a left vertebral artery arising aberrantly from the aortic arch in certain rare configurations). In most people, the two vertebral arteries operate symmetrically, but variations can influence susceptibility to ischemia or complicate surgical and endovascular procedures. For example, a dominant vertebral artery can play a larger role in posterior circulation in the event of disease on the contralateral side.
Clinical relevance of segments and branches - The precise course and branches of the vertebral arteries matter in procedures involving the cervical spine, craniocervical junction, and skull base. Knowledge of these arteries is essential to avoid inadvertent injury during neck surgery, radical neck dissection, or endovascular interventions.
Development and evolution
Embryology - The vertebral arteries develop from the longitudinal anastomosis of the cervical intersegmental arteries that arise in the embryo. Normal development yields a pair of vessels that ascend in the vertebral foramina and join to form the basilar artery. Variations in embryologic development can result in the anatomical variants discussed above.
Evolutionary perspective - The posterior circulation, supplied by the vertebral arteries and their derivatives, represents an evolutionary specialization for coordinating brainstem and cerebellar control, integrating autonomic functions with motor coordination and sensory integration that underlie balance, gait, and postural control.
Function and clinical significance
Physiologic role - The vertebral arteries supply blood to the spinal cord, medulla, pons, cerebellum, and portions of the occipital lobes. Their branches support vital brainstem nuclei, vestibular pathways, and cerebellar circuits that govern balance and coordination. The integrity of this blood supply is essential for maintaining consciousness, cranial nerve function, and motor coordination.
Pathology and controversies - Vertebral artery dissection is a recognized cause of posterior circulation stroke, particularly in younger patients or after neck trauma or sudden neck movements. Symptoms can include neck pain or headache, vertigo, ataxia, limb weakness, and sensory changes. Risk factors include connective-tissue disorders and minor trauma. Management typically involves antithrombotic therapy or, in select cases, endovascular intervention, with decisions guided by lesion location, extent, and patient factors.
Vertebrobasilar insufficiency or posterior circulation stroke can arise from atherothrombotic disease, embolism, or vertebral-artery stenosis. The clinical presentation often features gait disturbance, vertigo, dysarthria, and cortical-like signs if cortical areas are involved.
Subclavian steal syndrome occurs when proximally advanced stenosis or occlusion of a subclavian artery causes retrograde flow in the ipsilateral vertebral artery, reducing perfusion to the posterior circulation. This condition highlights how proximal vascular disease can manifest in brain perfusion symptoms, especially with exertion.
Aneurysm and dolichoectasia of the vertebral arteries, while less common than aneurysms in more proximal vessels, can present with headache, cranial nerve palsies, or compressive symptoms depending on the aneurysm’s size and location.
Ischemia related to vertebral-arterial disease may contribute to stroke risk in the posterior circulation, sometimes in combination with lesions in the anterior circulation. Contemporary management emphasizes risk-factor modification and appropriate use of imaging to assess both the vertebral arteries and the broader cerebral vasculature.
Imaging and diagnosis - Diagnosis relies on noninvasive and invasive imaging modalities. Magnetic resonance angiography (Magnetic resonance angiography) and CT angiography (CT angiography) are commonly used to visualize vertebral arteries, assess stenosis or dissection, and map the posterior circulation. Digital subtraction angiography (Digital subtraction angiography) remains the gold standard in certain complex cases or when endovascular treatment is planned.
- In the clinic, symptoms attributable to vertebral-arterial disease are correlated with imaging findings and bedside neurologic assessment. The choice of treatment depends on the etiology (dissection, thrombotic disease, aneurysm, or mechanical compression) and patient-specific factors, balancing risks and benefits of medical therapy versus intervention.
Surgical and interventional considerations - In surgical planning or endovascular therapy, accurate knowledge of the vertebral arteries’ course helps minimize iatrogenic injury. Understanding variant origins and dominance informs decisions about catheter access, navigation through the cervical vasculature, and targeted treatment of lesions in the vertebral or basilar territories.