Basilar ArteryEdit
The basilar artery is a central component of the brain’s posterior circulation, delivering oxygenated blood to critical regions of the brainstem, cerebellum, and parts of the occipital lobes. It is formed by the fusion of the two vertebral arteries and runs along the ventral surface of the pons before it terminates by dividing into the two posterior cerebral arteries. Its flow is supplemented by perforating branches that reach deep structures of the brainstem and cerebellum, and by branches that feed the inner ear and the dorsolateral aspects of the brain. Understanding its anatomy helps explain a range of clinical syndromes that arise from disruption of blood supply to the posterior circulation, from dizziness and gaze palsies to profound motor and sensory deficits.
The basilar artery’s position and connections to nearby vessels make it a hub of neurological blood supply. Its performance depends on the integrity of the vertebral arteries and the collateral pathways that include the posterior communicating arteries and the circle of Willis. The artery’s course and its branches are a focal point in neuroanatomy, neurology, and neurosurgery, and it is frequently evaluated in imaging studies when posterior circulation symptoms arise. For broader context on how this artery fits into cerebral circulation, see cerebral circulation and basilar artery in context with related vessels such as vertebral arteries and posterior cerebral arteries.
Anatomy and course
Origin and path - The basilar artery forms at the ventral medulla by the junction of the two vertebral arteries, which themselves ascend through the cranium to supply the posterior brainstem. The basilar artery then travels upward along the clivus and the anterior surface of the pons, within the basilar groove, before giving off branches and ultimately dividing near the upper pontine region into the two posterior cerebral arteries.
- Its length is relatively short, but its anatomical reach is extensive because of its multiple branches that perforate the brainstem and cerebellum. In some individuals, variations such as dolichoectasia (elongation and widening) or fenestrations may be seen, which can have clinical implications.
Branches and supply - Perforating pontine arteries originate from the basilar artery to supply the ventral pons and adjacent structures, playing a crucial role in maintaining brainstem function.
Anterior inferior cerebellar arteries (AICA) arise from the basilar artery near its origin or at the pontomedullary junction and supply portions of the cerebellum and the inner ear.
Superior cerebellar arteries (SCA) arise more proximally toward the upper basilar region and supply the superior aspect of the cerebellum and nearby brainstem structures.
The basilar artery also gives rise to other cerebellar perforators and branches that help maintain perfusion to the cerebellar hemispheres and midline structures.
At the distal end, the basilar artery bifurcates into the two posterior cerebral arteries (PCAs), which supply the occipital lobes and portions of the temporal lobes, contributing to the posterior circulation of the cerebral cortex.
The labyrinthine (internal auditory) artery, which supplies the inner ear, often arises from the AICA but may originate directly from the basilar artery in some individuals.
Functional significance of branches - The perforating arteries and small pontine branches are essential for maintaining function of the brainstem, where cranial nerve nuclei and reticular formation regulate vital functions such as respiration and consciousness.
- The cerebellar branches (AICA and SCA) are key for coordination, balance, and motor control, while the PCAs contribute to vision and higher-order processing in the occipital and posterior temporal lobes.
Variations and anomalies - Anatomical variation is common in the basilar system. Dolichoectasia can alter flow dynamics and increase the risk of hemorrhagic or ischemic events. Fenestrations (where a vessel splits and then rejoins) and atypical origins of branches can be encountered and are clinically relevant for planning surgeries or endovascular interventions. See also basilar dolichoectasia for more detail.
- Individual differences in the precise point where the basilar artery terminates into the PCAs can influence the pattern of ischemic injury in the event of occlusion.
Function and clinical significance
Role in cerebral perfusion - The basilar artery supplies a substantial portion of the brainstem, cerebellum, and parts of the occipital lobes through its perforators and distal branches. This region houses critical centers for breathing, heart rate, eye movements, and coordination, making the basilar system vital for maintaining life-sustaining and complex neurological functions.
Clinical syndromes related to basilar territory - Basilar artery occlusion is a major cause of posterior circulation stroke and carries a high risk of severe disability or death if not promptly treated. Symptoms can include dizziness, vertical or horizontal gaze abnormalities, double vision, dysarthria, ataxia, and weakness or sensory loss that may progress to coma in extensive occlusions.
Locked-in syndrome is a dramatic consequence of ventral pontine infarction, typically due to basilar artery occlusion, resulting in quadriplegia and loss of most linguistic and voluntary movements with preserved consciousness and some eye movement.
Top of the basilar syndrome refers to occlusion at or near the basilar tip, affecting midbrain and thalamic regions. Presentations can include memory disturbance, visual and oculomotor abnormalities, and altered alertness.
Posterior circulation stroke, arising from basilar artery disease, often requires rapid assessment with neuroimaging such as CT angiography or MR angiography to determine the location and extent of ischemia. In some cases, digital subtraction angiography (DSA) is used for definitive vascular mapping.
Imaging, diagnosis, and treatment - Noninvasive imaging (CTA and MRA) is commonly used to visualize the basilar artery's patency and branches. Invasive angiography (DSA) may be employed for diagnostic confirmation or therapeutic intervention.
Acute management aims to restore blood flow and limit brain injury. Treatments include systemic thrombolysis within established time windows and, in appropriate cases, endovascular thrombectomy to remove clots from the basilar artery or its branches. Supportive care addresses airway protection, hemodynamics, and prevention of secondary injury.
Aneurysms at the basilar tip or along the basilar artery are a recognized risk, often presenting with subarachnoid hemorrhage. Management may involve microsurgical clipping or endovascular coiling, depending on anatomy and patient factors. See basilar tip aneurysm for related discussion.
Prognosis and outcomes - Outcomes after basilar artery events are highly dependent on the extent of ischemia, the patient’s baseline health, timing of treatment, and the effectiveness of collateral circulation. Early recognition and revascularization can markedly improve prognosis, but injuries to the brainstem and cerebellum carry significant potential for lasting deficits.
History and research context - The basilar artery has long been a focus of neuroanatomy and neurosurgery due to its central role in posterior circulation and the technical challenges of accessing brainstem vessels. Ongoing research in vascular neurology seeks to improve detection of basilar artery pathology, optimize acute treatment, and understand the nuances of collateral flow in the posterior circulation.