Vertebrobasilar Arterial System
1. Definition
| Category | Explanation |
|---|---|
| What is it? | A central arterial system formed by the union of the vertebral arteries, creating the basilar artery, which supplies the posterior circulation of the brain. |
| Structurally characterized by | – Originates from subclavian arteries (vertebrals) – Vertebral arteries ascend through transverse foramina (C6–C1) – Merge at the pontomedullary junction to form the basilar artery – Basilar artery gives rise to key branches supplying brainstem, cerebellum, and posterior cerebrum |
| Functionally important for | – Supplies blood to the brainstem, cerebellum, posterior cerebral hemispheres, visual cortex, and thalamus – Supports consciousness, coordination, vision, and autonomic function |
| Composed of: major parts/units | 1. Vertebral arteries (right & left) 2. Basilar artery 3. Posterior inferior cerebellar arteries (PICA) 4. Anterior inferior cerebellar arteries (AICA) 5. Superior cerebellar arteries (SCA) 6. Posterior cerebral arteries (PCA) |
| Common diseases include | – Vertebrobasilar stroke – Dissection of vertebral artery – Wallenberg (lateral medullary) syndrome – Basilar artery thrombosis |
| Diagnosis: clinical / imaging / labs | Clinical: Vertigo, ataxia, dysphagia, diplopia, altered consciousness Imaging: Diffusion MRI, MR/CT angiography Labs: Not specific; risk factor workup (lipids, glucose, inflammatory markers) |
| Treatment | – Acute stroke: Thrombolysis or thrombectomy (in selected cases) – Chronic disease: Antiplatelet therapy, risk factor control – Dissection: Anticoagulation or antiplatelet, depending on severity |
2. Structure Table
| Element | Details |
|---|---|
| Principles | – Occupies space in the posterior cranial fossa and upper cervical spine. – Develops embryologically from paired longitudinal neural arteries. – Aging increases risk of atherosclerosis, calcification, and stenosis. – Unit relies on optimal oxygenation, perfusion pressure, and vessel integrity for health. |
| Size | – Vertebral artery: ~3–5 mm diameter – Basilar artery: ~3 mm average diameter |
| Shape | – Paired vertebrals merge into a single midline trunk (basilar) that ascends vertically |
| Position | – Posterior and medial in brain circulation – Runs along ventral brainstem, from medulla to midbrain |
| Character | – High-flow, pulsatile arteries – Vulnerable to compression (e.g., in neck rotation or trauma) – Sensitive to changes in BP or CO₂ levels |
| Blood supply (parent) | – Vertebrals arise from subclavian arteries |
| Venous drainage | – Primarily into transverse sinuses, sigmoid sinuses, and internal jugular veins via dural venous sinuses |
| Lymphatic drainage | – CNS lacks traditional lymphatics; drainage through glymphatic system and cervical nodes via perivascular channels |
| Nerve supply | – Vascular tone modulated by sympathetic fibers from cervical ganglia |
| Ducts | – None |
| Coverings | – Protected by foramina transversaria, dura, arachnoid, and pia mater |
| Spaces | – Courses through subarachnoid space, vertebral canal, and posterior cranial fossa |
3. Function Table
| Stage | Function |
|---|---|
| Receive | Blood from the subclavian arteries (via vertebral arteries) |
| Process | Channels and distributes blood through critical posterior circulation branches for precise control of brainstem and cerebellar perfusion |
| Export | Oxygenated blood to brainstem, cerebellum, posterior cerebral cortex, and deep brain structures |
4. Parts Table
| Component | Details |
|---|---|
| Vertebral arteries (R & L) | Arise from subclavians, ascend through transverse foramina of C6–C1 |
| Basilar artery | Formed by vertebral union; lies anterior to the pons |
| Posterior inferior cerebellar artery (PICA) | Branches from vertebrals; supplies lateral medulla and inferior cerebellum |
| Anterior inferior cerebellar artery (AICA) | From basilar; supplies pons and anterior inferior cerebellum |
| Superior cerebellar artery (SCA) | Arises from basilar just before PCA; supplies upper cerebellum and midbrain |
| Posterior cerebral artery (PCA) | Terminal basilar branches; supply occipital lobes and thalamus |
5. History
| Aspect | Details |
|---|---|
| Discovery | – The vertebral arteries were described in the 16th century by anatomists like Vesalius. – The basilar artery was formally described in the 18th century by German anatomist Albrecht von Haller, who coined the term “arteria basilaris.” |
| Developmental Anatomy | – Vertebral arteries develop from cervical intersegmental arteries, which fuse to form a longitudinal channel in the embryo. – The basilar artery arises from an anastomosis of longitudinal neural arteries and persists into adulthood. |
| Clinical Milestones | – Wallenberg syndrome first described in 1901 by Adolf Wallenberg. – Endovascular stroke therapy, including basilar artery thrombectomy, became standardized in the 2010s for severe posterior circulation stroke. |
🎭 Cultural Associations – Vertebrobasilar System
| Domain | Associations & Significance |
|---|---|
| Symbolism & Language | – The brainstem and cerebellum, served by the vertebrobasilar system, control basic life functions—balance, breath, and consciousness. Their impairment is often dramatized as a sudden loss of control, both physically and existentially. – The phrase “off balance” or “losing one’s footing” may symbolically reflect cerebellar dysfunction or instability. |
| Medicine & Awareness | – Posterior circulation strokes are often underdiagnosed due to vague symptoms (e.g., dizziness, vertigo). Educational campaigns now stress “Don’t ignore dizziness.” – In patient narratives, vertebrobasilar strokes are feared because of their impact on autonomic and consciousness functions, often being disabling or fatal. |
| Art & Perception | – The cerebellum’s role in coordination ties to dance, athletics, and music—any form of fluid performance. Loss of cerebellar function is a metaphor for loss of grace or harmony. – Visual artists sometimes depict dizziness or instability using spirals, tipping figures, or blurred movement, echoing the loss of vestibular control from brainstem ischemia. |
🧠 Basic Science MCQs – Vertebrobasilar System
Q1. The vertebral arteries merge to form which artery?
A) Internal carotid artery
B) Basilar artery
C) Middle cerebral artery
D) Posterior communicating artery
✅ Correct Answer: B) Basilar artery
Explanation
-
B) Basilar artery: ✅ Correct. The vertebral arteries, one from each side, join at the pontomedullary junction to form the basilar artery, which ascends along the ventral brainstem.
-
A) Internal carotid artery: ❌ Incorrect. This is a separate anterior circulation vessel that does not arise from vertebral arteries.
-
C) Middle cerebral artery: ❌ Incorrect. This is a branch of the internal carotid artery, not derived from vertebral arteries.
-
D) Posterior communicating artery: ❌ Incorrect. This artery connects the internal carotid to the posterior cerebral artery, but it is not formed by vertebral arteries.
Q2. The vertebrobasilar system primarily supplies which part of the brain?
A) Frontal lobe
B) Brainstem and cerebellum
C) Basal ganglia
D) Temporal lobe
✅ Correct Answer: B) Brainstem and cerebellum
Explanation
-
B) Brainstem and cerebellum: ✅ Correct. The vertebral and basilar arteries supply blood to the brainstem, cerebellum, and posterior cerebral hemispheres (via the posterior cerebral arteries).
-
A) Frontal lobe: ❌ Incorrect. This is supplied by the anterior cerebral artery, part of the carotid circulation.
-
C) Basal ganglia: ❌ Incorrect. These deep gray structures are mainly supplied by lenticulostriate arteries, branches of the middle cerebral artery (carotid system).
-
D) Temporal lobe: ❌ Incorrect. The posterior part may receive supply from the PCA, but primary supply is from the MCA (middle cerebral artery) for lateral aspects.
🏥 Clinical MCQs – Vertebrobasilar System
Q3. Which of the following is a common symptom of vertebrobasilar insufficiency?
A) Aphasia
B) Hemiplegia only
C) Vertigo and ataxia
D) Right facial droop only
✅ Correct Answer: C) Vertigo and ataxia
Explanation
-
C) Vertigo and ataxia: ✅ Correct. These are classic symptoms of vertebrobasilar ischemia, due to involvement of the cerebellum and brainstem vestibular nuclei.
-
A) Aphasia: ❌ Incorrect. This is a symptom of dominant hemisphere cortical stroke, typically in the carotid/MCA territory.
-
B) Hemiplegia only: ❌ Incorrect. While possible, isolated hemiplegia is more typical of anterior circulation strokes.
-
D) Right facial droop only: ❌ Incorrect. A focal facial droop is more common with anterior circulation (e.g., MCA) stroke.
Q4. What syndrome is classically associated with vertebral artery occlusion?
A) Gerstmann syndrome
B) Wallenberg syndrome
C) Broca’s aphasia
D) Horner syndrome only
✅ Correct Answer: B) Wallenberg syndrome
Explanation
-
B) Wallenberg syndrome: ✅ Correct. Also known as lateral medullary syndrome, caused by vertebral artery or PICA occlusion. Symptoms include vertigo, dysphagia, hoarseness, contralateral body pain/temperature loss, and ipsilateral facial symptoms.
-
A) Gerstmann syndrome: ❌ Incorrect. Involves the dominant parietal lobe, not vertebrobasilar system.
-
C) Broca’s aphasia: ❌ Incorrect. Due to left frontal lobe infarction in the MCA territory.
-
D) Horner syndrome only: ❌ Incorrect. Horner syndrome may occur in Wallenberg, but not as an isolated finding.
🖼️ Imaging MCQs – Vertebrobasilar System
Q5. Which imaging modality best visualizes the vertebral and basilar arteries noninvasively?
A) Carotid ultrasound
B) CT head without contrast
C) MR angiography (MRA)
D) Chest CT
✅ Correct Answer: C) MR angiography (MRA)
Explanation
-
C) MR angiography (MRA): ✅ Correct. MRA provides detailed visualization of the vertebrobasilar system without contrast (TOF technique), showing vessel patency, stenosis, or occlusion.
-
A) Carotid ultrasound: ❌ Incorrect. Limited in accessing deep vertebral or basilar arteries.
-
B) CT head without contrast: ❌ Incorrect. Good for detecting infarct/bleed, but not arterial anatomy.
-
D) Chest CT: ❌ Incorrect. Not used to image brain or neck vessels.
Q6. Which imaging finding supports vertebrobasilar stroke on diffusion-weighted MRI?
A) Hyperdensity in the Sylvian fissure
B) Restricted diffusion in the cerebellum
C) Calcification of the carotid siphon
D) Normal MRI
✅ Correct Answer: B) Restricted diffusion in the cerebellum
Explanation
-
B) Restricted diffusion in the cerebellum: ✅ Correct. Indicates acute infarction in the posterior circulation, consistent with vertebrobasilar stroke.
-
A) Hyperdensity in the Sylvian fissure: ❌ Incorrect. Suggests MCA clot, part of anterior circulation.
-
C) Calcification of the carotid siphon: ❌ Incorrect. Atherosclerosis in carotid system, not vertebrobasilar.
-
D) Normal MRI: ❌ Incorrect. Would not support the diagnosis of infarction.
Memory Image Idea – Vertebral Artery
Concept: “The Twin Climbers Through the Spine”
Visual Metaphor:
-
Picture two mountain climbers (right and left vertebral arteries) ascending through a rocky spiral staircase made of cervical vertebrae (C6–C1).
-
Each climber is carrying a lantern, symbolizing oxygenated blood lighting the path to the brain.
-
At the summit (foramen magnum), the two climbers join hands, merging into a river (the basilar artery) that flows upward across the face of a mountain (the brainstem).
-
Along the way, side trails diverge to nourish the forest of balance (cerebellum) and village of consciousness (thalamus and occipital lobe).
-
If one climber stumbles or the path collapses (dissection or occlusion), the lantern flickers—and coordination is lost, vertigo begins, or the path to awareness dims.
Why it works:
-
Emphasizes paired anatomy.
-
Reflects ascending course through vertebrae.
-
Highlights fusion into basilar.
-
Symbolizes life-sustaining flow and catastrophic consequences if disrupted.