Circle of Willis Quiz
Questions: 16 · 10 minutes
1. A patient has an aneurysm near the junction of the internal carotid and posterior communicating arteries, with compression of the nearby oculomotor nerve. Which artery names the key communicating branch at this site?
Anterior communicating artery
Posterior communicating artery
Middle cerebral artery
Posterior inferior cerebellar artery
2. Which artery is not normally considered part of the Circle of Willis itself?
Middle cerebral artery
Anterior communicating artery
Posterior communicating artery
Proximal posterior cerebral artery
3. A healthy person’s scan reveals an asymmetrical or incomplete Circle of Willis. Which conclusion is most appropriate?
A stroke is currently occurring
The finding proves that cerebral blood flow is inadequate
Anatomical variation is common, though it may influence collateral flow in some circumstances
Immediate surgery is required to reconstruct the arterial circle
4. A diagram shows blood passing from the internal carotid circulation toward the posterior cerebral circulation without entering the basilar artery first. Which vessel provides this connection?
Posterior communicating artery
Anterior communicating artery
Superior cerebellar artery
Anterior inferior cerebellar artery
5. A proximal left internal carotid artery becomes obstructed. Which route could potentially carry blood from the right internal carotid system into the left anterior cerebral territory?
Right anterior cerebral artery across the anterior communicating artery
Right middle cerebral artery to left middle cerebral artery
Right vertebral artery to left external carotid artery
Right posterior cerebral artery to basilar artery
6. Angiography shows that one posterior communicating artery is extremely narrow. How should this finding be interpreted anatomically?
The basilar artery must also be absent
The anterior circulation has no connection across the midline
The circle may be anatomically incomplete or have limited collateral capacity on that side
The corresponding middle cerebral artery must arise from the vertebral artery
7. Imaging shows a posterior cerebral artery supplied predominantly by the internal carotid artery through a large posterior communicating artery, while its P1 segment is small. What variant is this?
Persistent trigeminal artery
Duplicated anterior communicating artery
Fetal-type posterior cerebral artery
Azygos anterior cerebral artery
8. Which label identifies the posterior cerebral artery segment between the basilar bifurcation and its junction with the posterior communicating artery?
A1 segment
M1 segment
P2 segment
P1 segment
9. Which paired arteries normally arise at the terminal bifurcation of the basilar artery?
Posterior communicating arteries
Anterior cerebral arteries
Middle cerebral arteries
Posterior cerebral arteries
10. What is the name of the anterior cerebral artery segment located between the internal carotid bifurcation and the anterior communicating artery?
A2 segment
M1 segment
P1 segment
A1 segment
11. Where is the Circle of Willis located?
Within the superior sagittal sinus
Inside the lateral ventricles
In the subarachnoid space at the base of the brain
Between the skull and the scalp
12. A clinician needs a rapid, noninvasive view of the cerebral arteries using X-rays and intravenous iodinated contrast. Which study best matches that description?
CT angiography
Noncontrast head CT
Electroencephalography
Carotid Doppler ultrasonography alone
13. Which vessel directly connects the left and right anterior cerebral arteries?
Basilar artery
Anterior communicating artery
Posterior communicating artery
Anterior choroidal artery
14. What is the principal functional role of the Circle of Willis?
Draining venous blood from the cerebral hemispheres
Providing potential collateral blood flow between major cerebral arterial territories
Producing cerebrospinal fluid near the brainstem
Regulating blood pressure through autonomic nerve output
15. Why are junctions within the Circle of Willis clinically important when evaluating intracranial aneurysms?
They are the only cerebral sites exposed to arterial blood
They contain valves that can become obstructed
They normally lack all supporting layers of the arterial wall
Arterial branch points are common sites for saccular aneurysm formation
16. On each side, the posterior communicating artery normally links the posterior cerebral artery with which vessel?
Anterior cerebral artery
Internal carotid artery
Vertebral artery
Middle cerebral artery