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Station Topic: Brain Anatomy – Internal Carotid Artery
Question (20 marks)
You are asked to demonstrate your knowledge of the internal carotid artery (ICA) and its relation to brain anatomy.
Identify and describe the course of the internal carotid artery from the neck to the brain. (5 marks)1 The ICA arises from the common carotid artery at the level of C3–C4 vertebrae.
Cervical segment: Ascends vertically in the neck without branching.
Petrous segment: Enters the carotid canal in the petrous temporal bone; runs anteromedially.
Cavernous segment: Courses through the cavernous sinus; forms an S-shaped curve (the carotid siphon).
Cerebral (supraclinoid) segment: Exits the cavernous sinus and pierces the dura mater at the roof of the cavernous sinus to enter the subarachnoid space; gives terminal branches to the brain.
Tip: Remember mnemonic “Cervical, Petrous, Cavernous, Cerebral” to recall ICA segments.2 List and explain the main branches of the internal carotid artery in the cranial cavity. (5 marks)
Ophthalmic artery: First branch; supplies the orbit and optic nerve.
Posterior communicating artery (PComm): Connects ICA to posterior cerebral artery; part of Circle of Willis.
Anterior choroidal artery: Supplies choroid plexus, internal capsule, optic tract.
Terminal branches:
Anterior cerebral artery (ACA): Medial frontal and parietal lobes.
Middle cerebral artery (MCA): Lateral convexity of cerebral hemisphere.
Tip: ACA + MCA = terminal branches; remember PComm is part of collateral circulation.3 Describe the areas of the brain supplied by these branches. (5 marks)
Branch Area Supplied
Ophthalmic Eye, orbit, optic nerve
Posterior communicating Connects ICA to posterior cerebral artery; collateral supply to occipital lobe
Anterior choroidal Posterior limb of internal capsule, optic tract, globus pallidus, choroid plexus
Anterior cerebral (ACA) Medial frontal and parietal lobes; leg motor/sensory cortex
Middle cerebral (MCA) Lateral convexity of hemisphere; face and upper limb motor/sensory cortex, Broca/Wernicke areas- Clinical Relevance of ICA (5 marks)
Outline the clinical relevance of the internal carotid artery. Include at least two common pathologies and their implications.
Atherosclerosis / ICA stenosis:
Can cause transient ischaemic attacks (TIAs) or stroke in MCA/ACA territories.
Risk factors: hypertension, diabetes, smoking.
Aneurysm formation:
Common at bifurcation into MCA and ACA or posterior communicating artery.
May cause subarachnoid haemorrhage or cranial nerve III palsy if PComm involved.Other considerations:
ICA injury during carotid endarterectomy.
Compression by tumours (e.g., pituitary adenoma in cavernous sinus) → ophthalmoplegia. - Clinical Relevance of ICA (5 marks)
