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Tempral (inferior) horn of lateral ventricle

3

Third ventricle

4

Head of caudate nucleus

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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)

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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)

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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

4. Clinical Relevance of ICA (5 marks)
   Outline the clinical relevance of the internal carotid artery. Include at least two common pathologies and their implications.

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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:

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ICA injury during carotid endarterectomy.
Compression by tumours (e.g., pituitary adenoma in cavernous sinus) → ophthalmoplegia.

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A Faux cerebri
B Inferior sagittal sinus
C Middle meningial vessles
D Inferior sagittal sinus
E Occipital sinus

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C

Optic nerve and ophthalmic artery

D

Maxillary nerve

E

Mandibular nerve, lesser petrosal nerve, emissary veins

F

Jugular vein, Cranial Nerves IX, X, XI