Makindo Medical Notes

Related Subjects: |Cerebral Arterial Perfusion and Clinical Correlates |Anterior circulation Brain |Posterior circulation Brain |Acute Stroke Assessment (ROSIER&NIHSS)

🫀 Internal Carotid Artery (ICA)

• Cervical Segment: In the neck, runs without branches. Closely associated with the sympathetic plexus → disruption can cause Horner’s syndrome.
• Petrous Segment: Enters skull via the foramen lacerum, travels anteriorly.
• Cavernous Segment: Runs within the cavernous sinus alongside CN VI (abducens). Gives off superior hypophyseal arteries to the posterior pituitary.
• Supraclinoid Segment: Pierces dura, then bifurcates into the Anterior Cerebral Artery (ACA) and Middle Cerebral Artery (MCA).

👁️ Ophthalmic Artery

• Gives rise to the central retinal artery, essential for vision (occlusion → amaurosis fugax).
• Also supplies scalp around the eye, frontal sinus, and ethmoidal sinuses.
• Important collateral with branches of the maxillary artery in ICA occlusion.

🔗 Posterior Communicating Artery

• Links anterior and posterior circulations (ICA ↔ PCA).
• Runs close to CN III → aneurysms here can cause a pupil-involving third nerve palsy.
• Also supplies thalamus, hypothalamus, and caudate tail.

🟡 Anterior Choroidal Artery

• Supplies key deep structures:
  • Posterior limb of internal capsule (motor & sensory tracts).
  • Choroid plexus of lateral ventricle.
  • Optic tract & lateral geniculate body → occlusion may cause contralateral homonymous hemianopia.
  • Globus pallidus, substantia nigra, and midbrain regions.

🟥 Anterior Cerebral Artery (ACA)

• Arches around the corpus callosum to supply the medial surfaces of the frontal and parietal lobes → leg weakness is a hallmark of ACA stroke.

ACA – A1 Segment

• From ICA bifurcation to the Anterior Communicating Artery (AComA).
• Medial Lenticulostriates: Supply anterior limb of internal capsule & basal ganglia.
• Anterior Communicating Artery: Joins left & right ACA, common site of berry aneurysms.
• Recurrent Artery of Heubner: Supplies head of caudate & anterior limb of internal capsule.
• Pericallosal Branch: Continuation of ACA, supplies medial cortex & corpus callosum (branches include orbitofrontal, polar frontal, callosomarginal).

🟦 Middle Cerebral Artery (MCA)

• M1 Segment: Horizontal portion, from ICA bifurcation to the insula.
  • Occlusion → large hemispheric infarcts.
  • Hyperdense MCA sign may be seen on CT.
• Lateral Lenticulostriates: Small penetrating vessels branching at right angles, supplying basal ganglia, posterior limb of internal capsule, and optic radiations (Meyer’s loop).
  • Occlusion → lacunar strokes, prone to lipohyalinosis in hypertension.
• M2 Segment: Within Sylvian fissure.
  • A thrombus here may give the “dot sign” on CT.
• M3 Segments: Cortical branches divided into:
  • Upper Division: Prefrontal, precentral, central, postcentral, parietal (motor & sensory cortex).
  • Lower Division: Temporal & occipital gyri, angular gyrus (language functions in dominant hemisphere).

⭕ Circle of Willis

The Circle of Willis provides critical collateral circulation. Aneurysms here account for up to 85% of subarachnoid haemorrhages, most commonly at the junction of the anterior communicating artery, PComA–ICA junction, or MCA bifurcation.