Stroke syndromes by vascular territory

Circle of Willis - The Brain's Roundabout

An arterial anastomosis at the base of the brain, providing collateral circulation. Formed by:

• Anterior Circulation (from Internal Carotids):
  • Anterior Cerebral Artery (ACA)
  • Middle Cerebral Artery (MCA)
• Posterior Circulation (from Vertebral Arteries → Basilar Artery):
  • Posterior Cerebral Artery (PCA)
• Communicating Arteries:
  • Anterior Communicating (AComm): Connects the two ACAs.
  • Posterior Communicating (PComm): Connects PCA to the ICA/MCA.

⭐ Aneurysm Hotspot: The most common site for saccular (berry) aneurysms is the junction of the Anterior Communicating Artery (AComm) with the Anterior Cerebral Artery (ACA).

Anterior Circulation - Front-End Failures

• Anterior Cerebral Artery (ACA)

  • Presentation: Contralateral paralysis & sensory loss, lower limb > upper limb.
  • Key Signs: Frontal lobe signs (disinhibition, personality changes), urinary incontinence.
  • 📌 Mnemonic: A in ACA for Abdominal muscles down to feet (midline).

• Middle Cerebral Artery (MCA)

  • Presentation: Contralateral paralysis & sensory loss, upper limb & face > lower limb.
  • Key Signs (Hemisphere Dependent):
    • Dominant: Aphasia (Broca's, Wernicke's, or global).
    • Non-Dominant: Hemineglect, anosognosia.
  • Homonymous hemianopia (contralateral) is common.

⭐ Exam Favourite: MCA strokes are the most common type of ischemic stroke. A resulting global aphasia (impaired fluency, comprehension, and repetition) indicates a large lesion affecting both Broca's and Wernicke's areas.

Posterior Circulation - Back-End Blackouts

• Posterior Cerebral Artery (PCA):
  • Supplies the occipital lobe.
  • Occlusion causes contralateral homonymous hemianopia with macular sparing.
  • Can also cause alexia (inability to read) without agraphia (inability to write).
• Basilar Artery:
  • Complete occlusion leads to catastrophic "Locked-in Syndrome."
  • Affects the pons, causing quadriplegia and mutism with preserved consciousness and vertical eye movements.
• Cerebellar Arteries (PICA & AICA):
  • General signs: Vertigo, nystagmus, ipsilateral ataxia.
  • PICA → Lateral Medullary (Wallenberg) Syndrome:
    • Ipsilateral: Facial pain/temp loss, Horner's syndrome.
    • Contralateral: Body pain/temp loss.
    • Hoarseness & dysphagia.

⭐ Wallenberg syndrome (PICA occlusion) spares the corticospinal tracts, so patients present with dramatic sensory and cerebellar signs but notably have minimal motor weakness.

Lacunar Strokes - Tiny Territory Trouble

• Pathophysiology: Occlusion of single, deep-penetrating arteries (e.g., lenticulostriate, thalamoperforating).
• Etiology: Strongly associated with chronic hypertension and diabetes, leading to lipohyalinosis and microatheroma.
• Classic Syndromes:
  • Pure Motor: Contralateral paralysis (face, arm, leg).
  • Pure Sensory: Contralateral numbness/paresthesia.
  • Ataxic Hemiparesis: Ipsilateral ataxia with contralateral motor weakness.
  • Dysarthria-Clumsy Hand: Slurred speech and clumsiness in one hand.

⭐ Key feature: Absence of cortical signs (e.g., aphasia, neglect, visual field loss).

High‑Yield Points - ⚡ Biggest Takeaways

• ACA stroke classically presents with contralateral lower extremity deficits, greater than upper.
• MCA stroke is most common, affecting the contralateral face and arm; look for aphasia (dominant) or hemineglect (non-dominant).
• PCA stroke causes contralateral hemianopia with macular sparing.
• Basilar artery occlusion can lead to catastrophic “locked-in” syndrome.
• PICA strokes cause Wallenberg syndrome (lateral medullary), with vertigo, dysphagia, and ipsilateral ataxia.
• Lacunar strokes cause pure motor or sensory deficits.