Epidemiology

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Etiology

Embolic strokes (∼ 20% of all strokes)

• Most commonly affect the middle cerebral artery (MCA)
• Dislodged emboli can affect multiple cerebral vascular territories simultaneously.

Thrombotic strokes (∼ 40%)

• Large vessel atherosclerosis (∼ 20%)
  • Rupture of an atherosclerotic plaque and exposure of subendothelial collagen → formation of a thrombus
  • Thrombus formation most commonly occurs at branch points in arteries (e.g., internal carotid artery bifurcation or where the MCA branches from the circle of Willis).
• Small vessel occlusion (e.g., lacunar infarct) (∼ 20%)

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Classifications

Tip

Most vulnerable: hippocampus (CA1 region), neocortex, cerebellum (Purkinje cells), watershed areas (“vulnerable hippos need pure water”).

Anterior circulation

Posterior circulation

Posterior cerebral artery

A left posterior cerebral artery stroke can lead to alexia without agraphia in which someone is unable to read but can still write, speak, and listen.

Mnemonic

Someone cannot read letters if the post office workers have left for the day.

Anterior spinal artery

Medial medullary syndrome involves contralateral hemiplegia, contralateral epicritic numbness, and ipsilateral tongue weakness.

Mnemonic

“MM! These açaí (ASA-i) berries are so tasty I want to lick them!”

Posterior inferior cerebellar artery (Wallenberg syndrome)

Lateral medullary syndrome involves loss of protopathic sensation in the contralateral extremities and ipsilateral face, ipsilateral Horner’s syndrome, cerebellar signs, dysarthria, and dysphagia.

Mnemonic

PICA-chew: A Posterior Inferior Cerebellar Artery stroke makes it so you can’t chew.

Anterior inferior cerebellar artery (Lateral pontine syndrome)

Lateral pontine syndrome is similar to lateral medullary syndrome but also involves facial paralysis and hearing loss.

Mnemonic

A stroke in the Anterior Inferior Cerebellar Artery messes up the fAICAl nerve.

Basilar artery

• If RAS spared, consciousness is preserved.
• Quadriplegia; loss of voluntary facial (except blinking), mouth, and tongue movements.
• Loss of horizontal, but not vertical, eye movements.

Mnemonic

Locked-in syndrome (locked in the basement).

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Pathophysiology

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Clinical features

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Subtypes and variants

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Lacunar infarction

• Definition: noncortical infarcts characterized by the absence of cortical signs (e.g., no aphasia, hemianopsia, agnosia, apraxia)
• Etiology
  • Most common: chronic hypertensive vasculopathy → lipohyalinosis of the small vessels → occlusion of small, penetrating arteries (e.g., lenticulostriate artery) → lacunar stroke resulting in specific lacunar syndromes
• Risk factors
  • Hypertension
  • Diabetes mellitus
• Clinical features
  • Pure motor stroke
    • Location
      • Posterior limb of the internal capsule (most common)
      • May also involve striatum, corona radiata, basal pons, medial medulla
      • Often caused by occlusion of the lenticulostriate artery
    • Clinical features
      • Contralateral hemiparesis of the face, arm, and leg (causes circumduction gait)
      • No sensory impairment
      • Most common type of lacunar stroke (> 50%)

Tip

If an infarction causes abnormalities in multiple body parts (e.g., legs + arms + face), it is unlikely to be a cortical infarction, because the cortical areas corresponding to different parts are supplied by different vessels. A thalamic (sensory) or internal capsule (motor) infarction is more likely.

Diagnostics

Pathology

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Treatment

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