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Stroke
Arterial Territories, Brain Regions, and Neurologic Deficits
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Stroke occurs when blood flow to part of the brain is interrupted, causing rapid loss of oxygen and glucose delivery to neurons. Because different arteries supply different brain regions, the neurologic deficits depend strongly on which vascular territory is affected. Learning arterial territories helps students connect anatomy to bedside findings such as weakness, aphasia, neglect, or visual loss. This is a core skill in early neurology and emergency medicine because stroke localization guides urgent diagnosis and treatment.
The major cerebral vessels include the anterior cerebral artery, middle cerebral artery, posterior cerebral artery, and the vertebrobasilar circulation. Each artery supplies characteristic cortical, subcortical, and brainstem structures, so infarction produces recognizable patterns of motor, sensory, language, visual, and cranial nerve deficits. For example, middle cerebral artery stroke often affects face and arm function more than leg function, while anterior cerebral artery stroke more often affects the leg. Posterior circulation strokes can involve the brainstem, cerebellum, or occipital lobe and may cause vertigo, ataxia, diplopia, dysarthria, or visual field defects.
Key Facts
- Cerebral perfusion pressure: CPP = MAP - ICP
- ACA stroke classically causes contralateral leg weakness and sensory loss greater than arm and face deficits.
- MCA stroke classically causes contralateral face and arm weakness and sensory loss greater than leg deficits.
- PCA stroke often causes contralateral homonymous hemianopia due to occipital cortex ischemia.
- Left dominant hemisphere MCA stroke may cause aphasia, while right nondominant hemisphere MCA stroke may cause hemispatial neglect.
- Lacunar infarcts involve small penetrating arteries and can produce pure motor stroke, pure sensory stroke, or ataxic hemiparesis.
Vocabulary
- Arterial territory
- An arterial territory is the specific region of brain tissue supplied by a particular blood vessel.
- Aphasia
- Aphasia is an acquired disorder of language affecting speech production, comprehension, reading, or writing, usually from dominant hemisphere injury.
- Hemianopia
- Hemianopia is loss of one half of the visual field in one or both eyes, often caused by lesions behind the optic chiasm.
- Neglect
- Neglect is failure to attend to one side of space, commonly seen after injury to the nondominant parietal cortex.
- Lacunar stroke
- Lacunar stroke is a small deep infarct caused by occlusion of penetrating arteries, often related to chronic hypertension.
Common Mistakes to Avoid
- Assuming all unilateral weakness means MCA stroke, which is wrong because ACA, internal capsule, brainstem, and spinal lesions can also cause weakness and the body distribution helps localize the lesion.
- Forgetting hemisphere dominance when predicting language deficits, which is wrong because aphasia usually localizes to the dominant hemisphere, most often the left.
- Equating visual symptoms only with eye disease, which is wrong because occipital or optic radiations infarction can cause homonymous visual field loss with normal eye structures.
- Ignoring posterior circulation stroke signs, which is wrong because dizziness, diplopia, dysarthria, ataxia, and crossed findings can indicate dangerous brainstem or cerebellar ischemia.
Practice Questions
- 1 A patient has sudden right face and right arm weakness with expressive aphasia. Which arterial territory is most likely affected, and in which hemisphere?
- 2 A patient has sudden left leg weakness greater than left arm weakness and urinary incontinence. Which cerebral artery is most likely occluded?
- 3 A patient has vertigo, ataxia, dysarthria, and diplopia but no clear cortical sensory loss. Explain why this pattern suggests posterior circulation stroke rather than a typical MCA cortical stroke.