Cerebral Arterial Vascular Territories and Associated Neurological Deficits
The cerebral circulation divides into three major arterial territories—anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA)—each producing distinct, predictable neurological deficits when occluded.
Major Arterial Territories and Their Deficits
Anterior Cerebral Artery (ACA) Territory
The ACA supplies the medial frontal and parietal lobes, including the motor and sensory cortex for the lower extremities 1.
Classic deficits include:
- Contralateral leg weakness and sensory loss (more severe than arm/face)
- Executive dysfunction and behavioral changes (frontal lobe involvement)
- Abulia and apathy
- Urinary incontinence
- Grasp reflex and primitive reflexes
In large-vessel vascular dementia, ACA territory infarcts demonstrate 100% impairment in attention, executive function, and behavior 2.
Middle Cerebral Artery (MCA) Territory
The MCA supplies the lateral frontal, parietal, and temporal lobes—the largest vascular territory and most commonly affected in stroke 3.
Classic deficits include:
- Contralateral face and arm weakness (greater than leg)
- Contralateral sensory loss (face and arm predominant)
- Aphasia (dominant hemisphere—typically left)
- Broca's aphasia (inferior frontal): nonfluent, poor repetition
- Wernicke's aphasia (superior temporal): fluent but nonsensical, poor comprehension
- Global aphasia (extensive MCA territory)
- Neglect and hemianopia (nondominant hemisphere—typically right)
- Gaze preference toward the lesion side
- Homonymous hemianopia
In vascular dementia studies, MCA territory infarcts show predominant impairment in language (53.8%) and memory (53.8%) 2.
Posterior Cerebral Artery (PCA) Territory
The PCA supplies the occipital lobe, inferior temporal lobe, and portions of the thalamus 4.
Classic deficits include:
- Contralateral homonymous hemianopia (most common)
- Visual agnosia (inability to recognize objects despite intact vision)
- Prosopagnosia (inability to recognize faces—bilateral PCA)
- Alexia without agraphia (dominant hemisphere with splenium involvement)
- Memory impairment (medial temporal lobe involvement)
- Thalamic syndromes (sensory loss, pain syndromes, cognitive changes)
PCA territory infarcts demonstrate predominant visuoperceptual domain impairment (33.3%) in vascular dementia 2.
Brainstem Vascular Territories
The brainstem has four distinct intrinsic vascular territories 5:
1. Anteromedial Territory
- Supplies: Corticospinal tracts, medial lemniscus, cranial nerve nuclei
- Deficits: Contralateral hemiparesis, contralateral sensory loss, ipsilateral cranial nerve palsies
2. Anterolateral Territory
- Supplies: Spinothalamic tracts, cranial nerve nuclei
- Deficits: Contralateral pain/temperature loss, ipsilateral cranial nerve deficits
3. Lateral Territory
- Supplies: Middle cerebellar peduncle, lateral pontine structures
- Deficits: Ataxia, dysmetria, nystagmus
4. Dorsal (Dorsolateral) Territory
- Supplies: Cerebellum, vestibular nuclei
- Deficits: Vertigo, nystagmus, ataxia, Horner syndrome (lateral medullary/Wallenberg syndrome)
Clinical Application Using NIHSS
The National Institutes of Health Stroke Scale (NIHSS) systematically assesses these territorial deficits 3:
- Items 5-6 (Motor arm/leg): Identify ACA vs MCA patterns
- Item 2 (Gaze): MCA territory involvement
- Item 3 (Visual fields): MCA or PCA territory
- Item 9 (Language): Dominant MCA territory
- Item 11 (Extinction/inattention): Nondominant MCA territory
Critical Pitfalls to Avoid
Hemispheric laterality matters: Left-sided lesions produce more severe dementia (mean CDR 1.750) compared to right-sided lesions (mean CDR 1.292), with bilateral lesions being worst (CDR 2.000) 2.
Collateral circulation creates variability: The actual infarct territory may not match the occluded vessel due to leptomeningeal collaterals, particularly in chronic conditions like moyamoya disease 6, 7.
Watershed zones: Infarcts between arterial territories produce unique patterns—proximal weakness (shoulder/hip) with hand/foot sparing in ACA-MCA watersheds.
Thalamic infarcts: PCA territory includes thalamic perforators; thalamic strokes produce complex syndromes combining sensory, motor, cognitive, and behavioral deficits that don't fit typical cortical patterns 4.