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Cerebral Arterial Territories
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Cerebral Arterial Territories

Cerebral Arterial Territories
Overview
The cerebral arterial territories divide into:
  • Superficial (leptomeningeal) arterial branches
  • Deep (perforating) arterial branches.
Superficial, Leptomeningeal Branches
Stroke Correlations
Arterial Territories: AXIAL VIEW
Drawn at 3 heights: superior, middle, and inferior.
Superior level
  • Anterior cerebral artery (ACA) supplies the medial one third of the superior cerebrum.
  • Middle cerebral artery (MCA) supplies the lateral two thirds.
    • For reference, the superior frontal sulcus separates the MCA and ACA supply.
Mid-vertical level (at the level of the lateral ventricles)
  • ACA supplies the medial one third of the hemisphere.
  • MCA supplies the lateral two thirds.
  • PCA supplies a small portion of the posterior cerebral hemisphere, as anterior as the parieto-occipital sulcus.
Inferior level
  • ACA covers the medial one third of the cerebrum only as far posterior as the Sylvian fissure.
  • MCA covers the lateral two thirds of the hemisphere — the MCA territory terminates just posterior to the medial-lateral axis of the posterior midbrain.
  • PCA covers the posterior cerebrum.
  • The superficial portion of the anterior choroidal artery covers the medial temporal lobe.
arterial territories: sagittal view
Lateral View
  • MCA supplies the majority of the lateral cerebral hemisphere, except for:
  • A strip of the anterosuperior hemisphere, which the ACA supplies &
  • A strip of the postero-inferior hemisphere, which the PCA supplies.
Medial View
  • ACA supplies the antero-superior hemisphere.
  • PCA supplies the postero-inferior hemisphere, and also indicate that the anterior choroidal artery supplies the medial temporal lobe.
superficial arterial borderzones
  • Vascular insufficiency within these arterial borders produces borderzone infarcts (aka watershed strokes).
Again, we divide the arterial territories into:
  • The superficial, leptomeningeal arterial supply & the deep, perforating arterial supply.
  • The anastomoses (ie, collateralizations) that exist between these territories are limited to capillary connections, which cannot sustain arterial perfusion in low blood-flow states.
  • Infarcts that occur within these borderzones are called "end-zone infarcts," so named because these arteries are essentially end-arteries.
Vascular supply: coronal view
  • ACA supplies the supero-medial hemisphere
  • PCA supplies the infero-medial hemisphere
  • MCA supplies the lateral two thirds of the cerebral hemisphere.
    • Anastomoses that exist within these borderzones are insufficient to maintain cerebral perfusion in low-blood-flow states, resulting in watershed strokes.
The Homunculus
In order to understand the clinical effect of an important type of watershed infarct, we draw the motor homunculus.
  • The homunculus is a representation of the topographical distribution of neurons that command volitional muscle.
  • Starting laterally, just above the Sylvian fissure, lie the:
    • tongue, face, thumb, and hand, which are enlarged compared to the rest of the body – the upper limb, trunk, and the lower limb, and foot which stretch around to the medial aspect of the cerebrum.
  • The somatotopic sensorimotor area that corresponds to the borderzone between the MCA and ACA encodes the proximal arms and legs.
  • Patients with a stroke here develop weakness of their proximal arms and legs with preservation of hand and feet strength – they act like a "man in a barrel."
  • The MCA/ACA borderzone infarct, which produces the "man in a barrel" syndrome.
To demonstrate this clinical effect for yourself, sit with your arms at your side and wiggle your fingers and toes but be unable to raise your arms or your legs.*
  • We also see from this diagram that the MCA covers the arm whereas the ACA covers the leg – clinically, this helps us distinguish MCA and ACA strokes.
deep (perforating) territories: Simplification
  • Lenticulostriate arteries (of the MCA) – antero-supero-lateral basal ganglia.
  • ACA – antero-infero-medial basal ganglia.
  • ICA supplies – genu of the internal capsule.
  • A. Comm. – anterior hypothalamus.
  • P. Comm. – posterior hypothalamus.
  • Anterior choroidal artery – posterior limb of the internal capsule.
  • Thalamic arteries – thalamus.

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