Cerebral Arterial Territories
Anterior Cerebral Artery (ACA) Territory
The anterior cerebral artery supplies the medial surfaces of the frontal and parietal lobes, including the paracentral lobule, which contains the motor and sensory cortex for the lower extremities. 1
Specific Regions Supplied:
- Medial frontal lobe: The entire medial surface of the frontal lobe from the frontal pole posteriorly 1, 2
- Medial parietal lobe: The medial surface of the parietal lobe, including the precuneus 1, 2
- Paracentral lobule: This critical region contains the motor and sensory representation of the contralateral leg and foot 3, 4
- Superior portion of lateral hemisphere: Approximately one-third of the outer (lateral) surfaces of the frontal and parietal lobes, particularly the superior portions of the precentral and postcentral gyri 2, 4
- Corpus callosum: The ACA is the principal arterial supply to the corpus callosum 5
- Subcortical structures: The recurrent artery (arising from the A2 segment in 78% of cases) supplies the anterior limb of the internal capsule and surrounding subcortical areas 5
Anatomical Course:
The ACA begins at the bifurcation of the internal carotid artery and is divided into segments A1 through A5, with cortical branches arising at different levels along this course 5, 6
Middle Cerebral Artery (MCA) Territory
The middle cerebral artery is the largest terminal branch of the internal carotid artery and supplies the lateral surfaces of the cerebral hemispheres, including most of the frontal, parietal, and temporal lobes. 1
Specific Regions Supplied:
- Lateral frontal lobe: Most of the lateral surface of the frontal lobe, including the motor cortex for the face, arm, and hand 1
- Lateral parietal lobe: The lateral surface of the parietal lobe, including the sensory cortex for the face, arm, and hand 1, 7
- Temporal lobe: Most of the lateral temporal lobe 1
- Insula: The insular cortex deep to the sylvian fissure 1
- Deep structures: The lenticulostriate arteries (small-caliber end arteries arising from the MCA) supply the basal ganglia and internal capsule, making these regions particularly vulnerable to hypertensive damage and embolic occlusion 8
Clinical Significance:
Large MCA territory infarctions commonly involve both cortical and gangliocapsular (basal ganglia and internal capsule) structures, resulting in severe deficits including hemiplegia 8. The combination of cortical, basal ganglia, and internal capsule involvement produces more severe deficits than isolated involvement of any single region 8.
Posterior Cerebral Artery (PCA) Territory
The posterior cerebral artery supplies the occipital lobes, inferior temporal lobes, and portions of the thalamus. 1
Specific Regions Supplied:
- Occipital lobes: The entire occipital lobe bilaterally, responsible for primary visual cortex 1
- Inferior temporal lobe: The inferior and medial portions of the temporal lobe 1
- Thalamus: Portions of the thalamus receive blood supply from PCA branches 1
- Midbrain structures: Branches supply portions of the midbrain 1
Anatomical Origin:
The PCA arises from the basilar artery, which is formed by the confluence of the vertebral arteries, constituting the posterior circulation 1. Vertebral artery atherosclerosis accounts for approximately 20% of posterior circulation strokes 1.
Important Vascular Considerations
Circle of Willis Connections:
- The anterior communicating artery connects the left and right ACAs 1
- The posterior communicating artery connects the internal carotid artery to the PCA, linking anterior and posterior circulations 1
- A complete circle of Willis exists in fewer than 50% of individuals, significantly affecting collateral flow capacity during arterial occlusion 1
Watershed/Border Zones:
The territories between ACA-MCA, MCA-PCA, and anterior-posterior circulations represent watershed zones that are particularly vulnerable during hypoperfusion states 9.