What is the blood supply of the internal capsule?

From the Guidelines

The internal capsule is primarily supplied by branches of the middle cerebral artery (MCA), anterior choroidal artery, and posterior cerebral artery (PCA), with a rich vascular supply that is critical for maintaining motor and sensory functions. The blood supply to the internal capsule is complex, with different regions receiving blood from various arteries. The anterior limb of the internal capsule receives blood from the medial lenticulostriate arteries, which are branches of the anterior cerebral artery (ACA) and lateral lenticulostriate arteries from the MCA 1. The genu and posterior limb are supplied by the lateral lenticulostriate arteries from the MCA and the anterior choroidal artery, which is a direct branch of the internal carotid artery. The retrolenticular and sublenticular portions receive blood from the anterior choroidal artery and thalamogeniculate branches of the PCA.

Some key points to consider about the blood supply to the internal capsule include:

• The anterior choroidal artery is especially important clinically, as its occlusion can cause a characteristic syndrome of contralateral hemiplegia, hemianesthesia, and homonymous hemianopia due to its supply to the internal capsule, optic tract, and parts of the basal ganglia.
• Interruption of blood flow to the internal capsule, particularly to the posterior limb, often results in contralateral hemiplegia due to damage to the corticospinal tract.
• The presence of collaterals, such as those formed by the lenticulostriate arteries, can influence the outcome of ischemic events in the internal capsule, with patients having better outcomes when collaterals are present 1.
• The location of the occlusion, such as a proximal MCA clot, can also impact the blood supply to the internal capsule and the resulting clinical presentation.

The importance of the blood supply to the internal capsule cannot be overstated, as it contains important motor and sensory fibers connecting the cerebral cortex with the brainstem and spinal cord. Understanding the complex vascular anatomy of the internal capsule is crucial for diagnosing and managing ischemic events in this region.

From the Research

Blood Supply of the Internal Capsule

The internal capsule receives its blood supply from several arteries, including:

• The lenticulostriate arteries (LSA), which consist of medial, intermediate, and lateral branches 2
• The anterior cerebral artery (ACA) perforators, predominantly Heubner's artery 2, 3
• The anterior choroidal artery (AChA), which gives off three main groups of branches, including the lateral, medial, and superior branches 2
• The middle cerebral artery (MCA) perforators, which arise from the M1 segment and leptomeningeal branches 3
• The internal carotid artery (ICA) perforators, which arise close to the AChA originating site or from the ICA bifurcation point 3

Arterial Territories and Supply

The internal capsule's vascular supply varies, with different arteries supplying different parts of the capsule:

• The anterior limb is most often supplied by the medial lenticulostriate arteries (MLA) 4
• The genu and posterior limb are dominated by the lateral lenticulostriate arteries (LLA) and the anterior choroidal artery (AChA) 4
• The dorsal part of the anterior limb, knee, and posterior limb are commonly supplied by lateral MCA perforators 3
• The intermediate part of the anterior limb is perfused by medial MCA perforators, while its ventral part is nourished by ACA perforators and Heubner's artery 3

Clinical Significance

Infarcts in the territory of the lenticulostriate arteries can result in various clinical features, including:

• Pure motor deficits, which are associated with infarcts in the medial and posterior part of the LS territory 5
• Sensori-motor deficits, which are present in 30% of patients 5
• Ataxic hemiparesis, which is present in 20% of patients 5
• Neuropsychological deficits, which are common in infarcts in the anterior and posterior subdivisions of LS territory 5