Neuroanatomy, Internal Capsule

The internal capsule (IC) is a white matter structure composed of bundles of myelinated fibers that course past the basal ganglia. It is located in the inferomedial portion of each cerebral hemisphere and separates the caudate nucleus and thalamus from the lentiform nucleus. Ascending and descending fiber tracts course within the internal capsule to connect the cerebral hemispheres with subcortical structures, the brainstem, and the spinal cord. The internal capsule can subdivide into the anterior limb, genu, posterior limb, retrolenticular segment, and sublenticular segment. The various portions of the internal capsule mostly receive their vascular supply from perforating arteries that arise from the anterior cerebral artery, middle cerebral artery, anterior choroidal artery, and the internal carotid artery. These perforating arteries are prone to lipohyalinosis leading to ischemic damage of areas of the internal capsule resulting in clinically significant motor and sensory deficits.