Anatomy

The internal capsule is bounded medially by the Caudate nucleus and the Thalamus, and laterally by the Putamen and the globus pallidus. The most important fiber tract, the Corticospinal tract, runs within the internal capsule toward the Brainstem.

Schematic illustration of the internal capsule — Schematic axial section of the telencephalon including the internal capsule. Figure adapted from Gray's Anatomy.

Anterior limb of the internal capsule

The frontopontine tract and the anterior thalamic peduncle run through the anterior limb of the internal capsule. Most of the blood supply to the anterior limb is provided by capsular branches of the Middle cerebral artery[^1].

Genu of the internal capsule

The corticonuclear tract runs through the genu of the internal capsule. The blood supply to the genu is usually provided by direct vascular branches from the Arteria carotis interna

Posterior limb of the internal capsule

The posterior limb contains the corticospinal tract and corticorubral tract, as well as the superior and posterior thalamic peduncles and parts of the auditory and visual pathways. Most of the blood supply to the posterior limb is likewise provided by capsular branches of the MCA[^1] and by the Anterior choroidal artery.

Anatomical contents of the internal capsule — Schematic illustration of the anatomical contents of the internal capsule. Figure adapted from Greenberg’s Handbook of Neurosurgery.

Imaging

The internal capsule can be visualized on MRI imaging.

Capsula interna MRI MDEFT sequence — Capsula interna on both sides on an axial MRI (MDEFT sequence) image.