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Topic

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Posterior limb of internal capsule

The posterior limb of the internal capsule is a critical white matter structure in the brain, located between the thalamus medially and the lentiform nucleus laterally. It serves as a major conduit for both ascending and descending neural pathways, including important motor and sensory fibers. Due to its dense concentration of fibers and vital role in neurological function, the posterior limb is a key landmark in neuroimaging and clinical neurology.

Synonyms

  • Posterior crus of the internal capsule

  • Pars posterior capsulae internae (Latin)

Function

  • Transmits corticospinal fibers (primary motor pathway) to the contralateral body

  • Carries sensory fibers from the thalamus to the cerebral cortex (thalamocortical projections)

  • Contains corticopontine and corticobulbar tracts

  • Integral for voluntary motor control and somatosensory transmission

Arterial Supply

  • Lenticulostriate arteries (branches of the middle cerebral artery)

  • Anterior choroidal artery (branch of the internal carotid artery)

  • Occasionally supplemented by perforating branches of the posterior cerebral artery

Venous Drainage

  • Deep cerebral veins

    • Primarily the thalamostriate vein

    • Also drained by the internal cerebral veins

  • Eventually drains into the great cerebral vein of Galen

MRI Appearance

  • T1-weighted (T1):

    • Appears bright (hyperintense) due to high myelin content

  • T2-weighted (T2):

    • Appears dark (hypointense) relative to surrounding gray matter

  • FLAIR:

    • Remains dark (similar to T2), unless there is pathology (e.g., demyelination or infarct)

  • Post-contrast T1:

    • No enhancement in healthy tissue; enhancement only seen if there is pathology (e.g., inflammation, tumor, or infarct)

CT Appearance

  • Non-contrast CT:

    • Appears as a hypodense (darker) linear structure between the thalamus and lentiform nucleus

    • Subtle compared to MRI, but can be seen as a white matter band

MRI images

Posterior limb of internal capsule mri 3t coronal image