A patient sustains a lesion at the level of the right internal capsule posterior limb. The expected combination of deficits on examination is:

• A Right-sided hemiplegia and right-sided hemisensory loss
• B Left-sided hemiplegia with left-sided hemisensory loss and right-sided facial weakness (upper motor neuron type)
• C Left-sided hemiplegia, left-sided hemisensory loss, and left-sided homonymous hemianopia (if posterior limb extends to optic radiation) ✓
• D Right-sided cerebellar ataxia and left-sided hemisensory loss (Brown-Séquard at capsule)

Explanation

The posterior limb of the internal capsule carries: (1) corticospinal fibers (upper limb and lower limb) crossing at the medullary pyramids to supply the contralateral body; (2) thalamocortical somatosensory fibers from VPL/VPM nuclei to contralateral somatosensory cortex; (3) optic radiations (from lateral geniculate nucleus to primary visual cortex). A right internal capsule posterior limb lesion therefore causes: left-sided hemiplegia (UMN, spastic), left-sided hemisensory loss, and left homonymous hemianopia (if the optic radiation component is involved). The face is spared or shows contralateral UMN facial weakness (lower face only). Option A incorrectly places deficits ipsilateral.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.