This patient is exhibiting signs of a left anterior choroidal artery (AChA) stroke. The AChA is a branch of the internal carotid artery and supplies multiple structures including the posterior limb of the internal capsule, the ventral posterolateral nucleus of the thalamus, and the lateral geniculate body. Occlusion of this artery, therefore, can cause the triad of contralateral hemiplegia, hemianesthesia, and homonymous hemianopia. There are overlapping features between a left AChA stroke and a left MCA infarct, except speech is preserved in the former.
Lesions to the anterior spinal artery (ASA) can manifest with bilateral paralysis and loss of pain and temperature sensation below the level of the lesion, while vibration and proprioception (dorsal columns) remain intact if the lesion is below the brainstem. Lesions to the posterior inferior cerebellar artery (PICA) or vertebral artery can cause Wallenberg syndrome (lateral medullary syndrome). Clinical manifestations include ipsilateral Horner syndrome, palatal weakness, hemi-ataxia, and contralateral sensory disturbances.