The patient is having an ischemic stroke and is presenting with dysphagia, hoarseness, decreased gag reflex, decreased pain/temperature sensation, ataxia, and dysmetria. Dysphagia, hoarseness, and decreased gag reflex are specific to posterior inferior cerebellar artery (PICA) lesions, as they are related to the nucleus ambiguus (CN IX, X, and XI). The decreased sensation of temperature and pain are due to PICA’s supply to the lateral spinothalamic tract and spinal trigeminal nucleus. The patient has ataxia and dysmetria due to PICA’s supply of the inferior cerebellar peduncle. PICA most often branches off of the vertebral arteries before they join to form the basilar artery, although variant origins do exist, such as extracranial (20%) and basilar (10%).

Pontine arteries branch off the basilar artery and lesions here can cause the locked-in syndrome. The ophthalmic artery branches off of the internal carotid artery and a lesion here can cause ipsilateral blindness. The posterior communicating artery gives off small perforating branches. The anterior choroidal artery comes off of the communicating segment (C7) of the internal carotid artery (ICA). This is an uncommon site for isolated occlusion, but a lesion here may cause contralateral hemiplegia due to its supply to the posterior limb of the internal capsule. However, the internal capsule receives a redundant supply from the lenticulostriate arteries of the middle cerebral arteries as well