National Physical Therapy Examination (NPTE) Practice Exam

In the context of acute internal carotid artery dissection, the cranial nerve most commonly affected is CN XII, also known as the hypoglossal nerve. This nerve is responsible for controlling the movements of the tongue. During a dissection of the internal carotid artery, there can be compression or ischemic changes to adjacent structures, including the hypoglossal nerve, due to its anatomical proximity to the carotid artery.

When patients experience an internal carotid artery dissection, they may present with symptoms such as unilateral tongue weakness, atrophy, or deviations in tongue positioning upon protrusion, which are indicative of hypoglossal nerve involvement. The risk of neurological complications, including those affecting cranial nerves, increases as the dissection progresses.

The other cranial nerves listed have varying roles and anatomical relations to the internal carotid artery, but they do not have the same direct vulnerability or typical presentation of injury associated with dissection. This specific relationship of the hypoglossal nerve to the internal carotid artery is what makes it the most affected nerve in this situation.