During an acute dissection of the internal carotid artery, which cranial nerve is most likely affected?

• A. CN 9
• B. CN 10
• C. CN 12
• D. CN 8

Answer: (C)

The internal carotid artery is located in close proximity to several cranial nerves, but when considering an acute dissection of this artery, the cranial nerve most likely affected is the hypoglossal nerve, which is cranial nerve twelve (CN 12).

The hypoglossal nerve plays a critical role in the motor innervation of the tongue. During a dissection or vascular event involving the internal carotid artery, the anatomical positioning of CN 12 makes it susceptible to injury due to its pathway as it exits the skull. The nerve travels inferiorly and laterally toward the tongue, lying in close proximity to the carotid artery, which increases its risk of being impacted during pathologies like dissections.

While the other cranial nerves listed may be associated with other structures in the neck or cranium, they do not have the same direct anatomical relationship with the internal carotid artery that increases their likelihood of being affected in the scenario of an acute arterial dissection. Thus, the hypoglossal nerve, due to its proximity and vulnerability during such vascular events, is the most likely to be affected.