Internal Carotid Artery Dissection Presenting as Partial Horner's Syndrome and Vertigo.

Distinguishing between central and peripheral causes of vertigo can be challenging not only in an acute setting but also in chronic settings. A thorough review of systems and physical exam can assist providers in differentiating central versus peripheral etiologies and the need for urgent imaging. In this case, a 47-year-old man presented with vertigo, right-sided hearing loss, right-sided headache, and right-sided facial pain that began 4 weeks before while the patient was on a cruise ship. His physical exam findings were notable for anisocoria with right pupil 3.5 and left pupil 4.5, mild ptosis on the right side, positive Romberg test to the right, and Fakuda test with deviation to the right. Urgent magnetic resonance imaging revealed dissection of the right cervical internal carotid artery with a nonocclusive intramural hematoma. This case illustrates the importance of imaging in vertigo patients in which a central etiology is suspected. It further demonstrates that isolated partial Horner's or unilateral headache may indeed be the only presenting sign in a carotid dissection.