Isolated Third Nerve Palsy as a Rare and Solo Presentation of Internal Carotid Artery Dissection in a Young Female - a Surprising Finding in the Angiogram

Internal carotid artery dissection (ICAD) is a known but uncommon cause of ischemic stroke among young and middle-aged patients. A common presentation includes ipsilateral headache, unilateral oculosympathetic palsy (partial Horner syndrome), or ischemic stroke but some reported cases present with less common manifestations, such as lower cranial nerve syndrome (IX, X, XI, XII). However, third cranial nerve palsy is an extremely rare presentation of ICAD. We present a case of ICAD with pseudoaneurysm presenting with third nerve palsy, with ptosis, outward deviation, and binocular diplopia, emphasizing the importance of considering ICAD as a differential diagnosis in patients with third nerve palsy due to the anatomical proximity of ICA to third nerve within the cavernous sinus.