A 55-year-old, right-handed man comes to the emergency departm | Uworld | Step 1

A 55-year-old, right-handed man comes to the emergency department due to recent onset of severe, throbbing, right-sided headache and double vision. His medical history includes poorly controlled hypertension and chronic tobacco use. Neurologic examination shows that he is awake, alert, and oriented and can follow commands. Visual fields and optic fundi are normal. The position of the right eye is down and out with ipsilateral ptosis, and the right pupil is dilated and nonreactive to both light and accommodation. Left eye examination is normal. Based on this patient's neurologic deficits, CT angiography of the head is most likely to reveal an aneurysm arising