Shown here is a patient with a third-nerve palsy attempting to gaze up. Classic signs of a third-nerve palsy include ptosis and limitation of ocular movements in all fields of gaze except abduction. The pupil may be involved (dilated with minimal to no reactivity) or not involved (normal size and reactivity). Typically the patient will complain of double vision. The most common causes of a third-nerve palsy include a compressive lesion, typically an aneurysm of the posterior communicating artery, and microvascular ischemia, commonly seen in diabetic patients. If the pupil is not involved and there are no other neurologic signs or symptoms, the etiology is usually ischemia, and the patient can be closely observed for resolution, which typically occurs over several months. If the pupil is involved, urgent imaging with MRI/MRA is indicated to rule out an aneurysm.