MS-3565

A 65-year-old man presents to the hospital with a 3-day history of headaches. He has a medical history of type 2 diabetes mellitus and hypertension.

During the examination, it is observed that his left pupil is constricted with enophthalmos and ptosis of the left eyelid. However, the right side of his face appears to be unaffected.

What could be the probable reason for this patient’s symptoms?