Review Question - QID 210959

A 68-year-old woman with type 2 diabetes mellitus, hypertension, and hypothyroidism presents to the emergency room with 6 months of worsening headaches and vision changes. Initially, her headaches were dull and infrequent, but they now occur daily and have become quite severe. She states that her symptoms are worse in the morning. They do not improve substantially with ibuprofen or acetaminophen. The patient requests prescription medication as she can no longer tolerate the pain. She has also been experiencing fatigue, nausea, increased thirst, and frequent urination. Her current medications include insulin, metformin, atorvastatin, lisinopril, hydrochlorothiazide, and levothyroxine. She confirms that she has been taking all her medications as prescribed. She also reveals that her peripheral vision has been getting worse, though she thinks this may be due to old age. Her temperature is 97.9°F (36.6°C), blood pressure is 139/89 mmHg, pulse is 82/min, respirations are 11/min, and oxygen saturation is 98% on room air. Physical exam is notable for mild impairment of her lateral visual fields. A non-contrast CT scan of the head is performed and shown in Figure A. Which of the following is the most likely diagnosis?