History: A 34-year-old man with a history of HIV and medical noncompliance is brought by his family to his primary care provider after 2 weeks of generalized weakness, mild headache, wobbly gait, and intermittent confusion. The patient states that his family is exaggerating and he feels fine except for a headache and intermittent double vision. He states that the headache goes away with Tylenol but keeps coming back. He also noticed that the double vision seems to be triggered by looking to the right. He denies any vomiting, fever, falls, or other complaints.
Examination: The patient is alert and oriented. He has binocular diplopia when looking to the right only, but it resolves if either eye is kept closed. He cannot move his eyes upward. The other cranial nerves are intact. He has no focal weakness or numbness. His gait is wide based. The rest of his exam is essentially normal.
Testing: His head CT scan is shown in Figure 1 at right (Click on image to enlarge)
What does the case image show?
What is the most likely diagnosis?
Where can I get a quick refresher on this topic?
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