Headache and abnormal brain MRI, what’s the diagnosis?

A 44-year-old man is sent to the ED directly from a radiology facility after a MRI brain showed “meningitis”.
The report says “….diffuse enhancement of the meninges, indicating an infectious or neoplastic meningitis”.
He has had a 2 week history of occipital headaches that get progressively worse during the day, and were relieved by laying down, with some associated neck pain and tinnitus.
His exam in normal, he has no fever and he doesn’t look sick.
Here’s the MRI:

Would you do a lumbar puncture? Why? What would you do?
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