4/ Finally, in severe cases you can get a meningoencephalitis. This can cause edema/T2 signal in the deep gray structures, cortex, and white matter. There can also be leptomeningeal enhancement. Lumbar puncture with CSF analysis can help in diagnosis.
@TheAJNR 2/Since the prehistoric days of medicine (1979!), we knew that some brain tumor patients treated w/radiation (XRT) initially declined, but then get better.
Today, we see this on imaging, where it looks worse early, but then gets better.
Now we call this pseudoprogression.
@TheAJNR 3/Why does this happen?
XRT induces a lot of inflammatory changes—from initiating the complement cascade to opening the blood brain barrier (BBB)
It’s these inflammatory changes that make the imaging look worse.