Frnd had brain edema due to japanese encephalitis. mri & spect scan says no major damage. but recovery is very slow. not able to speak clearly. why?

MRI isn't sensitive: Although MRI and ct scans are good to detect structural damage, they do not have the sensitivity to detect the cellular injury. With encephalitis there is diffuse injury to many cells at the subcellular level. Thus the MRI and spect scan may not detect this. The fact that these are read out as no major damage suggests the possibility of recovery as those individual cells may recover over time.

Cannot rely on tests: Encephalitis is an inflammatory disorder of the brain. Cat scan and MRI are tests of anatomy, not brain function. These tests may be normal while the function of the cells is abnormal.