Sequential brain perfusion abnormalities in various stages of Japanese encephalitis.

There is a paucity of regional cerebral blood flow studies on Japanese encephalitis (JE) with none of these studies describing brain perfusion abnormalities in all three stages of the disease. In this communication we report the changes noted in brain perfusion as detected by single photon emission tomography (SPET), in the acute, subacute and chronic stages of JE . Between December 2000 and March 2006, 31 patients, 19 men and 12 women, mean age 49 y, range 6-64 y of various stages of JE underwent brain perfusion SPET. ∆hese patients were at the following stages of the disease: acute stage, five patients, subacute stage 17 and chronic stage nine. The acute stage was considered as up to seven days from the onset of symptoms, the subacute, from seven to 56 days and any duration beyond 56 days was considered as the chronic stage. In the acute stage all five patients demonstrated focal areas of hyperperfusion involving mainly the thalamus. Additionally, bilateral thalami involvement was noted in three, frontal lobe involvement in four and parietotemporal hyperperfusion in three of these patients. In the subacute stage group, hypoperfusion of the thalamus was noted in all patients while frontoparietal hypoperfusion in seven patients. In the chronic stage group, hypoperfusion of thalamus was noted in four, one patient demonstrated additional occipital lobe hypoperfuion whereas normal perfusion was noted in the remaining five patients. In conclusion, the brain perfusion abnormalities observed depended on the stage of the disease. In the acute stage there was focal hyperperfusion to sites of the brain where JE virus is considered to replicate. In the subacute stage focal hypoperfusion was found to be possibly due to virus induced damage of cellular protein synthesis and in the chronic stage perfusion returns to normal due to regeneration of cellular organelles. Our results also confirm the high frequency of thalamic involvement in JE.