HYPERFIXATION OF TC-99M-HMPAO AND HYPOFIXATION OF I-123 IOMAZENIL IN ACUTE HERPES-ENCEPHALITIS

WE studied two patients with herpes encephalitis (HSE) by [Tc-99m]HMPA O and [I-123]iomazenil single photon emission computed tomography. Inc reased uptake of HMPAO was seen for up to 63 days in the HSE affected brain area. Iomazenil binds to benzodiazepine receptors and can measur e neurone loss. Decreased iomazenil uptake was observed a few days aft er onset, at a time when hyperfixation of HMPAO occurred. Because in H SE neurone loss occurs simultaneously with hyperfixation of HMPAO, it is unlikely that this hyperfixation is caused by increased neuronal ac tivity, as in epilepsy. This suggests that the hyperfixation of HMPAO in HSE occurs in glia and is sustained by inflammation-related hyperme tabolism and acidity. The early neurone loss in HSE stresses the impor tance of immediate antiviral treatment.