Tc-99m-HMPAO SPECT Findings in Clinically Suspected HSE

ABSTRACT

Herpes simplex virus type I (HSV-I) causes an acute necrotizing encephalitis that selectively affects tempioral and frontal lobes. The sequelae and mortality of herpes simplex encephalitis(HSE) may be reduced by available antiviral therapy and therefore early diagnosis of HSE is essential. We have assessed the potential of brain perfusion scintigraphy using Tc-99m-HMPAO single photon emission computed tomoglaphy(SPECT) in HSE. Nine Tc-99m-HMPAO SPECTs were performed in eight patients with clinically suspected herpes simplex encephalitis. The examinations were made between 18 days and 10 months after onset of encephalitic symptoms The SPECT images in seven patients revealed decreased accumulation ol radioactivity in the affected temporal, frontal or parietal lobes. In a 30 yr-old female patient, two SPECT images were obtained on 18th day after the onset of symptoms and 3 months later. Her initial SPECT showed increased accumulation of radioactivity in the affected temporal and inferior frontal lobes. 3 month later follow-up SPECT image revealed the decreased radioactivity in the affected temporal, inferior frontal, and inferior parietal lobes. We found that the SPECT done at early stage of HSE may show increased cerebral perfusion due to inflammatory or other pathologic mechanism and the later stage SPECT may show decreased cerebral perfusion due to decreased cerebral metabolism caused by neuronal death We suggest that Tc-99m-HMPAO SPECT may support the clinical diagnosis of HSE.