Early Dynamic SPECT Imaging in Acute Viral Encephalitis

BACKGROUND AND PURPOSE: Several cases have reported that dynamic single-photon emission computed tomography (SPECT) shows increased tracer uptake in acute herpes simplex viral encephalitis (HSVE). The purpose of this study was to evaluate the clinical usefulness of dynamic Tc-ECD SPECT in patients with acute viral encephalitis. METHOD: We performed the dynamic SPECT in 9 patients with acute viral encephalitis (4 women, 5 men, 49.5 +/- 17.4 years of age at onset). SPECT and magnetic resonance imaging (MRI) were performed within 2 weeks after acute clinical onset and at the time of resolution of acute symptoms. RESULTS: Cranial MRI showed high intensities in all patients (7 medial temporal and 2 lateral temporal lobes, 1 inferior temporal lobe, 2 insula and adjacent regions, 1 thalamus, 1 putamen). The initial dynamic SPECT showed increased accumulation of tracer, corresponding to the lesions on MRI in 3 patients with HSVE. Resolution of acute symptoms was associated with a reduction in increased tracer uptake. Six patients with non-HSVE showed no increased accumulation of tracer. CONCLUSIONS: Dynamic SPECT may be a new optional neuroradiologic technique that may help to establish a diagnosis in patients with suspected HSVE.