MR imaging features of Nipah encephalitis

OBJECTIVE, The newly discovered Nipah virus causes an acute febrile encepha litic illness in humans that is associated with a high mortality. The purpo se of this study is to describe the MR imaging findings of Nipah encephalit is. MATERIALS AND METHODS. MR imaging of the brain was performed in 31 patients with Nipah encephalitis divided into three groups. The first group (14 pat ients) underwent MR imaging during the acute phase of the illness and the s econd,group (10 patients) during the later phase of the acute illness. The third group consisted of six patients who underwent MR imaging because they experienced neurologic relapse and one patient who had late-onset encephal itis. Spin-echo T1- and T2-weighted sequences and T2-weighted fluid attenua ted inversion recovery (FLAIR) sequences were performed. Contrast-enhanced MR imaging was performed in four patients. RESULTS. The FLAIR sequences revealed abnormalities in all patients studied . MR imaging findings in both the acute and later phases of encephalitis we re similar; the main feature of both phases was the presence of discrete hi gh-signal-intensity lesions, measuring 2-7 mm, disseminated throughout the brain, mainly in the subcortical and deep white matter of the cerebral hemi spheres. Neither mass effect nor cerebral edema was seen. There was no corr elation with the focal neurologic signs, depth of coma, and outcome of the patients. The lesions were attributed to widespread microinfarctions from u nderlying vasculitis of cerebral small vessels. Features found on MR imagin g in relapsed and late-onset encephalitis differed from the features in acu te encephalitis in that confluent cortical involvement was the prominent fi nding in the former, as opposed to discrete focal lesions in the subcortica l and deep white matter in the latter. CONCLUSION. MR imaging is a sensitive and specific diagnostic tool for eval uating Nipah encephalitis.