DIAGNOSTIC NEURORADIOLOGY MRI in Japanese encephalitis

Introduction Japanese encephalitis (JE) is the commonest endemic encephalitis in southeast Asia, including India Patients and methods We examined seven patients with JE by MRI 10-60 days after the onset of their illness. Their ages ranged between 2 and 47 years; five were male. The diagnosis was confirmed in all patients by a positive haemagglutination inhibition test, for IgM and IgG antibodies to JE MRI of the brain and spine was carried out on a 1.5 T imager using a circularly polarised head coil and oval spinal coil, respectively. The patients were sedated if indicated. The brain was imaged in all patients, and the spine in three only. Spin-echo pulse sequences were used to image the brain in the axial and cervical spine in the sagittal plane. T1-weighted images were obtained using repetition time (TR) 600-680 ms, echo time (TE) 15 ms, number of excitations (nex) 3, slice thickness 3-5 mm, interslice gap 0.3-0.5 mm, field of view 230-280 mm, and a 256 × 256 matrix. For proton-density and T2-weighted images, the parameters were: TR 2200-2500, TE 20/80 ms, 1 nex, slice thickness 3-5 mm, interslice gap 0.3-0.5 mm, field of view 230-280 mm and matrix 256 × 256. Abstract We document the MRI features in seven patients with Japanese encephalitis. MRI was carried out on a 1.5 T system within 10-60 days of onset. In all the patients MRI revealed bilateral thalamic lesions, haemorrhagic in five. Signal changes were present in the cerebrum in four patients, the midbrain and cerebellum in three each, the pons in two and the basal ganglia in one. The lesions were haemorrhagic in three of the four patients with lesions in the cortex, two of the three with lesions in the midbrain and cerebellum, but the pontine lesions were haemorrhagic in both patients. Spinal cord involvement was seen in one of the three patients who underwent MRI. In two patients MRI was repeated 3 years after the onset, showing marked reduction in abnormal signal; and all the lesions gave low signal on both T1-and T2-weighted images. Bilateral thalamic involvement, especially haemorrhagic, may be considered characteristic of Japanese encephalitis, especially in endemic areas