Radiological and neurophysiological changes in Japanese encephalitis.

Six patients with Japanese encephalitis, four males and two females whose age ranged between 2 and 47 years, were subjected to neurophysiological and radiological studies. An EEG in five of the patients showed diffuse delta wave activity and one had an alpha coma. Delta activity seems to be due to thalamic involvement, which was seen on CT of two and MRI of all the patients. The thalamic lesions were characteristically bilateral and were haemorragic in five. Changes on MRI included abnormalities of the brainstem in three and the basal ganglia and spinal cord in one patient each. Lower motor neuron signs were present in three patients but abnormal MRI signals in the spinal cord were present in only one out of three patients in whom spinal MRI was carried out. Central motor conduction time in the upper limb was prolonged in three patients (five sides) and in the lower limbs in one (both sides), which was consistent with involvement of the cerebral cortex, thalamus, brainstem, and spinal cord. Changes in MRI and EEG in the acute stage may provide early diagnostic clues in patients with Japanese encephalitis.