EEG in Japanese encephalitis: a clinico-radiological correlation

Abstract

This study was undertaken due to the paucity of studies on electroencephalographic (EEG) changes in Japanese encephalitis (JE) and their clinical and radiological correlation. Twenty seven patients with JE were included whose age ranged between 2 and 54 years, 8 of whom were females and 10 aged 12 or less. On admission, Glasgow coma scale (GCS) ranged between 4 and 9. Seizures were present in 9 patients which were generalised tonic clonic in all except one who had partial motor seizure. Behavioural abnormalities were present in 3 patients. Three patterns of EEG were noted which included diffuse continuous delta in 21, diffuse delta with spikes in 3; and nonmodulating non responsive alpha activity ('alpha pattern' coma) in 3 patients. The background EEG activity became normal in all at 3 months although seizure activity was noted in 3 patients. MRI or/and CT scan revealed bilateral thalamic involvement in all, pons in 2, midbrain in 7, basal ganglia in 5, cerebral cortex in 4 and white matter oedema in 5 patients. Five patients died in the acute stage and 3 patients lost from follow-up. At 3 months, 7 patients had complete, 6 partial and 6 poor recovery. The EEG pattern did not correlate with the GCS and outcome. In JE, EEG reveals non-specific delta showing in acute stage and 'alpha pattern' coma may be a more common presentation than realised and does not always predict a poor outcome.