Brainstem auditory evoked potential in Japanese encephalitis

Japanese encephalitis (JE) is associated with varying degrees of coma and b rainstem involvement is frequent which can be evaluated and monitored by br ainstem auditory evoked potential (BAEP). The present study has been undert aken to evaluate the BAEP changes and their role in predicting the outcome. Twelve adult patients with JE were subjected to CT scan, MRT and BAEP stud ies after detailed neurological evaluation. The severity of coma was assess ed by Glasgow coma scale and outcome was defined at the end of 3 months int o good and poor recovery on the basis of Barthel Index score (BI). The mean age of the patients was 28.3 years (range 14-50), and four of them were fe males. Most of the patients were comatose. The mean Glasgow coma scale (GCS ) score was 7 (range 4-11). There were no brainstem signs or cranial nerve palsy. Cranial CT scan revealed thalamic hypodensity in four, whitematter o edema in three and left putaminal hypodensity in one patient. Cranial MRI w as carried out in eight patients which revealed bilateral thalamic lesions in all, basal ganglia and midbrain lesions in three each and pontine and ce rebellar lesions in one patient each. Brainstem auditory evoked potentials were recordable bilaterally. The absolute latency of wave I, II, III, IV an d V and interpeak latencies (IPL) of I-V, III-V, and I-m were normal. The V /I amplitude ratio were significancy reduced in five patients The BAEP abno rmalities correlated with brainstem lesions on CT or MRT but not with sever ity of coma or outcome. The reduced amplitude ratio of wave V/I may be due to raised intracranial tension or brainstem involvement in JE. (C) 1999 Els evier Science B.V. All rights reserved.