Cognitive impairment in encephalitis: P3 and MRI correlation.

Abstract

Objective: In view of paucity of studies on P3 in encephalitis, we report clinical, MRI and P3 changes in encephalitis patients.

Design: The diagnosis of encephalitis was based on clinical, MRI, ELISA and/or PCR and categorized into Japanese encephalitis (JE), dengue, herpes (HSE) and nonspecific group. Cognitive functions were evaluated 1 month after the illness when patient was able to cooperate for Mini Mental State examination (MMSE). P3 was carried out by odd ball auditory paradigm recording from Cz, Fz and Pz referred to linked mastoids.

Results: 30 encephalitis patients including 16 JE, 2 HSE and 12 nonspecific whose median age was 24 (13-53) years were prospectively evaluated. P3 was studied after a median duration of 3 months. MMSE was abnormal in 19 patients. CzP3 was abnormal in 6; 5 of whom had abnormal MMSE. MRI was abnormal in 18 showing thalamic lesion in 13, basal ganglia in 3 and cortical in 7 patients. MMSE was abnormal in all the patients with HSE, 81% with JE and 33% with nonspecific encephalitis. P3 was more frequently abnormal in patients with abnormal MMSE and MRI.

Conclusion: Cognitive impairment is common in HSE and JE; abnormal MMSE and MRI are associated with P3 abnormality.