Can we differentiate between herpes simplex encephalitis and Japanese encephalitis?
BACKGROUND
Herpes simplex encephalitis (HSE) occurs without regional and seasonal predilections. HSE is important to differentiate from arboviral encephalitis in endemic areas because of therapeutic potential of HSE. This study evaluates clinical features, MRI and laboratory findings which may help in differentiating HSE from Japanese encephalitis (JE).


METHODS
Confirmed patients with JE and HSE in last 10years were included. The presenting clinical symptoms including demographic information, seizure, behavioral abnormality, focal weakness and movement disorders were noted. Cranial MRI was done and location and nature of signal alteration were noted. Electroencephalography (EEG), cerebrospinal fluid (CSF), blood counts and serum chemistry were done. Outcome was measured by modified Rankin Scale (mRS). Death, functional outcome and neurological sequelae were noted at 3, 6 and 12months follow up, and compared between HSE and JE. Outcome was categorized as poor (mRS;>2) and good (mRS≤2).


RESULTS
97 patients with JE and 40 HSE were included. JE patients were younger than HSE and occurred in post monsoon period whereas HSE occurred throughout the year. Seizure (86% vs 40%) and behavioral abnormality (48% vs 10%) were commoner in HSE; whereas movement disorders (76% vs 0%) and focal reflex loss (42% vs 10%) were commoner in JE. CSF findings and laboratory parameters were similar in both the groups. Thalamic involvement in JE and temporal involvement in HSE were specific markers of respective encephalitis. Delta slowing on EEG was more frequent in JE than HSE. 20% JE and 30% HSE died in the hospital, and at 1year follow up JE patients showed better outcome compared to HSE (48% vs 24%). Memory loss (72% vs 22%) was the predominant sequelae in HSE.


CONCLUSIONS
Seizure and behavioral abnormality are common features in HSE whereas focal reflex loss is commoner in JE. In a patient with acute encephalitis, thalamic lesion suggests JE and temporal lobe involvement HSE. Long term outcome in JE is better compared to HSE.
Department of Neurology, Sanjay Gandhi Post Graduate Medical Sciences, Lucknow, India.
Jayantee
J
Kalita
Department of Neurology, Sanjay Gandhi Post Graduate Medical Sciences, Lucknow, India. Electronic address: drukmisra@rediffmail.com.
Usha Kant
UK
Misra
Department of Neurology, Sanjay Gandhi Post Graduate Medical Sciences, Lucknow, India.
Vinita Elizabeth
VE
Mani
Department of Neurology, Sanjay Gandhi Post Graduate Medical Sciences, Lucknow, India.
Sanjeev Kumar
SK
Bhoi
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D015415:Biomarkers / Q000134:cerebrospinal fluid; D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D004569:Electroencephalography; D020803:Encephalitis, Herpes Simplex / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D004672:Encephalitis, Japanese / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology / Q000628:therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016896:Treatment Outcome; D055815:Young Adult
D015415:Biomarkers
EEG; Encephalitis; Herpes simplex encephalitis; Japanese encephalitis; MRI; Outcome