Temporal Lobe Involvement in Japanese Encephalitis: Problems in Differential Diagnosis

• Published in: American Journal of Neuroradiology Vol. 27; no. 5; pp. 1027 - 1031
• Main Authors: Handique, S.K, Das, R.R, Barman, K, Medhi, N, Saharia, B, Saikia, P, Ahmed, S.A
• Format: Journal Article
• Language: English
• Published: Oak Brook, IL Am Soc Neuroradiology 01.05.2006; American Society of Neuroradiology
• Subjects: Adolescent; Adult; Biological and medical sciences; Brain; Cardiovascular system; Child; Cognition. Intelligence; Diagnosis, Differential; Encephalitis, Japanese - diagnosis; Female; Fundamental and applied biological sciences. Psychology; Humans; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Imaging; Male; Medical sciences; Mental imagery. Mental representation; Middle Aged; Nervous system; Prospective Studies; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Temporal Lobe; Tomography, X-Ray Computed; Infection; Temporal lobe; Nervous system diseases; Radiodiagnosis; Viral disease; Arbovirus disease; Central nervous system disease; Differential diagnostic; Cerebral disorder; Japanese encephalitis
• ISSN: 0195-6108; 1936-959X; 1432-1920

On MR imaging and CT, Japanese encephalitis (JE) shows lesions in the thalami, substantia nigra, basal ganglia, cerebral cortex, cerebellum, brain stem, and white matter, whereas temporal lobe involvement is characteristically seen in Herpes simplex encephalitis (HSE). Temporal lobe involvement in JE may cause problems in differentiating it from HSE. We undertook this study to show the temporal lobe involvement pattern in JE and highlight differentiating features from temporal lobe involvement in HSE. Sixty-two patients with JE underwent CT or MR imaging or both. MR imaging was done in 53 and CT in 53. The diagnosis of JE was confirmed by cerebrospinal fluid (CSF) IgM enzyme-linked immunosorbent assay. Eleven (17.7%) patients showed temporal lobe involvement with abnormal MR imaging in all. All the patients showed hippocampal involvement. Two patients showed extension of lesions into the amygdala and uncus with insular involvement in 1. The rest of the temporal lobe was spared. All patients had thalamic and substantia nigra involvement with basal ganglia involvement in 7. Six of 9 CT scans were abnormal and the temporal lesions were seen in 2. The temporal lobe involvement pattern is fairly characteristic and mostly involves the hippocampus, usually sparing the rest of the temporal lobe. This and the concurrent involvement of the thalami, substantia nigra (SN), and basal ganglia allow differentiation from HSE. However, if the temporal lobe involvement is more severe, laboratory tests may be the only way to differentiate it from HSE, and it may be prudent to start antiviral therapy in the interim period.