Diffusion-weighted imaging and apparent diffusion coefficient evaluation of herpes simplex encephalitis and Japanese...

Area of Science:

• Neuroradiology
• Infectious Diseases
• Medical Imaging

Background:

• Herpes simplex encephalitis (HSE) and Japanese encephalitis (JE) are distinct forms of acute encephalitis.
• Differentiating between HSE and JE is crucial for appropriate patient management.
• Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values offer insights into tissue microstructure.

Purpose of the Study:

• To evaluate the utility of DWI and ADC values in distinguishing between necrotizing HSE and non-necrotizing JE.
• To correlate ADC values with the duration of illness in patients with HSE and JE.

Main Methods:

• MRI including DWI and ADC mapping was performed on 45 encephalitis patients (38 JE, 7 HSE).
• Diagnosis was confirmed using IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA) for JE and PCR for HSE.
• ADC values were analyzed in relation to lesion characteristics and time since clinical presentation.

Main Results:

• HSE lesions showed restricted diffusion with low ADC values in the acute stage, and facilitated diffusion with high ADC values in the chronic stage.
• JE lesions did not exhibit restricted diffusion or significantly low ADC values in the acute stage.
• Facilitated diffusion and high ADC values were observed in chronic stage JE lesions.

Conclusions:

• Diffusion abnormalities and lesion conspicuity on DWI differ between acute HSE and JE.
• Distinct ADC values in acute HSE and JE reflect varying degrees of water molecule diffusability.
• Acute HSE may involve abundant cytotoxic edema, while acute JE may have a paucity of cytotoxic edema.