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Herpes simplex encephalitis: diffusion MR imaging findings
1Department of Radiology, Ege University Hospital, Bornova, 35100, Izmir, Turkey. rnsener@hotmail.com
Abstract:
We studied five patients with herpes simplex encephalitis type 1 with diffusion-weighted MR imaging, as this sequence provides information regarding tissue integrity. Diffusion-weighted imaging was obtained using the echo-planar sequence. True diffusion images (i.e. b=1000s/mm(2) images), and the ADC (apparent diffusion coefficient) values were studied. In addition, diffusion imaging of 12 normal cases, 46 patients with acute ischemia (cytotoxic edema), and 12 patients with vasogenic edema were studied for comparison. In patients with herpes encephalitis, two distinct types of diffusion imaging findings (on b=1000s/mm(2) images, and ADC maps) were noted: lesions similar to cytotoxic edema, and lesions similar to vasogenic edema. The patients with the former type of lesions had fulminating disease, and were in severe clinical condition. Those with the latter represented early cases, and they were in fairly good clinical condition with a good outcome by prompt therapy. Diffusion imaging appears to be a promising sequence to monitor the changes in the brain tissue in herpes encephalitis, and in other infections as well with respect to restriction of movement (cytotoxic edema) or relatively high-motion (vasogenic edema) of water molecules, providing data on the severity of the disease.
Insights
Diffusion-weighted MRI reveals two distinct lesion types in herpes simplex encephalitis, aiding in disease severity assessment. This imaging technique shows promise for monitoring brain tissue changes in infections.
Area of Science:
- Radiology
- Neurology
- Infectious Diseases
Background:
- Herpes simplex encephalitis (HSE) is a severe brain infection.
- Diffusion-weighted magnetic resonance imaging (DW-MRI) offers insights into tissue integrity.
Purpose of the Study:
- To investigate the utility of DW-MRI in characterizing brain tissue changes in HSE.
- To correlate DW-MRI findings with clinical presentation and disease severity in HSE patients.
Main Methods:
- Studied five patients with HSE type 1 using DW-MRI (echo-planar sequence).
- Analyzed true diffusion images (b=1000s/mm²) and apparent diffusion coefficient (ADC) maps.
- Compared findings with normal cases and patients exhibiting cytotoxic or vasogenic edema.
Main Results:
- Identified two distinct DW-MRI patterns in HSE lesions: cytotoxic-like and vasogenic-like.
- Cytotoxic-like lesions correlated with severe, fulminant disease.
- Vasogenic-like lesions indicated early disease stages with good prognosis and response to therapy.
Conclusions:
- DW-MRI is a promising tool for monitoring brain tissue changes in HSE.
- The imaging sequence can differentiate lesion types, reflecting disease severity and water molecule movement.
- Findings suggest DW-MRI's potential application in other brain infections.