Diffusion MRI in Rasmussen's encephalitis, herpes simplex encephalitis, and bacterial meningoencephalitis.

Three patients with Rasmussen's encephalitis, herpes simplex type 1 encephalitis, and bacterial meningoencephalitis are included in this study. Echo-planar diffusion MRI was acquired with the trace protocol at 1.5 T. b= 1000 s/mm(2) images, and apparent diffusion coefficient (ADC) maps were studied with respect to lesion identification. ADC values were also studied, and compared to those of 25 normals. In Rasmussen's encephalitis b= 1000 s/mm(2) images were uninformative while ADC maps had superior information. In herpes simplex type 1 encephalitis both b= 1000 s/mm(2) images, and ADC maps had diagnostic information. In meningoencephalitis b= 1000 s/mm(2) images had superior information, especially with respect to early cerebritis while ADC maps were negative. In conclusion, diffusion MRI provided useful imaging data on different types of encephalitis, either on b= 1000 s/mm(2) images or on ADC maps, or on both.