Rasmussen's encephalitis: proton MR spectroscopy and diffusion MR findings.

Rasmussen's encephalitis is a chronic inflammation of the brain that leads to progressive neurologic deficits. The condition has previously been studied by various imaging modalities including MR imaging and MR spectroscopy. We studied three patients presenting with Rasmussen's encephalitis by using proton MR spectroscopy, and diffusion-weighted MR imaging. In these patients, on diffusion-weighted MR imaging, mean apparent diffusion coefficient (ADC) value was 1.74 x 10(-3) mm(2)/sec within the parenchyma, apparently higher than that of the normal parenchyma (0.88 x 10(-3) mm(2)/sec) of a control group of five healthy subjects. Proton MR spectra were obtained with a TR value of 1,500 msec and differing TE values (135, 40, and 20 msec), and were compared with a control group of fourteen cases. In the affected regions of the brain, MR spectroscopy revealed decreased NAA, and increased Cho peaks associated with apparently decreased NAA/Cho, NAA/Cr ratios, and increased Cho/Cr ratios. Slightly increased mI peaks, and increased mI/NAA ratios were noted. A prominent lactate peak was noted in one of the patients.