Experimental allergic encephalomyelitis in non‐human primates: mri and mrs may predict the type of brain damage

Abstract

Volume‐localized proton spectroscopy and T₂‐weighted MRI were performed on 23 monkeys with experimental allergic encephalomyelitis (EAE). The purpose of this study was to determine the relationships between temporal changes in lesion activity (measured on T₂‐weighted MRI), MRS [N‐acetyl aspartate (NAA), creatine (CR), choline (CHO)], and the histologic definition of disease determined post‐mortem. Animals were scanned in the same areas of the brain once a week before and after sensitization to myelin basic protein (BP). Histologic lesion types were predicted by a combination of preceding MRI and MRS measurements. Acutely fatal EAE lesions were large and monophasic as visualized by MRI, and increased CHO (p<0.02, n=16) and CHO/CR ratio (p<0.001, n = 16) were detected by MRS at disease onset. Chronic EAE lesions were preceded by multiple inflammatory attacks as visualized by MRI and consistently low levels of NAA (p<0.02, n = 13) and NAA/CR (p<0.01, n = 13) which occurred after the initial attack. MRI negative brain regions (from animals that were sensitized to BP) were associated with low CHO/CR (p<0.1, n = 5). The temporal correlation of MRI lesion activity and absolute MRS proton metabolites shows promise for predicting the subsequent duration and histologic type of lesions in EAE in non‐human primates.