TRANSSYNAPTIC REDUCTION IN N-ACETYL-ASPARTATE IN CEREBELLAR DIASCHISIS - A PROTON MR SPECTROSCOPIC IMAGING STUDY

Objective: To determine if the transneuronal cerebellar hemispheric me tabolic asymmetry seen in crossed cerebellar diaschisis, and readily d etected with positron emission tomography (PET), is associated with al terations in metabolite signal intensities on [H-1]MR spectroscopic (M RS) imaging when compared with the normal pattern and distribution of cerebellar metabolites. Materials and Methods: The pattern and distrib ution of metabolites [N-acetyl-aspartate (NAA), choline-containing com pounds, creatine, phosphocreatine, and lactate] in the cerebellum, usi ng [H-1]MRS imaging, were studied in a patient with documented long-st anding (3 years duration) crossed cerebellar diaschisis and seven norm al subjects. Cerebellar diaschisis was detected with fluorodeoxyglucos e-PET imaging. Single slice [H-1]MRS imaging was carried out at 1.5 T. Results: There was a marked reduction in NAA signal intensity in the diaschitic cerebellar hemisphere but minimal reduction in choline and creatine signal intensities. The decrease in NAA signal intensity was most marked in the middle cerebellar peduncle and white matter of the diaschitic cerebellar hemisphere. In the normal subjects and in the un involved cerebellar hemisphere of the patient the NAA signal intensity was more prominent in the white matter than the cerebellar cortex. Co nclusion: Our data indicate (a) transneuronal metabolic effects can be detected with [H-1]MRS imaging and (b) there is a differential distri bution of metabolite signal intensities in the cerebellum with NAA sig nal intensity predominantly localized to axons of the cerebellar fiber tracts rather than neuronal cell bodies in the cortex and the convers e is true for choline and creatine signal intensities.