Linkage and DNA analysis, magnetic resonance (MR) imaging, and single- voxel proton MR spectroscopy were obtained in 10 members of an Italian kindred with spinocerebellar ataxia type 1 (SCA1). The size of the basis pontis, cerebellar hemispheres, middle cerebellar peduncles, and medulla oblongata were decreased in 4 members carrying the SCA1 gene, compared with 6 unaffected subjects. Diffuse signal changes in the ponts and cerebellum were observed only in the carrier with the longest disease duration and greatest disability. The N-acetylaspartate/creatine ratio and the choline/creatine ratio in the basis pontis were markedly decreased in 2 symptomatic SCA1 carriers and modereately decreased in 2 asymptomatic SCA1 carriers, compared with the unaffected family members and a control group of 10 healthy volunteers. Minor decreases in the N-acetylaspartate/creatine ratio and the normal choline/creatine ratio were observed in the cerebellar hemisphere of the SCA1 carriers. Reduction of the N-acetylaspartate/creatine ratio, demonstrated by MR spectroscopy in the pons, is likely to reflect a loss of neuronal viability and might represent a biochemical marker of SCA1 more sensitive than brainstem and cerebellum atrosphy and signal changes shown by MR imaging.
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