A magnetic resonance imaging analysis of cognitively discordant monozygotic and dizygotic twins: a comparative study of visual rating method and tensor-based morphometry.

BackgroundAtrophy of the medial temporal lobes and deep gray matter, along with ventricular enlargement, are typical structural magnetic resonance imaging (MRI) findings in the brains of patients with Alzheimer's disease (AD). However, there are few twin studies on this subject.PurposeTo determine whether the visual rating method (VRM) and tensor-based morphometry (TBM) can detect the structural brain changes in monozygotic and dizygotic twin pairs discordant for memory performance.Material and MethodsA total of 12 monozygotic and 24 same-sex dizygotic twin pairs discordant for memory performance and 44 cognitively healthy non-twin volunteers were studied.ResultsSignificant within-twin pair differences in brain atrophy were detected in the medial temporal lobes and ventricular areas (both with VRM and TBM), and in deep gray matter structures (TBM only). When monozygotic and dizygotic twin pairs were analyzed separately, the differences were not statistically significant.ConclusionOur study yielded promising TBM results in distinguishing memory-discordant co-twins in temporal and deep gray matter atrophy. In addition, the findings confirm the assumption that AD affects twins in the same way, independent of genes. Studies with larger twin cohorts would better reveal possible differences between monozygotic and dizygotic twin pairs.