Differential age-related changes in the regional metencephalic volumes in humans: a 5-year follow-up.

We examined changes in the metencephalon of healthy adults who underwent magnetic resonance imaging twice, 5 years apart. The volumes of the cerebellar hemispheres, anterior and posterior vermis, declive-folium-tuber of the vermis, and the ventral pons were measured by operators unaware of subjects' characteristics and the time of scan. The cerebellar hemispheres and the cerebellar vermis, but not the ventral pons, were smaller in older people at both measurements. Significant linear shrinkage was observed in all examined metencephalic regions. Annualized rate of shrinkage was the greatest in the cerebellar hemispheres, somewhat smaller in the vermis, and minimal in the pons. Neither sex differences, nor sex-specific aging trends were found. We conclude that differential age-related shrinkage of the metencephalic structures occurs in healthy adults, but its magnitude differs from cross-sectional estimates.