FMR1 and fragile X-associated tremor/ataxia syndrome: In this study, we found systematic atrophy of both the midbrain and pons, and thus an increase pons/midbrain ratio in both FMR1 premutation carriers with and without FXTAS, as well as accelerated age-related increase in the pons/midbrain ratio in the FXTAS group (and a trend for the FMR1 premutation carriers without FXTAS group) compared to controls.