One of the most common genetic causes of frontotemporal dementia (FTD) is mutation in the progranulin ( PGRN ) gene. The aim of this study is to assess the early effects of the PGRN mutations on brain volumes by longitudinal voxel based morphometric (VBM) evaluation in asymptomatic mutation carriers.

We recruited 17 asymptomatic members of families with FTD caused by PGRN mutations; 7 mutation carriers (51.0±11.6 yr) and 10 non-carriers (55.2±6.0 yr, p =0.404). The MRI follow-up intervals of carriers and non-carriers were 788.6±103.8 and 922.0±225.1 days ( p =0.124) respectively. We performed cross-sectional and longitudinal VBM analysis on both groups.

At baseline, the carriers had lower white matter (WM) volumes in left frontal regions ( p <0.001, uncorrected), but had no gray matter (GM) volume reduction. The carrier's global GM ( p =0.924) and WM volume ( p =0.364) reduction rate were not different from the non-carrier's. However, statistical parametric mapping T-maps showed differentially increased GM volume reductions in the bilateral parietal areas of carriers ( p <0.001, uncorrected).

The findings from this study to examine WM and GM cross-sectional and longitudinal changes in PGRN mutation carriers suggest that WM atrophic changes could precede both GM changes and symptom onset in FTD. Asymptomatic PGRN mutation carriers have measurably higher rates of regional GM atrophy than non-carriers even in the pre-dementia stages.