Cerebral blood flow in presymptomatic MAPT and GRN mutation carriers: A longitudinal arterial spin labeling study

Abstract

Objective: Frontotemporal dementia (FTD) is characterized by behavioral disturbances and language problems. Familial forms can be caused by genetic defects in microtubule-associated protein tau (MAPT), progranulin (GRN), and C9orf72. In light of upcoming clinical trials with potential disease-modifying agents, the development of sensitive biomarkers to evaluate such agents in the earliest stage of FTD is crucial. In the current longitudinal study we used arterial spin labeling MRI (ASL) in presymptomatic carriers of MAPT and GRN mutations to investigate early changes in cerebral blood flow (CBF).

Methods: Healthy first-degree relatives of patients with a MAPT or GRN mutation underwent ASL at baseline and follow-up after two years. We investigated cross-sectional and longitudinal differences in CBF between mutation carriers (n = 34) and controls without a mutation (n = 31).

Results: GRN mutation carriers showed significant frontoparietal hypoperfusion compared with controls at follow-up, whereas we found no cross-sectional group differences in the total study group or the MAPT subgroup. Longitudinal analyses revealed a significantly stronger decrease in CBF in frontal, temporal, parietal, and subcortical areas in the total group of mutation carriers and the GRN subgroup, with the strongest decrease in two mutation carriers who converted to clinical FTD during follow-up.

Interpretation: We demonstrated longitudinal alterations in CBF in presymptomatic FTD independent of grey matter atrophy, with the strongest decrease in individuals that developed symptoms during follow-up. Therefore, ASL could have the potential to serve as a sensitive biomarker of disease progression in the presymptomatic stage of FTD in future clinical trials.

Keywords: AD, Alzheimer's disease; ASL, arterial spin labeling; Arterial spin labeling; BDI-II, Beck Depression inventory II (BDI-II); BNT, Boston Naming Test; CBF, cerebral blood flow; Cerebral blood flow; FDG-PET, positron emission tomography with 18F-fluorodeoxyglucose; FTD, frontotemporal dementia; Frontotemporal dementia; GRN, progranulin; LDST, Letter Digit Substitution Test; MAPT, microtubule-associated protein tau; MMSE, Mini-Mental State Examination; Presymptomatic; RAVLT, Rey Auditory Verbal Learning Test; SAT, Semantic Association Test; TMT, Trailmaking Test; VAT, Visual Association Test; WCST, Wisconsin Card Sorting Test.

Fig. 1

Significant cross-sectional CBF differences between GRN mutation carriers and controls at follow-up. Maps illustrate clusters of significantly lower CBF in mutation carriers compared with controls. Color bar represents p-values corrected for multiple comparisons.

Fig. 2

Significant longitudinal CBF differences between mutation carriers and controls in the total study group (A) and the GRN subgroup (B). Maps illustrate clusters of significantly stronger decline in CBF over time in mutation carriers compared with controls. Color bar represents p-values corrected for multiple comparisons.

Fig. 3

Individual values of decline in CBF over time in cluster 2 (superior frontal gyrus, frontal pole, anterior cingulate cortex, paracingulate gyrus (Supplementary Table 2)). The blue line represents mutation carriers and the yellow line control subjects. For reasons of anonymity individual mutation status is not shown. The orange arrow points to the converted subject with a MAPT mutation and the green arrow to the converter with a GRN mutation. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)