Advances in neuroimaging in frontotemporal dementia

Cognition and gray and white matter characteristics of presymptomatic C9orf72 repeat expansion

Objective:

To investigate cognitive function, gray matter volume, and white matter integrity in the presymptomatic stage of chromosome 9 open reading frame 72 repeat expansion (C9orf72RE).

Methods:

Presymptomatic C9orf72RE carriers (n = 18) and first-degree family members without a pathogenic expansion (healthy controls [HC], n = 15) underwent a standardized protocol of neuropsychological tests, T1-weighted MRI, and diffusion tensor imaging within our cohort study of autosomal dominant frontotemporal dementia (FTD). We investigated group differences in cognitive function, gray matter volume through voxel-based morphometry, and white matter integrity by means of tract-based spatial statistics. We correlated cognitive change with underlying gray or white matter.

Results:

Our data demonstrate lower scores on letter fluency, Stroop card I, and Stroop card III, accompanied by white matter integrity loss in tracts connecting the frontal lobe, the thalamic radiation, and tracts associated with motor functioning in presymptomatic C9orf72RE compared with HC. In a subgroup of C9orf72RE carriers above 40 years of age, we found gray matter volume loss in the thalamus, cerebellum, and parietal and temporal cortex. We found no significant relationship between subtle cognitive decline and underlying gray or white matter.

Conclusions:

This study demonstrates that a decline in cognitive functioning, white matter integrity, and gray matter volumes are present in presymptomatic C9orf72RE carriers. These findings suggest that neuropsychological assessment, T1-weighted MRI, and diffusion tensor imaging might be useful to identify early biomarkers in the presymptomatic stage of FTD or amyotrophic lateral sclerosis.

Imaging and fluid biomarkers in frontotemporal dementia

Frontotemporal dementia (FTD), the second most common type of presenile dementia, is a heterogeneous neurodegenerative disease characterized by progressive behavioural and/or language problems, and includes a range of clinical, genetic and pathological subtypes. The diagnostic process is hampered by this heterogeneity, and correct diagnosis is becoming increasingly important to enable future clinical trials of disease-modifying treatments. Reliable biomarkers will enable us to better discriminate between FTD and other forms of dementia and to predict disease progression in the clinical setting. Given that different underlying pathologies probably require specific pharmacological interventions, robust biomarkers are essential for the selection of patients with specific FTD subtypes. This Review emphasizes the increasing availability and potential applications of structural and functional imaging biomarkers, and cerebrospinal fluid and blood fluid biomarkers in sporadic and genetic FTD. The relevance of new MRI modalities - such as voxel-based morphometry, diffusion tensor imaging and arterial spin labelling - in the early stages of FTD is discussed, together with the ability of these modalities to classify FTD subtypes. We highlight promising new fluid biomarkers for staging and monitoring of FTD, and underline the importance of large, multicentre studies of individuals with presymptomatic FTD. Harmonization in the collection and analysis of data across different centres is crucial for the implementation of new biomarkers in clinical practice, and will become a great challenge in the next few years.

Frontotemporal dementia: from molecular mechanisms to therapy

Frontotemporal dementia (FTD) is a heterogeneous clinical syndrome characterized by frontotemporal lobar degeneration (FTLD). Neuropathologically, FTLD is characterized by abnormal protein deposits and almost all cases can now be classified into three major molecular subgroups based on specific accumulating proteins with the most common being FTLD-tau and FTLD-TDP (accounting for ~40% and 50%, respectively) and FTLD-FET (accounting for ~5-10%). In this special issue, the molecular and genetic basics as well as clinical approaches and therapeutics are reviewed in a series of articles. This article is part of the Frontotemporal Dementia special issue.