Progression of behavioural disturbances in frontotemporal dementia: a longitudinal observational study

Background and purpose: Behavioural disturbances are the core features of frontotemporal dementia (FTD); however, symptom progression is still not well characterized during the entire course of the disease. The aim of the present study was to investigate behavioural symptoms at baseline and during the disease course in a large cohort of patients with behavioural variant FTD (bvFTD), non-fluent/agrammatic variant primary progressive aphasia (nfvPPA) and semantic variant primary progressive aphasia (PPA). Methods: We evaluated 403 patients with FTD, 167 of whom had at least 1-year follow-up evaluation (for a total of 764 assessments). Behavioural symptoms were assessed and rated through the Neuropsychiatric Inventory (NPI) and Frontal Behavioural Inventory (FBI). Disease severity was evaluated through the Frontotemporal Lobar Degeneration -Clinical Dementia Rating scale (FTLD-CDR). Linear mixed models were used to model behavioural measures (NPI, FBI and the five FBI-behavioural core criteria scores) as a function of disease severity (FTLD-CDR score) and clinical phenotype. Results: At baseline, patients with bvFTD showed more behavioural disturbances compared with those with nfvPPA (P = 0.004). Negative symptoms (apathy and loss of empathy) showed a trend to an increase throughout the course of the disease in both bvFTD and PPA (P < 0.001 until intermediate stages). Positive symptoms (disinhibition, perseverations and hyperorality) increased until intermediate phases (P < 0.001) followed by a progressive reduction in later phases, whereas they were less common in nfvPPA throughout the disease course. Conclusion: We demonstrated that behavioural disturbances differed in FTD and with disease severity. Positive symptoms appeared to improve in the advanced stages, highlighting the importance of taking into account the disease severity as outcome measure in clinical trials.