Prevalence and motor-functional correlates of frontotemporal-spectrum disorders in a large cohort of non-demented ALS patients

Background: This study aimed at (1) delivering generalizable estimates of the prevalence of frontotemporal-spectrum disorders (FTSDs) in non-demented ALS patients and (2) exploring their motor-functional correlates. Methods: N = 808 ALS patients without FTD were assessed for motor-functional outcomes—i.e., disease duration, severity (ALSFRS-R), progression rate (ΔFS), and stage (King’s and Milano–Torino—MiToS—systems)—cognition—via the cognitive section of the Edinburgh Cognitive and Behavioural ALS Screen (ECAS)—and behaviour—via the ECAS-Carer Interview. Neuropsychological phenotypes were retrieved via Strong’s revised criteria—i.e., ALS cognitively and behaviourally normal (ALScbn) or cognitively and/or behaviourally impaired (ALSci/bi/cbi). Results: Defective ECAS-Total performances were detected in ~ 29% of patients, with the ECAS-Executive being failed by the highest number of patients (~ 30%), followed by the ECAS-Language, -Fluency, and -Memory (~ 15–17%) and -Visuospatial (~ %8). Apathy was the most frequent behavioural change (~ 28%), followed by loss of sympathy/empathy (~ 13%); remaining symptoms were reported in < 4% of patients. The distribution of Strong’s classifications was as follows: ALScbn: 46.7%; ALSci/bi/cbi: 22.9%/20.0%/10.4%. Multinomial regressions on Strong’s classifications revealed that lower ALSFRS-R scores were associated with a higher probability of ALSbi and ALScbi classifications (p ≤.008). Higher King’s and MiToS stages were associated with a higher probability of ALSbi classification (p ≤.031). Conclusions: FTSDs affect ~ 50% of non-demented ALS patients, with cognitive deficits being as frequent as behavioural changes. A higher degree of motor-functional involvement is associated with worse behavioural outcomes—with this link being weaker for cognitive deficits.