Amyotrophic lateral sclerosis and frontotemporal dementia: A behavioural and cognitive continuum

Abstract

Our objective was to compare the cognitive and behavioural profile of patients with amyotrophic lateral sclerosis (ALS) and behavioural variant frontotemporal dementia (bvFTD), and to explore the continuum between these disorders according to neuropsychological and behavioural performance using novel methods of testing and analysis. Twenty patients with ALS, 20 bvFTD patients and 20 healthy controls completed a neuropsychiatric and neuropsychological assessment including cognitive screening, working memory, inhibitory control, decision making and emotion recognition. The resulting neuropsychological and behavioural data were analysed by Rasch analysis. ALS patients showed a similar profile to bvFTD patients on tests of working memory, inhibitory control and behavioural measures. Nine ALS patients (45%) had cognitive impairment and five (25%) met criteria for bvFTD. Even in a subset of MND patients with no impairment on the ACE-R, subtle impairment of inhibitory control together with moderate to severe apathy, were found. The Rasch analysis confirmed that all patients could be ranked on the same continuum, based on their neuropsychological performance and behaviour. Thus, the cognitive and behavioural profiles of ALS mirror those seen in bvFTD. Impaired inhibitory control and behavioural changes suggest subtle orbitofrontal dysfunction in ALS. The Rasch analysis revealed a clear overlap between bvFTD and ALS.

Key words::

• Amyotrophic lateral sclerosis
• frontotemporal dementia
• behavioural symptoms
• cognitive impairment

Acknowledgements

We are extremely grateful to all our patients and carers who participated in this study. We also would like to thank to Steve Vucic, the multidisciplinary teams of Motor Neurone Disease clinics (Prince of Wales Hospital and St. Joseph's Hospital) and The Motor Neurone Disease Association of New South Wales.

Declaration of interest: Study funding was supported by the Australian Research Council Federation Fellowship (J. R. Hodges). Patricia Lillo is supported by a CONICYT scholarship (Government of Chile) and the Faculty of Medicine, University of Chile. E. Mioshi serves on the editorial board of Dementia and Geriatric Cognitive Disorders. M. C. Kiernan is Chief Editor of Journal of Neurology, Neurosurgery & Psychiatry. J. R. Hodges serves on the editorial boards of Aphasiology, Cognitive Neuropsychiatry, and Cognitive Neuropsychology; receives royalties from publication of Cognitive Assessment for Clinicians (Oxford University Press, 2007) and Frontotemporal Dementia Syndromes (Cambridge University Press, 2007); and receives fellowship support from the Australian Research Council Federation.

The authors alone are responsible for the content and writing of the paper.