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The spectrum of cognitive and behavioural changes occurring in patients with motor neuron disease (MND) has become an area of great research interest over recent years. In addition to the well-known association with frontotemporal dementia (FTD), which occurs in approximately 15% of patients, many more have evidence of milder behavioural and/or cognitive impairment.1 As a result of this increased awareness, patients with MND are now much more likely to have their cognition assessed as part of the routine care they receive in clinic. Standardised tools such as the Edinburgh Cognitive and Behavioural ALS Screen (ECAS) are making this process more reliable, and its routine use in MND clinics can generate useful data for both clinical management and research. Questions remain, however, as to why some patients with MND develop cognitive and behavioural changes and some do not. McHutchison et al,2 using data from a large MND patient registry, report how personal and family history of neuropsychiatric conditions affects this aspect of disease phenotype in patients with MND.
Increased rates of neuropsychiatric disorders in patients prior to their diagnosis of MND have previously been demonstrated.3 In the study by Turner et al 3 there was an association between patients hospitalised with psychiatric symptoms and a diagnosis of MND in the following year. This may be interpreted as evidence that psychiatric symptoms can be a prodromal feature of MND. In the study by McHutchison et al a history of mood disorder increased the likelihood of patients having apathy post-MND diagnosis. The majority of premorbid mood diagnoses predated the diagnosis of MND by many years, suggesting these were genuine cases of depression rather than early MND symptoms in the form of apathy.
McHutchison et al found that a family history of any neuropsychiatric disorder, and specifically a mood disorder, was associated with increased risk of MND-FTD and poorer cognition overall. Studies have previously shown higher than expected rates of psychiatric conditions in the families of patients with MND.4 This increase is not fully explained by the presence of C9ORF72 hexanucleotide repeat expansions, the genetic abnormality most commonly associated with MND and FTD. Similarly, in the study by McHutchison et al, controlling for the presence of C9ORF72 did not alter the findings.
The phenotype of MND is far broader than the motor syndrome for which it is most well known; behavioural and cognitive changes are common. Why do some patients with MND develop these changes? This study suggests that a history of mood disorder and a family history of neuropsychiatric conditions may play part. The study also demonstrates the great utility of well-designed patient registries and standardised cognitive and behavioural data collection in patients with MND.
Contributors MJ wrote the editorial commentary.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Commissioned; internally peer reviewed.
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