Cognitive and behavioural deficits occur in about half of individuals with amyotrophic lateral sclerosis (ALS) and this is linked to shorter survival.1 Typical cognitive impairments are in the executive function, language and social cognition domains.2 The JNNP paper by Palumbo et al 3 examined the relationship between social cognition, executive functions and behavioural impairments in 121 patients with ALS. They identified a social cognition impairment in ~45% of patients with ALS, based on a comprehensive ‘gold standard’ neuropsychological assessment. This impairment was largely independent of executive functions and behavioural disorders, although theory of mind was associated with select executive function measures. Patients were initially diagnosed according to the Strong 2017 ALS-FTSD criteria but following neuropsychological assessment and incorporating the social cognition assessment, 10 patients were reclassified and changed the category to cognitively impaired (eg, from ALS-CN → ALSci, or ALSbi → ALScbi). The findings by Palumbo et al highlight the critical question of how to accurately assess cognition in ALS.4

In ALS clinics, brief cognitive screening rather than neuropsychological assessment is typical (and understandable given the multi-faceted and complex issues to address). However, cognitive screening tools are limited and can lack sensitivity, failing to detect impairments.5 For example, recently the widely used Edinburgh Cognitive and Behavioural ALS Screen (ECAS) was found to lack sensitivity for detecting social cognition and executive function (inhibition and working memory) deficits in patients with ALS compared with neuropsychological tests.6 This means that impairments remained undetected and patients with ALS with true deficits were not identified by the ECAS.

The study by Palumbo et al reinforces that social cognition and executive functions are distinct cognitive functions. Yet, a pitfall of cognitive screening tools is that they provide a global measure with a cut-off score. The ECAS is by far superior to most screening tools, and it was developed with specific ALS motor and speech deficits considered. However, the ECAS combines social cognition and executive functions into one ‘Executive Function Subscale’. As Tjokrowijoto et al 6 found, this can mask true deficits and make it more difficult to disentangle specific cognitive impairments, for example, in social cognition and not executive functions.

When identifying neuropsychological deficits in ALS, it is also important to consider the task demands and an individual patient’s level of function (eg, motor, speech) and psychological status (eg, mood and behaviour). For instance, if a task requires a motor or verbal response, it is crucial to consider whether a specific patient’s performance was affected by any motor or speech impairment because this could confound the results. On the contrary, if a patient presents with low mood or apathy, this will also impact negatively on cognitive test performance.

In summary, a comprehensive assessment of cognition, behaviour and mood—that is, a neuropsychological assessment—is the ‘gold standard’ rather than brief screening tools. Experienced clinicians need to navigate the many pitfalls when interpreting test results. Identifying neuropsychological impairments is important for managing difficulties and facilitating understanding by providing appropriate information and for the broader research community to gauge the extent of deficits in ALS.