Cognitive impairment within and beyond the FTD spectrum in ALS: development of a complementary cognitive screen.

Objective: To investigate cognitive impairments in amyotrophic lateral sclerosis (ALS), extending both within and beyond the established frontotemporal dementia (FTD) spectrum, using the Complementary Cognitive ALS Screen (C-CAS).

Methods: The C-CAS, designed to complement the Edinburgh cognitive and behavioural ALS screen (ECAS), explores cognitive (sub)domains not investigated by the ECAS. Normative data were collected, and models adjusted for age, sex, and education level were developed. Item scores below the 5th percentile in controls were considered abnormal. A sum score was constructed, and C-CAS impairments were compared between ALS patients and controls, and to ECAS impairments.

Results: Data from 314 controls and 184 ALS patients were analyzed. The C-CAS is feasible, well-tolerated, and takes 15-20 min to complete. ALS patients performed worse across all 12 items. Within the FTD spectrum, impairments in social cognition, inhibition, and cognitive flexibility were identified in up to 16%, 14%, and 12% of ALS patients, respectively, with minimal overlap with ECAS impairments. Beyond the FTD spectrum, impairments were found in visuoconstruction, incidental non-verbal memory and body orientation (13% each), with minimal overlap with ECAS memory or visuospatial impairments. Overall, 24% of the ALS patients obtained an abnormal C-CAS sum score. Compared to the ECAS, the C-CAS detected additional impairments in 15% of ALS patients. Item-specific and sum score results based on normative data can be accessed at ( https://apps4mnd.com/ccas/ ).

Interpretation: We identified cognitive impairments in ALS within and beyond the FTD spectrum not captured by existing screening tools. The C-CAS complements the ECAS, improving personalized counseling and research stratification in ALS.