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Whether cognitive and behavioural impairment in amyotrophic lateral sclerosis (ALS) is progressive is unknown. The majority of longitudinal studies (summarised in online supplementary material) are characterised by stable test results, high attrition and under-representation of patients with a short disease duration.1 2 The aim of this study was to determine progression of cognitive and behavioural impairment in patients with early symptomatic ALS.
At our tertiary ALS clinics, we consecutively recruited patients with ALS with a short disease duration (<12 months). Comprehensive neuropsychological examination and behavioural assessment were conducted at baseline and at 6 months. Patients with behavioural variant frontotemporal dementia (bvFTD) and healthy controls (HC) served as control groups. We used validated tests to correct for motor and speech impairment, for example, the verbal fluency index. Inclusion and exclusion criteria and neuropsychological tests, including parallel versions are listed in online supplementary material 1. Test scores were considered abnormal below the fifth percentile, corrected for age and education.3
Patients with ALS were classified according to consensus criteria, as having ‘no’, ‘mild’ or ‘severe’ cognitive impairment. ‘No’ is determined by ≤1 abnormal neuropsychological test (letter fluency excluded), ‘mild’ by impaired letter fluency, or impairment on either two (non-overlapping) executive tests or two (non-overlapping) language tests (maximum of 3 abnormal tests); ‘severe’ by >3 abnormal tests (including letter fluency, and either two executive or two language tests, as described above).3
We used the ALS-FTD-Questionnaire (ALS-FTD-Q) to subdivide patients into groups with ‘no’ (<22 points), ‘mild’ (≥22 and <29 points) or ‘severe’ (≥29) behavioural impairment based on validated cut-off scores.
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