Objective: The primary objective in this study is to identify which (pheno)type of ALS patient has the most benefit from NIV in improving quality of life. Study population: Adult patients with ALS, PLS (Primary Lateral Sclerosis) of PSMA (Progressive Spinal Muscular Atrophy) in the Netherlands. Patients will be included during their first visit to one of the HMV centres in the Netherlands. Main study parameters/endpoints: The main study parameter is change in Quality of Life (QoL) defined as change in ALS Assessment Questionnaire (ALSAQ-40) in patients with ALS after initiation of NIV.

Design: Multi-centre prospective cohort study consisting of 2 non-randomized cohorts, i.e. ALS patients who start NIV and ALS patients who do not start NIV at the time of inclusion in the present study. Duration: The total duration of the study: 3,5 years. Inclusion period: 30 months. Follow up time after initiation of NIV: 9 months. Thereafter, 6 months will be used for data analysis. Setting: Involvement of all (4) HMV centres in the Netherlands (Groningen, Maastricht, Rotterdam, Utrecht). Procedure: 250 ALS patients will be included. During the first regular visit to the HMV centre patients will be asked to participate in the study. Data will be recorded during regular visits to the HMV centre.