Year: 2026
Type: article
Abstract: Background Defining motor phenotypes in amyotrophic lateral sclerosis (ALS) is important for individualized care and optimal therapeutic trial design. The “ALS-OPM” classification is based on the onset region (O), the propagation of motor symptoms (P), and the degree of clinical upper (UMN) and/or lower (LMN) motor neuron dysfunction (M).Methods An international ALS expert focus group was held in September 2025, followed by a consensus process through which revisions of the OPM classification were finalized.Results Onset (O1-4) identifies first motor symptoms as relating to the head (O1), distal/proximal arm (O2d/p), respiratory/axial trunk (O3r/a), or distal/proximal leg (O4d/p). Onset symptoms are defined by weakness or slowed, poorly coordinated voluntary movements in the muscles of the head, arm, trunk, or leg, including dysarthria, dysphagia, dysphonia, dyspnea, and axial instability. Propagation (P1(n)) or absence of propagation (P0(n)) of motor symptoms from the onset region to another body region are designated, where n denotes the number of months from onset to propagation or assessment. The degree of UMN dysfunction (slowed, poorly coordinated voluntary movements, hyperreflexia and/or spastic muscle tone, emotional lability) and/or LMN dysfunction (weakness with associated muscle atrophy) is classified as follows: balanced UMN and LMN dysfunction (M0); dominant (M1d) or pure UMN dysfunction (M1p); dominant (M2d) or pure LMN dysfunction (M2p); and dissociated UMN/LMN dysfunction (M3), in which the arms and legs predominantly show LMN and UMN involvement, respectively.Conclusion The revised ALS-OPM classification aims to make it routine, practical and feasible to capture phenotype in clinical practice and therapeutic trials.
Authors: Thomas Meyer, Nicola Ticozzi, Markus Weber, John Ravits, Paul Lingor, Magdalena Kuźma-Kozakiewicz, Matthias Boentert, Torsten Grehl, Philippe Corcia, Mónica Povedano Panadés, André Maier, Caroline Ingre, Hakan Cetin, Patrick Weydt, Christian Lunetta, Leonard van den Berg, Albert C. Ludolph, David Brenner, Martin R Turner, Angela Genge
Institutions: Humboldt-Universität zu Berlin, Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Freie Universität Berlin, Charité - Universitätsmedizin Berlin, University of Milan, IRCCS Istituto Auxologico Italiano, Muskelzentrum/ALS Clinic, University of California San Diego, German Center for Neurodegenerative Diseases, TUM Klinikum, Technical University of Munich, Medical University of Warsaw, Alfried Krupp Hospital, Hôpital Bretonneau, Bellvitge University Hospital, Karolinska Institutet, Medical University of Vienna, University of Bonn, Istituti Clinici Scientifici Maugeri, University Medical Center Utrecht, University Hospital Ulm, John Radcliffe Hospital, University of Oxford, Montreal Neurological Institute and Hospital, McGill University
Language: English
Subfield: Neurology
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Awards: G1303340219, G1864982059, G7039972366
OpenAlex ID: W7138394987