Brain grey matter perfusion in primary progressive multiple sclerosis: Mild decrease over years and regional associations with cognition and hand function. - Testud, Benoit; Delacour, Clara; El Ahmadi, Ahmed Ali; Brun, Gilles; Girard, Nadine; Duhamel, Guillaume; Heesen, Christoph; Häußler, Vivien; Thaler, Christian; Has Silemek, Arzu Ceylan; Stellmann, Jan‐Patrick (European Journal of Neurology, 2022)