Amyotrophic lateral sclerosis (ALS) is a disabling and rapidly progressive neurodegenerative disorder. There is no treatment that significantly slows progression. Our project aims to find new biomarkers in MRI at three levels: cerebral, medullary and muscular. These markers could allow an earlier diagnosis of the disease by showing more specific lesions of ALS and to quantify these lesions to measure the progression of the disease. This study will use advanced Magnetic Resonance Imaging (MRI) techniques High field (3T) and very high field (7T) MRI. Results from neurological and electrophysiological tests will be compared to the MRI. Subjects will be recruited from ALS center of Marseille, France. MRI will be done on ALS patients at baseline, at 3 month and at 6 month intervals.