Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting the central and peripheral motor neurons, characterized by the rapidity of its evolution (median survival of 3 years). The pathophysiology of the disease is still poorly understood. Neuronal death results from several cellular mechanisms entangled, including mitochondrial dysfunction. The absence of diagnostic marker causes a significant delay in diagnosis, on average a year. On the other hand, the wish biomarker is important for therapeutic trials. Recently, MRI sodium (23Na) demonstrated its importance to detect noninvasively sodium accumulations associated with neuronal suffering. This neuronal pain can be caused by mitochondrial dysfunction causing the accumulation in the sodium and calcium cell causing neuronal death. These studies were conducted in multiple sclerosis, Alzheimer's disease, Huntington's disease, stroke and brain tumors. They demonstrated that sodium MRI could be an effective and sensitive biomarker for detecting and quantifying neuronal degeneration. The goal of this study is to assess neuronal damage noninvasively by MRI sodium in amyotrophic lateral sclerosis.

Inclusion Criteria:

• Amyotrophic lateral sclerosis patient according to the El Escorial criteria revised Brooks et al. 2000 bulbar or spinal beginning

Exclusion Criteria:

• patient or healthy volonteer presenting MRI contre indications to this exam.
• patient or healthy volonteer presenting severe high blood pressure undergoing medication to treat it or not.
• patient or healthy volonteer having chronic psychiatric illness, dementia