Nearly 60% of Amyotrophic Lateral Sclerosis (ALS) patients have a low level of diagnostic certainty (possible, probable) at the time of diagnosis. In the absence of biomarkers, this diagnosis is based, among other things, on the demonstration of the diffusion of signs of denervation by electroneuromyography (ENMG). The objective of this study is to improve the earliness and the level of diagnostic certainty by better demonstrating the diffusion of the denervation process by whole body muscular MRI.

The objective of this study is to show that the combination of ENMG and whole body muscle MRI (WB-MRI) can increase the diagnosis of definite ALS at the onset of the disease For 50 consecutive patients with suspected ALS, the present study will prospectively perform needle electromyography (EMG) and muscle analyses on whole body MRI. The diagnostic category will be determined by revised El Escorial criteria and Awaji criteria. On whole body MRI acquisition, for 83 muscles, will be explored fatty infiltration and atrophy on fat images (chronic denervation) and muscle edema on water images (acute denervation). EMG studies will be performed in at least 10 muscles (tongue, biceps brachii, first dorsalis interosseous, T10 paraspinalis, vastus lateralis, and tibialis anterior). Diagnostic classification according EMG and/ or MRI abnormalities in bulbar and the 3 spinal regions will be compared independently.

Inclusion Criteria:

• Consent form signed by the patient
• Patients suspected ALS defined according Awaji Shima criteria (possible, probable, defined)
• Clinical assessment of upper motor neuron involvement
• Electrophysiologic assessment of lower motor neuron involvement

Exclusion Criteria:

• inability to give informed consent
• a contraindication to MRI
• respiratory failure impairing ability to lie flat in the scanner.
• Patient placed under judicial protection or under another protective regime,
• Females who are pregnant