Amyotrophic lateral sclerosis (ALS) is a rapidly fatal neurodegenerative disease characterized by upper (in brain) and lower (in spine) motor neuron degeneration. As conventional MRI fails to show brain motor neurons impairment in ALS, advanced techniques are needed to improve the diagnosis and to monitor the progression of the disease. In this study, brain 23Na MRI was applied in 15 ALS patients and 31 controls. A common pattern of sodium accumulation was found in patients in the primary motor areas while no atrophy was detected. The occurrence of sodium accumulation without atrophy probably reflects early neuronal injury in ALS.