What is the main characteristic of Amyotrophic Lateral Sclerosis?
['Motor neuron diseases (MND), such as amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA), are progressive neurodegenerative diseases that share the common characteristic of upper and/or lower motor neuron degeneration.', 'Amyotrophic lateral sclerosis (ALS) is a progressive degeneration of upper and lower motor neurons.', 'There are four main hypotheses about the cause of ALS: excitotoxicity linked to glutamate receptor overactivation; mutation of the superoxide dismutase gene; production of autoantibodies to calcium channels; neurofilament accumulation. The motoneuron degeneration characteristic of ALS could be caused by any one or a combination of these mechanisms.', 'Amyotrophic lateral sclerosis is the most common adult-onset motor neuron disease and evidence from mice expressing amyotrophic lateral sclerosis-causing SOD1 mutations suggest that neurodegeneration is a non-cell autonomous process where microglial cells influence disease progression']
['Amyotrophic lateral sclerosis (ALS) is a progressive degeneration of upper and lower motor neurons. ', 'Amyotrophic lateral sclerosis (ALS) is a progressive degeneration of upper and lower motor neurons.']
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