Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig disease, is a rapidly progressive degenerative disease characterized by loss of motor neurons. ALS leads to paralysis and respiratory failure and inevitably results in death. Characteristic findings include muscle atrophy, fasciculations, asymmetric limb weakness, dysarthria, dysphagia, foot drop, dyspnea, and drooling. Presentation is varied and may include findings such as fatigue, muscle cramps, spasticity, neck pain, weight loss, trismus, paralysis, hoarseness, cough, impaired cognition, mood changes, sensory loss, bradypnea, orthostatic hypotension, hypoventilation, hyporeflexia, and hyperreflexia. Symptoms typically start in the limbs, but in about 30% of cases, symptoms start in lower cranial nerve innervated muscles that control speech and swallowing (bulbar onset ALS).

The majority of cases occur sporadically without family history. Approximately 5%-10% of cases are genetically inherited. Approximately 15%-20% of familial cases are associated with mutations in the superoxide dismutase-1 (SOD1) gene.

ALS is more likely to occur in men, with a peak incidence in the fifth to seventh decade of life. Veterans are more likely to develop the disease. There are some familial forms of ALS that are associated with concomitant frontotemporal dementia.

Patients typically survive 2-5 years following diagnosis.