Fasciculation may be due to fatigue, cold, medications, metabolic disorders, nerve damage, or neurodegenerative disease, including amyotrophic lateral sclerosis (ALS, also known as Lou Gehrig's disease).
Possible causes include stroke, multiple sclerosis, cerebral palsy, neurodegenerative diseases, trauma, spinal cord injury, and nervous system poisons such as strychnine, tetanus, and certain insecticides.