Amyotrophic lateral sclerosis ( Lou Gehrig disease ) is a disease that causes degeneration of motoneurons that control voluntary muscle movement. Surprisingly, the bladder and rectum sphincters remain normal even during the final terminal stages of the illness. Since these muscles are controlled by Onuf's nucleus, it is of great importance in the study of this disease. In amyotrophic lateral sclerosis, Onuf's nucleus is preserved but the other anterior horn cell groups atrophy. This discovery reinforced the notion that Onuf's nucleus controlled the muscles related to sphincter function in the anus and urethra.