Alien hand syndrome (AHS) is when a single limb, usually a hand but sometimes a leg, moves involuntarily. It can signify a serious underlying issue, such as stroke or neurodegenerative disease. Share ...

Split hand syndrome is a potential sign of amyotrophic lateral sclerosis (ALS). This means that some of the muscles in the hand are weak and thin (atrophied), while others are less affected.

Mirror hand syndrome, also known as ulnar dimelia, is an extremely rare congenital (meaning it's there from the time you're born) birth defect that affects your hand. In some cases, your forearm and ...