Ataxia (say: ah-TACKS-ee-ah) is a movement disorder. Movement disorders are conditions that cause involuntary body movements. Uncontrolled movement starts in the brain, in the area you use to move, speak, and pay attention. When a child has ataxia, he has trouble controlling his muscles and can be clumsy and awkward. Common examples of ataxia include epilepsy and multiple sclerosis (MS).