Athetoid cerebral palsy affects about 10 percent of children with cerebral palsy. Athetoid cerebral palsy, which is caused by damage to the cerebellum or basal ganglia. These areas of the brain are responsible for processing the signals that enable smooth, coordinated movements as well as maintaining body posture. Damage to these areas may cause a child to develop involuntary, purposeless movements, especially in the face, arms, and trunk. These involuntary movements often interfere with speaking, feeding, reaching, grasping, and other skills requiring coordinated movements. For example, involuntary grimacing and tongue thrusting may lead to swallowing problems, drooling and slurred speech. The movements often increase during periods of emotional stress and disappear during sleep. In addition, children with athetoid cerebral palsy often have low muscle tone and have problems maintaining posture for sitting and walking.