Children with motor impairments often have the motor speech disorder dysarthria, a condition which effects the tone, power and coordination of any or all of the muscles used for speech. Resulting speech difficulties can range from mild, with slightly slurred articulation and low-pitched voice, to profound, with an inability to produce any recognisable words. Children with dysarthria are often prescribed communication aids to supplement their natural forms of communication. However, there is variation in practice regarding the provision of therapy focusing on voice and speech production. Descriptive studies have suggested that therapy may improve speech, but its effectiveness has not been evaluated.