Speech disorders or speech impediments, as they are also called, are a type of communication disorder where 'normal' speech is disrupted. This can mean stuttering, lisps, etc. Someone who is totally unable to speak due to a speech disorder is considered mute. Speech disorders refer to problems in producing the sounds of speech or with the quality of voice. In many cases the cause is unknown. However, there are various known causes of speech impediments, such as hearing loss, neurological disorders, brain injury, mental retardation, drug abuse, physical impairments such as cleft lip and palate, and vocal abuse or misuse. This new and important book gathers the latest research from around the globe in the study of speech disorders with a focus on such topics as: speech and voice disorders in Parkinson's Disease, genetic causes, stuttering therapy for adolescents and adults, prosody and autism spectrum disorder, speech rehabilitation after oropharyngeal cancer, mutism, dyslexia and others. - Publisher.