Muteness

Treatment or management also varies by cause and this can often be determined after a speech assessment. Treatment can sometimes restore speech. If not, a range of assistive and augmentative communication devices are available.

Causes

Biological causes

Biological causes of mutism may stem from several different sources. One cause of muteness may be problems with the physiology involved in speech, for example, the mouth or tongue. Mutism may be due to apraxia, that is, problems with coordination of muscles involved in speech. Another cause may be a medical condition impacting the physical structures involved in speech, for example, loss of voice due to the injury, paralysis, or illness of the larynx. Anarthria is a severe form of dysarthria, in which the coordination of movements of the mouth and tongue or the conscious coordination of the lungs are damaged.

Neurological damage due to stroke may cause loss or impairment of speech, termed aphasia. Neurological damage or problems with development of the area of the brain involved in speech production, Broca's area, may cause muteness. Trauma or injury to Broca's area, located in the left inferior frontal cortex of the brain, can cause muteness. Muteness may follow brain surgery. For example, there is a spectrum of possible neurobehavioural deficits in the posterior fossa syndrome in children following cerebellar tumor surgery.

Psychological causes

When children do not speak, psychological problems or emotional stress, such as anxiety, may be involved. Children may not speak due to selective mutism. Selective mutism is a condition in which the child speaks only in certain situations or with certain people, such as close family members. Assessment is needed to rule out possible illness or other conditions and to determine treatment. Prevalence is low, but not as rare as once thought. Selective mutism should not be confused with a child who does not speak and cannot speak due to physical disabilities. It is common for symptoms to occur before the age of five. Not all children express the same symptoms.

Selective mutism may occur in conjunction with autism spectrum disorder or other diagnoses. Differential diagnosis between selective mutism and language delay associated with autism or other disorders is needed to determine appropriate treatment.

Adults who previously had speech and subsequently ceased talking may not speak for psychological or emotional reasons, though this is rare as a cause for adults. Absence or paucity of speech in adults may also be associated with specific psychiatric disorders.

Developmental and neurological causes

Absence of speech in children may involve communication disorders or language delays. Communication disorders or developmental language delays may occur for several different reasons.

Language delays may be associated with other developmental delays. For example, children with Down syndrome often have impaired language and speech.

Children with autism, categorized as a neurodevelopmental disorder in the DSM-5, often demonstrate language delays.