There are many types of speech and language disorders, each caused by different reasons. Some speech disorders are caused by various parts of the nervous system, muscles, and other parts that are involved in speech. Language disorders are caused by other factors which we will discuss.
One type of language disorder is known as aphasia. This type can be due to a stroke, head injury, or a brain tumor. This is not considered a speech disorder but a language impairment because there is no voice. Children and adults can be affected. With a language disorder, as opposed to a speech disorder, the ability to speak and write or to understand written or spoken words is impaired, depending on the site and extent of the damage.
In children, delayed development of language is characterized by slowness to understand speech and slow growth in vocabulary. Some people may think a child is mentally retarded when there is a delayed development of speech, but this is not necessarily so. There can be many causes for slow development of language. It can be caused by a hearing loss, lack of stimulation, or an emotional problem. It is important to know these factors so that parents will not jump to conclusions.
There are several types of speech disorders. One type of speech disorder is articulation. People with this problem can make sounds but the speech is either slurred, slow, or nasal. This type of speech can be caused by damage to nerves passing from the brain to muscles in the larynx,(voice box) mouth or lips. The damage of this type of speech can also be caused by a stroke, head injury, or tumors just as it is in aphasia. Other causes can be multiple sclerosis or Parkinson’s disease.
Other causes of speech disorders may be caused by structural abnormalities of the mouth, such as cleft palate or cleft lip. A bad alignment of the teeth can also cause a speech problem, such as a lisp.
Sometimes there are no speech problems with individuals, but there could be problems in the voice. These disorders can be hoarseness, harshness, pitch, or loudness of the voice. Sometimes there are people who have a nasal sound which is not due to a cold. In such cases like these, the cause can be closure of the vocal cords, known to be a larynx disorder.
When the voice is nasal, and it is not due to a cold, it is caused by too much air or too little air flowing through the nose when the person is talking.
These speech problems can be helped by a speech therapist. Depending on the cause of the speech problem, a good speech therapist will try to get information from a physician, a teacher, parents, or any source related to the type of speech disorder.
Source: The American Medical Association, Encyclopedia of Medicine
Speech and Language Disorders