A speech disorder is a communication disorder characterized by an impaired ability to produce speech sounds or normal voice, or to speak fluently.
Speech disorders belong to a broad category of disorders called communication disorders that also include language and hearing disorders. Communication disorders affect one person out of every ten in the United States. Speech disorders refer to difficulties producing speech sounds or problems with voice quality. They may be characterized by an interruption in the flow or rhythm of speech such as stuttering, or by problems with the way sounds are formed, also called articulation or phonological disorders, or they may involve voice problems such as pitch, intensity, or quality. Often, there is a combination of several different problems.
Speech disorders can either be present at birth or acquired as a result of stroke, head injury, or illness. The production of intelligible speech is the result of very complex interactions originating in the brain. When the brain sends a series of speech signals to the speech muscles, the muscles need to produce the series of sounds that will convey the intended message. Major speech disorders that can impair this process include:
- Articulation disorders: Articulation is the production of speech sounds, and persons affected by articulation disorders experience difficulty in being understood because they produce incorrect speech sounds. As a result, their speech is not intelligible. They may substitute one sound for another or may distort the sound with the result that it sounds incorrect, even though still recognizable, or omit one or more sounds in a word.
- Phonological disorders: Phonology is the science of speech sounds and sound patterns and of the language rules that dictate how sounds may be combined to produce language. Persons affected by phonological disorders do not use the conventional rules for their native language but substitute their own variants. This affects classes of sounds, as opposed to single sounds. Sounds are characterized by where in the mouth they are produced, how they are produced, and by how the larynx (voice box) is used. Any unusual deviation in these features is called a phonological process. Fronting and backing are examples of phonological processes, characterized by the production of sounds at the front or at the back of the mouth when they should be produced the other way around. For example, the word "go," produced at the back of the mouth, might be used instead of "doe," which is produced in the front.
- Stuttering: Normal speech is fluent, in that it is spoken effortlessly and without hesitation. A break in fluent speech is called a dysfluency. Although some degree of dysfluency occurs in normal speech from time to time, stuttering has more dysfluencies than is considered average. Normally developing preschool children often demonstrate dysfluencies that are effortless and last for brief periods of time. However, changes in the types of dysfluency behavior and the frequency of occurrence may signal the development of a problem. Normal dysfluencies consist of word or sentence repetitions, fillers ("um," "ah"), or interjections. Stuttering behavior includes sound or syllable repetition, prolongations (the unnatural stretching out of sounds), and blocks, which refers to an inability to produce the sound, as if it gets stuck and cannot come out. Stuttering dysfluencies are also often accompanied by tension and anxiety.
- Voice disorders : There are two types of voice disorders: organic voice and functional voice disorders.
- Organic voice disorders are associated with disease and require medical intervention. Functional voice disorders are the result of abuse or misuse of the larynx. Sounds are produced when the vocal cords of the throat come close together and vibrate with air coming from the lungs. These vibrations produce a series of pulses that then cause the air to resonate and produce voice sounds. People have unique voice characteristics and it is therefore difficult to define a normal voice. Generally speaking, a normal voice is pleasant sounding and has appropriate pitch and loudness for the age and gender of the speaker. A voice disorder is therefore present when the voice is not pleasant sounding, or when it is too loud or too soft or too high-pitched or low-pitched for the speaker's gender.
- Apraxia : This is a speech disorder in which voluntary muscle movement is impaired without muscle weakness. There are two main types of apraxias: buccofacial apraxia and verbal apraxia. Buccofacial apraxia impairs the ability to move the muscles of the mouth for non-speech purposes such as coughing, swallowing, and wiggling of the tongue. Verbal apraxia impairs the proper sequencing of speech sounds. Apraxias can either be acquired or developmental and have different degrees of severity, ranging from the inability to initiate speech to mild difficulties with the pronunciation of multi-syllabic words.
- Dysarthria : This is a speech disorder that affects the muscles involved in the production of speech. As a result, speech is slow, weak, inaccurate, and hesitant. The production of clear speech requires that several muscle systems work together. First, the lungs must provide the air required to activate speech. Then, the larynx must allow the air to vibrate. The soft palate that separates the oral and nasal cavities must also direct the air to one or both cavities to produce the different sounds. Finally, the lips, tongue, teeth, and jaw then must all move in a concerted way to shape the sounds into the various vowels, consonants, and syllables that make up the sounds of language. Dysarthria results from a weakness in any one of these elements or in the absence of proper coordination between them. If, for example, the lungs are weak, then speech will be too quiet or produced one word at a time. Childhood dysarthria can be present at birth or acquired as a result of disease or accident, as is the case for adult dysarthria.
Causes and symptoms
The causes of articulation and phonological disorders are unclear, although it has been observed that they tend to develop in children before age four and run in families. The symptoms vary, depending on whether other disorders are present, but typically involve difficulty in making specific speech sounds Articulation is considered a disorder when it is unintelligible or draws negative attention to the speaker. For example, the word "super" is pronounced as "thuper."
The causes of stuttering are not very well understood. There is some evidence that stuttering has a genetic cause since it has been observed to run in some families. According to the National Stuttering Association (NSA), current research suggests a connection between stuttering and the brain's ability to coordinate speech. The major symptom of stuttering, found in preschoolers but not adults, is persistent dysfluency of language that exceeds 10%.
The main causes of organic voice disorders include neuromuscular disorder, cancer, vocal cord paralysis, endocrine changes, various benign tumors such as inflammatory growths (granulomas), or consisting of a mass of blood vessels (hemangiomas) or occurring on mucous membranes (papillomas). Functional voice disorders are caused by abuse or misuse of the larynx. Misuse of the voice includes talking for excessively long periods of time or yelling. Abuse occurs as a result of excessive throat clearing, laughing, crying, coughing, or smoking. Both abuse and misuse of the voice can damage the vocal cords, or may result in nodules, polyps, contact ulcers, or edema.
Acquired apraxias occur as a result of brain damage and can often be linked to specific lesion sites on the brain. They can result from stroke, head injury, brain tumors, toxins, or infections. In the case of developmental apraxia of speech (DAS), it is usually present at birth. There are no specific lesion sites in the brain associated with DAS, and no direct cause has been identified. However, since young children only use a few words, it has been proposed that delays in language expression can impair a child's ability to gain control over the speech muscles.
Childhood dysarthria can be present at birth or acquired with diseases such as cerebral palsy, Duchenne muscular dystrophy, or myotonic dystrophy. Adult dysarthria may be caused by stroke, degenerative diseases such as Parkinson's or Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, myasthenia gravis, meningitis, brain tumors, toxins, drug or alcohol abuse, or lead poisoning.
Speech disorders are usually identified using a combination of hearing tests and physical exams. Physicians
A stuttering diagnosis is established on the basis of the type, frequency, and duration of speech dysfluency. The number of dysfluencies occurring in 100 words is counted to determine the dysfluency percentage. One half a stuttered word per minute is the usual criterion. Determining the type of stuttering behavior, either overt or covert, is the most important factor in diagnosing stuttering.
Organic and functional voice disorders are diagnosed with the assistance of an ear, nose, and throat specialist, a otolaryngologist, who can identify the organic cause of the voice disorder, if present. Several tests can be used to screen for possible tumors in the throat or laryngeal box area. Only in the absence of an organic cause will the voice disorder be diagnosed as functional, indicating that it is due to abuse or misuse of the voice.
A diagnosis of apraxia is not easy to establish but is usually indicated when children do not develop speech normally and are unable to produce consonant sounds.
Speech pathologists have designed approaches for treating speech disorders with the type of treatment depending upon the type of impairment. A wide variety of treatment techniques are available for treating affected children, adolescents, and adults. A thorough assessment is normally conducted with the aim of determining the most effective and acceptable treatment approach for each disorder on an individual basis. A common treatment for many patients involves increasing sensory motor awareness of selected aspects of speech and systematically shaping the target speech behaviors.
Treatment for articulation/phonological disorders is usually based on increasing the affected person's awareness about how speech sounds make the meaning of words different. As a result, therapy often involves pronunciation exercises designed to teach how to produce sounds and words more clearly to increase understanding of the differences between the various speech sounds and words.
Treatment plans for stuttering depend on the severity of the dysfluency and may include seeing a speech-language pathologist. Most treatment plans include breathing techniques, relaxation strategies to help relax speech-associated muscles, posture control, and other exercises designed to help develop fluency.
Speech-language pathologists use many different approaches to treat voice problems. Functional voice disorders can often be successfully treated by voice therapy. Voice therapy involves identifying voice abuses and misuses and designing a course of treatment aimed at eliminating them. Voice disorders may require surgery if cancer is present.
Treatment of apraxia depends on the extent of the impairment. For individuals diagnosed with moderate to severe apraxia, therapy may be for them to start saying individual sounds and contrasting them, thinking about how the lips and tongue should be placed. Other specialized drills use the natural rhythm of speech to increase understanding. Individuals affected with mild apraxia are taught strategies to help them produce the words that give them difficulty. Several treatment programs have been developed for developmental apraxias. Some feature the use of touching cues, others modify traditional articulation therapies.
Treatment of dysarthria usually aims at maximizing the function of all speech systems with the use of compensatory strategies. Patients may be advised to take frequent pauses for breath, or to exaggerate articulation, or to pause before important words to emphasize them. If there is muscle weakness, oro-facial exercises may also be prescribed to strengthen the muscles of the face and mouth that are used for speech.
The prognosis depends on the cause of the disorder; many speech disorders can be improved with speech therapy. In the case of childhood speech disorders, prognosis also significantly improves with early diagnosis and intervention. Children who do not receive speech therapy and do not outgrow their speech difficulties will continue to have the disorder as adults.
Health care team roles
The treatment of speech disorders belongs to the field of speech-language pathology. Speech-language pathologists assist individuals who have speech disorders and collaborate with families, teachers, and physicians to design an appropriate course of treatment, which depends on the specific nature of the disorder. They also provide individual therapy to affected persons, consult with teachers about effective classroom strategies to help children with speech disorders, and work closely with families to develop effective therapies.
Prevention of speech disorders is centered on identifying at-risk infants. The following conditions are considered
represent high-risk factors, and children exposed to them should be tested early and regularly:
- diagnosed medical conditions such as chronic ear infections
- biological factors such as fetal alcohol syndrome
- genetic defects such as Down syndrome
- neurological defects such as cerebral palsy
- family history such as family incidence of literacy difficulties
Stuttering can be prevented by parents avoiding undue corrections of dysfluency in their children. As young children begin to speak, some dysfluency is normal because they have a limited vocabulary and have difficulty expressing themselves. This results in dysfluent speech, and if parents place excessive attention on the dysfluency, a pattern of stuttering may develop. Speech therapy with children at risk for stuttering may prevent the development of a stuttering speech disorder.
Apraxia—Motor disorder in which voluntary movement is impaired without muscle weakness.
Articulation disorder—Also called phonological disorder; type of speech disorder characterized by the way sounds are formed.
Communication disorder—Disorder characterized by an impaired ability to communicate, including language, speech, and hearing disorders.
Dysarthria—Speech disorder due to a weakness or lack of coordination of the speech muscles.
Dysfluency—Any break or interruption in speech.
Language disorder—Communication disorder characterized by an impaired ability to understand and/or use words in their proper context, whether verbal or nonverbal.
Phonological process—Any unusual change in the place, manner, or larynx characteristics of a produced sound.
Phonology—The science of speech sounds and sound patterns.
Speech disorder—Communication disorder characterized by an impaired ability to produce speech sounds or by problems with voice quality.
Speech-language pathology—This field, formerly known as speech therapy, is concerned with disorders of speech and language.
Stuttering—Speech disorder characterized by speech that has more dysfluencies than is considered average.
Vocal cords—Either of the two pairs of folds of mucous membrane located in the throat and projecting into the cavity of the larynx.
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Monique Laberge, Ph.D.