Speech Disorders: Types, causes, and treatment

Language is everywhere. It’s in the books we read and the lyrics we hear over the radio. However, language is primarily in the conversations we engage in with the people around us. Speech disorders are immense barriers to communication, as they hinder individuals from forming or understanding spoken language. Continue reading to gain insight on the types of speech disorders, risk factors for developing speech disorders, and how to treat speech disorders.

Speech Disorders: Types, causes, and treatment
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What are Speech Disorders?

A speech disorder is a disorder of communication. It occurs when an individual is unable to create speech sounds that form words. This prevents them easily expressing messages to listeners. Speech disorders affect all ages and genders. However, speech disorders are more prevalent in males with a history of problems of the ears, nose, or throat.

Types of Speech Disorders

There are several types of speech disorders. Each speech disorder is unique, as they affect a specific characteristic involved in creating, articulating, or understanding speech.

Childhood Apraxia of Speech

Childhood apraxia of speech is when the brain fails to deliver signals to coordinate muscle movements during speech. The muscles are not weak but are so uncoordinated that the brain cannot move the mouth, lips, and tongue. This interferes with speech by slowing the speed and rhythm, as well as preventing accurate word sounds.

The symptoms of childhood apraxia of speech appear between 18 months and 2 years of age. The child is delayed in saying their first words and forms few vowel or consonant sounds. As they develop, they experience further vowel and consonant distortions, have a limited vocabulary, and frequently confusing words with similar sounds (i.e. “cat” sounding like “hat”).


Dysarthria is a speech disorder in which the part of the brain that controls the muscles used to produce speech becomes damaged, and the muscles are weakened or paralyzed. Because the muscles of the lips, tongue, vocal cords and diaphragm do not function normally, speaking is difficult. Those with dysarthria often have slurred speech that is hard to understand. They speak quietly with an uneven speech volume and rhythm. In most cases, dysarthria is secondary to neurological disorders.

Orofacial Myofunctional Disorders

Orofacial myofunctional disorders are characterized by abnormal movements of the face and mouth. In some cases, these disorders occur from poor growth of the facial bones. Aside from speech, eating, drinking, talking, breathing, and swallowing are affected.

Children, adolescents, and adults can have an orofacial myofunctional disorder. The main sign of the disorder is a resting facial position with the lips apart. Smaller children are prone to drooling and engage in sucking habits longer than the first twelve months of life. As speech problems arise, someone with this disorder may have a lisp. They mispronounce the “s” and “z” sounds.

Fluency Disorders

Fluency disorders are a group of speech disorders that interrupt the flow of speaking with pauses, prolongations, and repetitions. Stuttering is the most common fluency disorder. The ways fluency disorders impact speech are called disfluencies and consist of:

  • Blocks—Long pauses mid-speech or trouble initiating speech.
  • Repetitions—Repeating sounds, syllables, and words. “P-p-please take me h-h-h-home.”
  • Prolongations—Lengthening the sounds of consonants. “Cccccccan I go to the store?”

Anxiety is a trigger for disfluencies. Physical movement like blinking can accompany stuttering.

Voice Disorders

In people without voice disorders, air passes from the lungs to the larynx and vocal cords to create speech with normal pitch, volume, or tone. If a voice disorder is present, the vocal chords do not vibrate correctly. Pitch, volume, or tone are atypical for the person’s age and culture. Quivering, hoarseness, breathy, or too high or too low in pitch are classic symptoms of voice disorders. The presence of growths on the vocal cords leads to voice disorders. However, the condition is also caused by a nerve problem, inflammation, or vocal abuse.

Articulation Disorders

An articulation disorder is a speech disorder stemming from difficulty forming speech sounds. The term also includes phonological disorders. While speaking, someone with an articulation disorder substitutes one sound for another and leaves out certain letters in words. Children develop articulation disorders more frequently than adults. A common example is the inability to say the “sh” sound, as well as speaking with a lisp.

Resonance Disorders

Resonance describes quality of voice produced from the vibrations in the throat, mouth, and nose. Resonance disorders interfere with resonance because there is too much or too little nasal energy in speech. These disorders produce a distinct nasal sound, and occur when there are structural or functional defects. A cleft palate is one of the primary causes of resonance disorders.

Causes of Speech Disorders

According to the American Speech-Language Hearing Association, 5 to 10 percent of Americans have a speech disorder. There are many causes of speech disorders ranging from injury to intellectual disabilities. Some of the causes include brain damage from a stroke, a head injury, muscle weakness, damaged vocal cords, dementia, cancer, autism spectrum disorder, Down syndrome, hearing loss, and even degenerative neurological diseases. Occasionally, the underlying cause of speech disorders remains unknown.

Diagnosing Speech Disorders

The diagnostic evaluation for speech disorders is performed by a speech-language pathologist who specializes in speech and language disorders. First, they take a through family and medical history. They rule out other medical conditions that mimic the symptoms of speech disorders, as well as pre-existing conditions that contribute to speech difficulties.  A speech-language pathologist also examines the throat and muscles in the face and mouth (i.e. lips, jaw, tongue) that could impede language.

They use a number of screening tools depending on the age and background of the patient:

  • Denver articulation screening examination—This screens children with potential speech problems who are economically disadvantaged or do not have Enghlish as their native language.
  • Prosody-voice screening profile—A test for children and adults with atypical speech.It trains patients in several conversational domains such as phrasing, rate, stress, loudness, pitch, laryngeal quality, and resonance.

Dynamic evaluation of motor speech skills (DEMSS) manual—Designed for children aged 3 and under, the DEMSS evaluates children with reduced phonemics, poor speech intelligibility, vowel or prosodic errors.

Speech Disorders: Types, causes, and treatment
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Speech Disorders and the Nervous System

The nervous system, comprised of the brain and the spinal cord, regulates speech. That is one reason why speech disorders sometimes develop after an injury to the brain. To speak appropriately, the sounds are made from movement of the muscles in the mouth, tongue, and throat. The cerebellum motor cortex coordinates the movement of the muscles once they receive information from the Broca’s area in which speech ideas originate. It words in tandem with a band of nerves known as the arcuate fasciculus, and the Wernicke’s area of the brain, to understand and process language.

Treating Speech Disorders

Treatment for speech disorders depends on the underlying cause. Speech therapy by a speech-language pathologist apply a number of techniques to improve speech. These include:

  • Ear device—Similar to a hearing aid, an ear device replays the speakers voice as they are speaking to control stuttering.  
  • Oral-motor therapy—Oral motor therapy focuses on muscle strength, motor control, and breath control to produce smoother speech sounds.
  • Medication—Many with speech disorders feel anxious when in social situations that require talking, which increases their speech related symptoms. Anxiety medication can eliminate some of the fear.
  • Contrast therapy—Speech pathologists train patients how to produce different speech sounds by pairing words together.
  • Contextual utilization—Speech sounds contain different syllable-based contexts. Contextual utilization teaches patients to identify the sounds.
  • Target selection—Patients recognize speech sounds by repeated practicing specific words and word sounds that typically lead to their speech problem.


Lewis BA, Ekelman BL, and Aram DM (1989) A familial study of severe phonological disorders. Journal of Speech and Hearing Research 32 (4):713-724.

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