Speech disorders include articulation (phonological), stuttering (fluency), and voice disorders. A phonological or articulation involves errors in sound production, use, representation or organization. There is the substitution of one sound for another, omissions of sounds or distortion of sound. The severity varies from mild to severe and is more common in males.
In stuttering or fluency disorder, there is frequent repetitions or prolongations of sounds or syllables and this ends in a lack of speech fluency. The cause is thought to be genetic. It is more common in males and there is a family history of expressive language impairment, articulation disorder, or stuttering. In addition, there may be associated anxiety, depression, and low self-esteem.
Voice disorders include deficits relative to atypical loudness, pitch, duration, and resonance. The pitch is inappropriate (too high, too low, never changing, or interrupted by breaks). The quality is harsh, hoarse, breathy, or nasal.
Another classification of speech disorders includes: speech disorders of known causes in children (speech disorders due to mental retardation, cleft palate), Speech disorders of unknown origin (includes functional articulation disorders, phonological disorders, articulation and phonological disorders, and persistent sound system disorders).
Neuromotor speech disorders are of two major types: dysarthria and apraxia. The causes include myasthenia gravis, Parkinson’s disease, amyotrophic lateral sclerosis, cortical lesions, cerebellar ataxias etc.
Aphasia is the impaired ability to formulate, retrieve, and/or decode the symbols of language. They include Broca’s or motor aphasia, transcortical motor aphasia, anomic aphasia, Wernicke’s aphasia, global aphasia etc.