Speech disorders or speech impediments are a type of communication disorders where 'normal' speech is disrupted. This can mean stuttering, lisps, etc. Someone who is unable to speak due to a speech disorder is considered mute.
Classification
Classifying speech into normal and disordered is more problematic than it first seems. By a strict classification[citation needed], only 5% to 10% of the population has a completely normal manner of speaking (with respect to all parameters) and healthy voice; all others suffer from one disorder or another.
Stuttering affects approximately 1% of the adult population.[citation needed]
Cluttering, a speech disorder that has similarities to stuttering.
Dysprosody is the rarest neurological speech disorder. It is characterized by alterations in intensity, in the timing of utterance segments, and in rhythm, cadence, and intonation of words. The changes to the duration, the fundamental frequency, and the intensity of tonic and atonic syllables of the sentences spoken, deprive an individual's particular speech of its characteristics. The cause of dysprosody is usually associated with neurological pathologies such as brain vascular accidents, cranioencephalic traumatisms, and brain tumors.
Muteness is complete inability to speak
Speech sound disorders involve difficulty in producing specific speech sounds (most often certain consonants, such as /s/ or /r/), and are subdivided into articulation disorders (also called phonetic disorders) and phonemic disorders. Articulation disorders are characterized by difficulty learning to physically produce sounds. Phonemic disorders are characterized by difficulty in learning the sound distinctions of a language, so that one sound may be used in place of many. However, it is not uncommon for a single person to have a mixed speech sound disorder with both phonemic and phonetic components.
Voice disorders are impairments, often physical, that involve the function of the larynx or vocal resonance.
Dysarthria is a weakness or paralysis of speech muscles caused by damage to the nerves and/or brain. Dysarthria is often caused by strokes, parkinsons disease, ALS, head or neck injuries, surgical accident, or cerebral palsy.
Apraxia of speech may result from stroke or be developmental, and involves inconsistent production of speech sounds and rearranging of sounds in a word ("potato" may become "topato" and next "totapo"). Production of words becomes more difficult with effort, but common phrases may sometimes be spoken spontaneously without effort. It is now considered unlikely that childhood apraxia of speech and acquired apraxia of speech are the same thing[citation needed], though they share many characteristics.
There are three different levels of classification when determining the magnitude and type of a speech disorder and the proper treatment or therapy:
1. Sounds the patient can produce
Phonemic- can be produced easily; used meaningfully and contrastively
Phonetic- produced only upon request; not used consistently, meaningfully, or contrastively; not used in connected speech
2. Stimulable sounds
Easily stimulable
Stimulable after demonstration and probing (i.e. with a tongue depressor)
3. Cannot produce the sound
Cannot be produced voluntarily
No production ever observed
Causes
In many cases the cause is unknown. However, there are various known causes of speech impediments, such as "hearing loss, neurological disorders, brain injury, mental retardation, drug abuse, physical impairments such as Cleft lip and palate, and vocal abuse or misuse."[3] Child abuse may also be a cause in some cases.
