What is Apraxia of Speech?
Apraxia is a motor disorder in which volitional or voluntary movement is impaired without muscle weakness. The ability to select and sequence movements is impaired. Oral apraxia affects one’s ability to move the muscles of the mouth for non-speech purposes. Someone with oral apraxia would have trouble coughing, swallowing, wiggling their tongue, or blowing a kiss when asked to do so. Verbal apraxia, or apraxia of speech, is an impairment in the sequencing of speech sounds.
Apraxia is different from dysarthria in that there is no muscle weakness. The errors heard in dysarthric speech are usually consistent and predictable, while errors in apraxic speech are unpredictable. Apraxic speakers “grope” for the correct word; they may make several attempts at a word before they get it right.
Acquired Apraxia
Apraxia that happens as a result of a incident causing brain damage is said to be “acquired”. This can result from stroke, head injury, brain tumors, toxins, or infections. It can be so severe that the individual is unable to initiate speech or so mild that an individual only has occasional difficulties in conversation pronouncing multi-syllabic words.
Treatment approaches for apraxia of speech depend on the severity of the impairment. For people with moderate to severe apraxia, therapy may start by saying individual sounds and contrasting them, thinking about how the lips and tongue should be placed. Tapping or clapping out the rhythm of speech helps some speakers to speak more clearly. Contrastive stress drills use the natural rhythm of speech to increase intelligibility. In this exercise, the same sentence is repeated with a different stress patterns, changing the meaning of the sentence. Individuals with mild apraxia learn strategies to use to help them produce the longer words that give them trouble. For the very severe apraxia, alternative and augmentative systems are often employed.
Developmental Apraxia
Developmental apraxia of speech (DAS) is not well understood. This is a disorder that occurs in children and is present from birth. There are no specific lesion sites in the brain in cases of developmental apraxia; acquired apraxia can be linked to specific lesion sites. When children do not develop speech normally and are unable to produce consonant sounds, they may be apraxic. It is difficult to diagnose as expressive language impairment may cloud the issue. Young children only use a few words at at time and it has been argued that delays in language expression can disrupt a child’s ability to gain voluntary motor control over their speech muscles. Some children with DAS have generalized incoordination.
There are several treatment programs for DAS. Some approaches use tactile cues: PROMPT (Prompts for Restructuring Oral Muscular Phonetic Targets, Deborah Hayden), Touch-Cue, or motokinesthetic. Traditional articulation therapies are modified, using phonetic placement, progressive approximation approaches. For children with limited expressive language, the development of a core vocabulary can simultaneously target improving speech. Therapy usually focuses on sound combinations and movement patterns rather than isolated sounds. Children also benefit from pairing speech with other rhythmic motor activities like clapping or marching.