What is Apraxia?
The term apraxia is used to describe the inability to perform particular purposeful actions despite normal muscle strength and tone. People who suffer from apraxia are usually unable to perform common expressive gestures on request, such as waving good-bye, beckoning, or saluting, or to pantomime drinking, brushing teeth, etc. Apraxia may also affect oral, non-speech movements, like pretending to cough or blow out a candle.
What is Apraxia of Speech?
Apraxia of speech (AOS) is an impaired ability to perform speech movements. It is differentiated from dysarthrias in that it is not due to problems in strength, speed, and coordination of the articulatory musculature. The primary behavioral characteristics of AOS are slowed speech, abnormal prosody, distortions of speech sounds such as sound substitutions and highly inconsistent errors. Individuals with AOS often appear to be groping for the right way to position their mouth, tongue and lips (articulators) when producing words and sounds.
What causes Apraxia?
Apraxia of Speech (AOS) can be divided into two types based on what caused the condition: childhood apraxia of speech and acquired apraxia of speech. Acquired AOS typically results from brain injury in people who have already learned how to speak. Damage to a wide range of brain areas has been associated with the disorder, mostly in the left hemisphere. Developmental AOS begins very early in life and in many cases may be genetic. As a result, developmental AOS is characterized not only by symptoms seen in acquired AOS, but also by a multitude of other developmental issues.
At present, the diagnosis of AOS remains purely behavioral, based primarily on perceptual evaluation of speech characteristics without evaluation of brain tissue damage. This sometimes may result in confounding disorders with shared behavioral symptoms. However, in future apraxia evaluation may change as more is understood about what type of brain damage causes AOS and diagnosis may rely more heavily on evaluation of specific damage to brain regions important for speech.
How does Apraxia relate to Aphasia?
Both aphasia and apraxia are speech disorders, and both can result from brain injury most often to areas in the left side of the brain. However apraxia is different from aphasia in that it is not an impairment of linguistic capabilities but rather of the more motor aspects of speech production. People with aphasia who also have apraxia may be further limited in their ability to compensate for the speech impairment by using informative gestures.
Organizations with emphasis on Apraxia of Speech:
- Duffy, JR (2005). Motor speech disorders: substrates, differential diagnosis, and management (2nd edition). St. Louis, MO: Mosby-Year Book, Inc.
- Kent, RD (2004). The MIT encyclopedia of communication disorders. Cambridge, MA: MIT Press.
- Maassen, B (2002). Issues contrasting adult acquired versus developmental apraxia of speech. Semin Speech Lang, 23, 257-266
- Mailend, ML and Maas, E (2013). Speech motor programming in apraxia of speech: evidence from a delayed picture-word interference task. Am J Speech Lang Pathol, 22, S380-S396.
- McNeil, MR, Doyle, PJ, and Wambaugh, J (2000). Chapter 9: Apraxia of speech: a treatable disorder of motor planning and programming. In: SE Nadeau, LJ Gonzalez-Rothi, and B Crosson (Eds.), Aphasia and language: theory to practice. (pp. 221-266). New York: Guilford Press.
- Guenther, FH, (2016). Neural Control of Speech. MIT Press pp: 252-256
- Rothi, LJ and Heilman, KM (1997). Apraxia: the neuropsychology of action. Hove, UK: Psychology Press.
- Strand, EA, Duffy, JR, Clark, HM, and Josephs, K (2014). The apracia of speech rating scale: a tool for diagnosis and description of apraxia of speech. J Commun Disord, 51, 43-50.
- Wambaugh, J, Duffy, JR, McNeil, MR, Robin, DA, and Rogers, MA (2006). Treatment guidelines for acquired apraxia of speech: a synthesis and evaluation of the evidence. J Med SpeechLang Pa, 14, xv-xxxiii.
- Ziegler, W (2002). Psycholinguistic and motor theories of apraxia of speech. Semin Speech Lang, 23, 231-243.