The Motor Speech Disorders: Apraxia and Dysarthria Defined

The late Pam Marshalla, a renowned Speech Pathologist, said it best in the opening to her book, Apraxia Uncovered- Seven Stages of Phoneme Development, "Children with apraxia and dysarthria do not respond well to traditional speech therapy methods and procedures, rather they need a therapy that actually teaches them how to make their speech mechanism function correctly." Let's take a more detailed look at the causes, theories, and characteristics that define apraxia and dysarthria.

Dysarthria is an impairment in muscle movements for speech caused by damage in the central or peripheral nervous system.  Speech productions may sound weak or breathy, or productions may sound strained; it all depends on the site of the lesion.  The articulators (lips, tongue) may be reduced in range of motion, speed, or coordination of movement.  Therapy sessions would be catered to the needs of the individual, be progressive in nature, and may involve oral motor activities.

Apraxia of speech is a condition that impacts one's ability to plan sequential movements for speech productions.  Like dysarthria, apraxia can be acquired or developmental.  Probably the most frustrating thing about a developmental apraxia diagnosis for some families is that it's cause is unknown.  Since there are no definitive answers in these idiopathic situations, there are a few theories for causation ranging from motor programming/planning theories to breakdowns in linguistic process theories.  The latter implies that language frameworks are inadequate and thus cannot support segmenting sounds into words.  Still another theory proposes that impairments in sensorimotor integration and/or sensory processing make it difficult for children to feel placements for articulators or interpret sensory feedback in the mouth.  While we can't always provide answers to causation questions, we can provide effective therapy by structuring programs that best meet your child's ability and needs.

Below is a list of characteristics common to many clients with apraxia of speech.  This information was adapted from an informative website, www.apraxia-kids.org:

•  Errors on vowel productions
•  Variety of errors for one sound target (For example, may produce "mat", "sat" or "hat" for the word "cat")
•  Productions that are difficult to understand or distorted
•  Increase in errors as length or complexity of words increases
•  May be heard saying a target sound correct once, but not again 
•  More successful with predictable, learned targets, like counting and reciting abc's, but not able to produce sounds in spontaneous conversations
• Slower rates/speeds when talking because sequencing sounds/words is such a struggle
• Awkward prosody with limited to no use of stress on words
• Significant difficulty with repetitions
• Clear, physical signs of difficulty talking
• Age appropriate receptive/comprehension ability.  Your child knows what he or she wants to say, but can't sequence the complicated stages necessary for speech.

As speech pathologists it is within our scope of practice to diagnose and treat apraxia and there are several tools available for these purposes.  We also seek additional training to help us enhance our diagnostic and clinical skills in treating children with apraxia.  In addition to speech interventions, we may need to teach other effective means for communication, determine if there are comprehension needs, address social communicative concerns, and work at your child's level. 

In severe to profound motor speech disorders, speech pathologists support functional, effective communication for a child by finding the appropriate augmentative communication (i.e., pictures, voice output) that assist in making a child's needs known.  Once the method is identified, the next steps in therapy involve teaching both the child and caregivers how to communicate effectively with the new support system.

PROMPT therapy is an evidence-based option that may suitable for your child, but rigorous clinical training is necessary for this approach.  I will further discuss PROMPT in my next blog post.