Apraxia of Speech Vs. Dysarthria
Apraxia of speech (AOS) refers to a neurogenic speech disorder that is caused by central nervous system (CNS) damage. AOS is associated with impairment to motor planning and/or programming. Although there is no weakness of paralysis of the muscles, the CNS damage makes it difficult to program and precise movements necessary for smooth articulated speech.
Childhood Apraxia of Speech is pediatric speech sound disorder associated with impaired accuracy and consistency of movements underlying speech. These individuals demonstrate sensorimotor difficulties in positioning and sequentially moving muscles for the volitional production of speech. It is hard for these individuals to plan and program the movement sequences and they frequently show groping behaviors and poor intelligibility due to inconsistent and multiple articulation errors.
- Children with CAS usually show:
- Slow, effortful speech
- Prolonged speech sounds
- Repetition of sounds and syllables
- Most difficulty with consonant clusters followed by fricatives, affricates, stops and nasals
- More frequently occurrence of omissions and substitutions
- Voicing and devoicing errors
- Vowel errors
- Groping and silent posturing of articulation
- Problems with hypernasality and nasal emission
- History of feeding problems
- Limited sound inventory
- Inconsistency in sound productions
Treatment for CAS and adults with apraxia involve extensive drills that stress sequences of movement involved in speech production, imitation, decreased rate of speech, normal prosody and increased accuracy in the production of individual consonants, vowels, and consonant clusters. The overall goal for treatment is to have the individual spontaneously produce words naturally, effectively, and efficiently with a focus on articulation and prosody. It is important to master this goal both inside and outside the clinic. Most recently, a system called PROMPT (prompts for restructuring oral muscular phonetic targets) has been used to treat children with CAS. This approach uses tactile kinesthetic proprioceptive cues to support and shape movements of the articulators.
The term dysarthria refers to a group of speech disorders associated with an impairment to motor speech control and execution resulting from damage to the central nervous system (CNS) and/or the peripheral nervous system (PNS). The area of damage categorizes the type of dysarthria, the associated characteristics, and treatment goals. This damage typically leads to weakness, or incoordination of the muscles of speech. Dysarthria can be caused by cerebral palsy, head injury, degenerative disease, tumor, and stroke. This disorder impacts all of the speech systems, therefore, all of the speech systems must be incorporated in assessment and treatment. Individuals with dysarthria typically show:
- Breathy or harsh voice
- Monopitch or monoloudness
- Hypernasality or hyponasality
- Nasal emission
- Distorted vowels
- Imprecise consonants
- Prolonged phonemes
- Reduced or excess stress
Dysarthria treatment is very repetitive and structured. It involves increasing muscle tone and strength, increasing range of motion, rate of speech and treating other parameters that affect intelligibility. It involves systematic drill, modeling, phonetic placement and emphasis on accuracy of sound production. The focus of treatment for each individual with dysarthria is based on the severity of the disorder.
What is the difference between Apraxia and Dysarthria?
- Predominant lesion for AOS occurs in frontal lobe
- Speakers with apraxia do not exhibit neuromuscular conditions, as seen in dysarthria
- Speakers with apraxia do not exhibit swallowing deficits, as seen in dysarthria
- Typically, only articulation and prosody are impaired with AOS, meanwhile, all subsystems are impaired with dysarthria
- Speakers with AOS demonstrate inconsistent speech sound errors
- Volitional phonation can be impaired at times with apraxia, however both volitional and reflective behaviors are impaired with dysarthria
- Well practiced tasks will be easier for AOS than less familiar task
-Lauren LaGreca, M.A, CF-SLP