Developmental Verbal Dyspraxia

Developmental Verbal Dyspraxia  (DVD), also known as developmental apraxia of speech (DAS), is an impaired ability of the child, in the absence of muscular disturbance of the speech mechanism, to execute voluntarily the expected motor gestures and programming of gestures needed for the articulation of speech. A striking feature of DVD or DAS is the child’s inability to produce an appropriate motor gesture for speech but yet demonstrate the same motor gesture in a more automatic nonverbal act.  The disability in developmental verbal dyspraxia is one of voluntary motor programming and sequencing of speech rather than one of motor force and control in both speech and nonspeech acts, as in the case of dysarthria.

Developmental oral apraxia (buccofacial apraxia): an inability to perform voluntary movements of the muscles of the pharynx, tongue, cheeks, lips, although automatic movements are preserved.

It is assumed that lesions are generally localized a high cortical levels, but to date, there is limited neurological evidence to support this view and it is highly controversial.

DVD is currently ill-defined and poorly documented.   There is significant disagreement in the literature about the presence or absence of critical signs and symptoms of DVD.  One of the reasons for trying to “diagnose” a child with DVD is that treatment techniques differ from that of a functional articulation disorder including: motor and orosensory training for articulation, special cueing techniques, visual approaches to speech and language, augmentative communication via manual sign language, melodic intonation therapy and the use of palatal lifts.

The most widely reported and consistent definition of DVD is that it is a motor programming disorder.  The defining motor problem, an inability to consistently position the articulators for speech, may lead to a variety of symptoms—some motor such as oral diadochokinesis disability, some phonological such as inconsistent articulatory errors, vowel distortions, consonant omission, and distortion and addition errors; and some linguistic, such as word retrieval and syntactic disability.

DVD may be present in speech alone (verbal apraxia) or may coexist with nonspeech oral movement problems (oral apraxia). However, each of these have not been accepted in childhood disorders either.
It is very unlikely when considering the issue of symptom variability that any given child suspected of DVD will fit exactly the symptom picture proposed in any of the specific descriptions of the DVD syndrome.  The lack of common symptoms in DVD children is the heart of the controversy concerning the validity of the DVD syndrome.  However, it is quite uncommon to see complete syndromes in neurologic medicine and syndrome variability often leads to confusion among clinicians about the concept of a syndrome.  A neurologic syndrome is not a completely fixed and invariant group of findings as some may think.

It is possible to retain the concept of a DVD syndrome, if the necessary and sufficient conditions of a voluntary motor programming disorder either at the speech or nonspeech level are met.  The motor programming disability may or may not result in a rigidly consistent set of motor, phonologic, linguistic, or neurologic signs or symptoms, and inconsistency among symptoms should be expected as typical rather than atypical.

Phonologic-Linguistic Variables:
Are phonological or linguistic variables significantly different in DVD from those identified a phonologically disorder or language impaired according to group studies?  Studies are controversial. Controlled studies using equated groups have failed to replicate phonologic and other characteristics said to be typical of DVD in misarticulating children.  So investigators have turned to single case studies for in depth analysis.

Some results have been: 1.  a palatal lift to improve hypernasality, articulation, and language over time.  2.  observations that  a child had a productive phonology system exhibiting a well-developed segmental phonetic repertoire in conjunction with extremely restricted phonetic structures.  The authors argue that the severe constraints upon combining and sequencing the segments of the phonetic system were directly caused by the motor programming disability which in turn restricted phonetic potential eventually creating a constrained and disordered phonologic system.

Several recent studies have been done, but no findings which are conclusive.

Assessment:
There is only one published screener for DVD; however, it has been highly criticized and is not recommended in its present form.

Suggested battery might include:
1. Volitional movements of the oral muscles in isolation and in sequence at both the non-speech and speech levels
2. rates of oral diadochokinesis  in non speech and speech activities
3. articulatory proficiency of isolated phonemes, polysyllabic words, and connected speech.  Authors suggest an articulation analysis by place manner and error type as well as a judgment of overall speech intelligibility
4. language testing with standardized language tests
5. presence or absence of “soft” neurologic signs

Others also recommend:
1. orosensory perception and oral awareness
2. Ruling out signs of spasticity or flaccidity and incoordinations of basal ganglia disorders or cerebellar dysfunction;
3. perceptual analysis of vocal characteristics to rule out vocal signs of dysarthria
4. Completed longitudinal assessments/placed in diagnostic therapy
 
 

Management of Developmental Verbal Dyspraxia

The effectiveness of most DVD programs is essentially unknown
Some believe that similar approaches that are appropriate with adults will be effective with children.  Others disagree saying that they find little similarity between child and adult verbal dyspraxics, and that child hood dyspraxia, dysarthria, and functional misarticulation  are more alike than they are different, implying that similar approaches to articulation therapy is effective in all three.

Prevailing notion is that specialized approaches to DVD are called for.
Author recommends the following:
a. imitation of articulatory postures
b. phonetic placement
c. auditory-visual sound stimulation
d. motor repetitions
(The author deemphasizes auditory discrimination drills and rule-based phonologic approaches)

Traditional approaches:
1.  Oral-Motor and Oral Sensory Training:  Purpose is to heighten visual sensory awareness of articulatory postures.
a. Mirror work to increase ROM of muscles, encourage accurate placement of articulators and discourage dyspraxic movements of the oral mechanism.
b. Drills on movement of the tongue and lips in imitation and then upon command
c. Uses foods and mouthwash to elicit desired movement patterns (the child places the tongue where the stimulus is placed.) Visual feedback is provided during the task.
d. Tactile stimulation is stressed
e. Uses textures (cotton, sandpaper to articulators.
f. Deep pressure and resistance techniques to facilitate oral awareness
The role of oral-sensory function in the speech mechanism is questioned in terms of it being beneficial to speech

2. Developing articulatory postures
(Some oppose this therapy because a child with DVD finds it difficult to imitate the articulatory postures of the SLP)
a. For developing vowel postures the advocates suggest observing your own mouth in a mirror and then placing manually the child tongue and lips into a like posture and position and then ask the child to make a noise.
3. Training Sound sequences
Usually meaningful stimuli are employed beginning with the production of visible consonants in CV, VC and CVC sequences and then proceeding to words, and phrases.
4. Speech training associated with rhythm, hand and or body movement:
Some advocate that non-speech behaviors such as foot tapping or finger tapping are helpful in the treatment of DVD.  IT is believed that these activities tend to highlight sequence and changes in placement of the articulators.

Other Approaches:
    Tactile Stimulation:
5. Adapted Cueing techniques (ACT) from the manual alphabet for the deaf to enhance oral stimuli and elicit more correct articulations
6. Touch-cue method hand shapes from the American Manual Alphabet for Signed Target Phonemes; concurrent with nonspeech, signed English, and oral-motor approach arguing for early intervention and alternate communication techniques
7. PROMPTS a system of tactile stimulation and phonetic placement procedures

Feedback
8. Wisconsin Test Apparatus (feedback for correct responses)

Singing
9. Melodic Intonation Therapy

Prosthetic

10. Palatal Lift

Seminar available from ASHA:
Dynamic Remediation Strategies for Children with Developmental Verbal Dyspraxia by Shelly Velleman and Kristine Strand (1988) Advocates a phonotaxic perspective and provides a suggested treatment program that aims at increasing early grammatical skills in children with DVD.