Showing papers on "Dysarthria published in 2011"
TL;DR: VAI seem to be superior to tVSA in the description of impaired vowel articulation in Parkinson's disease speakers suffering from mild hypokinetic dysarthria as compared with healthy controls in correlation to net speech rate (NSR) and intonation variability (F(0)SD).
222 citations
TL;DR: The results showed that acoustic predictors of speech intelligibility differed slightly across diseases and classification accuracy by dysarthria type was typically worse than by disease type or severity.
Abstract: Purpose This study examined acoustic predictors of speech intelligibility in speakers with several types of dysarthria secondary to different diseases and conducted classification analysis solely by acoustic measures according to 3 variables (disease, speech severity, and dysarthria type). Method Speech recordings from 107 speakers with dysarthria due to Parkinson’s disease, stroke, traumatic brain injury, and multiple system atrophy were used for acoustic analysis and for perceptual judgment of speech intelligibility. Acoustic analysis included 8 segmental/suprasegmental features: 2nd formant frequency slope, articulation rate, voiceless interval duration, 1st moment analysis for fricatives, vowel space, F0, intensity range, and Pairwise Variability Index. Results The results showed that (a) acoustic predictors of speech intelligibility differed slightly across diseases and (b) classification accuracy by dysarthria type was typically worse than by disease type or severity. Conclusions These findings were...
169 citations
TL;DR: Appropriate timing of referral for AAC assessment and intervention continues to be a most important clinical decision-making issue.
Abstract: Almost all people with amyotrophic lateral sclerosis (ALS) experience a motor speech disorder, such as dysarthria, as the disease progresses. At some point, 80 to 95% of people with ALS are unable to meet their daily communication needs using natural speech. Unfortunately, once intelligibility begins to decrease, speech performance often deteriorates so rapidly that there is little time to implement an appropriate augmentative and alternative communication (AAC) intervention; therefore, appropriate timing of referral for AAC assessment and intervention continues to be a most important clinical decision-making issue. AAC acceptance and use have increased considerably during the past decade. Many people use AAC until within a few weeks of their deaths.
142 citations
TL;DR: Online treatment for hypokinetic dysarthria associated with Parkinson's disease appears to be clinically valid and reliable and Suggestions for future research are outlined.
Abstract: Background: Telerehabilitation may be a feasible solution to the current problems faced by people with Parkinson's disease in accessing speech pathology services.
Aim: To investigate the validity and reliability of online delivery of the Lee Silverman Voice Treatment (LSVT®) for the speech and voice disorder associated with Parkinson's disease.
Method & Procedures: Thirty-four participants with Parkinson's disease and mild-to-moderate hypokinetic dysarthria took part in the randomized controlled non-inferiority laboratory trial and received the LSVT® in either the online or the face-to-face environment. Online sessions were conducted via two personal computer-based videoconferencing systems with real-time and store-and-forward capabilities operating on a 128 kbit/s Internet connection. Participants were assessed pre- and post-treatment on acoustic measures of mean vocal sound pressure level, phonation time, maximum fundamental frequency range, and perceptual measures of voice, articulatory precision and speech intelligibility.
Outcomes & Results: Non-inferiority of the online LSVT® modality was confirmed for the primary outcome measure of mean change in sound pressure level on a monologue task. Additionally, non-significant main effects for the LSVT® environment, dysarthria severity, and interaction effects were obtained for all outcomes measures. Significant improvements following the LSVT® were also noted on the majority of measures. The LSVT® was successfully delivered online, although some networking difficulties were encountered on a few occasions. High participant satisfaction was reported overall.
Conclusions & Implications: Online treatment for hypokinetic dysarthria associated with Parkinson's disease appears to be clinically valid and reliable. Suggestions for future research are outlined.
136 citations
TL;DR: The aim of this study was to describe speech, expressive language, and verbal cognition of children with cerebral palsy.
Abstract: Aim The aim of this study was to describe speech, expressive language, and verbal cognition of children with cerebral palsy (CP).
Method A population study included 152 Icelandic children with congenital CP (74 males, 78 females; mean age 5y 5mo, range 4y–6y 6mo). Children who spoke in sentences, phrases, or one-word utterances were categorized as verbal. Speech was classified as normal, mild dysarthria, or severe dysarthria. Cognition was reported as IQ (Wechsler Preschool and Primary Scale of Intelligence – Revised) or developmental quotient (DQ).
Results Most children (81%) had spastic CP and bilateral symptoms (76%); 74 (49%) were at Gross Motor Function Classification System (GMFCS) level I, 27% at levels II and III, and 24% at levels IV and V (p<0.001). One hundred and twenty-eight children (84%) communicated verbally whereas 24 were nonverbal. Nonverbal status and severe dysarthria were associated with greater motor impairment (GMFCS; p<0.001). Twenty-five children (16%) had severe dysarthria. Most (88%) of the nonverbal children had multiple disabilities compared with 18% of the verbal group (p<0.001). Median (interquartile range) verbal IQ was 93 (73–104) and performance IQ 77 (61–94; p<0.001). Sixty-eight children (45%) had normal verbal cognition and almost a quarter of the children with severe dysarthria had a full-scale IQ/DQ of 70.
Interpretation Most children with CP express sentences and almost half of them have normal verbal IQ. Nonverbal status frequently indicates multiple impairments whereas severe dysarthria may be associated with normal cognition.
124 citations
TL;DR: A complex association between the severity of an individual's dysarthria and the impact on their social participation is suggested, which has important implications for the prioritisation, planning and delivery of therapeutic interventions for people with Dysarthria.
Abstract: Introduction. Each year an estimated 30,000–45,000 UK individuals experience stroke-related dysarthria (impairment of movements required to produce speech). Many will experience persistent dysarthria long after discharge from stroke services. Although we have some insight into the impact of other communication impairments, we have very limited information on the impact of dysarthria on social participation.Purpose. To explore the impact of dysarthria on social participation following stroke.Methods. We report data from in-depth semi-structured interviews with 24 individuals with stroke-related dysarthria.Results. Our findings suggest a complex association between the severity of an individual's dysarthria and the impact on their social participation. Participants' descriptions highlighted their experiences of social participation and isolation. We further suggest that, in some cases, the coping strategies adopted by the participants could be seen to further exacerbate this isolation. These results have im...
93 citations
TL;DR: A speaker’s overall intelligibility in dysarthric speech is better represented by the overlap degree among vowels than by the vowel space.
Abstract: Background/Aims: This study examined the spectral characteristics of American English vowels in dysarthria associated with cerebral palsy (CP), and investigated the relationship between a speaker’s overall speech intelligibility and vowel contrast. Methods: The data were collected from 12 American English native speakers (9 speakers with a diagnosis of CP and 3 controls). Primary measures were F1 and F2 frequencies of 3 corner vowels /i, a, u/ and 3 noncorner vowels /I, 3, */. Six acoustic variables were derived from the formant measures, and were regressed against intelligibility: corner vowel space, noncorner vowel space, mean distance between vowels, F1 and F2 variability, and overlap degree among vowels. Results: First, the effect of vowel was significant for both F1 and F2 measures for all speakers, but post hoc analysis revealed a reduced distinction at lower intelligibility. Second, regression functions relating intelligibility and acoustic variables were significant for overlap degree among vowels, F1 variability, corner vowel space and mean distance between vowels. Overlap degree among vowels accounted for the greatest amount of variance in intelligibility scores. Conclusion: A speaker’s overall intelligibility in dysarthric speech is better represented by the overlap degree among vowels than by the vowel space.
92 citations
TL;DR: It is suggested that the experience of living with dysarthria is highly individual and the need to consider the individual experience in clinical practice is re-emphasised.
Abstract: Purpose. To explore the speaker's experience of living with acquired chronic dysarthria.Method. Ten people with dysarthria and progressive neurological illness and one person with dysarthria following stroke were interviewed in depth about their experience of living with dysarthria. They covered a range of ages, time post-onset and dysarthria severity levels. Interviews were transcribed and analysed using Framework Method of Analysis.Results. Acquired dysarthria can negatively impact on speakers' lives. Findings here suggest that the experience of living with dysarthria is highly individual. There were some common perspectives. Six key themes emerged from interviews: ‘dysarthria as only part of the picture’, ‘communication has changed’, ‘people treat me differently’, ‘dysarthria resulting in negative emotions’, ‘barriers to communication’ and ‘life is different now. The impact of co-existing physical disability and the need to consider dysarthria in context was emphasised by all participants.Conclusion. F...
90 citations
TL;DR: Although the statistics of vocal tract movement do not appear to be transferable between regular and disabled speakers, transforming the space of the former given knowledge of the latter before retraining gives high accuracy.
Abstract: Disabled speech is not compatible with modern generative and acoustic-only models of speech recognition (ASR). This work considers the use of theoretical and empirical knowledge of the vocal tract for atypical speech in labeling segmented and unsegmented sequences. These combined models are compared against discriminative models such as neural networks, support vector machines, and conditional random fields. Results show significant improvements in accuracy over the baseline through the use of production knowledge. Furthermore, although the statistics of vocal tract movement do not appear to be transferable between regular and disabled speakers, transforming the space of the former given knowledge of the latter before retraining gives high accuracy. This work may be applied within components of assistive software for speakers with dysarthria.
75 citations
22 May 2011
TL;DR: It is shown that acoustic model adaptation yields an average relative word error rate (WER) reduction and that pronunciation lexicon adaptation (PLA) further reduces the relative WER by an average of 8.29% on a large vocabulary task of over 1500 words for six speakers with severe to moderate dysarthria.
Abstract: Dysarthria is a motor speech disorder resulting from neurological damage to the part of the brain that controls the physical production of speech. It is, in part, characterized by pronunciation errors that include deletions, substitutions, insertions, and distortions of phonemes. These errors follow consistent intra-speaker patterns that we exploit through acoustic and lexical model adaptation to improve automatic speech recognition (ASR) on dysarthric speech. We show that acoustic model adaptation yields an average relative word error rate (WER) reduction of 36.99% and that pronunciation lexicon adaptation (PLA) further reduces the relative WER by an average of 8.29% on a large vocabulary task of over 1500 words for six speakers with severe to moderate dysarthria. PLA also shows an average relative WER reduction of 7.11% on speaker-dependent models evaluated using 5-fold cross-validation.
71 citations
TL;DR: The limited data available indicate that, regardless of stroke location, imprecise articulation and slow speaking rate are consistent features, and voice disturbances, especially harshness, and reduced prosodic variation are also common.
Abstract: Dysarthria is a frequent and persisting sequel to stroke and arises from varied lesion locations. Although the presence of dysarthria is well documented, for stroke there are scant data on presentation and intervention outcome. A literature search was undertaken to evaluate (a) the features of dysarthria in adult stroke populations relative to the conventional Mayo system for classification, which was developed from diverse pathological groups, and (b) the current status of evidence for the effectiveness of intervention in dysarthria caused by stroke. A narrative review of results is presented. The limited data available indicate that, regardless of stroke location, imprecise articulation and slow speaking rate are consistent features, and voice disturbances, especially harshness, and reduced prosodic variation are also common. Dysarthria is more prevalent in left than in right hemisphere lesions. There is a need for comprehensive, thorough analysis of dysarthria features, involving larger populations, wi...
TL;DR: Of the 61 acoustic variables studied, 36 showed good stability over all three stability experiments, and a number of frequency measures showed a change in response to increased vocal effort resulting from the Lombard effect challenge.
TL;DR: Results suggest that scaled estimates of intelligibility for reading show potential for indexing intelligibility of an extemporaneous monologue and the relationship between structural characteristics of utterances and scaled intelligibility was explored within speakers.
Abstract: Intelligibility tests for dysarthria typically provide an estimate of overall severity for speech materials elicited through imitation or read from a printed script. The extent to which these types of tasks and procedures reflect intelligibility for extemporaneous speech is not well understood. The purpose of this study was to compare intelligibility estimates obtained for a reading passage and an extemporaneous monologue produced by 12 speakers with Parkinson's disease (PD). The relationship between structural characteristics of utterances and scaled intelligibility was explored within speakers. Speakers were audio-recorded while reading a paragraph and producing a monologue. Speech samples were separated into individual utterances for presentation to 70 listeners who judged intelligibility using orthographic transcription and direct magnitude estimation (DME). Results suggest that scaled estimates of intelligibility for reading show potential for indexing intelligibility of an extemporaneous monologue. Within-speaker variation in scaled intelligibility also was related to the number of words per speech run for extemporaneous speech.
TL;DR: The present review considers speaking in a second language in terms of the accompanying foreign accent, which places demands on the integration of motor and sensory discharges not encountered when articulating in the most fluent language.
Abstract: This review considers speaking in a second language from the perspective of motor-sensory control. Previous studies relating brain function to the prior acquisition of two or more languages (neurobilingualism) have investigated the differential demands made on linguistic representations and processes, and the role of domain-general cognitive control systems when speakers switch between languages. In contrast to the detailed discussions on these higher functions, typically articulation is considered only as an underspecified stage of simple motor output. The present review considers speaking in a second language in terms of the accompanying foreign accent, which places demands on the integration of motor and sensory discharges not encountered when articulating in the most fluent language. We consider why there has been so little emphasis on this aspect of bilingualism to date, before turning to the motor and sensory complexities involved in learning to speak a second language as an adult. This must involve retuning the neural circuits involved in the motor control of articulation, to enable rapid unfamiliar sequences of movements to be performed with the goal of approximating, as closely as possible, the speech of a native speaker. Accompanying changes in motor networks is experience-dependent plasticity in auditory and somatosensory cortices to integrate auditory memories of the target sounds, copies of feedforward commands from premotor and primary motor cortex and post-articulatory auditory and somatosensory feedback. Finally, we consider the implications of taking a motor-sensory perspective on speaking a second language, both pedagogical regarding non-native learners and clinical regarding speakers with neurological conditions such as dysarthria.
TL;DR: It is concluded that speech deficits may persist even up to 10 years post-surgery in participants who have not shown mutism in the acute phase, and the important role of the cerebellum in the control of fine speech movements in children is confirmed.
TL;DR: In this paper, the authors measured phonation, intonation variability, speech velocity, and the fraction of intraword pauses as a measure of articulatory precision, whereas the percentage of speech pauses was prolonged as compared with the PD group.
25 May 2011
TL;DR: The results show that despite the encouraging performance of ASR systems, and contrary to the claims in other studies, on average human listeners perform better in recognizing single-word dysarthric speech.
Abstract: Speech is a complex process that requires control and coordination of articulation, breathing, voicing, and prosody. Dysarthria is a manifestation of an inability to control and coordinate one or more of these aspects, which results in poorly articulated and hardly intelligible speech. Hence individuals with dysarthria are rarely understood by human listeners. In this paper, we compare and evaluate how well dysarthric speech can be recognized by an automatic speech recognition system (ASR) and naive adult human listeners. The results show that despite the encouraging performance of ASR systems, and contrary to the claims in other studies, on average human listeners perform better in recognizing single-word dysarthric speech. In particular, the mean word recognition accuracy of speaker-adapted monophone ASR systems on stimuli produced by six dysarthric speakers is 68.39% while the mean percentage correct response of 14 naive human listeners on the same speech is 79.78% as evaluated using single-word multiple-choice intelligibility test.
TL;DR: For all speaker groups, a slower-than-normal articulatory rate and increased vocal loudness had distinct effects on F₀ relative to the habitual condition, including a tendency for measures of F⁀ variation to be greater in the loud condition and reduced in the slow condition.
Abstract: Objective: This study examined the extent to which articulatory rate reduction and increased loudness were associated with adjustments in utterance-level measures of fundamental frequency (F₀) variability for speakers with dysarthria and healthy controls that have been shown to impact on intelligibility in previously published studies. More generally, the current study sought to compare and contrast how a slower-than-normal rate and increased vocal loudness impact on a variety of utterance-level F₀ characteristics for speakers with dysarthria and healthy controls. Patients and Methods: Eleven speakers with Parkinson’s disease, 15 speakers with multiple sclerosis, and 14 healthy control speakers were audio recorded while reading a passage in habitual, loud, and slow conditions. Magnitude production was used to elicit variations in rate and loudness. Acoustic measures of duration, intensity and F₀ were obtained. Results and Conclusions: For all speaker groups, a slower-than-normal articulatory rate and increased vocal loudness had distinct effects on F₀ relative to the habitual condition, including a tendency for measures of F₀ variation to be greater in the loud condition and reduced in the slow condition. These results suggest implications for the treatment of dysarthria.
Journal Article•
TL;DR: Results suggest that existing skills or strategies used by patients should be emphasized in dysarthria training programs focusing on rate reduction, and a model of voluntary speech rate reduction based on neurologically normal speech shows promise as being applicable for mild to moderate Dysarthria.
TL;DR: The purpose of this paper is to introduce a novel framework for medical practitioners in which to conceptualize and justify potential targets for speech remediation, and the most commonly targeted deficits can be supported by this approach.
Abstract: Hypokinetic dysarthria is a common manifestation of Parkinson's disease, which negatively influences quality of life. Behavioral techniques that aim to improve speech intelligibility constitute the bulk of intervention strategies for this population, as the dysarthria does not often respond vigorously to medical interventions. Although several case and group studies generally support the efficacy of behavioral treatment, much work remains to establish a rigorous evidence base. This absence of definitive research leaves both the speech-language pathologist and referring physician with the task of determining the feasibility and nature of therapy for intelligibility remediation in PD. The purpose of this paper is to introduce a novel framework for medical practitioners in which to conceptualize and justify potential targets for speech remediation. The most commonly targeted deficits (e.g., speaking rate and vocal loudness) can be supported by this approach, as well as underutilized and novel treatment targets that aim at the listener's perceptual skills.
TL;DR: The perceptual characteristics of the speech of three genotypes of spino-cerebellar ataxia as manifest in four different speech tasks are explored to provide further information about the speech characteristics of genetic subtypes.
TL;DR: The findings suggest that seemingly objective intelligibility tests are subject to a number of factors that affect scores.
Abstract: Purpose This study was designed to assess potential contributors to listener variability in judgments of intelligibility. Method A total of 228 unfamiliar everyday listeners judged speech samples f...
TL;DR: An intensive speech treatment, the Lee Silverman Voice Treatment (LSVT) on dysarthria after STN‐DBS is examined, finding it to be an effective treatment for patients with Parkinson's disease.
Abstract: Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an established treatment for patients with Parkinson’s disease (PD). Speech impairment is a frequent side effect of the surgery. This study examined the efficacy of an intensive speech treatment (the Lee Silverman Voice Treatment, LSVT) on dysarthria after STN-DBS. The LSVT was administered in ten patients with STN-DBS (surgical group) and ten patients without (medical group). Patients were assessed before, immediately after and six months following the speech treatment using sustained phonation, a speech intelligibility scale and monologue. Vocal loudness, speech intelligibility and perceptual ratings were the primary outcome measures. Vocal loudness and perceptual scores improved significantly across tasks for the medical group only. Speech intelligibility did not significantly change for either group. Results in the surgical group were variable with some patients deteriorating. Treatment of dysarthria following STN-DBS needs further investigation due to the variable response to LSVT.
30 Jul 2011
TL;DR: The authors describes modifications to acoustic speech signals produced by speakers with dysarthria in order to make those utterances more intelligible to typical listeners, including the correction of tempo, the adjustment of formant frequencies in sonorants, the removal of aberrant voicing, the deletion of phoneme insertion errors, and the replacement of erroneously dropped phonemes.
Abstract: This paper describes modifications to acoustic speech signals produced by speakers with dysarthria in order to make those utterances more intelligible to typical listeners. These modifications include the correction of tempo, the adjustment of formant frequencies in sonorants, the removal of aberrant voicing, the deletion of phoneme insertion errors, and the replacement of erroneously dropped phonemes. Through simple evaluations of intelligibility with naive listeners, we show that the correction of phoneme errors results in the greatest increase in intelligibility and is therefore a desirable mechanism for the eventual creation of augmentative application software for individuals with dysarthria.
TL;DR: The results indicated that bilateral STN-DBS was associated with a significant improvement in the patients' motor disabilities but did not have much influence on speech performance during the short time after the stimulation switch was turned on.
TL;DR: A computerised, single-word intelligibility test that yields clinically feasible, reliable, and valid measures of segmental speech production in adults with aphasia is described and has potential utility for both clinical assessment and outcomes research.
Abstract: Background: Previous work indicates that single-word intelligibility tests developed for dysarthria are sensitive to segmental production errors in aphasic individuals with and without apraxia of s...
TL;DR: It is concluded that problems resulting from dysarthria in conversation can require extensive repair work involving both parties and may be usefully employed in informing both direct clinical work and through training those who work with this client group and their significant others.
Abstract: Background: People with acquired progressive dysarthria typically experience increased problems with intelligibility in everyday conversation as their disease progresses. Such problems are likely to impact on both the person with dysarthria and those with whom they interact. If this is the case then we may ask questions not just about the nature of these problems but how it is that such problems are dealt with by participants when they occur.
Aims: To investigate ways through which problems resulting from dysarthria in everyday conversation are resolved by participants. Further, to examine some of the features of repair resolution, particularly where understanding of self-repair attempts themselves prove difficult.
Methods & Procedures: Video data of natural conversation from two dyads were selected for this paper. One dyad features a 58 year-old man with multiple sclerosis and moderate intelligibility problems, the other a 79 year-old woman with motor neurone disease with mild to moderate intelligibility problems. Both elected to be recorded in conversation with their spouses. The dyads were video-recorded at home with no researcher present. Using the methods of Conversation Analysis (CA) a collection of sequences was identified and transcribed. The sequences were analysed with reference to how the participants resolve problems in the understanding of dysarthric speech.
Outcomes & Results: It is shown how some problems resulting from dysarthria in conversation can be resolved relatively quickly, particularly where a specific element of a prior turn is highlighted by the recipient as problematic. In other instances, the recipient's understanding problem may be more global. These result in longer repair sequences in which problematic elements are addressed individually. Such a resolution method is ultimately successful but may also be characterised by additional understanding problems. These findings draw attention to an important distinction between intelligibility and understandability.
Conclusions & Implications: It is concluded that problems resulting from dysarthria in conversation can require extensive repair work involving both parties. This has implications for the assessment of dysarthria in everyday conversation and also the promotion of intervention strategies that encompass the activities of both participants when dealing with dysarthria in interaction. These findings may be usefully employed in informing both direct clinical work and through training those who work with this client group and their significant others.
Journal Article•
TL;DR: Study results suggested the importance and need of speech-language therapy in the early rehabilitation of post-stroke patients; it should be initiated during their hospital stay and continued at long-term.
Abstract: The aim of the study was to determine the incidence and types of speech disorders in patients with acute stroke The study was performed in 936 acute stroke patients admitted to University Department of Neurology, Tuzla University Clinical Center, in the period from January 1, 2007 through December 31, 2008 Out of 936 study patients, speech disorders were verified on admission in 771 (8237%) patients Dysarthria was present in 540 (5769%) and aphasia in 231 (2467%) patients In the group with speech disturbances, dysarthria was present in 7004% and aphasia in 2996% of patients During hospital stay, lethal outcome was recorded in 51 patients, significantly higher in the group with speech disorders (P = 0004) At discharge from the hospital, speech disorders persisted in 671 (7581%), dysarthria in 468 (6975%), and different types of aphasia in 203 (3025%) of 885 surviving patients Among patients with aphasia at both admission and discharge, global aphasia was most common, followed by motor aphasia (Broca's aphasia) and nominal aphasia Although the rate of patients with speech disorders was lower at discharge, the difference was not statistically significant On admission, 8237% of patients were considered to have a speech-language disorder, dysarthria being most common Concerning the type of aphasia, global aphasia was most frequent Study results suggested the importance and need of speech-language therapy in the early rehabilitation of post-stroke patients; it should be initiated during their hospital stay and continued at long-term
TL;DR: Investigating whether the visual feedback method of electropalatography (EPG) could be an effective tool for treating five children with dysarthria and cerebral palsy and whether training improved the posteriorly placed articulation of the Swedish dental/alveolar target consonants produced in different positions suggests that EPG could be of potential benefit for diagnosing, treating and describing articulation errors associated with cerebral palsY.
Abstract: Some children with cerebral palsy have articulation disorders that are resistant to conventional speech therapy. The aim of this study was to investigate whether the visual feedback method of electropalatography (EPG) could be an effective tool for treating five children (mean age of 9.4 years) with dysarthria and cerebral palsy and to explore whether training improved the posteriorly placed articulation of the Swedish dental/alveolar target consonants /t/, /d/, /n/ and /s/ produced in different positions. An EPG analysis was conducted and some of the data were combined with a perceptual analysis. A more anterior placement was seen after treatment for the target sounds. Features of diagnostic importance revealed were unusual tongue-palate contacts, such as double articulation and abnormally retracted articulation. A possible change in stop closure duration was indicated. The results suggest that EPG could be of potential benefit for diagnosing, treating and describing articulation errors associated with cerebral palsy.