Why is childhood apraxia of speech controversial

While many papers have characterized the speech deficits associated with CAS, few studies have explicitly examined these other clinical characteristics. As illustrated above, there is much to be learned about the phenotypic diversity of CAS, which could potentially reveal clues about its biologic underpinnings. Because of the potential heterogeneity within CAS manifested in difficulties in written language [ 3 , 11 , 22 , 23 , 24 ], it is of interest to see if there are subgroups within CAS; this could have implications for treatment of other communication domains.

There is no widely agreed-upon metric to characterize CAS severity. Our objective was to use speech, language, and reading assessments to identify comorbid subgroups within CAS of varying severity and associated clinical characteristics, based on the aforementioned literature suggesting that these are variable within children with CAS. Specifically, we exploited the full range of phenotypic variation to identify more homogeneous subgroups of children, an approach that was advocated for autism another neurodevelopmental disorder several years ago for genetic mapping [ 25 ].

Subgroup classification of CAS and other communication disorders has been a long-standing interest for communication disorders professionals as it may potentially lead to differential diagnosis and treatment [ 3 , 26 ]. In addition, recognition of clinical characteristics associated with varying severity levels within CAS could help identify children in need of early or more intense remediation, thus improving later academic outcomes.

First, using endophenotypes of communication disorder severity, specifically articulation, vocabulary, phonological memory and reading, we used an unsupervised multivariate clustering method to mine the data for potential comorbid subgroups.

Then, we conducted a chart review of other clinical symptoms associated with CAS to examine if these symptoms were associated with comorbid subtypes of CAS as defined by the degree of impairment in language and reading ability. This analysis presents an unusually large cohort of children with CAS.

Together, these data suggest that there may be comorbid subgroups within CAS that can be defined by language and reading ability as well as the presence of specific clinical symptoms. In this study, we examined 31 individuals diagnosed with childhood apraxia of speech CAS as part of the Cleveland Family Speech and Reading Study [ 4 , 27 , 28 , 29 , 30 , 31 ] Supplemental Table 1. Children with CAS were identified from caseloads of speech-language pathologists in the Greater Cleveland area and referred to the study between and All participants met inclusion criteria based on information provided by a parent in an interview or via questionnaire including: normal hearing acuity; fewer than six episodes of otitis media prior to age 6; monolingual English speaker; absence of a history of neurological disorders other than CAS, such as cerebral palsy or autism spectrum disorder; and a diagnosis of a SSD or suspected CAS by a local speech-language pathologist or neurologist.

The diagnosis of CAS was confirmed based on direct testing of motor speech and articulation by an experienced licensed speech-language pathologist upon enrollment into the study. All children with CAS in this analysis were unrelated.

Each child in the study was given a battery of tests to assess articulation, vocabulary, phonological memory, and reading as described below. As data were obtained as part of a larger longitudinal study, test scores were based on the initial administration of each measure. If a child could not complete a test due to age, we utilized an assessment from a later age next visit for that measure, and age-adjusted accordingly see Statistical methods, described below.

Socioeconomic status was determined at the initial assessment based on parent education levels and occupations using the Hollingshead Four Factor Index of Social Class [ 32 ]. Presence of ADHD was determined by parent report based on the diagnosis by a psychologist or neurologist. Reading disability RD was determined if the child was receiving reading services in the schools, and language impairment LI was determined by the diagnosis of a speech-language pathologist.

This study was approved by the Institutional Review Board of Case Medical Center and University Hospitals and all parents provided informed consent and children provided written informed assent.

For the merged variable, referred to as the Diadochokinetic Syllable Rate or DDK, higher scores reflect better performance. We excluded the DDK measure from the cluster analysis, because the scores were uniformly low among participants with CAS with little variability. Inclusion of such a variable within the multivariate analysis would have concealed any difference among children with CAS because they all had poor scores particularly in contrast with the normal children.

These tests measure cognitive skills such as problem solving, spatial perception, working memory, and visual-motor co-ordination. Subtest scores were combined to form a PIQ score. Similarly, if they read the word aloud correctly they also received credit regardless of speech errors. Graphical illustration of NWR scores illustrates that children did not fail this task because of articulation issues associated with CAS Supplemental Fig.

See Supplemental Methods for additional information on these measures. Because there are no normative data for the NWR, Z-scores for the NWR were created by regressing raw scores on age in the subsample of unaffected siblings of probands from the larger Cleveland Family Study cohort. The resulting regression equations were used to derive age-adjusted NWR scores, as in our previous work [ 29 , 43 , 44 ]. Because examination of clinical and family characteristics associated with the CAS severity subgroups was exploratory in nature, a nominal p -value less than 0.

All analyses were conducted using R software. For the cluster analysis we used hierarchical clustering hclust. Many clustering methods tend towards equal cluster sizing, so a larger sample of controls would have overwhelmed the analysis, leading to no differentiation among subgroups within the children with CAS. Assignment of separate clusters was based on dissimilarity across the six test scores.

Dissimilarity was determined using Euclidean distance and clustering was done using complete linkage. The number of clusters was determined by visualizing the dendrogram cluster tree and cluster size was not predetermined. Lastly, to evaluate the stability of these severity groups with developmental trajectories on these tests, we compared the distribution of test scores across these groups with values taken at the last available assessment when the children were teenage in most cases.

The average age at first assessment was 5. Next, we examined how children with CAS clustered based on their scores on articulation, language, and reading endophenotypes. Analysis revealed 4 distinct clusters Fig. Three of these clusters consisted exclusively of individuals with CAS, while the 8 controls formed their own cluster. The mean score for each variable by cluster membership is shown in Fig. The three comorbid subgroups within CAS were divided into mild, moderate, and high severity, based on performance on these measures.

The lack of differentiation on GFTA is consistent with the literature [ 45 , 46 ]. There was no significant difference across clusters with respect to age at reading assessment, and among the CAS clusters, there was no significant difference with respect to age at vocabulary assessment. Cluster analysis dendogram illustrating clustering of subjects. Cluster assignment is indicated using color and the numbering scheme below. The y-axis shows the estimated Euclidean distance that was used for the clustering algorithm.

Distribution of trait scores by cluster membership. To examine the stability of these severity groups with respect to changes that may occur with age and resolution of CAS, we repeated the descriptive analysis described above, only this time utilizing the last available assessment for each measure Supplemental Table 4. In most cases, these observations were taken when the children were now teenagers.

We found that the pattern of differences seen between the severe, moderate, and mild groups was maintained when examining these later time points. This analysis suggests that classification of severity of CAS as defined by these measures is robust to age.

We also evaluated the impact of including the small sample of children unaffected for speech and language as a control group in the cluster analysis. We repeated the analysis without the control group, and the cluster membership of children with CAS remained the same Supplemental Fig. These findings suggest that the mild comorbid subgroup may have a higher PIQ than the more severe subgroups. Supplemental Table 6.

Because only one non-Caucasian child was present in the sample, we did not compare groups with respect to race. The goal of this study was to examine whether comorbid subtypes within CAS could be classified based on variability in reading, vocabulary, and articulation. Identification of more homogenous subgroups has potential utility in identification of causal genetic variants [ 25 ] and in understanding potential cognitive and educational outcomes for children with CAS.

Our analysis revealed 3 phenotypic subgroups with deficits of varying severity in language and reading skills. The high severity comorbid CAS subtype group performed the worst with respect to vocabulary compared to the other two subgroups, and the moderate severity comorbid CAS subtype group had poorer outcomes than the mild severity subgroup on measures of reading and non-word repetition. Consistent with our previous findings [ 6 ], the results suggest that comorbid subtype severity within CAS is manifested in deficits in language and phonological processing skills associated with reading disability.

We found that these subgroups were robust to age, as there were consistent differences between groups when examining assessments taken at later ages. In addition, the high severity comorbid subtype group had a significantly higher prevalence of early feeding issues and ADHD, and potentially more fine motor problems, although this difference did not achieve statistical significance. Both results suggest the possibility of more pervasive motor deficits in the high severity comorbid subtype group of children.

Feeding difficulties have long been reported in children with CAS [ 20 , 47 , 48 ] and may indicate a global motor apraxia.

This understanding of a constellation of deficits in written and spoken language is important for clinical care and educational planning. Our findings further suggest that CAS is a heterogeneous disorder [ 3 , 10 , 23 ].

Future studies of CAS may reveal a wide range of phenotypic manifestations associate with mutations in the same gene, as has been found for other developmental disabilities [ 49 , 50 ]. Examination of clinical characteristics revealed that all children with CAS in our sample had a family history of communication disorders, supporting a role for genetic factors in the etiology of CAS.

The findings also revealed that, while less-often endorsed than a family history of communication disorders, most children with CAS had delayed onset of language. Consistent with previous findings, results additionally document associations of vocabulary knowledge as a marker of CAS comorbid severity [ 26 ].

Vocabulary is one of many components that are core to speech sound acquisition. Finally, while CAS is more common in males, individual endophenotypes and clinical characteristics did not differ significantly in males compared to females. Sex differences are much more pronounced among children with other types of speech sound disorder [ 51 ], so this is a notable dissimilarity.

The lack of differences between the comorbid CAS subtype groups in articulation and oral-motor skills suggests that assessment of other skills is needed to predict outcomes for children with CAS, which is consistent with the idea that no single characteristic can be used to differentiate children with CAS [ 3 ].

Poor vocabulary scores were a key marker of severity, hence vocabulary knowledge is likely to be useful in early identification of the children at highest risk for more severe language and reading disabilities [ 52 ]. Children in the high comorbid severity CAS subgroup also had a higher prevalence of early feeding difficulties than the other two subgroups, thus this clinical feature of the disorder may also be useful in predicting further language and reading difficulties and poorer outcomes.

The results underscore the importance of early monitoring of language and phonological skills and suggest that remediation focusing on language and phonological therapy in addition to speech sound production may be useful in avoiding or attenuating later academic problems [ 5 ]. Associations of the severity of CAS with vocabulary knowledge is consistent with findings from a study of children at familiar risk for dyslexia by Viholainen et al.

Based on their findings, the researchers recommended early interventions to promote language development [ 53 ]. Nijland et al. Our work supports their hypothesis by showing there are varying levels of reading and vocabulary deficits among children with CAS, accompanied by other clinical characteristics related to motor function.

A second view of CAS has been as a motor-speech disorder with a core linguistic deficit. CAS, for instance, has been viewed primarily as a disorder of speech-motor planning; LI and RD are not included in the definition of CAS but are thought to be simply co-occurring [ 1 , 21 , 60 , 61 ]. Third, some researchers have gone further to define CAS as a syndrome, i. The CAS syndrome is a complex neurodevelopmental disorder with deficits in motor-speech, cognition, language and literacy [ 11 , 13 , 14 , 30 , 63 , 64 ].

Our findings, demonstrating that reading and language difficulties vary among subgroups within children with CAS, are less concordant with the second conceptualization than the first and third. CAS being a rare disorder, results in one limitation of the study, the sample size is necessarily small. A second limitation is that test scores, although age adjusted, were obtained at different ages depending on when children were seen for follow-up as part of the larger longitudinal project.

Additionally, clinical and family characteristics were based on parent report and thus subject to recall bias, and this information was not available for control participants. A third limitation was that the control group was predominantly female, though this is not surprising, since both CAS and SSD are more common in males, so a randomly-selected control group would more likely be predominantly female. Because of this demographic difference, comparisons between comorbid subtype groups could be biased towards the null hypothesis i.

While comparisons among children with CAS could be underpowered because of the rarity of female cases, they are still of interest to the field.

In summary, multivariate cluster analysis of scores of children with CAS on tests of vocabulary, nonword repetition, and reading revealed potential comorbid subgroups of varying severity. The subgroups suggest that comorbid subtypes within CAS of differing degrees of severity may be distinguished based on these features.

The most severe comorbid CAS subtype group also had higher rates of early difficulties in feeding and fine motor in-coordination than the other subgroups, indicating that these difficulties may also be useful in predicting comorbid CAS severity. The severe group also has a greater prevalence of ADHD. This heterogeneity of CAS implied by identification of these subgroups may be related to differences in neural development and associated with genetic variability [ 7 ] The findings support a need to design early interventions tailored to the different profiles of deficits associated with CAS [ 3 ].

Second, it would be fine to diagnose an apraxia via behavioral description except for one huge problem: professionals do not all agree on the characteristics that identify the problem.

Your physicians may be coming to different conclusions based on these reasons. In either case, one thing that most speech-language pathologists seem to agree upon is that it is too early to make the diagnosis in a child only two years of age. The best advice I can give you is to have your son seen by a professional speech-language pathologist who specializes in children.

A medical doctor may be very good in the diagnosis of ear infections and broken toes, but he or she is not qualified to make a diagnosis of speech delay or disorder. Have your physician make a referral to an SLP for evaluation in the private sector.

Note the circularity here: a biological correlate of childhood apraxia will eventually be needed to determine which behavioral assessment findings are the markers for the disorder. The third type of research finding providing support for this diagnostic classification would be tied to treatment outcomes for children with suspected childhood apraxia. As in other areas of medicine, a treatment regimen documented to be both necessary and sufficient to normalize a disorder provides some measure of support for the validity of a diagnostic category-particularly to the degree that the treatment differs significantly from treatments used with one or more other disorders that closely resemble the target disorder.

Such findings from controlled treatment studies can often be the only way to begin to understand the processes that eventually define the disorder. He is also a member of the Apraxia Kids Advisory Committee.

Posted at h in by apraxiaadmin. How is CAS diagnosed? The SLP will try to interact with your child and try to get them to use their speech in order to see what happens when they are asked to repeat syllables, words, or phrases a number of times.

Observations will be made about how your child combines sounds together and whether the length or difficulty level of words or phrases makes a difference in the accuracy with which the child says words. Some young children do not like strangers peering in their mouths, thus this part might be a challenge! Some children also might be sensitive to touch around the mouth and this will be noted.

They will observe what other forms of communication the child uses such as pointing and gesturing. For example, the SLP may slow down their own speech and ask the child to try a word or phrase with them at the same time simultaneously. Top Three Characteristics of Childhood Apraxia of Speech The top three characteristics of Childhood Apraxia of Speech, as reported by the American Speech-Language-Hearing Association ASHA Technical Report on Childhood Apraxia of Speech, that can help the SLP make a differential diagnosis are: Inconsistent errors with consonants and vowels on repeated productions of syllables and words your child says the same word in different ways when asked to repeat it several times.

This might be more apparent in new words or longer more complex words. Not all children exhibit this at all times or situations. If your child does not demonstrate groping of their speech musculature, that alone is not enough to rule out apraxia of speech.

Listen to more about how Childhood Apraxia is Diagnosed: Click below to move to the next section.