Whole-genome sequencing identifies functional noncoding variation in SEMA3C that cosegregates with dyslexia in a multigenerational family.

Dyslexia is a common heritable developmental disorder involving impaired reading abilities. Its genetic underpinnings are thought to be complex and heterogeneous, involving common and rare genetic variation. Multigenerational families segregating apparent monogenic forms of language-related disorders can provide useful entrypoints into biological pathways. In the present study, we performed a genome-wide linkage scan in a three-generational family in which dyslexia affects 14 of its 30 members and seems to be transmitted with an autosomal dominant pattern of inheritance. We identified a locus on chromosome 7q21.11 which cosegregated with dyslexia status, with the exception of two cases of phenocopy (LOD = 2.83). Whole-genome sequencing of key individuals enabled the assessment of coding and noncoding variation in the family. Two rare single-nucleotide variants (rs144517871 and rs143835534) within the first intron of the SEMA3C gene cosegregated with the 7q21.11 risk haplotype. In silico characterization of these two variants predicted effects on gene regulation, which we functionally validated for rs144517871 in human cell lines using luciferase reporter assays. SEMA3C encodes a secreted protein that acts as a guidance cue in several processes, including cortical neuronal migration and cellular polarization. We hypothesize that these intronic variants could have a cis-regulatory effect on SEMA3C expression, making a contribution to dyslexia susceptibility in this family.

Speech sound development in typically developing 2-7-year-old Dutch-speaking children: A normative cross-sectional study.

BACKGROUND: Dutch is a West-Germanic language spoken natively by around 24 million speakers. Although studies on typical Dutch speech sound development have been conducted, norms for phonetic and phonological characteristics of typical development in a large sample with a sufficient age range are lacking. AIM: To give a detailed description of the speech sound development of typically developing Dutch-speaking children from 2 to 7 years. METHODS & PROCEDURES: A total of 1503 typically developing children evenly distributed across the age range of 2;0-6;11 years participated in this normative cross-sectional study. The picture-naming task of the Computer Articulation Instrument (CAI) was used to collect speech samples. Speech development was described in terms of (1) percentage consonants correct-revised (PCC-R) and percentage vowels correct (PVC); (2) consonant, vowel and syllabic structure inventories; (3) degrees of complexity (phonemic feature hierarchy); and (4) phonological processes. OUTCOMES & RESULTS: A two-way mixed analysis of variance (ANOVA) confirmed a significant increase in the number of PCC-R and PVC between the ages of 2;0 and 6;11 years (p < 0.001). The consonant inventory was found to be complete at 3;7 years of age for the syllable-initial consonants, with the exception of the voiced fricatives /v/ and /z/, and the liquid /r/. All syllable-final consonants were acquired before age 4;4 years. At age 3;4 years, all children had acquired a complete vowel inventory, and at age 4;7 years they produced most syllable structures correctly, albeit that the syllable structure CCVCC was still developing. All phonological contrasts were produced correctly at 3;8 years of age. Children in the younger age groups used more phonological simplification processes than the older children, and by age 4;4 years, all had disappeared, except for the initial cluster reduction from three to two consonants and the final cluster reduction from two to one consonant. CONCLUSIONS & IMPLICATIONS: This paper describes a large normative cross-sectional study of Dutch speech sound development which, in clinical practice, can help Dutch speech-language pathologists to differentiate children with delayed or disordered speech development from typically developing children. What this paper adds What is already known on this subject In recent years many studies have been conducted worldwide to investigate speech sound development in different languages, including several that explored the typical speech sound development of Dutch-speaking children, but none of these latter studies explored both phonetic and phonological progress within a comprehensive age range and a large sample that is representative of the Dutch population. What this study adds to existing knowledge This study serves to fill this gap by providing normative cross-sectional results obtained in 1503 typically developing Dutch-speaking children aged between 2;0 and 6;11 years on informative parameters of speech development: PCC-R and PVC, consonant, vowel and syllabic structure inventories, degrees of complexity (phonemic feature hierarchy), and phonological simplification processes. What are the potential or actual clinical implications of this work? The detailed description of typical Dutch speech sound development provides speech-language pathologists with pertinent information to determine whether a child's speech development progresses typically or is delayed or disordered.

N1 lateralization and dyslexia: An event-related potential study in children with a familial risk of dyslexia.

The rapid automatic specialized processing of printed words is signalled by the left-lateralization of the N1 component in the visual event-related potential (ERP). In the present study, we have investigated whether differences in N1 lateralization can be observed between Dutch children with and without (a familial risk of) dyslexia around the age of 12 years using a linguistic judgement task. Forty-five participants were included in the ERP analysis, 18 in the low familial risk group without dyslexia, 15 in the high familial risk group without dyslexia, and 12 in the high familial risk group with dyslexia. The results showed that although the N1 peaked slightly earlier in the left hemisphere, the N1 amplitude was right-lateralized in all groups. Moreover, there were no group differences in N1 amplitude or latency, and there was no relationship between reading (related) test scores and N1 characteristics. The results of the present study and our previous findings in adults suggest that print-tuning lateralization is a process that is still developing in adolescence. Because other studies did find N1 lateralization in younger readers with a print versus nonprint contrast, the current results seem to indicate that differences in N1 lateralization also depend on the experimental paradigm.

A Psycholinguistic Framework for Diagnosis and Treatment Planning of Developmental Speech Disorders.

BACKGROUND: Differential diagnosis and treatment planning of developmental speech disorders (DSD) remains a major challenge in paediatric speech-language pathology. Different classification systems exist, in which subtypes are differentiated based on their theoretical cause and in which the definitions generally refer to speech production processes. Accordingly, various intervention methods have been developed aiming at different parts of the speech production process. Diagnostic classification in these systems, however, is primarily based on a description of behavioural speech symptoms rather than on underlying deficits. PURPOSE: In this paper, we present a process-oriented approach to diagnosis and treatment planning of DSD. Our framework comprises two general diagnostic categories: developmental delay and developmental disorder. Within these categories, treatment goals/targets and treatment methods are formulated at the level of processes and rules/representations. CONCLUSION: A process-oriented approach to diagnosis and treatment planning holds important advantages, offering direct leads for treatment aimed at the underlying impairment, tailored to the specific needs of the individual and adjusted to the developmental trajectory.

A Standardized Protocol for Maximum Repetition Rate Assessment in Children.

BACKGROUND/AIMS: Maximum repetition rate (MRR) is often used in the assessment of speech motor performance in older children and adults. The present study aimed to evaluate a standardized protocol for MRR assessment in young children in Dutch. METHODS: The sample included 1,524 children of 2-7 years old with no hearing difficulties and Dutch spoken in their nursery or primary school and was representative for children in the Netherlands. The MRR protocol featured mono-, tri-, and bisyllabic sequences and was computer-implemented to maximize standardization. RESULTS: Less than 50% of the 2-year-olds could produce >1 monosyllabic sequence correctly. Children who could not correctly produce ≥2 monosyllabic sequences could not produce any of the multisyllabic sequences. The effect of instruction ("faster" and "as fast as possible") was small, and multiple attempts yielded a faster MRR in only 20% of the cases. MRRs did not show clinically relevant differences when calculated over different numbers of repeated syllables. CONCLUSIONS: The MRR protocol is suitable for children of 3 years and older. If children cannot produce at least 2 of the monosyllabic sequences, the multisyllabic tasks should be omitted. Furthermore, all fast attempts of each sequence should be analyzed to determine the fastest MRR.

Pathways Into Literacy: The Role of Early Oral Language Abilities and Family Risk for Dyslexia.

The present study investigated the role of early oral language and family risk for dyslexia in the two developmental pathways toward reading comprehension, through word reading and through oral language abilities. The sample contained 237 children (164 at family risk for dyslexia) from the Dutch Dyslexia Program. Longitudinal data were obtained on seven occasions when children were between 4 and 12 years old. The relationship between early oral language ability and reading comprehension at the age of 12 years was mediated by preliteracy skills and word-decoding ability for the first pathway and by later language abilities for the second pathway. Family risk influenced literacy development through its subsequent relations with preliteracy skills, word decoding, and reading comprehension. Although performance on language measures was often lower for the family-risk group than for the no-family-risk group, family risk did not have a specific relation with either early or later oral language abilities.

Effectiveness of speech therapy in adults with intellectual disabilities.

BACKGROUND: This study investigated the effect of speech therapy in a heterogeneous group of adults with intellectual disability. METHOD: Thirty-six adults with mild and moderate intellectual disabilities (IQs 40-70; age 18-40 years) with reported poor speech intelligibility received tailored training in articulation and listening skills delivered in two 3-month periods. Pre- to post-changes in speech intelligibility and receptive vocabulary were assessed using standardized tasks. RESULTS: The results showed a positive effect of treatment on speech intelligibility and receptive vocabulary, irrespective of severity of intellectual disability, hearing loss and intellectual disability aetiology. CONCLUSIONS: Speech therapy for people with intellectual disability can be effective at adult age and hearing loss should not prevent treatment. Continued attention to speech can help augment verbal communication skills in this population.

Dichotic listening as an index of lateralization of speech perception in familial risk children with and without dyslexia.

Atypical language lateralization has been marked as one of the factors that may contribute to the development of dyslexia. Indeed, atypical lateralization of linguistic functions such as speech processing in dyslexia has been demonstrated using neuroimaging studies, but also using the behavioral dichotic listening (DL) method. However, so far, DL results have been mixed. The current study assesses lateralization of speech processing by using DL in a sample of children at familial risk (FR) for dyslexia. In order to determine whether atypical lateralization of speech processing relates to reading ability, or is a correlate of being at familial risk, the current study compares the laterality index of FR children who did and did not become dyslexic, and a control group of readers without dyslexia. DL was tested in 3rd grade and in 5/6th grade. Results indicate that at both time points, all three groups have a right ear advantage, indicative of more pronounced left-hemispheric processing. However, the FR-dyslexic children are less good at reporting from the left ear than controls and FR-nondyslexic children. This impediment relates to reading fluency.

Print-Tuning Lateralization and Handedness: an Event-Related Potential Study in Dyslexic Higher Education Students.

Despite their ample reading experience, higher education students with dyslexia still show deficits in reading and reading-related skills. Lateralized print tuning, the early sensitivity to print of the left parietal cortex signalled by the N1 event-related potential (ERP) component, differs between beginning dyslexic readers and controls. For adults, the findings are mixed. The present study aims to investigate whether print tuning, as indexed by the N1 component, differs between 24 students with dyslexia and 15 non-dyslexic controls. Because handedness has been linked to lateralization, first, a separate analysis was conducted including only right-handed participants (n = 12 in both groups), like in most previous studies. ERPs were measured during a judgement task, requiring visual, phonological, or semantic judgments. In both groups, the N1 was earlier and stronger in the left than in the right hemisphere. However, when only strongly right-handed participants were evaluated, the N1 was less left-lateralized for participants with dyslexia as compared with controls. Participants with dyslexia had longer reaction times during the ERP experiment and performed worse on many reading (-related) tasks. These findings suggest that abnormal print tuning can still be found among higher education students with dyslexia and that handedness should be regarded in the study of print tuning.

Speech Characteristics and Intelligibility in Adults with Mild and Moderate Intellectual Disabilities.

PURPOSE: Adults with intellectual disabilities (ID) often show reduced speech intelligibility, which affects their social interaction skills. This study aims to establish the main predictors of this reduced intelligibility in order to ultimately optimise management. METHOD: Spontaneous speech and picture naming tasks were recorded in 36 adults with mild or moderate ID. Twenty-five naïve listeners rated the intelligibility of the spontaneous speech samples. Performance on the picture-naming task was analysed by means of a phonological error analysis based on expert transcriptions. RESULTS: The transcription analyses showed that the phonemic and syllabic inventories of the speakers were complete. However, multiple errors at the phonemic and syllabic level were found. The frequencies of specific types of errors were related to intelligibility and quality ratings. CONCLUSIONS: The development of the phonemic and syllabic repertoire appears to be completed in adults with mild-to-moderate ID. The charted speech difficulties can be interpreted to indicate speech motor control and planning difficulties. These findings may aid the development of diagnostic tests and speech therapies aimed at improving speech intelligibility in this specific group.

Treatment intensity and childhood apraxia of speech.

BACKGROUND: Intensive treatment has been repeatedly recommended for the treatment of speech deficits in childhood apraxia of speech (CAS). However, differences in treatment outcomes as a function of treatment intensity have not been systematically studied in this population. AIM: To investigate the effects of treatment intensity on outcome measures related to articulation, functional communication and speech intelligibility for children with CAS undergoing individual motor speech intervention. METHODS & PROCEDURES: A total of 37 children (32-54 months of age) with CAS received 1×/week (lower intensity) or 2×/week (higher intensity) individual motor speech treatment for 10 weeks. Assessments were carried out before and after a 10-week treatment block to study the effects of variations in treatment intensity on the outcome measures. OUTCOMES & RESULTS: The results indicated that only higher intensity treatment (2×/week) led to significantly better outcomes for articulation and functional communication compared with 1×/week (lower intensity) intervention. Further, neither lower nor higher intensity treatment yielded a significant change for speech intelligibility at the word or sentence level. In general, effect sizes for the higher intensity treatment groups were larger for most variables compared with the lower intensity treatment group. CONCLUSIONS & IMPLICATIONS: Overall, the results of the current study may allow for modification of service delivery and facilitate the development of an evidence-based care pathway for children with CAS.

Infant ERPs separate children at risk of dyslexia who become good readers from those who become poor readers.

Dyslexia is heritable and associated with phonological processing deficits that can be reflected in the event-related potentials (ERPs). Here, we recorded ERPs from 2-month-old infants at risk of dyslexia and from a control group to investigate whether their auditory system processes /bAk/ and /dAk/ changes differently. The speech sounds were presented in an oddball paradigm. The children were followed longitudinally and performed a word reading fluency test in second grade. The infant ERPs were subsequently analyzed according to high or low reading fluency in order to find a neurophysiological precursor of poor reading fluency. The results show that the fluent reading children (from both the at-risk and the control group) processed the speech sound changes differentially in infancy as indicated by a mismatch response (MMR). In the control group the MMR was frontally positive and in the fluent at-risk group the MMR was parietally positive. The non-fluent at-risk group did not show an MMR. We conclude that at-risk children who became fluent readers were better at speech processing in infancy than those who became non-fluent readers. This indicates a very early speech processing deficit in the group of later non-fluent readers.

Precursors of developmental dyslexia: an overview of the longitudinal Dutch Dyslexia Programme study.

Converging evidence suggests that developmental dyslexia is a neurobiological disorder, characterized by deficits in the auditory, visual, and linguistic domains. In the longitudinal project of the Dutch Dyslexia Programme, 180 children with a familial risk of dyslexia (FR) and a comparison group of 120 children without FR (noFR) were followed from the age of 2 months up to 9 years. Children were assessed on (1) auditory, speech, and visual event-related potentials every half year between 2 and 41 months; (2) expressive and receptive language, motor development, behaviour problems, and home-literacy environment by questionnaires at the age of 2 and 3; (3) speech-language and cognitive development from 47 months onwards; and (4) preliteracy and subskills of reading, and reading development during kindergarten and Grades 2 and 3. With regard to precursors of reading disability, first analyses showed specific differences between FR and noFR children in neurophysiological, cognitive, and early language measures. Once reading tests administered from age 7 to 9 years were available, the children were divided into three groups: FR children with and without dyslexia, and controls. Analyses of the differences between reading groups yielded distinct profiles and developmental trajectories. On early speech and visual processing, and several cognitive measures, performance of the non-dyslexic FR group differed from the dyslexic FR group and controls, indicating continuity of the influence of familial risk. Parental reading and rapid naming skills appeared to indicate their offspring's degree of familial risk. Furthermore, on rapid naming and nonverbal IQ, the non-dyslexic FR group performed similarly to the controls, suggesting protective factors. There are indications of differences between the FR and control groups, irrespective of reading outcome. These results contribute to the distinction between the deficits correlated to dyslexia as a manifest reading disorder and deficits correlated to familial risk only.

Rate-related kinematic changes in younger and older adults.

AIMS: This study aimed to investigate the effects of speech rate changes on kinematic characteristics and stability of speech movements in younger and older speakers using electromagnetic midsagittal articulography. PATIENTS AND METHODS: Eight young adults and 8 older adults engaged in a series of syllable repetition tasks of /pa/, /sa/ and /ta/ obtained at self-paced slow, habitual and fast speech rates, as well as in a series of metronome-guided speech rates, ranging from 2 to 4 syllables per second. The kinematic parameters duration, amplitude and peak velocity were obtained for opening and closing movements. RESULTS: Older speakers were able to increase speech rate to the same degree or higher compared to younger speakers in both pacing conditions. Kinematic data show that older adults increased duration and decreased peak velocity in closing movements of alveolar constrictions at slower rates more prominently than younger adults. The results on movement stability revealed no differences between age groups. CONCLUSIONS: The results suggest that an age-related difference in speed-accuracy trade-off can be ruled out. Differences in kinematic characteristics point towards the possibility that older adults aimed to facilitate a closed-loop control system to maintain movement stability at slower speech rates.

Music and musical elements in the treatment of childhood speech sound disorders: A systematic review of the literature.

PURPOSE: Music-based interventions are used in the treatment of childhood speech sound disorders (SSDs). Hypotheses on working mechanisms are being developed, focussing on shared neural processes. However, evidence of the effect of treatment with musical elements in SSDs in children is lacking. This study reviews the literature regarding the use of music-based interventions in the treatment of childhood SSDs. METHOD: A systematic search in six databases was conducted, yielding 199 articles, eight of which met the inclusion criteria. Included articles were reviewed on study characteristics, patient characteristics, interventions, outcomes and methodological quality. RESULT: This review included four case studies, three single-subject design studies and one cohort study. Seven studies reported positive outcomes on speech production, but outcome measures in the four studies with experimental design were not all aimed at the level of speech (motor) processes. Methodological quality was sufficient in one study. CONCLUSION: Seven out of eight studies in this review report positive outcomes of music-based interventions in the treatment of SSDs. However, these outcomes are not sufficiently supported by evidence due to insufficient methodological quality. Suggestions for improving methodological quality in future research are presented.

Speech and Music Therapy in the Treatment of Childhood Apraxia of Speech: An Introduction and a Case Study.

PURPOSE: Speech-Music Therapy for Aphasia (SMTA), a method that combines speech therapy and music therapy, is introduced as a treatment method for childhood apraxia of speech (CAS). SMTA will be evaluated in a proof-of-principle study. The first case study is presented herein. METHOD: SMTA was evaluated in a study with a single-subject experimental design comparing 10 weeks of treatment with 2 months of no treatment. The research protocol included a pretest, baseline phase, treatment phase, posttest, no-treatment phase, and follow-up test. The participant was a boy with CAS aged 5;8 (years;months). Outcome measures were selected to reflect both intelligibility in daily communication as well as features of CAS and speech motor planning and programming. RESULTS: Results on the Intelligibility in Context Scale-Dutch (ICS-Dutch) and in the analysis of a spontaneous speech sample suggest generalization of treatment effects. Improvements were found in measures that reflect complex speech motor skills, that is, the production of consonant clusters and consistency. CONCLUSIONS: This case study showed that speech production of the participant improved after treatment with SMTA. Although intelligibility as measured with the ICS-Dutch improved over the study period, objectifying changes at the level of intelligibility in daily communication proved to be difficult. Additional measures may be necessary to gain more insight into treatment effects at this level. Overall, the results of this first case study provide sufficient support and important leads for further evaluation of SMTA in the treatment of CAS in a proof-of-principle study.

Dynamic assessment of the effectiveness of digital game-based literacy training in beginning readers: a cluster randomised controlled trial.

In this article, we report on a study evaluating the effectiveness of a digital game-based learning (DGBL) tool for beginning readers of Dutch, employing active (math game) and passive (no game) control conditions. This classroom-level randomized controlled trial included 247 first graders from 16 classrooms in the Netherlands and the Dutch-speaking part of Belgium. The intervention consisted of 10 to 15 min of daily playing during school time for a period of up to 7 weeks. Our outcome measures included reading fluency, phonological skills, as well as purpose built in-game proficiency levels to measure written lexical decision and letter speech sound association. After an average of 28 playing sessions, the literacy game improved letter knowledge at a scale generalizable for all children in the classroom compared to the two control conditions. In addition to a small classroom wide benefit in terms of reading fluency, we furthermore discovered that children who scored high on phonological awareness prior to training were more fluent readers after extensive exposure to the reading game. This study is among the first to exploit game generated data for the evaluation of DGBL for literacy interventions.

Child and parental literacy levels within families with a history of dyslexia.

BACKGROUND: The present study concerns literacy and its underlying cognitive skills in Dutch children who differ in familial risk (FR) for dyslexia. Previous studies with FR-children were inconclusive regarding the performance of FR-children without dyslexia as compared to the controls. Moreover, van Bergen et al. (2011) recently showed that FR-children with and without dyslexia differed in parental reading skills, suggesting that those who go on to develop dyslexia have a higher liability. The current study concerned 1) the comparison of three groups of children at the end of second grade and 2) the intergenerational transfer of reading and its underlying cognitive skills from parent to child. METHOD: Three groups of children were studied at the end of second grade: FR-dyslexia (n = 42), FR-no-dyslexia (n = 99), and control children (n = 66). Parents and children were measured on naming, phonology, spelling, and word and pseudoword reading. RESULTS: The FR-dyslexia children were severely impaired across all tasks. The FR-no-dyslexia children performed better than the FR-dyslexia children, but still below the level of the controls on all tasks; the only exception was rapid naming (RAN), on which they were as fast as the controls. Focusing on the FR subsample, parental reading and RAN were related to their offspring's reading status. CONCLUSIONS: We replicated and extended van Bergen et al.'s study in showing that the FR-children who develop dyslexia are likely to have a higher liability. Both the group comparisons and the parent-child relations highlight the importance of good RAN skills for reading acquisition.

Early Productive Vocabulary Composition as Precursor of Dyslexia.

PURPOSE: The aim of this study was to gain more insight into the linguistic characterization of dyslexia by investigating vocabulary acquisition. In a previous study, vocabulary at 17 months of age appeared to be related to familial risk (FR) of dyslexia. The aim of this study was to investigate how the differences in lexical composition further develop up to 3 years (35 months) of age and, more importantly, to what extent these differences can be considered specific precursors of dyslexia later on. METHOD: In a total number of 262 children from the Dutch Dyslexia Program, 169 with and 93 without FR for dyslexia, productive vocabulary was assessed with the Dutch version of the MacArthur Communicative Development Inventories at ages 17, 23, 29, and 35 months. Reading tests were administered in Grades 2 and 3, resulting in dyslexia diagnosis in 60 FR children (FR-dys), leaving 109 FR children who developed normal reading skills (FR-nondys) and 93 control children. Children's expressive vocabulary was scored according to the total number of words produced and according to the different major linguistic word categories: nouns, predicates, and closed-class words. The analyses comprised a comparison of total productive vocabulary and the number of words per grammatical category at four different ages for the three groups (FR-dys, FR-nondys, and control). Also, correlations were calculated between vocabulary scores and reading scores. RESULTS: Up to 29 months of age, the total numbers of nouns, predicates, and closed-class words are significantly lower for the FR-dys group as compared with the FR-nondys and control groups; for closed-class words at 23 and 35 months of age, the FR-nondys group's mean values are in between the mean of the FR-dys and control groups. Weak correlations were found between total vocabulary size, number of verbs, number and proportion of predicates at 23 months of age, and word and pseudoword reading fluency in Grades 2 and 3. CONCLUSIONS: These results indicate that development of vocabulary is a significant though weak predictor of reading fluency and dyslexia; vocabulary size and proportion of verbs at 23 months of age, as well as proportion of closed-class words up to 35 months of age, seem to be the most sensitive indicators of delayed vocabulary development and later reading difficulties. There is no indication that FR for dyslexia by itself is related to vocabulary development.

Process-Oriented Profiling of Speech Sound Disorders.

The differentiation between subtypes of speech sound disorder (SSD) and the involvement of possible underlying deficits is part of ongoing research and debate. The present study adopted a data-driven approach and aimed to identify and describe deficits and subgroups within a sample of 150 four to seven-year-old Dutch children with SSD. Data collection comprised a broad test battery including the Computer Articulation Instrument (CAI). Its tasks Picture Naming (PN), NonWord Imitation (NWI), Word and NonWord Repetition (WR; NWR) and Maximum Repetition Rate (MRR) each render a variety of parameters (e.g., percentage of consonants correct) that together provide a profile of strengths and weaknesses of different processes involved in speech production. Principal Component Analysis on the CAI parameters revealed three speech domains: (1) all PN parameters plus three parameters of NWI; (2) the remaining parameters of NWI plus WR and NWR; (3) MRR. A subsequent cluster analysis revealed three subgroups, which differed significantly on intelligibility, receptive vocabulary, and auditory discrimination but not on age, gender and SLPs diagnosis. The clusters could be typified as three specific profiles: (1) phonological deficit; (2) phonological deficit with motoric deficit; (3) severe phonological and motoric deficit. These results indicate that there are different profiles of SSD, which cover a spectrum of degrees of involvement of different underlying problems.