|Year : 2018 | Volume
| Issue : 2 | Page : 115-121
Associated comorbidities of specific language impairment
Hassan Ghandour1, Sally Kheir Eldin1, Yossra Sallam2, Shaimaa Mahmoud2
1 Phoniatric Unit, Faculty of Medicin, Ain Shams University, Phoniatric Unit, Faculty of Medicin, Ain Shams University, Cairo, Egypt
2 Phoniatric Unit, Faculty of Medicin, AL Azhar University for Girls, Phoniatric Unit, Faculty of Medicin, Ain Shams University, Cairo, Egypt
|Date of Submission||30-Jul-2017|
|Date of Acceptance||15-Oct-2017|
|Date of Web Publication||17-Aug-2018|
Dr. Shaimaa Mahmoud
Phoniatric Unit, Faculty of Medicin, AL Azhar University for Girls, Phoniatric Unit, Faculty of Medicin, Ain Shams University, Cairo
Source of Support: None, Conflict of Interest: None
The primary linguistic difficulties of individuals with specific language impairment (SLI) have been addressed in detail in previous research. Recently, several studies have also reported the presence of associated comorbidities in children with SLI such as memory disorders, motoric deficits, dyslexia, ADHD, auditory processing disorders, and psychosocial disorders. The aim of this paper is to highlight the issues in SLI associated with memory disorders, motoric deficits, and dyslexia. This is a literature review. Short-term memory and working memory are commonly affected in children with SLI. In addition, those children exhibit deficits in fine and gross motor skills both simple and complex. The risk of dyslexia is associated with language delays and speech difficulties in the preschool years. SLI is a multifaceted disorder with both linguistic and nonlinguistic features including memory disorders, motoric deficits, and dyslexia.
Keywords: dyslexia, memory disorders, motoric deficits, specific language impairment
|How to cite this article:|
Ghandour H, Eldin SK, Sallam Y, Mahmoud S. Associated comorbidities of specific language impairment. Benha Med J 2018;35:115-21
| Introduction|| |
Specific language impairment (SLI) is a neurodevelopmental disorder that affects around 3–7% of children . The estimated prevalence of SLI in 800 monolingual Arabic speaking kindergarten children in Cairo was 17% .
SLI occurs when children present language maturation at least 12 months behind their chronological age in the absence of sensory or intellectual deficits, pervasive developmental disorders, evident cerebral damage, and adequate social and emotional conditions .
The predominant focus of description and theory of SLI is that it is specifically linguistic deficit. However, over recent years there have been emerging suggestions of the presence of nonlinguistic deficits in children with SLI .
This article aims at reviewing the recent studies that have assessed memory disorders, motoric deficits, and/or dyslexia among children with SLI.
| Memory disorders with specific language impairment|| |
Most theoretical and empirical work examining this relationship has focused on short-term memory (STM) and working memory ,,,,.
The model of Baddeley  is often used to describe the operation of STM. The model involves two basic aspects in which phonological and visual information are briefly and statically retained, namely the phonological loop and the visual sketchpad. The processing of phonological information is thought to have an inner rehearsal aspect (the articulatory loop), which allows the phonological information needed for the process of language comprehension to be retained longer in memory. A third more central aspect of Baddeley’s model is the central-executive system, which constitutes the control mechanism to coordinate the storage and processing of basic information.
Deficits in phonological loop capacity in SLI have been widely reported in studies using nonword repetition task ,,, as well as studies using more conventional verbal STM measures, such as serial recall of digits or words ,. This literature suggests that children with SLI generally perform significantly worse than typically developing (TD) children on tests of verbal STM − that is, those that require the temporary storage of verbal information. Nickisch and Kries  argued that STM deficits in children with SLI are not confined to the auditory–verbal modality but constitute more general STM problems impacting auditory–verbal, as well as visual, STM.
On the other hand, age-appropriate performance has been reported for SLI groups on visuo-spatial storage tasks ,,. Similary, Lum et al.  postulated that individuals with SLI have problems with the short-term storage and manipulation of verbal information, but not necessarily with visual (and not easily verbally coded) information.
Alloway et al.  suggested that about 75% of children with SLI appear to have poor working memory. It has been suggested that children with SLI perform worse in working memory tasks involving the storage and processing of verbal ,, but not visuo-spatial, information ,. This dissociation has been explained in light of evidence that performance decrements occur only when the task additionally taps the impaired phonological but not preserved visuo-spatial storage abilities . However, Vugs et al.  postulated that the performance of children with SLI was impaired in all working memory components, including verbal storage, verbal central executive, visuo-spatial storage, and visuo-spatial central executive.
The procedural deficit hypothesis posits that SLI may be largely explained by abnormalities of brain structures underlying procedural memory, in particular portions of frontal/basal-ganglia circuits . They also suggested that the presence or severity of cognitive and language impairments (LIs) in SLI will depend not only on procedural memory deficits but also on the extent to which declarative memory, which is proposed to remain largely intact in SLI, can compensate for the procedural deficits. Thus, if declarative memory could fully compensate for such underlying problems, impairments in procedural memory might not be evident.
A number of studies using serial reaction time tasks have reported procedural learning impairments in SLI ,,,,.
In an early report, Tomblin et al.  argued that children with SLI evidenced slower procedural learning of the sequence compared with TD age-matched controls. Studies by Lum et al. ,, also suggested procedural memory deficits.
However, these results have not always been replicated ,,,,. Thus, it is not yet clear whether procedural memory impairments constitute a core deficit of SLI.
Almost all studies of procedural memory in SLI have used nonverbal stimuli (the serial reaction time task). However, learning tasks that involve verbal stimuli that seem to depend on procedural memory, such as the word segmentation task, also have shown deficits in SLI ,.
Nevertheless, on the whole, evidence seems to suggest that learning in this system is spared for nonverbal information such as for unknown faces or abstract visual stimuli, and even for verbal information once factors such as working memory abilities are held constant ,.
In contrast, declarative memory has been much less well studied in SLI. Learning in declarative memory appears to remain largely unaffected in individuals with SLI, particularly for nonverbal information such as for unknown faces or abstract visual stimuli, but possibly even in the verbal domain once working memory and LIs have been controlled for ,,,. Indeed, it appears that only children with SLI with poor verbal working memory show impairments on verbal declarative memory tasks .
| Motoric deficits in specific language impairment|| |
Over the past several years, it has been suggested that complex and hierarchical language production interacts in specific ways with motor skill .
Empirical studies examining the motor abilities of children with SLI go as far back as the mid-1960s. By the late 1990s, only a handful of studies provided evidence suggesting that children with SLI exhibited motor deficits. However, in a comprehensive literature review by , nearly 30 studies that explicitly examined the motor abilities of children with SLI were reviewed. She concluded that there is a ‘substantial comorbidity between SLI and poor motor skills’. These children show deficits in fine motor hand, limb, and finger movements , peg moving, bead threading, and buttoning , gross motor ability as measured by tasks of balance, aiming, catching, and hopping , representational gestures , as well as a weak hand preference .
A similar argument was later made by Leonard and Hill  after reviewing studies exploring the effects of motor development on social, cognitive, and language abilities in TD and in neurodevelopmental disorders including SLI. Their review of the SLI studies revealed significant correlations between standardized measures and parental reports of motor development and language measures including communication ability, expressive language scores, and articulation. They speculated that these significant relationships suggest that neural mechanisms underlying motor development may be shared by other areas of development such as language and social development.
Two studies examined the presence or absence of clinically significant motor deficits in children with SLI ,.
Finlay and McPhillips  compared the motor abilities of children with SLI to age-matched children with typical language development and age-matched children who had not been clinically identified as having SLI but exhibited low language abilities. They used the Movement Assessment Battery for Children (MABC-2)  and found that children with SLI scored significantly lower on all subscales of the MABC-2 than did the low language and typical comparison groups. These authors also reported that half the children with SLI were labeled at risk for motor difficulties, whereas about a third of children with SLI were not just at risk but also presented with significant motor difficulties .
Another pair of investigators, Flapper and Schoemaker , offered similar results. They examined the comorbidity of developmental coordination disorder (DCD) in children with SLI. Using the MABC-2, they found that the total MABC scores of about 32% of children with SLI fell below the 15th percentile, indicating that about a third of children with SLI also presented with DCD.
Vukovic et al.  assessed coordination and imitation in children with SLI using subtests from the McCarthy’s Scales of Children’s Abilities  and the Test of Imitation of Movements , respectively. They showed that children with SLI scored significantly lower on measures of coordination and imitation in comparison with their age-matched TD peers.
Zelaznik and Goffman  reported results consistent with Vukovic et al. . They examined the motor abilities and, specifically, motoric timing of children with SLI. Using the Bruininks–Oseretsky Test of Motor Proficiency , they found that children with SLI performed more poorly than age-matched TD children across all subsections of the test, which consists of several coordination-based tasks. Interestingly, on the measures of timing which included circle drawing, finger and hand tapping.
Botting et al.  explored the quality of gestures in relation to motor and language abilities in children with and without SLI. They showed children images of real objects and events and asked the children to produce a gesture that represented the target object or event. The resulting gesture production scores did not significantly differ between children with SLI and age-matched TD children.
Similar to Botting et al. , Iverson and Braddock  examined gesture production and motor ability and the association of these factors to language ability in children with SLI. They suggested that children with SLI use gesture to support their poor verbal communication, but their fine motor ability may limit the quality of their gesture production.
| Dyslexia with specific language impairment|| |
SLI and developmental dyslexia (DD) are developmental disorders of communication that affect 7–10% of the school-aged population .
Children diagnosed with SLI are also dyslexic, and dyslexic children are having delayed language development. It has been found that even though SLI and dyslexia are frequently comorbid, pure SLI exists, as well as pure dyslexia .
The relation between SLI and DD is an issue of high controversy. Studies indicate an overlap in the symptoms of SLI and dyslexia. First, children with SLI are at risk for reading disorders, especially in reading comprehension ,. Second, problems with morphosyntax are mainly associated with SLI, but dyslexic children have also been found to experience problems in this domain and this morphosyntactic deficit is often found for both clinical groups before and after reading acquisition. Third, before school age the main problem for children with dyslexia deals with phonological processing, especially phonemic awareness, whereas, as SLI children, children with DD often demonstrate what is called an ‘expressive language disorder’ ,.
Thus, some children fit the criteria of both disorders and are labeled as dyslexic or LI depending on the type of clinician that the child first encounters. McArthur et al. , for example, found that 50% of the children in their study who were diagnosed as dyslexic also fit the defining criteria of SLI, and vice versa.
Many researchers have tried to explain the overlap between these two developmental disorders. Propositions for this overlap are quite controversial and include evidence for a genetic and for a language overlap.
The relatedness between reading disability (RD) and LI goes deeper than similarity in clinical presentation. RD and LI share numerous risk factors and associated genes, as both are complex disorders with substantial genetic contributors . Some of these risk genes, including DCDC2, KIAA0319, FOXP2, CNTNAP2, and CMIP, contribute to both RD and LI . These studies suggest that RD and LI share certain risk genes that influence core language processes.
Overlap in phonological reading-related skills
It has been proposed that both dyslexia and SLI are characterized by a phonological processing deficit .
In particular, phonological processing includes skills that are involved in the following:
- Phonemic awareness.
- Phonological STM.
- Rapid automatic naming (RAN).
Deficits in phonemic awareness
A large body of evidence shows that phonemic awareness is impaired in dyslexia ,. Deficits in phonemic awareness have also been associated with reading failure in SLI ,,. This has led many researchers to argue that a deficit in phonemic awareness underlies reading impairment in both dyslexic and SLI children ,.
Deficits in phonological short-term memory
Comparisons between phonological (STM) abilities in both populations have been made and have consistently found poor results in both groups ,,, with the dyslexic groups generally performing better than children with SLI.
Therefore, although these results suggest that poor phonological STM abilities are a characteristic of both dyslexia and SLI, they indicate differences in the severity of the deficit in SLI and dyslexic group. To interpret this finding, Newbury et al.  suggest that poor phonological STM ability is an attribute of a comparable problem affecting language skills, owing to which the child fails to use language knowledge effectively because of incapacity to keep provisional (temporary) representations in working memory. As a result, SLI children show deficits in the domain of language, which concern expressive and receptive linguistic abilities ,.
Nithart et al.  performed a study on French, a language with moderate inflection and more transparent than English, and tried to detect the phonological deficit in SLI and dyslexia. They showed that at least in repetition tasks SLI children are more impaired than dyslexic children and suggested that SLI may be regarded as a disorder of phonological STM (pseudoword repetition).
Deficits in rapid automatic naming
RAN skills are also found to be impaired in both dyslexia and SLI. Bishop et al.  found that rapid serial naming was the strongest predictor of SLI-only versus dyslexia, with SLI-only children outperforming dyslexic children. The SLI-only group had phonological difficulties at 6 years old but by 9 years old they read words and nonwords accurately. Furthermore, RAN measured at 9 years was the strongest predictor to divide the SLI children in groups on the basis of literacy achievement. The authors concluded that RAN is not related to oral language ability, but it is related to reading ability and that good RAN skills protect the child against RD, even when oral language skills are impaired.Vandewalle et al.  examined longitudinally the phonological and the early literacy development of 18 Dutch-speaking children with SLI from age 5 to 7 and compared them with TD children. They found that RAN skills measured in kindergarten were strongly correlated with reading and spelling in both groups and that only SLI children who additionally failed on RAN in kindergarten developed reading and spelling problems at the end of grade 1. Their findings are consistent with the findings of previous studies .
Overlap in morphosyntax
Typically, children with SLI experience particular problems with morphosyntactic information, such as tense and subject–verb agreement marking , whereas the domain of phonology (more specifically phonological awareness) has traditionally been found to be impaired in dyslexia, indicating that dyslexia is related to the phonological component of language ,. However, recent studies have shown that children with SLI have also problems with phonological awareness , and word-decoding deficits , whereas studies in DD report weaknesses in oral language domains, outside that of phonology, such as tense marking  and sensitivity to subject–verb agreement .
In addition, Rispens and Been  investigated whether and how children with DD and SLI differ in their sensitivity to subject–verb agreement in spoken language. They found that both the children with dyslexia and with SLI made more errors than control children on the subject–verb agreement task, with the children with dyslexia scoring significantly better than the children with SLI, and suggested that a difference in severity of the phonological processing impairment may explain these differences rather than assuming qualitatively different cognitive profiles between the two groups.
| Methods|| |
Studies included in this review contain the following elements:
Articles that focus on the association between memory, motoric impairment, and dyslexia with SLI were reviewed.
Studies were performed on patients diagnosed with SLI in the age range of 3–9 years, both boys and girls.
Included studies contain some standardized assessment of language deficits and one of its associated comorbidities.
This study is a literature review.
Exclusion criteria were as follows:
- Patients with SLI without associated comorbidities.
- Patients with memory, motoric impairment, dyslexia without SLI.
- Review articles, case reports, and articles limited to populations smaller than five participants.
| Discussion and conclusion|| |
SLI is a multifaceted disorder with both linguistic and nonlinguistic features including memory disorders, motoric deficits, and dyslexia. Literature suggests that children with SLI generally perform significantly worse than TD children on tests of verbal STM. This STM deficit is not confined to the auditory–verbal modality but constitutes more general STM problems impacting auditory–verbal, as well as visual, STM.
Children with SLI appear to have poor working memory. It has been suggested that children with SLI perform worse in working memory tasks involving the storage and processing of verbal but not visuo-spatial information. This dissociation has been explained in light of evidence that performance decrements occur only when the task additionally taps the impaired phonological, but not preserved, visuo-spatial storage abilities.
From literature it appears that in children with SLI learning is affected by functioning in long-term memory systems in addition to known deficits in working memory. In the case of declarative memory, there is some evidence to suggest that problems with learning and retrieval in SLI may be secondary to working memory problems and/or language difficulties and do not reflect declarative memory deficit. With respect to the procedural memory system, it is to be noted that children with SLI perform worse than TD peer in verbal and nonverbal procedural memory tasks.
The findings of studies examining the motor abilities of children with SLI confirmed that these children suffered from deficits motor skills, both simple and complex. Fine motor abilities were measured by finger opposition and bead threading tasks, whereas gross motor abilities were measured by tasks of balance, aiming, catching, and hopping. These difficulties also extended to speech motor ability particularly with the control of these articulatory movements. The production of communicative gesturing did not appear to be significantly impaired even with unfamiliar gestures.
It has been found that even though SLI and dyslexia are frequently comorbid, pure SLI exists, as well as pure dyslexia. Studies indicate an overlap in the symptoms of SLI and dyslexia. First, children with SLI are at risk for reading disorders, especially in reading comprehension. Second, problems with morphosyntax are mainly associated with SLI, but dyslexic children have also been found to experience problems in this domain and this morphosyntactic deficit is often found for both clinical groups before and after reading acquisition. Third, before school age, the main problem for children with dyslexia deals with phonological processing, especially phonemic awareness, whereas, as SLI children, children with DD often demonstrate what is called an expressive language disorder. The relationship between SLI and dyslexia was explained on two different accounts: the genetic predisposition and linguistic account. Evidence suggested that RD and LI share certain risk genes including DCDC2, KIAA0319, FOXP2, CNTNAP2, and CMIP that influence core language processes.
The linguistic account comprises also two different dimensions: the phonological skills that under pins the development of decoding, and the grammatical and semantic skills that are critical for reading comprehension.
There needs to be a greater awareness of language as a barrier to learning and the policy agenda needs to shift from a preoccupation with literacy standards toward a greater emphasis on oracy in the early years of education.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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