NATURE
OF LANGUAGE, SPEECH AND COMMUNICATION DISORDERS
Author:
Tamador Mohamed Sir Elkhatim
Department
of English
College
of Administrative & Humanities
Al
Jouf University, Sakaka
Kingdom
of Saudi Arabia
Cell:
00 966 50 455 6754
Email:
stamador@hotmail.com
Abstract
Speech, language and communication disorders are most
common form of disorder among children in the world. The speech and
language disorders are classified as expressive language disorder, phonological
disorder, and communication disorder not-otherwise-specified (DSM-IV), mixed
receptive-expressive language disorder and stuttering. Each category of speech
and language impairment is prevalent among children from 5-15%. These disorders are mainly
heritable and thus their genetic factor plays an important role in influencing
these disorders. Genetic basis behind this defect is studied thoroughly in this
review. Literature findings have showed that the main genes responsible for
speech and language disorders are FOXP1 and FOXP2 genes which are identified
through genome study linkages and genomic screening. Further research is
required to UN reveal the biological pathways behind this deficit and to
improve the treatment methods. Though various genetic factors play a vital
role, other environmental factors also influences the speech and language
disorders. The environmental
factors must be considered importantly during childhood who already has genetic
risk disorder. The important environmental influences related to children’s
success or failures in reading are mainly educational experiences and home
environment. Children’s literacy is mainly gained through the effect of home
environment and through their oral language skills and reading comprehension
ability when compared to accurate reading. Children who have such disorders
must receive assistance from the speech-language pathologist. Speech-language
pathologists work with children, families and schools to assist a child’s
communication. This therapy can be useful to children all through their
educational trajectory for the understanding of language, vocabulary and
reading which is more complex. Their
transition must be from learning to employment along with the children.
Keywords: Speech and language impairment, Genetic factors, Environmental factors, Treatment.
1.0 Introduction
Speech, reading
and language disorder is the most common form of disorder among children in world.
A communication disorder is the state of problems in spelling and reading. These
disorders with general academic difficulties may be long lasting (Gierut, 1998).
The facts and figures of some of the communication disorders are
categorized and discussed here. Articulation disorders indicate the impairment in
his ability to express speech sounds. This type of disorders is prevalent among
8-9% of children. Approximately, 5% of children are facing speech and language
disorder problem. Fluency disorder is a state of speech flow interruption,
which is identified through rhythm, atypical rate and repetitions in syllables,
sounds, phrases and words. These disorders are observed through tension,
struggle behavior and other secondary characteristics. This type of disorders
is prevalent among 4-5% of young children. This type of disorder is more for
children between 2- 4 years of age. The voice disorders
are the state of abnormal vocal quality, loudness, pitch and resonance based on
individual’s age or sex. These types of voice disorders are prevalent among school-aged
children with 6 to 23%. A phonological disorder refers to a condition in which
the sound system of a language governing is abnormal. Because of this, it is
difficult to get expected speech sounds at a particular age. 8-9% of the
children are affected through this disorder. A Language disorder is the state of comprehension impairment and
spoken and written language usage. Individuals with this disorder have
difficulty in semantics, syntax, pragmatics, phonological awareness, reading,
spelling and writing. The prevalence of language disorder is among preschool
children and early school-age children are 6-8% and 2- 8% respectively. The prevalence of reading disorders among
school-age children is 17%. Apraxia is the state of difficulty in initiating
and executing the movement pattern which is a basic requirement to speech
sounds. This is due to difficulty with motor planning nerves. Dysarthria is a
speech disorder due to damage of central or peripheral nerves that leads to
weakness, paralysis, or in coordination of speech muscles. Aphasia is a language
disorder due to brain damage or some other diseases. This disorder results in
the difficulty of formulating, expressing and understanding language. Cleft
Palate is a state of speech and language disorder due to birth defect. An Cleft
opening is present between the soft palate and bony roof on the mouth, and this
part is surgically repaired during infant level. This type of disorder results
in hyper nasality and various articulation difficulties. In this paper, we have
reviewed the factors involving speech and language impairment and their
diagnosis as well as the different treatment methods for using these kinds of
impairments.
1.1 Speech, Language
and Communication Disorder
1.1.1 Categorizing
and diagnosis
Developmental
communication disorder is the most common disorder for medical appointments
among children (Harel et al., 1996). The speech and language disorders
are the indicative of other comprehensive developmental conditions, which
includes autistic spectrum disorder, hearing impairment or learning disability.
In certain cases, the language and speech deficit takes place due to normal
developmental stages, but it has no evident reason (Bishop, 1994). The language and speech disorders are categorized as
five different classes: phonological disorder, expressive language disorder, stuttering,
mixed receptive-expressive language disorder, and communication disorders
(DSM-IV). Speech disorder is mainly due to impairment in fluent and
understandable speech making. The main speech disorder is stuttering, where the
speech fluency is completely interrupted. Phonological disorder also includes speech
and Sound Disorder [SSD], is the impairment in making of speech sounds.
Developmental verbal dyspraxia is the impairment in harmonization and motor
control of the speech organs. Language disorder may be observable in a lesser
way but it is more reflective. The problems in language disorders are inaccurate
formation of words or sentences, the use of linguistic context and the
derivation of meaning. Developmental dyslexia is also included in this disorder
in which receptive or expressive language in the nonverbal language (e.g.,
reading and writing) is not normal. Specific Language Impairment (SLI)
terminology is a shaded version of mixed receptive-expressive language disorder,
expressive language disorder, and occasionally for phonological disorder.
Though some forms of speech and language disorder is distinguished at clinical
level, which is extremely co morbid with each other. Most of the children are
not particularly diagnosed during their language development. In some other
conditions, they may change between different categories of disorders during
growing up. Almost 15% of children have relentless speech disorders and they
are also having language disorder. 5% of children have speech-language
impairment (Shriberg et
al., 1999). More than 60% of
stutterers have associated speech and language disorders, which mainly includes
articulation disorder (Blood et al., 2003). The diagnostic criteria for
SLI is necessitate to checking of other medical conditions. Literature studies
have reported that the individuals having SLI are at an increased risk of
related developmental conditions such as developmental delays, social problems,
cognitive impairment, behavioural difficulties and literacy deficits (Conti-Ramsden & Botting, 1999;; Law et al., 2000; Conti-Ramsden et al., 2001; Wadman et al., 2008). The speech and language
deficiency and its developmental problems are related and discussed clearly and
must be concluded in a right way to find out the biological pathway mechanism, and
also the etiological basis of these overlaps must be clearly understandable.
1.2 Factors
influences SLI disorder
1.2.1 Genetic factors
influencing SLI disorder
Literature studies have reported that genetic
factors have greatest contribution on speech and language impairment. SLI is heritable
(Clark et
al., 2007; Barry et al., 2007; Lewis et al 2007; Conti-Ramsden
et al., 2007 ;) among different generations. Genetic mechanisms are more susceptible to
speech and language disorders. These genetic factors undergo complex
interactions between environmental factors and genetic variants/splices.. Proper
genetic risk factors involved in biological pathways should be identified. A
neurological mechanism behind the acquisition of speech and language plays an
important part in speech and language disorders etiology. In some genetic
disorders, a gene behind the particular disorder is sufficient. But in this
case, the underlying biological mechanism behind the speech-language disorder
is unclear. Thus, the gene responsible for SLC must be identified through
unbiased screening approach. This screening of approach is usually in the form
of genome-wide linkage or other genomic approaches (Elston & Anne Spence, 2006).
The important gene which is responsible for language and
speech disorder is FOXP2 was diagnosed through verbal dyspraxia. Verbal
dyspraxia is the state of difficulty in orofacial muscles control which results
in fluent speech deficit. The affected family members also had receptive and
expressive language deficits. In other cases, there is a problem in writing and
also in non verbal cognition along with speech problems (Watkins et al., 2002). Hence, it is confirmed
that this type of speech and language impairments has an inheritance pattern of
genes (Vargha-Khademet al., 1995). Based on genomic
wide linkage analysis, the mutation of FOXP2 gene loci on chromosome 7q (Fisher et al., 1998) was prominent in each
family member gene sequences (Lai et al., 2001). From FOX
family, FOXP2 gene encodes a DNA-binding protein. After translation, the
synthesized protein functions as a transcriptional repressor. There are four is
forms in FOXP2 gene (Lai et al., 2001; Schroeder and Myers,
2008; Bruce et al., 2002 ;). FOXP2 gene has been expressed in most of the
tissues. The gene and its complex expression pattern have been tightly
regulated in all the expressed tissues and their sequences are highly conserved
among different species (Schroeder & Myers, 2008; Lu et
al., 2002; Ferland et al., 2003;). The FOXP2 gene function in the
verbal dyspraxia has demonstrated clearly. FOXP2 gene plays a significant role
in certain brain development areas such as motor cortex, cerebellum and
striatum for fine motor control. This brain development plays vital role in
speech development. FOXP2 transcripts are also involved in the expression of
other genes responsible for speech and language deficits. Spiteri et al., (2007) reported that the
translated FOXP2 protein is accountable for down regulation of 300 to 400
neural genes, which plays an important role in language and speech disorders.
This is researched through gene-targeting screening studies (Vernes et al., 2008; Vernes et al., 2007).
Among FOXP2 regulated genes, CNTNAP2 (OMIM 604569)
presents on chromosome loci 7 (Vernes et al., 2008, Vernes et al., 2007) and its complex forms
due to genetic involvement plays an important role in impairment of language (Arking et
al., 2008). A single base pair
change analysis has been done through single nucleotide polymorphism method on CNTNAP2
gene sequence result in the formation of nine genetic invariants. These genetic
invariants have significant correlation in reduced linguistic performance and
also have coherence in language impairment (Arking et al.,
2008). These genetic
invariants also have an implication in neuro developmental disorders such as
autism (Belloso et
al., 2007, Bakkaloglu et al., 2008;), ADHD (Strauss et al., 2006), schizophrenia (O’Dushlaine et al., 2010; Mefford et al., 2010), Gilles de Tourette
syndrome (Verkerk et al., 2003; Friedman et al 2008), epilepsy (O’Dushlaine et al., 2010; Mefford et al., 2010), and learning disability
(Elia et al., 2010).
CNTNAP2 gene encodes a neurexin protein that has an
important role in the localization of potassium channels during neuronal
development and axonal-glial interactions (Zweier et al., 2009; Poliak et al., 2003). CNTNAP2 has an
important role in neuronal development. Disturbances in gene function might subject
to varying neuro developmental psychiatric disorders and also in brain function
(Corvin, 2010).
Based on DNA binding domain of FOX gene family in
human consists of 40 members which are classified in 19 subfamilies (FOXA to
FOXS) (Hannenhalli & Kaestner, 2009). FOXP has four subfamilies (FOXP1-4)
have different functions. In particular, FOXP1 and FOXP2 have close
relationship in tissue development in a coordinated way. FOXP1 gene and other
three genetic transcripts (GPR27, EIF4E3, and PROK2) mutation result in
condition of blepharophimosis and arthrogryposis, which is an indicative of
delayed speech and language development (Pariani et al., 2009). Few of the literature
studies have reported that cause of blepharophimosis and arthrogryposis is due
to the deletion of three additional transcripts. FOXP1 disruptions result in
delayed motor neuronal development and speech delays.
FOXP1 is associated with host-response to hepatitis
vaccines (Davila et al., 2010), skin disorder (Jin et al., 2010), , as well as cancer
survival. FOXP1 protein function on the brain is unclear, but some literature has
reported its function as motor neuron diversification interacts with Hot
proteins interactions, and also in neuronal differentiation, via Pitx3 protein
regulation (Konstantoulas et al., 2010). Thus, these results
suggest that FOXP2 and FOXP1 genes are involved in neural circuitry conviction
and these further develop the speech and language during growing up.
Downstream targets and its binding patterns of FOXP2
play an important role in dyslexia. SSD is the emission or substitution of
speech sounds leads to clear speech. SSD is a specific problem with
phonological awareness development. Speech and language disorders have etiological
overlaps with developmental dyslexia. This condition seems to be a major risk
factor for literacy impairments, mainly in speech - relevant loss (Peterson et al., 2009).
Recent researches on dyslexic family members have guided
to identify the specific candidate genes for dyslexia linkage loci. A critical
step in cortex development is depend on most genes function for neuronal migration.
It acts as a significant partin etiology of reading disorders (Galaburda et al., 1985).
When compared to SSD, SLI is the heterogeneous speech
disorder has no obvious motoric etiology, as a result in expressive language
deficits (e.g., syntax, grammar, and semantics) and sensitive language ability
impairment has occurred. The three primary sites are identified by implementing
two whole-genome linkage screening techniques. . It is on chromosome 1 16
(SLI1, OMIM 606711), 3 (SLI3, OMIM 607134),and 19 (SLI2, OMIM 606712).
Regression modeling study on ATP2C2 and CMIP genes showed that these genes and
effect on phonological memory ability. The function of translated CMIP and
ATP2C2 proteins in the brain are yet to be exemplified but both represent reasonable
candidates for speech and language disorder. ATP2C2 is the gene responsible for
encoding calcium ATP as which is liable for cellular calcium and manganese
level regulation. CMIP was identified from the screening of large proteins translated
in the brain. The translated protein mainly encodes the part of cytoskeleton
structure (Grimbert et al., 2003). Cytoskeleton re-modeling
remains play a vital role in neuronal migration and synaptic formation.
1.2.2 Environmental
factors influencing SLI disorder
Environmental
factors play a vital role in influencing SLI disorders. During language
development, the main targeted works include parents provide verbal stimulation
to children, perinatal problems is mainly comes under neurological impairments,
and middle ear disease is mainly linked with fluctuating hearing loss (Bishop, 1997). The above conditions have no impact on development
but its mild conditions such as verbal deficit effect, minor-to-major hearing
loss, and local brain injury are not particular to verbal skills, and thus it
does not show a clinical picture resembling SLI. Though, the preference for
such environmental factors must be considered importantly during childhood who
already has genetic risk disorder. The gene responsible for disorder and
environmental interaction has yet to be demonstrated to know exact principle
behind this. The main environmental influence associated with children’s
failure or success in reading is mainly depending on home environment and
educational experiences. The dyslexia definitions clearly indicate the cause of
reading failure is mainly due to scarce opportunity to learn. Based on
schooling of children in same area,
there must be a substantial difference in the achievement of reading (Rutter & Maughan, 2002). Children’s literacy is
mainly gained through the effect of home environment and their oral language
skills and reading comprehension ability than accurate reading (Whitehurst & Lonigan, 1998).
1.3
Treatment and Management
The knowledge on SLI genetic factors
will be helpful in diagnosis methods and can identify the risk of this disorder
at an early age. This will be further helpful to improve environmental
involvement (Fisher & DeFries, 2002). Communication disorders must
be identified earlier for the advancement of social and educational isolation (National Dissemination Center for Children
with Disabilities, 2004). At age 5,
communication and language skills must be learned properly. The initial speech
or language difficulties in the stage of baby talk must be characterized or
else the expected speech patterns could not be obtained results in obstruction
of learning (National Dissemination Center for Children
with Disabilities, 2004). Speech- language
pathologist aids the Children, who have these disorders. . These pathologists are
worked along with schools, children, and families and may helpful in child’s
communication. It can be done through special therapy. The goals and techniques
have been developed and used at home and the classroom (National Dissemination Center for Children
with Disabilities, 2004). This type of therapy
is useful for children all through their educational path for fine
understanding of language, vocabulary and reading. Along with that,
speech-language pathologists should furnish long term guidance provided to
children from school to employment transition. Literature studies have reported
that the early intervention with speech-language pathologists has a good effect
on communication of children with speech sound disorders (Gierut, 1998). Based on treatment, children must have received
better outcomes. This type of treatment is more significant than untreated,
communication disorders, which may results in deficits in reading, writing and
spelling (Fisher & DeFries, 2002). More efforts are required to
ensure that children receive intervention at an appropriate time.
1.4 Future studies
Researchers and
clinicians must work out for increasing understanding of inheritance of SLI and
genetic and biological pathways of communication disorders. These ideas can
authorize existing diagnostic techniques and/or develop the new diagnoses
methods. Genetic linkage studies and whole genome wide screening methods can
also enlighten the unidentified treatment for communication disorders. The
co-occurrence of language, reading, and spelling disorders should be clearly
described by new findings through gene sequence analysis in these types of disorders.
Identifying the genetic factors can also useful to bridge the gap between
different disciplines and also helpful in understanding the more comprehensive
communication disorders.
1.5 Conclusion
In this review, SLI, its types
and the genetic factors influencing the SLI disorders have been thoroughly
studied. In this study by using FOXP2 gene exemplify higher competitor genes
and elemental mechanisms of language and speech disorders. . Recent research in
this area is improved among all developmental disorders, but studies on speech
and language disorders will be required further to know the biological pathway,
and the underlying genes involved in it. The recent study related to speech and
language disorders has resulted in combination of higher throughput studies.
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