Etiology of speech and language disorders in children

INTRODUCTION — A communication disorder refers to "an impairment in the ability to receive, send, process, and comprehend concepts or verbal, nonverbal, and graphic symbol systems" [1]. Normal development of communication requires the interaction of an intact mechanism with a favorable environment. The components of an intact mechanism include hearing sensitivity, perception, intelligence, structural integrity, motor skill, and emotional stability. A favorable environment is one that provides the child with adequate language exposure and stimulation, reinforces the child's communicative attempts, and holds realistic expectations according to the child's developmental stage.

Developmental language disorder is the most common developmental disability of childhood, occurring in 5 to 10 percent of children [2]. Children learn language in early childhood; later they use language to learn. Children with language disorders are at increased risk for difficulty with reading and written language when they enter school [3-5]. These problems often persist through adolescence or adulthood [6,7]. Early intervention may help minimize the more serious consequences of later learning disabilities. (See "Specific learning disorders in children: Clinical features".)

CLASSIFICATION — Two major types of communication disorders are speech disorders and language disorders.

The term "speech disorder" refers to an impairment of the articulation of speech sounds, fluency, and/or voice.

●Articulation disorders are characterized by substitutions, omissions, additions, or distortions of speech sounds that interfere with intelligibility.

●Fluency disorder (stuttering) is an interruption in the flow of speaking characterized by atypical rate, rhythm, and repetitions in sounds, syllables, words, and phrases. Excessive tension, struggle behavior, and secondary mannerisms may be present.

●Voice disorder pertains to abnormal production of vocal quality, pitch, loudness, resonance, and/or duration that is inappropriate for the child's age and sex.

In contrast, the term "language disorder" refers to impaired comprehension and/or use of spoken, written, and/or other symbol systems. It may involve the form (grammar, syntax, morphology), content (vocabulary), and/or function (pragmatic use) of language [1].

The etiology of speech and language impairment is reviewed here. The evaluation and treatment of these disorders are discussed elsewhere. (See "Evaluation and treatment of speech and language disorders in children".)

SPEECH DISORDERS

Articulation disorders — The ability to produce speech sounds increases with age (figure 1). Difficulties with the production of speech sounds can occur for a variety of reasons, as described below. However, most children with disordered articulation and phonology do not exhibit an identifiable physical reason for the problem [8].

Hearing impairment — Children with hearing impairments have difficulty with all parameters of speech, not just articulation. These speech problems result from a limited ability to hear others and to monitor their own speech production. (See "Hearing loss in children: Etiology" and "Hearing loss in children: Screening and evaluation".)

Neurologic problems — Dysarthrias are speech problems caused by neuromuscular impairment resulting from a stroke, brain tumor, or disorder of the nervous system (eg, cerebral palsy). Dysarthria often is associated with a swallowing disorder (eg, dysphagia) because the same structures are employed for both speaking and swallowing. Long before the child begins speaking, dysphagia may be identified by choking or coughing with feedings; inability to handle secretions; nasal regurgitation; and recurrent upper respiratory infections, pneumonia, and congestion. (See "Neonatal oral feeding difficulties due to sucking and swallowing disorders".)

Apraxia — An impairment in the ability to program the speech musculature to select, plan, organize, and initiate a motor pattern is called apraxia. It is presumed to be neurologic in origin; however, the validity of considering developmental apraxia of speech or developmental verbal dyspraxia as a separate diagnostic category is one of the most controversial issues in clinical speech pathology [9,10].

Structural defects — Cleft lip and palate, ankyloglossia (tongue tie), and complete or partial glossectomy also impair articulation. The tongue tip must be able to move freely to produce sounds such as /t/, /d/, /n/, and /l/, but misarticulation caused by ankyloglossia is quite rare. Tongue size appears to have little relationship to articulation, but this variable has not been investigated thoroughly [11]. The term "tongue thrust" refers to excessive anterior tongue movement during swallowing or speech. It may be associated with malocclusion and articulation difficulty, usually a frontal lisp characterized by anterior tongue placement for /s/ and /z/ [11].

Fluency disorders — Developmental stuttering usually begins between the ages of two and five years. Although the etiology of stuttering is not completely understood, stuttering is more common in males and has a high familial incidence. Incidence and twin studies suggest that an interaction between genetic and environmental factors leads to stuttering in predisposed individuals [12].

Theories of developmental stuttering have included organic, behavioral, and psychological causes. The capacities-and-demands model proposes that stuttering develops when the capacities of the child for fluency (eg, motor skills, language production skills, emotional maturity, cognitive development) are not equal to the demands of the environment for speech performance [13].

By comparison, neurogenic stuttering is associated with neurologic disease or trauma. It is much less common than is developmental stuttering [14].

Voice disorders — Voice disorders are related to misuse or organic changes of the vocal mechanism. Vocal quality also can be affected by hearing loss because of difficulty in self-monitoring [15]. Causes of voice disorders in children include contact ulcers, vocal nodules, vocal polyps, cancer, endocrine changes, granuloma, hemangioma, hyperkeratosis, infectious laryngitis, laryngofissure, leukoplakia, papilloma, vocal fold paralysis, and webbing [16]. Vocal nodules, which occur more frequently in children than in adults, are the most frequently occurring laryngeal pathology encountered by speech-language pathologists working in schools [17]. Most voice problems, including those related to vocal nodules, are caused by the use of excessive effort and force while speaking [18]. This vocal behavior may be part of an overall pattern of hyperactivity in the preschool years [19]. (See "Common causes of hoarseness in children", section on 'Nodules'.)

Resonance disorders — Hypernasality and hyponasality characterize resonance disorders. Hypernasality results from clefts of the hard or soft palate, submucous clefts, inadequate length of the velum (muscular portion of the soft palate), and paralysis or paresis of the velum. These types of structural defects prevent normal closure between the soft palate, or velum, and the pharyngeal wall, thereby allowing air to escape into the nasal cavity (ie, velopharyngeal insufficiency [VPI]). VPI may be masked by the child's use of excessive force and tension to compensate for the structural weakness, resulting in a hoarse vocal quality. The opposite condition, hyponasal resonance or denasality, can be caused by enlarged adenoids, nasal polyps, and improper velar timing. In this disorder, the child sounds congested.

LANGUAGE DISORDERS — As defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision, language disorder is characterized by [20]:

●Persistent difficulties in the acquisition and use of language (expressive or receptive) across modalities (ie, spoken, written, sign language, or other) due to deficits in comprehension or production that include reduced vocabulary, limited sentence structure, and impairments in discourse (ability to use vocabulary and connect sentences)

●Language abilities substantially and quantifiably below those expected for age, resulting in functional limitations in effective communication, social participation, academic achievement, or occupational performance

In addition, the difficulties must have onset in the early developmental period and must not be attributable to hearing or other sensory impairment, motor dysfunction, or another medical or neurologic condition, including intellectual disability or global developmental delay.

Common features include slow rate of language development, a limited amount of speech, limited range of vocabulary, difficulty acquiring new words, word-finding vocabulary errors, shortened sentences, simplified grammatical structure, limited varieties of sentence types, use of unusual word order, formulation difficulty, and/or difficulty understanding words, sentences, or specific types of sentences.

Major categories

Developmental language impairment — Developmental language impairment (DLI) or disorder (DLD) is a broad term used to describe a variety of developmental disorders, including those associated with cognitive impairment, in which speech and language also are affected. DLI must be distinguished from specific language impairment (SLI), described below, because of important differences in the approach to treatment and prognosis.

Specific language impairment — SLI is a developmental disorder that occurs in the absence of intellectual disability, hearing loss, motor disorder, socioemotional dysfunction, or frank neurologic deficit [21]. Genetic factors are thought to contribute to poor language development in children who do not have other developmental or sensory disorders [22].

Case-control studies have identified various risk factors [23,24]. Risk factors that have been identified in more than one study include family history [23,25-27], male sex [23,25,26], lower education levels of parents [25,27,28], lower paternal occupational status [23,25,26], and more siblings [26,28].

The strong familial incidence of language and learning problems in the near relatives of children with SLI indicates a probable genetic component to this disorder. Genetic mapping has been difficult, as most families with speech and language deficits show complex patterns of inheritance. The study of three generations of one family with severe speech and language disorder transmitted as an autosomal dominant monogenic trait identified the involvement of the FOXP2 gene on chromosome 7q31 in the development of speech and language [29-31]. Other loci involved in SLI have been mapped to chromosomes 16q and 19q [32].

Causes — Many conditions are associated with language disorders (table 1). Language disorders may be acquired or developmental. Acquired causes include:

●Degenerative neurologic disorders

●Infection

●Neglect and abuse

●Head injury

Degenerative neurologic disorders — Loss of language skills may be associated with dementia from degenerative neurologic disorders, such as [33]:

●Leigh encephalopathy (see "Mitochondrial myopathies: Clinical features and diagnosis", section on 'Leigh syndrome')

●Rett syndrome (see "Rett syndrome: Genetics, clinical features, and diagnosis", section on 'Typical manifestations')

●Metachromatic leukodystrophy (see "Metachromatic leukodystrophy", section on 'Clinical manifestations')

●Mucopolysaccharidosis and other storage disorders (see "Mucopolysaccharidoses: Clinical features and diagnosis")

Infection — Otitis media with effusion is of particular concern to the language development of young children. Fluid in the middle ear can impair the transmission of sound, causing a mild conductive hearing loss. Although a relationship between otitis media and speech/language development has been suggested by several studies, the nature of the linkage remains controversial [34-42]. As examples (see "Hearing loss in children: Etiology" and "Acute otitis media in children: Epidemiology, microbiology, and complications", section on 'Hearing loss'):

●In a prospective study, the middle ear status of 6350 children was monitored during the first three years of life [36,38-42]. The following results were noted:

•Among 429 children with persistent middle ear effusion (MEE) who were randomly assigned to prompt or delayed insertion of tympanostomy tubes, there was no difference in developmental outcome between groups at 3, 4, 6, and 9 to 11 years [38-42].

•Among a sample of 241 children with a spectrum of MEE that ranged from none to a cumulative duration that was just short of meeting criteria for persistent MEE, a weak correlation was found between the duration of MEE in the first year of life and impairment of receptive language and verbal cognition at age three years [36]. However, a stronger, more consistent correlation was found between socioeconomic index (eg, maternal education and health insurance status) and language and cognitive skills at age three, raising the possibility that socioeconomic index is a marker for a confounding factor that predisposes children to both otitis media and developmental impairment in the first year of life.

●In a longitudinal study, differences were found in phonologic processing and working memory between groups of nine-year-olds with and without history of otitis media in the first year of life, indicating that subtle, long-term effects of early otitis media can be detected [37].

Neglect and abuse — Language problems are significantly affected by the quality of the child-caregiver interaction [43]. Neglect and abuse, both physical and emotional, are associated with language impairment. Prenatal maternal substance abuse (eg, alcohol, cocaine) also has been associated with speech and language problems in offspring [44,45].

Head injury — Children suffering from closed head injuries from motor vehicle, sports-related, or other types of accidents are likely to have cognitive-communicative problems, especially with regard to narrative discourse [46].

Central auditory processing disorder — Evaluation for a central auditory processing disorder (sometimes referred to as auditory processing disorder) in school-age children is based on the assumption that an auditory-specific perceptual deficit can be the basis for learning problems such as reading and language disabilities [47-50]. However, the diagnosis, management, and even the existence of auditory processing disorders are controversial. Some authorities suggest that it may exist as a primary deficit, whereas others believe that it may be secondary to cognitive deficits. The absence of a coherent theory renders diagnosis and management exceedingly difficult [51,52].

Differential diagnosis — The differential diagnosis of a language disorder includes autism spectrum disorder (ASD), Landau-Kleffner syndrome (LKS), selective mutism, and acquired aphasia.

ASD should be suspected in children who have delayed or immediate echolalia, formulaic speech, odd or overelaborate word choice, or gaze avoidance, and who fail to use language communicatively or to initiate meaningful verbal interaction [53]. (See "Autism spectrum disorder in children and adolescents: Clinical features", section on 'Terminology'.)

LKS (also called acquired epileptic aphasia) is characterized by the loss of previously established language milestones, inability to comprehend the spoken word, and seizures or an epileptiform electroencephalogram. It is discussed separately. (See "Epilepsy syndromes in children", section on 'Developmental and epileptic encephalopathy with spike-wave activation in sleep (DEE-SWAS)'.)

SUMMARY

●Speech disorders – Speech disorders include impairments of articulation, fluency, and/or voice. (See 'Speech disorders' above.)

•Articulation disorders are characterized by substitutions, omissions, additions, or distortions of speech sounds that interfere with intelligibility. Articulation disorders may be caused by hearing impairment, neurologic problems, apraxia, or structural defects. (See 'Articulation disorders' above.)

•Fluency disorder (stuttering) is an interruption in the flow of speaking characterized by atypical rate, rhythm, and repetitions in sounds, syllables, words, and phrases. The cause of fluency disorders is unknown. (See 'Fluency disorders' above.)

•Voice disorder pertains to abnormal production of vocal quality, pitch, loudness, resonance, and/or duration that is inappropriate for the child's age and sex. Voice disorders are related to misuse (excessive effort and force while speaking) or organic changes of the vocal mechanism. (See 'Voice disorders' above.)

●Language disorders – Language disorders refer to impaired comprehension and/or use of spoken, written, and/or other symbol systems. They may involve the form (grammar, syntax, morphology), content (vocabulary), and/or function (pragmatic use) of language. (See 'Language disorders' above.)

•Language disorders may be acquired or developmental (table 1). (See 'Causes' above.)

•The differential diagnosis of language disorder includes autism spectrum disorder, Landau-Kleffner syndrome, selective mutism, and acquired aphasia. (See 'Differential diagnosis' above and "Epilepsy syndromes in children", section on 'Developmental and epileptic encephalopathy with spike-wave activation in sleep (DEE-SWAS)' and "Autism spectrum disorder in children and adolescents: Clinical features", section on 'Impaired social communication and interaction'.)