Receptive Language Development

From birth, newborns demonstrate preferential response to human voices over inanimate sounds. The infant alerts and turns toward the direction of an adult who speaks in a soft, high-pitched voice. Over the first 3 mo, infants appear to recognize their parent’s voice and quiet if crying. Between 4 and 6 mo, infants visually search for the source of sounds, again showing a preference for the human voice over other environmental sounds. By 5 mo, infants can passively follow the adult’s line of visual regard, resulting in a “joint reference” to the same objects and events in the environment. The ability to share the same experience is critical to the development of further language, social, and cognitive skills. By 8 mo, the infant can actively show, give, and point to objects. Comprehension of words often becomes apparent by 9 mo, when the infant selectively responds to his or her name and appears to comprehend the word “no.” Social games, such as “peek-a-boo,” “so big,” and waving “bye-bye” can be elicited by simply mentioning the words. At 12 mo, many children can follow a simple, one-step request without a gesture (e.g., “Give it to me!”).

Between 1 and 2 yr, comprehension of language accelerates rapidly. Toddlers can point to body parts on command, identify pictures in books when named, and respond to simple questions (e.g., “Where’s your shoe?”). The 2 yr old is able to follow a 2-step command, employing unrelated tasks (e.g., “Take off your shoes, then go sit at the table”), and can point to objects described by their use (e.g., “Give me the one we drink from”). By 3 yr, children typically understand simple “wh-” question forms (e.g., who, what, where, why). By 4 yr, most children can follow adult conversation. They can listen to a short story and answer simple questions about it. Five yr olds typically have a receptive vocabulary of over 2000 words and can follow 3- and 4-step commands.

Expressive Language Development

Cooing noises are established by 4 to 6 wk of age. Over the first 3 mo of life, parents may distinguish their infant’s different vocal sounds for pleasure, pain, fussing, tiredness, etc. Many 3 mo old infants vocalize in a reciprocal fashion with an adult to maintain a social interaction (“vocal tennis”). By 4 mo, infants begin to make bilabial (“raspberry”) sounds, and by 5 mo monosyllables and laughing are noticeable. Between 6 and 8 mo, polysyllabic babbling (“lalala” or “mamama”) is heard and the infant might begin to communicate with gestures. Between 8 and 10 mo, babbling makes a phonologic shift toward the particular sound patterns of the child’s native language (i.e., they produce more native sounds than nonnative sounds). At 9 to 10 mo, babbling becomes truncated into specific words (e.g., “mama,” or “dada”) for their parents.

Over the next several mo, infants learn 1 or 2 words for common objects and begin to imitate words presented by an adult. These words might appear to come and go from the child’s repertoire until a stable group of 10 or more words is established. The rate of acquisition of new words is approximately 1 new word per wk at 12 mo, but it accelerates to approximately 1 new word per day by 2 yr. The first words to appear are used primarily to label objects (nouns) or to ask for objects and people (requests). By 18 to 20 mo, toddlers should use a minimum of 20 words and produce jargon (strings of word-like sounds) with language-like inflection patterns (rising and falling speech patterns). This jargon usually contains some embedded true words. Spontaneous 2-word phrases (pivotal speech), consisting of the flexible juxtaposition of words with clear intention (e.g., “Want juice!” or “Me down!”), is characteristic of 2 yr olds and reflects the emergence of grammatical ability (syntax).

Two-word, combinational phrases do not usually emerge until the child has acquired 50-100 words in their lexicon. Thereafter, the acquisition of new words accelerates rapidly. As knowledge of grammar increases, there is a proportional increase in verbs, adjectives, and other words that serve to define the relation between objects and people (predicates). By 3 yr, sentence length increases and the child uses pronouns and simple present tense verb forms. These 3-5 word sentences typically have a subject and verb but lack conjunctions, articles, and complex verb forms. The Sesame Street character Cookie Monster (“Me want cookie!”) typifies the “telegraphic” nature of the 3 yr old’s sentences. By 4-5 yr, children should be able to carry on conversations using adult-like grammatical forms and use sentences that provide details (e.g., “I like to read my books”).

Variations of Normal

Language milestones have been found to be largely universal across languages and cultures, with some variations depending on the complexity of the grammatical structure of individual languages. In Italian (where verbs often occupy a prominent position at the beginning or end of sentences), 14 mo olds produce a greater proportion of verbs compared with English speaking infants. Within a given language, development usually follows a fairly predictable pattern, paralleling general cognitive development. Although the sequences are predictable, the exact timing of achievement is not. There are marked variations among normal children in the rate of development of babbling, comprehension of words, production of single words, and use of combinational forms within the first 2-3 yr of life.

Two basic patterns of language learning have been identified: “analytic” and “holistic.” The analytic pattern is the most common and reflects the mastery of increasingly larger units of language form. As reflected in the previous discussion of milestones, the child’s analytic skills proceed from simple to more complex and lengthy forms. Children who follow a holistic or gestalt learning pattern might start by using relatively large chunks of speech in familiar contexts. They might memorize familiar phrases or dialogs from movies or stories and repeat them in an over-generalized fashion. Their sentences often have a formulaic pattern, reflecting inadequate mastery of the use of grammar to flexibly and spontaneously combine words appropriately in the child’s own unique utterance. Over time, these children gradually break down the meanings of phrases and sentences into their component parts, and they learn to analyze the linguistic units of these memorized forms. As this occurs, more original speech productions emerge and the child is able to assemble thoughts in a more flexible manner. Both analytic and holistic learning processes are necessary for normal language development to occur.

Epidemiology

Disorders of speech and language affect up to 8% of preschool-aged children. Nearly 20% of 2 yr olds are thought to have delayed onset of speech. By age 5 yr, 19% of children are identified as having a speech and language disorder (6.4% speech impairment, 4.6% both speech and language impairment, and 8% language impairment). Boys are nearly twice as likely to have an identified speech or language impairment as girls.

Etiology

Normal language ability is a complex function that is widely distributed across the brain through interconnected neural networks that are synchronized for specific activities. Early researchers in language disorders, noting what appeared to be clinical parallels between acquired aphasia in adults and childhood language disorders, expected to find similar lesions in the brains of affected children. For the most part, unilateral, focal lesions acquired in early life do not seem to have the same effects in children as in adults. Furthermore, risk factors for neurologic injury are absent in the vast majority of children with language impairment.

Genetic factors appear to play a major role in influencing how children learn to talk. Language disorders appear to cluster in families. A careful family history may identify current or past speech or language problems in up to 30% of 1st-degree relatives of proband children. Although children who are exposed to parents with language difficulty might be expected to experience poor language stimulation and inappropriate language modeling, studies of twins have shown the concordance rate for low language test score and/or a history of speech therapy to be approximately 50% in dizygotic pairs, rising to over 90% in monozygotic pairs. A number of potential gene loci have been identified, but no consistent genetic markers have been established.

The most plausible genetic mechanism involves a disruption in the timing of early prenatal neurodevelopmental events affecting migration of nerve cells from the germinal matrix to the cerebral cortex. Chromosomal lesions and point mutations of the FOXP2 gene and polymorphisms of the CNTNAP2 gene are associated with an uncommon but distinct speech and language disorder characterized by difficulties in learning and producing oral movement sequences (developmental verbal dyspraxia, childhood apraxia of speech). Affected children have a spectrum of impairment in expressive and receptive language as well as problems understanding grammar.

Pathogenesis

Language disorders are associated with a fundamental deficit in the brain’s capacity to process complex information rapidly. Simultaneous evaluation of words (semantics), sentences (syntax), prosody (tone of voice), and social cues can overtax the child’s ability to comprehend and respond appropriately in a verbal setting. Limitations in the amount of information that can be stored in verbal working memory can further limit the rate at which language information is processed. Electrophysiologic studies have shown abnormal latency in the early phase of auditory processing in children with language disorders. Neuroimaging studies have identified an array of anatomic abnormalities in regions of the brain that are central to language processing. MRI scans in children with specific language impairment (SLI) can reveal white matter lesions, white matter volume loss, ventricular enlargement, focal gray matter heterotopia within the right and left parietotemporal white matter, abnormal morphology of the inferior frontal gyrus, atypical patterns of asymmetry of language cortex, or increased thickness of the corpus callosum. Postmortem studies of children with language disorders have found evidence of atypical symmetry in the plana temporale and cortical dysplasia in the region of the sylvian fissure. Additionally, some researchers have identified a high incidence of paroxysmal EEG anomalies during sleep in children with SLI. Although these findings might represent a mild variant of the Landau-Kleffner syndrome (acquired verbal auditory agnosia), they likely represent an epiphenomenon in which paroxysmal activity is related to architectural dysplasia. In support of a genetic mechanism affecting cerebral development, a high rate of atypical perisylvian asymmetries has also been documented in the parents of children with SLI.

Clinical Manifestations

Primary disorders of speech and language development are often found in the absence of broader cognitive or motor dysfunction. Disorders of communication are the most common comorbid condition in persons with generalized cognitive disorders (intellectual disability or autism), structural anomalies of the organs of speech (velopharyngeal insufficiency from cleft palate), and neuromotor conditions affecting oral motor coordination (dysarthria from cerebral palsy or other neuromuscular disorders).

Classification

Each professional discipline has adopted a somewhat different classification system, based on cluster patterns of symptoms. One of the simplest classifications is the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (Table 32-2). This system recognizes 4 types of communication disorders: expressive language disorder, mixed receptive-expressive language disorder, phonological disorder, and stuttering. In clinical practice, childhood speech and language disorders occur as a number of distinct entities.

Specific Language Impairment

Also referred to as developmental dysphasia, or developmental language disorder, SLI is characterized by a significant discrepancy between the child’s overall cognitive level (typically nonverbal measures of intelligence) and functional language level. In addition, these children follow an atypical pattern of language acquisition and use. Closer examination of the child’s skills might reveal deficits in understanding and use of word meaning (semantics) and grammar (syntax). Often, children with SLI are delayed in starting to talk. Most significantly, they usually have difficulty understanding spoken language. The problem may stem from insufficient understanding of single words or from the inability to deconstruct and analyze the meaning of sentences. Many affected children show a holistic pattern of language development, repeating memorized phrases or dialog from movies or stories (echolalia). In contrast to their difficulty with spoken language, children with SLI appear to learn visually and demonstrate their ability on nonverbal tests of intelligence.

Although they have difficulty interacting with peers who are more verbally adept, many children with SLI play appropriately with younger or older children. Despite their communication impairment, they engage in pretend play, show imagination, share emotions (affective reciprocity), and demonstrate joint referencing behaviors appropriate to their age. Of note is the high incidence of fine-motor coordination difficulty found in these children. A combination of increased joint mobility and mild muscular hypotonia often results in motor clumsiness.

Over time, children with SLI respond to therapeutic/educational interventions and show a trend toward improvement of communication skills. Adults with a history of childhood language disorder continue to show evidence of impaired language ability, even when surface features of the communication difficulty have improved considerably. This suggests that many persons find successful ways of adapting to their impairment.

Many children with SLI show difficulties with social interaction, particularly with same-aged peers. Social interaction is mediated by oral communication, and a child deficient in communication is at a distinct disadvantage in the social arena. Children with SLI tend to be more dependent on older children or adults, who can adapt their communication to match the child’s level of function. They might gravitate toward younger children who communicate at a level they can comprehend. Generally, social interaction skills are more closely correlated with language level than with nonverbal cognitive level. Using this as a guide, one usually sees a developmental progression of increasingly more sophisticated social interaction as the child’s language abilities improve. In this context, social ineptitude is not necessarily a sign of asocial distancing (e.g., autism) but rather a delay in the ability to negotiate social interactions.

Pragmatic Language Disorder

The ability to communicate effectively with others depends on mastery of a range of skills that go beyond basic understanding of words and rules of grammar. These higher-order abilities include knowledge of the conversational partner, knowledge of the social context in which the conversation is taking place, and general knowledge of the world. Social and linguistic aspects of communication are often difficult to tease apart, and persons who have trouble interpreting these relatively abstract aspects of communication typically experience difficulty forming and maintaining relationships. Symptoms of pragmatic difficulty include extreme literalness and inappropriate verbal and social interactions. Proper use and understanding of humor, slang, and sarcasm depend on correct interpretation of the meaning and the context of language and the ability to draw proper inferences. Failure to provide a sufficient referential base to one’s conversational partner—to take the perspective of another person—results in the appearance of talking or behaving randomly or incoherently. Pragmatic language impairment often occurs in the context of SLI, but it has been recognized as a symptom of a wide range of disorders, including right-hemisphere damage to the brain, autism, Asperger’s syndrome, Williams syndrome, and nonverbal learning disabilities.

Mental Retardation

Most children with a mild degree of mental retardation learn to talk at a slower than normal rate; they follow a normal sequence of language acquisition and eventually master basic communication skills. Difficulties may be encountered with higher-level language concepts and use. Persons with moderate to severe degrees of cognitive retardation can have great difficulty in acquiring basic communication skills. About half of persons with IQ <50 are able to communicate using single words or simple phrases; the rest are typically nonverbal.

Autism and Pervasive Developmental Disorders

A disordered pattern of language development is one of the core features of autism and other pervasive developmental disorders (Chapter 28). In fact, the language profile of children with autism is indistinguishable from that in children with SLIs. The key points of distinction between these conditions are the lack of reciprocal social relationships that characterizes children with autism, limitation in the ability to develop functional, symbolic, or pretend play, and an obsessive need for sameness and resistance to change. Approximately 75-80% of children with autism are also mentally retarded, and this can limit their ability to develop functional communication skills. Language abilities can range from absent to grammatically intact, but with limited pragmatic features and/or odd prosody patterns. Some autistic persons have highly specialized, but isolated, “savant” skills, such as calendar calculations and hyperlexia (the precocious ability to recognize written words beyond expectation based on general intellectual ability). Regression in language and social skills (autistic regression) occurs in approximately one third of children with autism, usually before 2 yr of age. No explanation for this phenomenon has been identified. Once the regression has “stabilized,” recovery of function does not usually occur (Fig. 32-1).

Figure 32-1 Relationship of autism, language disorders, and mental retardation.

(From Simms MD, Schum RL: Preschool children who have atypical patterns of development, Pediatr Rev 21:147–158, 2000.)

Asperger’s Syndrome (Chapter 28.2)

Although sharing many characteristics of autism (deficits in social relatedness and restricted range of interests), individuals with Asperger syndrome typically show normal early language development (syntax and semantics). As they mature, higher-order social and language pragmatic impairments become prominent features of this disorder. Affected children have an unusually circumscribed range of interests, which are all-absorbing and interfere with learning of other skills and with social adaptation. These children may engage in long-winded, verbose monologues about their topics of special interest, with little regard to the reaction of others. Their inflection pattern (prosody) may be inappropriate to the content of their conversation, and they might not adjust their rate of speech or vocal volume to the setting.

Selective Mutism

Selective mutism is defined as a failure to speak in specific social situations despite speaking in other situations, and it is typically a symptom of an underlying anxiety disorder. Children with selective mutism can speak normally in certain settings, such as within their home or when they are alone with their parents. They fail to speak in other social settings, such as at school or at other places outside their home. Other symptoms associated with selective mutism can include excessive shyness, withdrawal, dependency on parents, and oppositional behavior. Most cases of selective mutism are not the result of a single traumatic event, but rather are the manifestation of a chronic pattern of anxiety. Mutism is not passive-aggressive behavior. Mute children report that they want to speak in social settings but are afraid to do so. It is important to emphasize that the underlying anxiety disorder is the likely origin of selective mutism. Often, one or both parents of a child with selective mutism has a history of anxiety symptoms, including childhood shyness, social anxiety, or panic attacks. This suggests that the child’s anxiety represents a familial trait. For some unknown reason, the child converts the anxiety into the mute symptom. The mutism is highly functional for the child in that it reduces anxiety and protects the child from the perceived challenge of social interaction. Treatment of selective mutism should focus on reducing the general anxiety, rather than focusing only on the mute behaviors (Chapter 23). Selective mutism reflects a difficulty of social interaction and not a disorder of language processing.

Isolated Expressive Language Disorder

More commonly seen in boys than girls, isolated expressive language disorder (late talker syndrome) is a diagnosis best made in retrospect. These children have age-appropriate receptive language and social ability. Once they start talking, their speech is clear. There is no increased risk for language or learning disability as they progress through school. A family history of other males with a similar developmental pattern is often reported. This pattern of language development likely reflects a variation of normal.

Dysarthria

Motor speech disorders can originate from neuromotor disorders such as cerebral palsy, muscular dystrophy, myopathy, facial palsy. The resulting dysarthria affects both speech and nonspeech functions (smiling and chewing). Lack of strength and muscular control manifests as slurring of words and distorting of vowels. Speech patterns are often slow and labored. Poor velopharyngeal function can result in mixed nasal resonance (hyper- or hyponasal speech). In many cases, feeding difficulty, drooling, open mouth posture, and a protruding tongue accompany the dysarthric speech.

Verbal Apraxia

Difficulty in planning and coordinating movements for speech production can result in inconsistent distortion of speech sounds. The same word may be pronounced differently each time. Intelligibility tends to decline as the length and complexity of the child’s speech increases. Consonants may be deleted and sounds transposed. As they try to talk spontaneously, or imitate other’s speech, children with verbal apraxia may display oral groping or struggling behaviors. Often, children with verbal apraxia have a history of early feeding difficulty, limited sound production as infants, and delayed onset of spoken words. They may point, grunt, or develop an elaborate gestural communication system in an attempt to overcome their verbal difficulty. Apraxia may be limited to oral-motor function, or it may be a more generalized problem affecting fine and/or gross motor coordination.

Phonologic Disorder

Children with phonologic speech disorder are often unintelligible, even to their parents. Articulation errors are not the result of neuromotor impairment but seem to reflect an inability to correctly process the words they hear. As a result, they lack understanding of how to fit sounds together properly to create words. In contrast to children with apraxia, those with phonologic disorder are fluent—although unintelligible—and produce a consistent, highly predictable pattern of articulation errors. Children with phonologic speech disorder are at high risk for later reading and learning disability.

Hearing Impairment

Hearing loss can be a major cause of delayed or disordered language development (Chapter 629). Approximately 16-30 per 1,000 children have mild to severe hearing loss, significant enough to affect educational progress. In addition to these “hard of hearing” children, approximately another 1 per 1,000 are deaf (profound bilateral hearing loss). Hearing loss can be present at birth or acquired postnatally. Newborn screening programs can identify many forms of congenital hearing loss, but children can develop progressive hearing loss or acquire deafness after birth.

The most common types of hearing loss are due to conductive (middle ear) or sensorineural deficit. Although it is not possible to accurately predict the impact of hearing loss on a child’s language development, the type and degree of hearing loss, the age of onset, and the duration of the auditory impairment clearly play important roles. Children with significant hearing impairment often have problems developing facility with language and often have related academic difficulties. Presumably, the language impairment is caused by lack of exposure to fluent language models starting in infancy.

Approximately 30% of hearing-impaired children have at least one other disability that affects development of speech and language (e.g., mental retardation, cerebral palsy, craniofacial anomalies). Any child who shows developmental warning signs of a speech or language problem should have a hearing assessment by an audiologist and an examination by a geneticist as part of a comprehensive evaluation.

Hydrocephalus

Children with hydrocephalus are described as having “cocktail-party syndrome.” Although they may use sophisticated words, their comprehension of abstract concepts is limited, and their pragmatic conversational skills are weak. As a result, they speak superficially about topics and appear to be carrying on a monologue (Chapter 585.11).

Hyperlexia

Hyperlexia is the precocious development of reading single words that spontaneously occurs in some young children (2-5 yr) without specific instruction. It is typically associated with children who have a pervasive developmental disorder (PDD) or SLI. It stands in contrast to precocious reading development in young children who do not have any other developmental disorders. Hyperlexia is a variation seen in young children with disordered language who do not have the social deficits or restricted or repetitive behaviors associated with autism. A typical manifestation is for a child with SLI to orally read single words, or match pictures with single words. Although hyperlexic children show early and well-developed word-decoding skills, they usually have no precocious ability for comprehension of text. Rather, text comprehension is closely intertwined with oral comprehension, and children who have difficulty decoding the syntax of language are also at risk for having reading comprehension problems.

Landau-Kleffner Syndrome (Verbal Auditory Agnosia)

Children with Landau-Kleffner syndrome have a history of normal language development until they experience a regression in their ability to comprehend spoken language (verbal auditory agnosia). The regression may be sudden or gradual, and it usually occurs between 3 and 7 yr of age. Expressive language skills typically deteriorate, and some children may become mute. Despite their language regression, these children typically retain appropriate play patterns and the ability to interact in a socially appropriate manner. An EEG might show a distinct pattern of status epilepticus in sleep (continuous spike-wave in slow-wave sleep), and up to 80% of children with this condition eventually exhibit clinical seizures. A number of treatment approaches have been reported, including antiepileptic medication, steroids, and intravenous gamma globulin, with varying results. The prognosis for return of normal language ability is uncertain, even with resolution of the EEG abnormality, which can represent an epiphenomenon of an underlying brain abnormality.

Metabolic and Neurodegenerative Disorders (See Also Part XI)

Regression of language development may accompany loss of neuromotor function at the outset of a number of metabolic diseases including lysosomal storage disorders (metachromatic leukodystrophy), peroxisomal disorders (adrenal leukodystrophy), ceroid lipofuscinosis (Batten’s disease), and mucopolysaccharidosis (Hunter’s disease, Hurler’s disease). Recently, creatine transporter deficiency was identified as an X-linked disorder that manifests with language delay in boys and mild learning disability in female carriers.

Psychologic Evaluation

There are two main goals for the psychologic evaluation of a young child with a communication disorder. Nonverbal cognitive ability must be assessed to determine if the child is mentally retarded, and the child’s social behaviors must be assessed to determine whether autism or a form of PDD is present. Additional diagnostic considerations may include emotional disorders such as anxiety, depression, mood disorder, obsessive-compulsive disorder, academic learning disorders, and attention-deficit/hyperactivity disorder (ADHD).

Speech and Language Evaluation

A certified speech-language pathologist should perform a speech and language evaluation. A typical evaluation includes assessment of language, speech, and the physical mechanisms associated with speech production. Both expressive and receptive language is assessed by a combination of standardized measures and informal interactions and observations. All components of language are assessed, including syntax, semantics, pragmatics, and fluency. Speech assessment similarly uses a combination of standardized measures and informal observations. Assessment of physical structures includes oral structures and function, respiratory function, and vocal quality. In many settings, a speech-language pathologist works in conjunction with an audiologist, who can do appropriate hearing evaluation of the child. If an audiologist is not available in that setting, then a separate referral should be made. No child is too young for a speech and language or hearing evaluation. A referral for evaluation is appropriate whenever there is suspicion of language impairment.

Medical Evaluation

As in any developmental disorder, careful history and physical examination should focus on the identification of potential contributors to the child’s language and communication difficulties. A family history of delay in talking, need for speech and language therapy, or academic difficulty can suggest a genetic predisposition to language disorders. Pregnancy history might reveal risk factors for prenatal developmental anomalies, such as polyhydramnios or decreased fetal movement patterns. Small size for gestational age at birth, symptoms of neonatal encephalopathy, or early and persistent oral-motor feeding difficulty may presage speech and language difficulty. Developmental history should focus on the age at which various language skills were mastered and the sequences and patterns of milestone acquisition. Regression or loss of acquired skills should raise immediate concern.

Physical examination should include measurement of height (length), weight, and head circumference. The skin should be examined for lesions consistent with phakomatosis (e.g., tuberous sclerosis, neurofibromatosis, Sturge-Weber syndrome) and other disruptions of pigment (hypomelanosis of Ito). Anomalies of the head and neck, such as white forelock and hypertelorism (Waardenberg syndrome), ear malformations (Goldenhar syndrome), facial and cardiac anomalies (Williams syndrome, velocardiofacial syndrome), retrognathism of the chin (Pierre-Robin anomaly), or cleft lip and/or palate, are associated with hearing and speech abnormalities. Neurologic examination might reveal muscular hypertonia or hypotonia, both of which can affect neuromuscular control of speech. Generalized muscular hypotonia, with increased range of motion of the joints, is commonly seen in children with SLI. The reason for this association is not clear but it might account for the fine and gross motor clumsiness often seen in these children. However, mild hypotonia is not a sufficient explanation for the impairments of expressive and receptive language.

No routine diagnostic studies are indicated for SLI or isolated language disorders. When language delay is a part of a generalized cognitive or physical disorder, referral for further genetic evaluation, chromosome testing (including high resolution banding karyotype, fragile X testing, and microarray comparative genomic hybridization), neuroimaging studies, and EEG may be considered, if clinically indicated.