Is a type of language disorder characterized by unintelligible speech?

Articulation Disorders

An articulation disorder exists when a child has difficulty physically producing a sound or sounds due to structural defects or difficulty with proper placement of articulators to create the target sound. For example, when a child substitutes a “w” for an “r” (“wed/”red”), or “y” for “l” (“yight” for “light”), they are exhibiting difficulty producing the “r” and “l” sounds.

Children with structural defects such as ankyloglossia (seeChapter 207) or cleft palate may exhibit obligatory and/or compensatory sound substitutions. A child with restricted tongue movement may be unable to produce interdental “th,” for example, and learns to substitute either a different sound (e.g., “vis” for “this”), or a different part of the tongue, protruding the mid tongue instead of the tongue tip to produce an interdental sound. A common compensatory behavior for children with limited tongue tip mobility is to use the mandible to bring the tongue into contact with the alveolar ridge. Unless ankyloglossia is very severe, these children typically learn to compensate for their restricted tongue movement and develop intelligible speech without need for frenulectomy.

Children with velopharyngeal insufficiency (seeChapter 189) secondary to cleft palate exhibit obligatory sound substitutions due to inability to close the velopharyngeal port. Substitution of a nasal for an oral sound (“m” for “b, p”; “n” for “t, d”; “ng” for “g, k”) is considered an obligatory substitution due to inability to close the palate. These children can also develop compensatory (mis)articulations, which are typically the result of attempts to valve the air stream in a different place of articulation, in the setting of palatal dysfunction. The most common compensatory articulation is glottal replacement, where a glottal stop (ʔ) is substituted for a stop consonant (e.g., ʔooʔie/”cookie”). Children with palatal dysfunction should be treated by SLP as early as possible—preferably as soon as they begin acquiring sounds—to facilitate accurate place of articulation for production of sounds, even if it promotes nasal air emission (obligatory sound substitution). These children will demonstrate significant improvement in speech intelligibility following palatal surgery. In contrast, palatal surgery may yield only minimal improvement in speech intelligibility in a child with compensatory misarticulations, since production of compensatory misarticulations will remain unchanged.

A less common articulation error is phoneme specific nasal air emission (PSNAE). This is often mistaken for velopharyngeal dysfunction due to a structural or functional defect. In PSNAE, a child has learned to create frication (e.g., s, z) by putting air through their nose, and it is unrelated to palatal function. Most often, PSNAE is limited to fricative sounds, and can be easily corrected with speech-language therapy.

Certain genetic syndromes may cause speech sound disorders secondary to structural or neurologic deficits. Beckwith-Wiedemann syndrome is characterized by macroglossia associated with upper airway obstruction, feeding issues, and speech defects due to inability to produce consonants with more anterior location of articulation. Specifically, sounds produced by placing the tongue tip to the alveolar ridge (e.g., t, d, n) or teeth to lower lip (f, v) become interdentalized (tongue between teeth/lips).7

Articulation and expressive dysfluency disorders

Phonologic (pure articulation) disorders. Most children will speak intelligibly by 2 years of age. By age 3 years, fewer than 15% of children have unintelligible speech. Minor articulation defects, such as a distortion of the “th” and “r” sounds may persist with little consequence. Phonologic awareness, however, is critically important in the acquisition of normal reading skills, and children with delayed phonologic acquisition are at greater risk for developmental reading disorders at school age.

Dysfluency (stuttering and cluttering). Some degree of dysfluency is common as language skills develop, particularly as the mean length of utterance reaches six to eight words between 3 and 4 years of age. Some children with dysfluency may be relatively fluent for days or weeks at a time, then experience a protracted interval of relative dysfluency. Both stuttering and developmental dysfluency may be influenced by factors such as the complexity of the thought to be expressed and by being rushed or when excited, happy, or angry. Between-word dysfluencies include interjecting ‘um’ in a sentence, repeating a phrase, or revising the sentence structure in midstream. Within-word dysfluencies include repetitions of individual sounds or syllables, prolongations of sounds, and blocks. Stuttering is a disorder in the rhythms of speech, in which an individual produces a disproportionately large frequency of within-word dysfluencies compared to normally fluent peers, particularly at grammatically important points in the sentence. It often is a genetic trait, and occurs more frequently in children with other DLDs as well as with mental retardation. It is equally common in boys and girls at its onset, but is three times more likely to persist in males. Associated behaviors such as head, torso, or limb movement, audible exhalation or inhalations immediately prior to the dysfluency, and visible muscle tension in the orofacial region are signs that the child is becoming aware that talking is difficult. In younger children, the earliest and most frequently observed associated behaviors involve the eyes (such as blinking, squeezing the eyes shut, side-to-side movements of the eyes, and consistent loss of eye contact with the listener). These behaviors are seen in stutterers and usually not in children who are simply developmentally dysfluent. Most children who begin to stutter at preschooler age will recover without specific therapy, especially those with onset prior to age 3 years, if family history is either negative or characterized by spontaneous resolution, and if there are no coexisting speech and language or learning problems. Cluttering, by contrast, is characterized by echolalia, palilalia (compulsive repetition in increasing rapidity and decreasing volume), incomplete sentences, perseveration, poor articulation, and stuttering, seen in children with fragile X syndrome.

Verbal dyspraxia. This condition, in which children are extremely dysfluent, as often been called ‘dilapidated speech’. Language is produced only with great effort. Phonology is impaired, including omissions, distortions, and substitutions. Language comprehension is preserved, and intelligence is normal.

Speech Therapy

The main role of speech therapy is to remediate articulation disorders. In addition, speech therapy may also be necessary to correct compensatory misarticulations that persist after surgical correction of VPD. In many instances, when performed by a therapist with expertise in VPD, only a brief postoperative evaluation is necessary.

Resonance therapy is effective chiefly for children with an “almost but not always” ability to achieve velopharyngeal closure. Indications for resonance therapy include mild VPD in children who have improved after appropriate stimulation; VPD that is phoneme-specific, intermittent, or occurring only with fatigue; and VPD accompanied by inappropriate articulation or oral-motor dysfunction. Aggressive long-term speech therapy may be justified when improved articulation and better velopharyngeal function are demonstrated.

Although a time-limited trial of speech therapy is reasonable to consider, definitive treatment should not be delayed when speech therapy alone will not be successful. In particular, speech therapy will not be successful in remediating VPD due to structural defects such as a partial soft palate cleft or submucous cleft, although not all submucous cleft palates require surgical intervention (seeChapter 188). Likewise, children with intact and appropriate articulation may be candidates for prompt surgery if no velopharyngeal closure is manifested on nasal endoscopy with appropriately articulated phonemes. When speech therapy is recommended, the duration and types recommended will depend on age, etiology, severity of VPD, cognition, hearing, phonetic inventory, expressive vocabulary, and the child's and family's ability to participate in a therapeutic program.

Articulation Disorders

The inability to produce sounds correctly in speech is referred to as an articulation disorder. Children with articulation disorders typically exhibit errors on a small subset of sounds (e.g., /r, l, s/). In most cases, there is no known cause of an articulation disorder, and they are presumed to be the result of mis-learning. An articulation error may occur in all contexts (e.g., at the beginning, middle, or end of a word) or in a single position (e.g., at the end of a word). Children with articulation disorders typically have mild-to-moderate deficits in speech, and most of their speech may be intelligible to unfamiliar listeners despite the errors.

One known cause of articulation disorders is permanent bilateral mild-to-moderate hearing loss. Children with mild hearing loss may benefit considerably from amplification with hearing aids. They also may benefit from speech therapy to correct inaccurate speech sound productions. Children with severe-to-profound hearing losses have severe speech sound errors and language deficits, and show resonance difficulties characterized by hypernasal speech patterns.

Management

Although dyslexia does not disappear, most children with early reading problems learn to read at average to above-average levels if they are diagnosed by the age of 8–9 years (third to fourth grade) and evidence-based reading instruction is provided. Children diagnosed later, even if remediated, are likely to continue to have reading problems. Three out of four children with reading problems at the end of third grade are still having trouble in seventh grade. In the Connecticut Longitudinal Study, dyslexic children (diagnosed after the third grade) never caught up to average or superior high school readers (Shaywitz et al., 1999). Early identification and provision of evidence-based reading instruction, systematic, phonetic, and multisensory approaches such as the Orton Gillingham or Wilson method can reduce the percentage of children reading below grade level in fourth grade from 37% to 6% (Bakker, 2006). However, large population studies suggest that some degree of reading disability persists into adulthood in most, and occupational attainment is lower in some (Undheim, 2009). The magnitude of phonological impairment alone does not appear to fully predict reading outcome. Phonological deficits appear to interact with other cognitive factors, such as nonverbal IQ and linguistic skills, particularly syntactic processing in determining long-term outcome (Peterson et al., 2009; Wiseheart et al., 2009).

Compensated readers, who are accurate but not fluent, demonstrate a relative underactivation in posterior neural systems for reading located in left parietotemporal and occipitotemporal regions.Persistently poor readers, who are both not fluent and less accurate, activate posterior reading systems but engage them differently from nonimpaired readers; they rely more on memory-based rather than analytic word identification strategies (Shaywitz et al., 2003). The majority of high-risk responder children benefit from systematic reading instruction and develop adequate reading abilities with successful recruitment of temporoparietal and visual association areas for reading (Simos et al., 2005). In another study correlating outcome with anatomy, 8- to 10-year-old poor readers had significantly lower fractional anisotropy (FA) in the left anterior centrum semiovale than good readers; 100 hours of intensive remedial instruction resulted in improved decoding ability and increased FA, consistent with enhanced myelination (Keller and Just, 2009). Although vision problems can interfere with reading, they are not the cause of dyslexia. Eye exercises, behavioral vision therapy, and special tinted filters or lenses are not effective treatments for dyslexia (American Academy of Pediatrics, 2009).

Articulation Disorders

The inability to produce sounds correctly in speech is referred to as an articulation disorder. Children with articulation disorders typically exhibit errors on a small subset of sounds (e.g., /r/, /l/, /s/). In most cases, there is no known cause of an articulation disorder, and they are thus presumed to be the result of mistaken learning. In an articulation error, the child is unable to produce the sound correctly in all contexts (i.e., at the beginning, middle, or end of a word). Children with articulation disorders typically have mild to moderate deficits in speech intelligibility. Their difficulties may be identified as early as the preschool years or not until elementary school age.

One known cause of articulation disorders is permanent bilateral mild to moderate hearing loss. In mild hearing loss in general, the speech sounds most difficult to detect are those of relatively high frequency (2000 to 4000 Hz) and low energy (20 to 30 dB). These sounds, including /s/, /f/, and /th/ as in thin, are late-developing sounds in children developing typically. Because high-frequency hearing loss is more prevalent than low-frequency loss, these sounds are difficult to discriminate and to produce by individuals with mild hearing loss. Children with mild hearing loss may benefit considerably from amplification with hearing aids. They may also benefit from speech therapy to correct inaccurate speech sound productions. Children with severe to profound hearing losses have severe speech sound errors and language deficits and also show resonance difficulties characterized by hypernasal speech patterns.

Treatment for articulation disorders is based on a behavioral model. Techniques include rewarding successive approximations toward accurate production, modeling, imitation, and reinforcement. Additional strategies to establish a new sound include phonetic placement cues (e.g., “Put your tongue tip behind your front teeth” to elicit a /t/ or /d/), mirror work (providing the opportunity for the child to see how the sound is produced), and labeling the sound with its descriptive name (e.g., “make the snake sound” for /s/). Treatment progresses from simple linguistic units, such as syllables, to more complex linguistic units, such as phrases and sentences. The goal is always improvements in functional communication. Children and adults with speech disorders often experience embarrassment and poor self-esteem. Therapy is designed to reduce the negative psychological consequences of the disorder, as well as to provide direct remediation.

Articulation abnormalities

When FSDs predominantly or exclusively affect articulation they are usually secondary to reduced jaw, face, or tongue movements in a manner suggestive of weakness, or they are secondary to abnormal, seemingly involuntary movements of those structures. In general, they need to be distinguished from effects of structural lesions, such as tumors or traumatic injuries (e.g., oral surgery, accidents), lower motor neuron weakness of cranial nerves V, VII, or XII, or hyperkinetic dysarthria secondary to dystonia, chorea, or tremor. When isolated, they may be associated with a history of physical trauma to speech structures (e.g., oral surgery, intubation). Pending litigation can complicate diagnosis because of possible secondary gain or malingering. Conversion or somatization disorders are probably more frequent causes of functional articulation disorders than are “simple” responses to life stresses (Duffy, 2013); abnormal articulation, characterized by pervasive glottal stop substitutions, has been reported in Munchausen syndrome (Kallen et al., 1986).

Articulatory distortions associated with dysarthria or apraxia of speech can range from subtle to severe, whereas functional articulation problems usually are not subtle. Error sounds, when the tongue is the main symptom locus, are often those associated with persistent developmental error sounds or those portrayed negatively in the media (i.e., /r/, /l/, and /s/). This is not necessarily helpful to differential diagnosis because those sounds are also among the most susceptible to genuine tongue weakness. However, distortion of only a single sound would be uncommon in any MSD. Lingual atrophy or fasciculations are often evident if the hypoglossal nerve is involved; obviously, those signs should not be present if the articulation problem is only functional. It would be unusual for significant articulatory distortions on multiple sounds, combined with poor performance on jaw, face, or lingual strength tasks suggestive of weakness, to be present without dysphagia or difficulties with chewing or saliva control. It can be very difficult to distinguish between functionally based bizarre posturing or movements of the jaw, face or tongue from focal speech-induced dystonia affecting those structures, although patients with genuine dystonia benefit from sensory tricks (e.g., a bite block, tongue blade, or piece of gum managed by the tongue during speech) more often than do those with functional movement disorders that affect articulation.

Plasticity

Plasticity refers to the ability of the human brain to change and adapt in response to environmental stimuli. This ability is important not only for general development, but it is also important for intervening with populations with language disabilities. It was previously thought that the brain lacked the ability to adapt or change after the onset of puberty and that if language was not acquired by this event it would never be acquired. While there is evidence that the brain becomes less plastic as we age, these critical periods of development are now conceptualized as sensitive periods in which there are optimal times during development for key linguistic skills to develop.

It is estimated that 8%–10% of the school age population evidences some type of developmental language difficulty that can be considered a language disability. Some of the major causes and patterns of language disabilities include hearing impairment, intellectual disability autism spectrum disorder, speech and articulation disorders, and reading disabilities. Research across a number of these areas is consistent in indicating that early intervention efforts are associated with better language development outcomes. The ability of the brain to change in response to intervention techniques intended to remediate language difficulties is believed responsible for these positive outcomes. Supporting this belief are studies that use imaging techniques like fMRI to compare the brains of atypically developing children with their typically developing peers. For example, brain imaging studies conducted with children with reading disabilities have shown that the brain anatomy of these children is different than those of children without reading problems. When exposed to a reading intervention, however, the brain structures of these children change to become similar to children who do not evidence difficulties with learning to read.

Brain plasticity also has been observed in individuals who have acquired language disabilities. Such language impairments may result from stroke, traumatic brain injury (TBI), or progressive neurological diseases. As with individuals with congenital language disabilities, positive outcomes have resulted from intervention and rehabilitation efforts. Individuals who have experienced a stroke may completely lose the ability to produce speech. Through intensive rehabilitation efforts, many of these individuals learn to speak again.

The most striking example of brain plasticity, however, comes from individuals who have undergone a complete hemispherectomy. There are rare cases of people who experience numerous epileptic seizures in a day. These repeated seizures are so debilitating to daily life that it may become necessary to remove an entire hemisphere of the brain to stop the electrical imbalance causing the seizures. After the removal of the problematic hemisphere, the remaining hemisphere must take over all of the functions previously served by the removed hemisphere. Even in individuals who are left-lateralized for language who have had the left hemisphere removed can re-learn and functionally use and understand language.

The concept of plasticity has two important implications for language development. The first implication is that the brain develops in response to experience with the environment. Thus, the more enriched the linguistic environment a child is exposed to during language development, the better a child's later linguistic outcomes. The second implication is that language difficulties that result because of biological (e.g., developmental disabilities) or environmental (e.g., TBI) reasons can be remediated, at least partially, through appropriate intervention efforts.

37-1.2 Language in Down’s Syndrome

A review of research on language development indicates that the pattern and sequence of development of language in DS children is similar to that of nonretarded children (babbling, developmental patterns of consonant production, etc.) (see Pruess, Vadasy, & Fewell, 1987 for a review). However, it has been postulated that deficits in expressive language development do occur, possibly due to auditory deficits, articulation disorders, cognitive delays, and environmental factors. For example, when DS and normal children were chronologically age-matched, DS children were found to show a distinct developmental lag in speech production (Leifer & Lewis, 1984). When matched with normal controls by mental age, however, DS children were found to be superior in conversational response abilities. Leifer and Lewis (1984) concluded that during the one-word stage of development, DS children may be more advanced than controls, but stay at this stage longer, resulting in delayed language development.

Evidence indicates that DS children are at risk for malformations of the auditory system, such as small external ears and a narrowed external auditory canal. These malformations frequently lead to an increased incidence of otitis media in this population. Whiteman, Simpson, and Compton (1986) report that the recurrence of early otitis media may be a contributing factor to language deficits often associated with DS children. Although a direct causal relationship between hearing loss and language deficits has not yet been established, it is imperative that children with DS receive comprehensive auditory assessments regularly in the first few years of life (Kumin et al., 1994; Pruess et al., 1987; Strome, 1981; Whiteman et al., 1986).

Another consideration in the cause of language delays observed in DS children is the presence of articulatory deficits due to hypotonicity of the orofacial musculature. Mahoney et al. (1981) examined the relationship between sensorimotor and language development in DS and non-retarded children with matched developmental ages of 17 months. They determined that the deficit in language ability was related to poor vocal imitation skills. However, Mahoney and Snow (1983) concluded that cognitive and sensorimotor factors were significantly correlated with expressive language delays. The relationship between cognitive abilities and language development has been investigated by various researchers (Hill & McCune-Nicolich, 1981; Moore & Meltzoff, 1978; Piaget & Inhelder, 1969; Smith & von Tetzchner, 1986). The development of object permanence and object identity has been found to be a crucial aspect of language formation. Hence both cognition and articulatory ability are implicated in the deficits in language seen in the DS population.

An additional aspect to the evaluation of expressive language development is the assessment of phoneme acquisition. Normative data previously reported require a mastery level based on achieving 75–90% accuracy in phonemic production (e.g., Smit, Hand, Freilinger, Bernthal, & Bird, 1990). More recently, Kumin et al. (1994) postulate a change in approach to the evaluation process in DS children. Rather than mastery of specific phonemes as measured by formalized articulation testing, the authors suggest looking at the emergence of sounds, and the use of these emergent phonemes in daily communication.

Other theories have been introduced in an attempt to account for the language deficits observed in DS children. For example, Bird and Chapman (1994) tested the hypothesis that DS patients experience most difficulty with language tasks due to a “pervasive sequencing” deficit, where recalling the order of information is problematic (Rosin, Swift, Bless, & Kluppel Vetter, 1988). According to Bird and Chapman (1994), neither a deficit in sequential processing nor specific difficulties in recalling order of information were found. Alternatively, these authors suggest that deficits in auditory working memory span and a rate-based limitation to the phonological loop could account for the problems in language production observed in DS individuals. However, these possibilities need to be validated by future research.

Mundy, Kasari, Sigman, and Ruskin (1995) proposed that the acquisition and development of nonverbal communication skills impact development of language. These skills reflect the development of cognitive processes (e.g., capacity for representational thought, executive functions such as selective inhibition of responses, and planned action sequences). Mundy et al. (1995) found that DS children were impaired in nonverbal requesting regardless of developmental level. In addition, nonverbal requesting was positively correlated with language outcome. These findings supported those of Mundy, Sigman, Kasari, and Yirmiya (1988) and Beeghly, Weiss-Perry, and Cicchetti (1990).

Few studies have investigated language comprehension in DS individuals. Chapman, Schwartz, and Bird (1991) found that the differences between lexical and syntactic skills differed with increasing age in DS children. Although the differences are distinct, the source of the discrepancy remains unresolved. Chapman et al. (1991) suggest that the differences may be either the result of a lexical advantage or due to a syntactic deficiency.

The studies cited above provide evidence for many contributing factors, but further research in psycholinguistics and the acquisition of language is needed in many areas before the language deficiency associated with DS can be fully understood. Causes of language delays in DS children are still debatable, with problems with hearing and cognitive difficulties being contributors, but not necessarily causal factors. Instructional strategies need to be highly structured and a clear “best way” has not been found. Language intervention should occur early, with families and school being very involved in the process so that the best use can be made of experiences occurring naturally.

Speech and Language Disorders

Speech is verbal expression for human communication. Students with good expressive abilities can produce or articulate the different sounds of speech, they can speak clearly and without difficulty (e.g., with ease and appropriate rhythm), and they are able to produce good voice (e.g., adequate volume and no hoarseness/breathiness) for articulate/intelligible speech. A speech disorder may be present in the absence of one or more of these characteristics. Childhood speech disorders are categorized as childhood apraxia of speech (CAS), orofacial myofunctional disorders (OMD), speech sound disorders, articulation and phonological processes, stuttering, and voice (ASHA, 2008).