Clinical manifestations

Presentation and course

Disorders of articulation manifest with impaired intelligibility in the form of incorrect pronunciation, particularly of consonants. As language skills advance, preschool children make known developmental errors of speech that are not considered disorders of articulation. However, most of the time most typically developing children are fully intelligible by 4 years of age (18). Therefore, disorders of articulation are typically not identified until early school age with the persistence of immature articulation patterns. Children with the presence of atypical articulation patterns are often identified earlier. The most problematic consonants are the later acquired “r” and “s,” and easier to pronounce consonants are typically substituted, such as “w” for “r.” Substitutions tend to be consistent. Difficulty being understood can result in social difficulties.

Prognosis and complications

Evidence from natural history studies demonstrate that speech-only problems may be less persistent than language problems, with reports of 78% of articulation errors resolving (Bralley & Stoudt 1977). However, a 28-year follow-up of adults with a history of preschool phonological disorders showed residual articulation errors and poorer language performance than typically developing controls, though favorable emotional adjustment (15). The strongest predictor of ongoing speech impairment is poor early phonological skills (04). Likewise, at time points from preschool to adulthood, people with articulation disorders show deficits in phonology and phonological awareness, albeit increasingly subtle with age (41). Concomitant reading and spelling deficits were only noted in those children who had language problems in addition to articulation disorders in preschool (27). In fact, in 1 group of 125 children aged 3 to 6 years with articulation disorders, no relationship between early reading and writing scores and severity of the articulation disorder was found once comorbid language impairments were taken into account (46). However, children with dyslexia generally have more difficulty with speech production tasks, suggesting there is an association between dyslexia and underlying phonological awareness (53).

Clinical vignette

MM was an ex-premature (30-week) 3-year-old boy with minor neuromotor abnormalities resulting in hypotonia, a receptive and expressive language delay, and articulatory problems. His 10-word vocabulary was unintelligible due to consonant omissions and vowel distortions. His struggles to communicate were frustrating for both him and his family.

Speech-language therapy incorporated sign language and pictures. MM worked on pronouncing his name and the word “potty” as preschool readiness skills. He learned to say “ear hurts,” with frequent ear infections. While he continued to add new sounds to his phonemic repertoire, he used alternative ways to communicate and learn more words and became more willing to participate in school and activities. His family’s frustration decreased as did his own as he was able to use effective alternative ways to express his needs.

Biological basis

Etiology and pathogenesis

The term “articulation” implies moving surfaces from opposing positions into positions that come into contact. Articulators, such as the lips, teeth, tongue, palate, and jaw shape and direct the flow of air from the larynx into speech sounds. However, difficulties with speech intelligibility often localize poorly because speech production can be affected by lack of accurate feedback (hearing impairment), deficits in cognition, breath support, phonation, and articulation. Production of speech sounds can be disrupted at multiple levels: cerebral cortex, basal ganglia, cranial nerves (V, VII, IX-X, and XII), peripheral nerves, neuromuscular junction, and the structural apparatus of the lips, palate, tongue, velopharynx, and vocal folds. The cerebellum has also been implicated in speech motor control as well as processing and planning (47).

Disorders of articulation in children are usually idiopathic, though there is probably a genetic component given hereditability patterns. In 74 children with developmental language disorders, 47 immediate family members had some sort of speech-language problem, 55% specifically with articulation problems (36). Speech sound disorders have been linked to the 15q14 locus (49) and FOXP2 deletions on chromosome 7 (24; 50). However, these regions have also been implicated in more global language disabilities and other neurodevelopmental disorders.

Motor difficulties in cerebral palsy can cause articulation difficulties that persist into adulthood. Naive listeners evaluated speech as only about 50% intelligible in a series of adults reading both single words and prose (40). Minor neuromotor abnormalities, associated with many developmental disabilities, may manifest with low oral tone and contribute to articulatory difficulties in such neurodevelopmental disabilities as ADHD, learning disorders, and epilepsy. In a small case-control study, children with epilepsy without intellectual disability or cerebral palsy had more articulation difficulties than typically developing children (44). In addition, cognitive impairment may also contribute to articulation problems, probably due to mislearning of speech sounds. Down syndrome affects speech production via intellectual disability, macroglossia, and hypotonia (23).

Other syndromes that affect the motor anatomy necessary for speech can result in disorders of articulation. For example, Moebius syndrome involves congenital paralysis of bilateral facial and abducens nerves and can result in speech sound difficulties. Cleft palate may affect speech through anatomic changes as well as other coexisting factors such as cognitive immaturity, coexisting language disorder, middle ear effusion, and conductive hearing loss (34). Congenital or acquired malformations of the temporomandibular joint can also be a contributing factor to speech sound difficulties (02).

In fact, hearing impairment can independently affect speech by impairing auditory feedback, which can hinder correct learning and reproduction of speech sounds. In children with profound hearing loss, 1 option is cochlear implants. The minimum age for implantation recommended by the United States FDA is 12 months, with language exposure through sign language until implantation. Supporting the idea that early implantation allows for added phonologic development, one study of 11 young cochlear implant recipients demonstrated progress with consonant acquisition though they were still delayed compared to typically developing peers (14). It also appears that the children with cochlear implants followed both typical and atypical patterns of articulation development. Another study that followed 32 children implanted before 30 months of age for 4 years reported that length of cochlear implant use could be used as a proxy for chronological age when predicting articulation development (48).

Epidemiology

Speech disorders are common in childhood, but prevalence declines by adolescence. The National Center for Health Statistics estimates a 1% prevalence of speech disorders among all ages in the United States. Up to 8.4% of 6 to 11 year olds were reported to have speech problems, compared to 4.2% in 12 to 17 year olds. Among almost 40,000 children, 5.7% aged 6 to 18 years had speech problems affecting articulation and voice, including stuttering.

A study of over 12,000 Australian children up to 14 years of age showed a 1.7% prevalence of speech disorders. Peak prevalence in boys was 7.4% at 5 years of age; whereas in girls, it was 1.8% at 3 to 4 years of age. Even after excluding children with developmental delay, children with speech disorders were more likely to have additional health problems. Socioeconomic status did not affect the likelihood of an articulation disorder (22).

In a systematic review of epidemiologic studies, prevalence ranged from 2.3% to 24.6% for speech sound disorders and 4.56% to 19% for combined speech and/or language disorders (25). A community study of Australian children demonstrated that a significant number of preschool age children with speech sound disorders did not have contact with speech language pathologists; therefore, these prevalence rates may be underestimates (30).

Differential diagnosis

Children typically learn to pronounce consonants in an orderly sequence. It is important to determine whether the child’s pronunciation is delayed compared to peers and normal samples, as certain sounds are mastered later even in typical development (43).

Table 1. Speech Milestones in Young Children:

Consonant Production and Intelligibility

Once a difficulty with articulation is identified, it is important to consider other reasons a child is difficult to understand, and one should look for any underlying causes and rule out acquired disorders before concluding there is an idiopathic articulation disorder. Hearing impairment can lead to mislearning certain speech sounds and should be evaluated. Children with expressive language disorders may present as difficult to understand due to problems in language structure, although these conditions can coexist. Stuttering affects fluency rather than articulation. Variations in pronunciation attributable to dialect do not constitute phonological disorders. Acquired epileptic aphasia (Landau-Kleffner syndrome) causes acute onset speech-language problems and seizures. Atopy, particularly allergic rhinitis, may also affect articulation, possibly via transient hearing loss (01).

Acquired disorders of articulation, or dysarthrias, involve paralysis, weakness, or incoordination of speech musculature that interferes with speech and can also occur during development (52). Dysarthrias are generally classified as flaccid, spastic, hypokinetic, hyperkinetic, ataxic, and mixed. Causes include acquired brain injuries, such as stroke, traumatic brain injury, or tumor, as well as neurodegenerative disorders affecting the motor system such as Parkinson disease and amyotrophic lateral sclerosis (33; 13). Isolated dysarthria or posterior fossa syndrome following surgical resection of posterior fossa tumors is not uncommon (32). Finally, chemoradiation can also affect articulation of patients with head and neck cancer (21). Dysarthrias usually share imprecise consonants, monotone quality, lack of variation in loudness, and harsh voice (11; 12), however, they also have distinctive features. For instance, ataxic dysarthria, found in cerebellar disorders, involves excess and equal stresses (the “scanning speech” described by Charcot), irregular articulatory breakdown, and distorted vowels.

Nonfluent or transcortical aphasias can cause difficulties with intelligibility. These can coexist with dysarthrias, particularly in strokes (37). Paraphasic speech involves sound substitutions that are less predictable than in dysarthrias, in which the same sounds tend to be consistently misarticulated or omitted.

Diagnostic workup

A complete history including neonatal feeding difficulties should be obtained. Dysphagia, choking, swallowing difficulties, and gag, including saliva management, should be assessed as these 2 conditions frequently co-occur. Audiologic evaluation is advised, particularly in young children. Structural defects such as cleft palate or dental malocclusion should be noted. It is important to identify cognitive impairment and dysmorphisms suggestive of genetic syndromes and to look for any additional neurologic signs that would suggest a broader disability. Spasticity, dystonia, or flaccidity should be noted. Cerebellar signs, such as gait ataxia or dysdiadochokinesia, may aid in localization. If there are concerns, swallow study, often performed by occupational or speech therapists, may be considered. Consider magnetic resonance imaging of the brain and spine in cerebral palsy, where underlying etiology may be defined.

Referral to a speech-language pathologist is the most effective way to define disorders or articulation. Tests include the Assessment of Intelligibility of Speech, the Assessment of Phonological Processing, the Goldman-Fristoe Test of Articulation-Third Edition, and the Khan Lewis Phonologic Analysis-Third Edition. The Oral Speech Mechanism Screening Examination-Third Edition identifies anatomical or functional problems. Many full language batteries also include an articulation screening component. Other techniques include multisyllabic word lists, tongue twisters, Pig Latin tasks, and nonsense word repetition. Currently, there is no specific pediatric dysarthria scale (19); however, the Verbal Motor Production Assessment for Children does attempt to determine if articulation difficulties are related to more general neuromotor abnormality. Analysis of a language sample is also informative. Language may be observed informally or during an interview. In addition to specific sound articulation testing, it is important to measure intelligibility of single words and continuous speech in order to determine the functional severity of an articulation disorder (28).

Management

Speech therapy is the major treatment modality for articulation disorders. A variety of approaches are used. It is important to identify the type of speech sound disorder in order to identify appropriate therapy techniques (articulation vs. phonologic approach). A small intervention study of 14 children with phonologically based speech sound disorders found that although both groups improved in articulation, only the group with phonological intervention showed improvement in intelligibility (28). One major difference in the main therapies is whether to focus directly on speech or to shape speech while focusing on language (51). Some therapies emphasize starting with isolated phonemes of difficulty and building to connected language. Other therapies encourage children to master more complex sounds through language acquisition and then less complex ones fall into place (17). Additional literature has encouraged generalization through the teaching of nonwords rather than real words (10). New work piloting visual biofeedback has been promising in some populations (09). A systematic review of screening and treatment for speech and language delays found that most treatment studies demonstrated improvement, with characteristics of effective studies, including higher intensity of treatment, more severely affected children, and individualized treatment (03). However, a Cochrane review found no randomized controlled trails or group studies for efficacy of speech therapy for children with dysarthria under 3 years of age (39). In children with cleft palate, speech pathology intervention is indicated alongside cleft palate repair to support intelligibility at their earliest stages of development. One study of 51 children aged 3 or 5 with repaired cleft palate suggested that such children are able to approximate typically-developing children by 5 years (07). Another study of 180 children with clef palate repair between ages 3 to 7 found that age at the time of palatal repair was significantly associated with compensatory misarticulations, which further supports earlier intervention (42).

A sizable number of clinicians report using non-speech oral motor therapy or exercises of the oral musculature that do not include speech production, attempting to influence speech despite the fact that data for their efficacy are controversial at best (08; 35). An updated Cochrane review confirmed previous conclusions that there is no strong evidence that suggests that nonspeech oral motor therapy is an effective single or adjunctive treatment for developmental phonological disorders. The 3 studies they found evaluating efficacy of nonspeech oral motor therapy were small in scale and had a number of serious methodological limitations (26).

There is a gap in the literature regarding efficacy of speech therapy for articulation disorders related to cerebral palsy (45). However, a study of 77 children with cerebral palsy suggested that speech characteristics identified at 2 years of age could predict communication and speech performance at 5 years (38). There is noted impairment at multiple levels of speech production in children with cerebral palsy (31). Therefore, early speech pathology intervention may be recommended based on individual assessment.

More severe cases may require augmentative communication devices such as picture boards and voice output devices (55; 54).

Surgical intervention for velopharyngeal insufficiency is not recommended (55; 54).

Special considerations

Anesthesia

There is no published literature specifically addressing anesthesia in patients with disorders of articulation. However, persons with abnormalities and neuromuscular disorders may present special challenges for anesthesiologists.

Acknowledgements

Thanks to Mary Katherine Boyle, CCC-SLP, for her invaluable comments on this manuscript.