Subtypes of primary and secondary speech-language disorders at different developmental ages
10.1.3 Types of Comorbid Conditions
‘Comorbid conditions’ refer to diseases that with a high probability occur along with DDSL as reported by high-standard studies. Profound hearing loss is a typical example of such a ‘comorbid condition’, often being even the main reason for a speech-language delay or disorder, if unaided. The impact of a comorbid condition on speech and language development depends much on its severity and disease progression over time and on the individuals’ idiosyncratic (mental) capacity to compensate for such a condition. For instance, many children with a mild conductive hearing loss may not experience a speech-language delay, whereas children with a developmental delay or other risk factors may do.
The impact of mild conductive hearing loss—often fluctuating in presence and severity—and developmental speech-language delay or disorder has been a matter of debate for three decades. Several meta-analyses of studies aiming at quantifying such an impact have demonstrated effect sizes below significance (e.g. Paradise et al. 2005; Rosenfeld et al. 2011), but the underlying studies contained substantial flaws in methodology (Schönweiler 2006), indicating that no robust conclusion pro or contra ventilation tubes (grommets) or pro and contra early versus late insertion could be drawn. Therefore, guidelines on the treatment of otitis media with effusion by insertion of grommets do not follow these meta-analyses (Rosenfeld et al. 2013a). Rather, they recommend that clinicians determine if a child with recurrent acute otitis media, or with otitis media with effusion of any duration, is at increased risk for speech, language or learning problems from the otitis. Such risks could stem from baseline sensory, physical, cognitive or behavioural factors—e.g. permanent hearing loss independent of otitis media with effusion, suspected or confirmed speech and language delay or disorder, autism-spectrum disorder or other pervasive developmental disorders, syndromes or craniofacial disorders (including cognitive, speech or language delays, cleft palate or developmental disorders). For children classified ‘at risk’, earlier examination of hearing and speech-language development and earlier insertion of grommets have been recommended (Rosenfeld et al. 2004, 2013b), with the expectation of improved speech-language outcome, even if no scientific proof for this exists at present. This recommendation is underscored by reports that children with such a risk benefit more from ventilation tubes in their speech, language, learning and school performance outcome than children without risk factors (Rosenfeld et al. 2011).
The negative impact of comorbid diseases, e.g. of hearing disorders, developmental delay, oral motor disorders and others, is outlined by various guidelines and also in this book. In terms of duration and potential for improvement, comorbid conditions can be classified as fluctuating/intermittent and permanent types. Examples of fluctuating/intermittent comorbid conditions are periods of otitis media with effusion and cases of hospitalisation due to severe illness or family crises. Examples of permanent comorbid conditions are sensorineural hearing loss, seizure disorders with developmental delay and genetic disorders.
A third category, ‘sociogenic’ or ‘environmental’ language abnormalities that are caused by adverse social conditions such as poor language stimulation or language abnormalities during multilingual language acquisition with low input in the common language, does not count as a ‘medical’ comorbid condition. Consequently, they do not require medical treatment but a language-stimulating input of sufficient quality and quantity (e.g. early literacy, language-stimulating conversation, narratives; see Sect. 12.2). It has to be taken into consideration, however, that DDSL may coincide with such adverse conditions, and it is challenging but necessary for a phoniatrician to discern a DDSL from the sociogenically caused language abnormalities in order to make an appropriate recommendation for intervention.
10.1.4 Subtypes of Developmental Disorders of Speech and Language at Different Ages
Which type of primary or secondary speech-language disorder is found in a differential diagnostic procedure depends, in part, on the individual developmental age (Fig. 10.1). First verbal skills usually appear around the age of 10 months when infants begin to understand first words (Fig. 10.1A) (de Langen-Müller et al. 2013). Between 18 and 24 months of age, they typically acquire up to 50 words, provided that speech is developing within the realm of what is considered normal language development (Fig. 10.1B). Those struggling with language development at the age of 2 are called ‘late talkers’. These children carry an increased risk for the later diagnosis of a DDSL (developmental language disorder, Fig. 10.1C) (de Langen-Müller et al. 2013; Desmarais et al. 2008). About 41–50% of ‘late talkers’ finally catch up to peers at the age of 3 years (‘late bloomers’, Fig. 10.1D). If they still fall behind their peers in speech and language skills at the age of 3 years, they could be classified as having a DDSL (Fig. 10.1E) (de Langen-Müller et al. 2013). About one third of these children may have a ‘secondary’ disorder due to permanent comorbid conditions, suggesting the need for a causal therapy (Fig. 10.1F). The remaining two thirds may be classified as having a SDDSL and need a speech-language intervention (Fig. 10.1G).
Children showing normal speech and language development (Fig. 10.1B, D) may either continue in this development (Fig. 10.1H) or may be affected by later illness. If such a late-onset illness, e.g. fluctuating hearing loss, late-onset hearing loss or diseases of the central nervous system, hinders speech-language development, the affected children may develop a DDSLC (secondary speech-language disorder) despite having had a good start (Fig. 10.1I). Because both DDSL and sociogenic language abnormalities are more prevalent in socially weak regions, the occurrence of both disturbances may underlie regional differences. Finally, the majority of children treated for speech and language disorders develop ‘normal’ speech and language skills by the time they start school (Fig. 10.1K).
10.1.5 Comorbid Conditions, Differential Diagnoses and Adverse Social Conditions
In the following, comorbid conditions, differential diagnoses and adverse social conditions are explained.
10.1.5.1 Hearing Disorders
Permanent sensorineural or conductive types of hearing loss, whether aided or not, are certainly well-known comorbid conditions and may be seen as the main reason for DDSLC (secondary speech-language disorders). This is because hearing loss reduces the quantity and quality of linguistic information necessary for language acquisition. As a general rule, the higher the degree of hearing loss, the higher the risk of a speech-language disorder (Northern and Downs 2002). Therefore, children with a bilateral moderate or profound hearing loss often show significantly reduced language abilities compared with children with a bilateral mild hearing loss. However, one should keep in mind that even mild hearing loss may establish a huge barrier to the child’s ability to acquire language (Paradis et al. 2003), so that it makes sense that children with mild and minimal hearing loss (bilateral or even unilateral pure tone thresholds between 16 and 25 dB) are fitted with hearing aids. Whether fluctuating/intermittent (not permanent) hearing loss due to otitis media with effusion (OME) has a negative impact on speech-language development has been subject of controversial debate. Many of the North American paediatric cohort studies failed to confirm such an impact; however, as the critics rightly pointed out, all these studies were plagued by serious methodological flaws (Schönweiler 2004). Certainly, hearing loss significantly increases the risk for a speech-language disorder if there are additional comorbid medical conditions, developmental disorders or deprivation (de Langen-Müller et al. 2013; Northern and Downs 2002; Rosenfeld et al. 2013a; Schönweiler 1994, 2004).
10.1.5.2 Other Sensory Deficits
Loss of vision has been shown to cause at maximum some delay in the early phase of language acquisition; however, it is not a true comorbidity of a DDSL (de Langen-Müller et al. 2013; Neumann et al. 2008).
10.1.5.3 Developmental Disorders and Mental Retardation
Speech-language disorders and delay can be observed as part of many developmental disorders (e.g. autism-spectrum disorders), mental retardation and syndromes (specifically genetic syndromes) (de Langen-Müller et al. 2013). Typically, speech and language skills, judged from observed test results, match the individual developmental scores. Such a developmental profile is consistent with the observed speech-language delay being secondary in nature (de Langen-Müller et al. 2013; Schönweiler 2004). In many syndromes, a developmental delay is often combined with a hearing disorder or another sensory deficit. If untreated, speech and language screening results can be much worse than expected from non-verbal developmental test results.
10.1.5.4 Disorders and Diseases of the Central Nervous System
Comorbid neurological diseases may increase the risk for a secondary speech-language disorder. Examples of such diseases are cerebral palsy, structural malformation of the brain (e.g. agenesis of the corpus callosum) and abnormal functional findings (e.g. lacking development of hemispheric dominance) (de Langen-Müller et al. 2013).
10.1.5.5 Risk Factors at Birth and Preterm Birth
In general, risk factors at birth and premature birth per se are not causes for developmental speech and language disorders. However, they establish a risk factor, and their impact depends on the severity of the adverse perinatal conditions and the presence of comorbidities. In particular, children with gestational age under 28 weeks at birth and those with birth weight below 1100 g have been shown to be at an increased risk for hearing disorders (Jimenéz et al. 2008; Rieger-Fackeldey et al. 2010; Robertson et al. 2009), other sensory deficits (Marston et al. 2007), developmental delay, developmental language delays or language disorders (see Sect. 9.6). In clinical practice protocols, most infants at risk are monitored for many diseases and developmental delay, including congenital and late-onset hearing loss as well as speech-language delay or disorder, regardless of the individual risk.
10.1.5.6 Differential Diagnoses
Landau-Kleffner syndrome is an acquired childhood aphasia, but not a typical developmental language disorder, although it is classified as ICD 10 F80.3. It is accompanied by paroxysmal abnormalities on the EEG, and in the majority of cases also by epileptic seizures, which symptoms, if anticonvulsive treatment is successful, could to an extent be similar to those of a secondary speech-language disorder.
Elective mutism can sometimes be observed as a result but not a cause of a primary or secondary speech-language disorder. Speech-language disorders may lead to social interaction disorders, low self-esteem, social withdrawal, depressive mood and aggressiveness.
10.1.5.7 Adverse Social Conditions
Adverse social conditions are considered to be a frequent environmental non-medical cause of speech-language abnormalities. They do not establish a disease but nonetheless need to be addressed by medical professionals, predominantly by counselling and training parents to promote speech and language development of their child. Twins sometimes talk to each other in a ‘secret language’, but this is not a medical problem and can be solved by educational modifications in the family. Multilingual education (see Sect. 9.5) is another non-medical condition that may be associated with speech-language abnormalities but does not cause speech-language disorders. It is important to note that symptoms of a DDSL are typically observed in all languages spoken by the child (Håkansson et al. 2003; Paradis et al. 2003).
10.2 Developmental Verbal Dyspraxia
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