Learning and language disorders are a heterogeneous group of neurobiological disorders involving impairments in the acquisition and/or use of spoken (oral) language, written language (reading/spelling/writing), and mathematical skills.1–3 “Learning disability” (LD) is a broad term that encompasses language and learning disorders.

The definitions and diagnostic criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision (DSM-IV-TR)1 provide a guide for the diagnosis of LDs in clinical settings. DSM-IV-TR uses a categorical approach to the classification of LDs and other disorders. Reading disorder (RD), disorders of written expression, mathematics disorder (MD), and learning disorder not otherwise specified fall into the learning disorders category (Table 10-1). As defined in DSM-IV-TR, learning disorders are “diagnosed when the individual’s achievement on individually administered, standardized tests in reading, mathematics, or written expression is substantially below that expected for age, schooling, and level of intelligence.”1 The terms (developmental) dyslexia and (developmental) dyscalculia may be used synonymously with RD and MD, respectively.

Expressive and/or receptive language disorders are classified as communication disorders in DSM-IV-TR (Table 10-2). The defining features of these spoken language disorders are impairments in oral expression and/or listening comprehension associated with dysfunction in one or more subdomains of language, including morphology (word structure), semantics (word meaning), and syntax (sentence structure). By definition, these deficits significantly interfere with academic achievement and/or social communication.1 As with learning disorders, DSM-IV-TR outlines specific inclusionary and exclusionary diagnostic criteria for language disorders, which are further defined as “developmental” or “acquired.” Specific language impairment (SLI) and developmental dysphasia are terms that refer to developmental language disorders that are characterized by a delay in, or lack of, normal language acquisition at an appropriate age in the absence of pervasive cognitive impairments, sensorimotor abnormalities, and frank neurological deficits.4,5 In contrast to developmental language disorders, acquired language disorders are, by definition, the “result of a neurological or other general medical condition (eg, encephalitis, head trauma, irradiation).”1

While the clinical diagnosis of LDs is guided by DSM-IV-TR, identification and classification of LDs in public school systems, and thereby access to early intervention, exceptional student education (ESE), and related services, is governed by the federal definition of LD, as outlined in the Individuals with Disabilities Education Improvement Act of 2004 (commonly referred to as IDEA 2004). Clinicians should also be aware that consensus about the definition (both conceptual and operational) LD is lacking.6 Furthermore, it is important to be familiar with differences in the use of terminology across disciplines and the potential implications thereof. For example, while the term “dyslexia” is often used synonymously with RD by clinicians, school districts generally do not recognize that term as referring to a “specific learning disability” in reading, as it is termed in educational settings. Thus, a child may be deemed ineligible for necessary educational supports and services if the clinical terminology used by physicians, neuropsychologists, and clinical psychologists is inadequately translated into terms that are more familiar to educators and other professionals who participate in educational planning teams in school settings. Two widely used definitions are included in Table 10-2.

Learning disabilities are common, and without effective intervention, children with these disorders are at high risk of school failure with far-reaching consequences on their economic and, thus, health outcomes. Data from the 2003 National Survey of Children’s Health indicates that learning disabilities are the most common parent-reported diagnosis in children aged 6 to 17 years (11.5%).7 A more recent U.S. Department of Education report indicates that approximately 5.6% of children aged 2 through 21 years served by federally supported programs (ie, 2.5 million prekindergarten through 12th grade students enrolled in public school) have a specific learning disability, and another 1.5 million (3.0%) are identified as speech or language impaired.8 Moreover, data from the National Assessment of Education Progress (NAEP) suggest that a far greater percentage of students struggle to meet proficiency levels in reading, writing, and mathematics. According to 2007 NAEP results, only 31% of U.S. fourth graders, and 29% of eighth graders, read at or above proficiency levels, while 70% of eighth graders are below proficiency in writing.9,10 Mathematics proficiency levels were similar, with only 38% of fourth graders and 31% of eighth graders at or above proficiency levels.11

Reading disorder (dyslexia) affects 80% of individuals with learning disabilities, comprising the most common type of LD.6,12 Prevalence rates for reading disorder range from 5% to 17.5%,13 depending on what definitions are applied and the method of ascertainment. In contrast, disorders of written expression are rare in the absence of comorbid learning and/or attention problems, thus, prevalence estimates are difficult to determine.1 Population-based estimates of the prevalence of mathematics disorder (developmental dyscalculia) in school-age children are in the range of 3% to 6%.14 Reported prevalence rates for language disorders vary with age.1 As noted in the DSM-IV-TR, expressive language delays occur in 10% to 15% of children under the age of 3 years with a subsequent drop in prevalence estimates to between 3% and 7% by school age. Prevalence estimates for mixed receptive/expressive language disorder of approximately 5% in preschoolers and 3% in school-age children are reported.1

Learning disabilities have complex etiologies involving multiple genetic and environmental influences.15–17 Reading disorder (dyslexia), the most common type of LD, has been studied most extensively. Among investigators there is broad consensus that the underlying cognitive basis is a phonological deficit associated with poor awareness of the sound-structure of spoken language and limited appreciation of the relationship between phonemes (the discrete, elemental sound units of spoken language—for example, the words “you” and “see” each consist of two phonemes) and graphemes (letters, eg, the words “you” and “see” each consist of three graphemes), resulting in impaired word reading (decoding) and spelling (encoding) abilities.12,16 Research has revealed a significant genetic influence on both word reading and spelling abilities.18,19 While the mode(s) of transmission of this genetically and phenotypically heterogeneous disorder remains unclear, there is strong evidence that reading disorder (dyslexia) is both highly familial and heritable.20–23 Family studies indicate that first-degree relatives are four to ten times as likely as controls to be affected.24 Heritability estimates from twin studies indicate that between 44% and 65%, and 62% and 75%, of the variance in reading and spelling abilities, respectively, is explained by genetic factors.18,19,24,25 Susceptibility loci have been identified on several chromosomal regions including 2p, 3p, 6p, 15q, and 18p.24,26 Cytoarchitectonic studies of dyslexic brains have found cortical anomalies in areas important for language, and more recently molecular genetic studies have linked (four) genes involved in neuronal migration and cortical development to dyslexia.27–30 Imaging studies comparing the brains of individuals with dyslexia to those of controls have found a number of structural differences, including normal or increased planum temporale asymmetry.31–33 Functional neuroimaging studies examining brain activation patterns during phonological and reading tasks provide additional insight into the neural basis of dyslexia, with converging evidence implicating aberrant functional connectivity in the left hemispheric regions subserving language functions, including the inferior frontal gyrus, middle and superior temporal gyrus, and the angular gyrus.22,34–37

Written expression disorders usually occur in association with other disorders, notably reading disorder, and there is little evidence to support a specific learning disability in written expression when not associated with other learning disabilities.38 Thus, difficulty with written expression warrants assessment for underlying deficits including language and executive dysfunction.

Unlike RD, mathematics disorder (developmental dyscalculia) has not been studied extensively, and so the underlying cognitive deficits and neurobiological factors that may play a role in mathematical difficulties are less well understood. Current evidence implicates deficits in the mental representation of numerical quantities (“number sense”)39–41 or impaired links between numerical magnitude representations and learned numerical symbols42 as the neuropsychological basis of mathematics disorder. Neuroimaging studies indicate that intraparietal brain regions play a key role in numerical cognition,43 and functional abnormalities in this area appear to underlie impairment in numerical processing.44 As with RD, twin and family studies provide strong evidence of a genetic component to mathematical disorder. The prevalence rate in twins is approximately ten times that of the general population (58% of monozygotic and 39% of dizygotic twins of a child with MD meet the criteria).45,46 Furthermore, among first-degree relatives of individuals with mathematical disorder, more than half have mathematical difficulties.47 There appear to be different subgroups of children with mathematical difficulties, including those with isolated MD and those with MD in association with other LDs or comorbid conditions.48,49 The latter constitutes two-thirds of children with MD.50 Numeracy deficits are common among children with ADHD, epilepsy, and genetic disorders, including Turner, fragile X, Down, Williams, and velocardiofacial syndromes.51,52 Whether the mathematical difficulties experienced by these subgroups are related to general cognitive deficits or a specific deficit in numerical cognition is uncertain.49

Language disorders comprise a wide range of phenotypes with diverse etiologies. In the case of developmental language disorders, as with other types of LDs, evidence implicates a complex interplay of environmental, neurobiological, and genetic influences.53–56 In addition to decreased cerebral volumes, neuroimaging findings in developmental dysphasia have most consistently involved a loss of normal left-right asymmetry in perisylvian and planum temporale regions (which are known to subserve language).32,57 Known causes of language impairments include hearing loss, global cognitive impairment, specific genetic and chromosomal disorders (Down, fragile X, and Klinefelter syndromes), neurobehavioral disorders (autism), and neurological disorders (Landau-Kleffner syndrome).58,59 A period of typical development before the occurrence of language impairments suggests an acquired etiology and the need for prompt medical investigation.

The clinical presentation of learning disabilities is diverse and reflects the underlying deficits, the severity of the disorder, and the age of the child.1 Children with developmental language disorders typically present prior to school entrance with a delay in emergence of spoken language, while learning disorders are often not recognized until after a child enters school and is identified as lagging behind peers in the acquisition of foundational academic skills. Signs and symptoms that can serve to alert the clinician to a language or learning problem are listed in Table 10-3.

Expressive and/or receptive language disorders are characterized by deficits in vocabulary (lexical development), acquisition and use of appropriate word conjugations and derivations, knowledge and understanding of word meanings, and/or aberrations in sentence structure.60 Caregivers may characterize children with expressive language impairments as “quiet” due to sparse speech output, trouble putting thoughts into words, and short, simplified, agrammatical utterances.1 Children with receptive language impairments often have trouble following directions and may respond tangentially or inappropriately to questions.1 As a result of their limited understanding of oral instructions and narratives, they may be described as confused and/or be perceived as inattentive.

Prior to school entrance, when compared to peers, children at risk for reading problems exhibit relative deficits in syntax (grammar) and difficulty pronouncing words correctly; but by school entrance, deficits in phonological awareness are predominant.61 School-aged children with RD exhibit difficulty decoding (“sounding out”) unfamiliar words, trouble recognizing sight words, and difficulty spelling (encoding) new or unfamiliar words. Their oral reading is dysfluent or “choppy,” and they often have trouble understanding what they have read. Thus, notwithstanding a comorbid attention or core language problem, children with RD usually find it easier to understand a passage that is read aloud to them (ie, their listening comprehension is better than their reading comprehension).

Clinical features of mathematical disorder are included in Table 10-3. Early manifestations include difficulty grasping basic numerical concepts and trouble learning to count.62 As they progress through school, children with MD have trouble learning and recalling basic mathematical facts as well as difficulty performing arithmetic computations and learning mathematical procedures, and struggle to solve complex mathematical problems.63

It is important to note that rather than language or learning difficulties, behavioral disturbance and/or social/emotional problems may be the presenting concern for a child with LD, and some children with LD may be simply be (mis)labeled “lazy” or “unmotivated.”

History and Physical

A primary focus of the history and physical examination is identification of medical, psychiatric, or psychosocial problems that may underlie or be contributing to the child’s language or learning difficulties.64 Table 10-4 outlines important elements of the history and physical examination.

Thorough medical and family histories are key components of the clinical evaluation of a child with language impairments or learning problems. Risk factors for language delays and learning difficulties include complications during the prenatal and perinatal periods (in-utero infections, exposure to teratogens, prematurity, hyperbilirubinemia), infections of the central nervous system, traumatic brain injury, epilepsy, psychiatric disorder, and chronic or debilitating health conditions. A positive family history of speech and/or language delay, difficulty learning to read or spell, grade retention, behavior problems or trouble in school, and/or school failure (or “drop out”) is also a risk factor.

A detailed review of the development history is important in identifying aberrations in fine-motor, gross-motor, language, personal-social, cognitive, and adaptive skill acquisition. Language delay is often the presenting feature of a pervasive developmental disorder or general cognitive impairment, and delay in more than one domain is indicative of global neurocognitive dysfunction. A history suggesting loss of previously acquired skills or functions or other evidence of psychomotor regression should shift the focus of the examination to a medical investigation targeted at pinpointing the underlying cause.

The review of systems should include a thorough sleep history. Sleep problems affect one in three school-aged children and can adversely impact attention, memory, and learning.74 A history of snoring, snorting or gasping during sleep, and daytime sleepiness (symptoms that have been found to predict poor academic performance75) should prompt consideration of polysomnographic evaluation.

A detailed psychosocial history is necessary to identify socioemotional problems, environmental factors (economic disadvantage, impoverished linguistic environment, chaotic family life), and other psychosocial and emotional disturbances that can impact language acquisition, learning, and exposure to appropriate academic instruction. Compared to unaffected peers, children with LD more commonly exhibit poor self-concept, social adjustment problems, frustration, loneliness, withdrawal behavior, anxiety, mood, and emotional problems.76–81 Thus, it is important to assess the child’s relationships with peers and teachers, emotional state, adaptive functioning, family situation, and the extent of peer, community, and family support. Information about the child’s self-concept and experiences as a learner, as well as his or her interests and parental attitudes, should also be sought.

Physical examination findings in children with isolated, primary LDs are usually minimal;82 however, subtle (“soft”) neurological signs (eg, obligatory synkinesis) may be present.57, 83–86 Hearing and vision screening is essential, particularly if records indicate a lack of prior vision and audiometric testing. If the child fails screening tests or results are equivocal, referral for full ophthalmologic and/or audiologic evaluation is indicated. A detailed physical examination targeted at identifying dysmorphic features, neurological deficits, and other abnormal findings indicative of an underlying congenital or acquired disorder should be completed.

Communication difficulties, academic underachievement, and school performance problems may arise from a range of conditions, examples of which are included in Table 10-5. The differential diagnosis of LD includes vision and hearing impairments; genetic, neurological, and psychiatric disorders; psychosocial deprivation or neglect; sociocultural disadvantage; excessive school absenteeism; and inadequate academic instruction.1

Attention-deficit hyperactivity disorder (ADHD) may result in academic underachievement independent of a learning disability; however, the coexistence of ADHD and LD is common and diagnosis of either disorder warrants assessment for the other. Of children with ADHD, an estimated 25% to 40% have a comorbid language or learning disorder,89 and approximately 20% to 50% of children with a reading disorder have co-occurring ADHD.90,91 High rates of ADHD and other behavioral disorders are also found in children with language impairments.92 Overall, some 50% of children with language and learning disorders have a co-occurring psychiatric disorder,93 and receptive language impairment appears to place a child at particularly high risk.94

Mood and anxiety disorders are associated with an increased risk of low academic achievement.95,96 Distinguishing a primary emotional or behavioral disorder from emotional problems generated by LD-related difficulties—including frustration, performance anxiety, poor self-efficacy, and low self-esteem as a result of recurrent or chronic failure—requires a careful history to determine the chronology of symptom onset and identify risk factors, such as a positive family history of anxiety or depression.

Numerous neurological disorders are associated with language and learning difficulties. For example, the rate of comorbid LD is high in children with Tourette syndrome (1 in 3 have LD and 50% to 60% have co-occurring ADHD).97 Children with epilepsy are also known to be vulnerable to attention, learning, memory, and behavior problems.59,98–100 Approximately half meet criteria for LD,101,102 and learning impairments may occur even when seizures are well controlled.103 Children with neurocutaneous disorders (eg, 20%-61% of children with neurofibromatosis-1 have LD97,104), neuromuscular disorders (eg, Duchenne and Becker muscular dystrophies105–108), and central nervous system lesions may also exhibit impairments in language and learning.

Marked impairment in communication is a characteristic feature of disorders within the autism spectrum. While children with LDs exhibit higher levels of withdrawn behavior and poorer social competence than peers without LDs,6,109–111 they lack the pronounced deficits in pragmatic language (language use), abnormal prosody of speech, atypical eye gaze, poor or absent joint attention, profound limitations in perspective taking, marked impairments in social reciprocity, and stereotypical behaviors that define autism spectrum disorders. Children who are deaf and hard of hearing may also exhibit marked impairments in language and literacy development, particularly in cases where identification and appropriate interventions occur after 6 months of age.112

Mild mental retardation (MR) may not be identified until school entry when the child’s generalized cognitive impairments and learning problems become apparent. Unlike LD, mild MR is associated with globally depressed critical thinking, problem-solving, reasoning abilities, and deficits in adaptive functioning.1 Moderate to profound MR is associated with marked global developmental delays and is usually identified prior to school entrance.

General medical conditions impacting a child’s general health and well-being, school attendance, and cognitive functioning should also be considered. The prevalence of sleep-disordered breathing is remarkably higher among low-performing students. While it affects 1% to 2% of children as a whole,113 in a prospective study of low-performing elementary school students who were screened for obstructive sleep apnea (OSA), 18% were found to have sleep-associated gas exchange abnormalities.114 As one might predict, the severity of neurocognitive (attention, memory, learning, and language) deficits associated with OSA appears to be inversely related to the frequency of apneic/hypopneic events.115–117 Importantly, therapeutic intervention can result in significant improvements in school grades.114 Physical examination findings such as obesity, tonsillar hypertrophy, and other risk factors for OSA, warrant further investigation including polysomnography.

Environmental factors, such as the amount and type of parental input, and psychosocial disadvantage and neglect, may either underlie or contribute to deficits in language development and academic achievement.

Lastly, it should be noted that one type of LD commonly coexists with another; thus, as is the case with ADHD, identification of one should prompt evaluation for another (Table 10-5).6,16,118

Definitive diagnosis of a learning or communication disorder requires a multidisciplinary approach. A comprehensive history and physical examination by the physician is the first step in the diagnostic process, as outlined in Table 10-6 and Figure 10-1. Subsequent steps include evaluation of oral language, cognitive function, academic achievement, socioemotional function, and adaptive skills using standardized, norm-referenced measures. Such assessment requires the involvement of a qualified speech/language pathologist, school psychologist, clinical psychologist, or neuropsychologist, as indicated by the presenting concern and findings of the clinical examination. Referrals to other clinicians and specialists may also be warranted. For example, if dysgraphia (or handwriting) is a concern, the child may be referred to a pediatric occupational therapist for evaluation of graphomotor and related skills.

The clinical evaluation process is typically informed by the diagnostic criteria delineated in DSM-IV-TR. Thus the psychological evaluation involves determination of whether the child’s performance on individually administered, standardized tests of academic achievement is substantially below that anticipated for chronological age, measured intellectual abilities, and exposure to age-appropriate education; and whether the child’s difficulty “significantly interferes with academic achievement or activities of daily living” that require the particular skill (eg, reading).1 “Substantially below” is variably defined as a discrepancy of 1 to 2 standard deviations between aptitude and achievement.1 Similarly, diagnosis of an expressive or mixed receptive-expressive disorder involves demonstration that “scores obtained from a battery of standardized individually administered measures [expressive language development or both receptive and expressive language development, respectively] are substantially below those obtained from standardized measures of nonverbal intellectual capacity.”1 As noted in DSM-IV-TR, a detailed functional assessment of language ability may serve as the basis for diagnosis “when standardized instruments are not available or appropriate.” A list of commonly used measures of language, intellectual abilities, and academic skills is included in Table 10-7. Test selection and result interpretation should both be guided by, and take into consideration, variables that may impact test performance such as language proficiency, attention regulation, the sociocultural background of the individual, and any motor or sensory deficiencies.

A large number of children undergo evaluations for LD within school systems. The assessment procedures employed by local education agencies (LEAs) are shaped by the guidelines for determination of LD specified by federal and state statutes.

While both DSM-IV-TR and special education laws include aptitude-achievement discrepancy criteria, this discrepancy-based approach for identification of LD has long been criticized by researchers and leaders in the field. Such criticism has highlighted the poor reliability and discriminant validity of the discrepancy model, as well as concerns about the limited instructional relevance of the type of assessments that are typically conducted when determination of intellectual quotient (IQ)-achievement discrepancy is the focus, and the frequently long gap between identification of a struggling learner and determination of eligibility and initiation of appropriate interventions.16,119–124 The latter is of particular concern because remediation becomes an increasingly challenging undertaking as time elapses, and the prognosis for achieving typical skills declines.6,125

In part spurred by these concerns, the 2004 reauthorization of IDEA by Congress brought new guidelines and directions for LD determination. Of particular interest is the option that local education agencies (LEAs) may employ a “process that determines if [a] child responds to scientific, research-supported intervention as part of the evaluation procedures.” Importantly, LEAs are no longer required to “take into consideration whether a child has a severe [IQ-achievement] discrepancy.”3 This response-to-intervention (RTI) approach to LD determination is a multi-tiered process that targets early intervention and prevention.16,126–128 In general, the first tier involves universal screening at the beginning of the school year to identify children who may be at risk for LD, along with the provision of empirically supported classroom instruction to all students in the general education setting. At-risk children who demonstrate poor responsiveness to tier 1 interventions as determined by serial (curriculum-based) assessments receive further interventions at the tier 2 and 3 levels, which include small-group tutoring and more intensive, individualized instruction. Progress monitoring occurs throughout, and those at-risk children who continue to struggle (ie, “nonresponders”) are considered for multidisciplinary evaluation for possible LD or other disability classification (eg, intellectual disability) and special education and related services (eg, language therapy).126–129 The LD designation is reserved for those students who demonstrate “unexpected underachievement” (a core LD construct) in spite of evidence-based interventions that are validated as effective for most students.16,122,130 The dynamic, formative assessment methods employed in RTI models differ from the singular, summative assessment approach that characterizes the evaluation procedures used in the discrepancy model.124,131