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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.
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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.
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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
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