PubMed1991
Developmental language and learning disabilities in children can take many different forms and can result from a variety of causes. Research to date has focused primarily on specific disabilities in learning, which are characterized by a significant delay or disorder in one aspect of learning against a background of otherwise normal development. Learning disabilities affecting language and/or reading acquisition (developmental dysphasia and dyslexia) have been studied most thoroughly. Verbal learning disabilities occur more frequently in boys than in girls, and there is a higher than expected incidence of left-handedness among affected children. Although there are many reasons why a child may have delayed or disordered language development, differential diagnosis of specific developmental language or reading disorders calls for ruling out mental retardation, peripheral auditory or visual dysfunction, autism, frank neurological impairments such as hemiplegia or seizure disorder, and severe social deprivation or lack of educational opportunity. The typical profile of a developmentally dysphasic or dyslexic child is one who shows a marked discrepancy between nonverbal (performance) IQ and verbal IQ, with a history of delayed or disordered speech, language and/or reading development. Such a child usually performs quite normally on visual spatial tasks, while demonstrating severe deficits in tasks of auditory temporal processing, motor sequencing, phonological processing and memory, language, reading and spelling. This characteristic neuropsychological profile may suggest left hemisphere dysfunction or a failure to develop normal cerebral lateralization. The etiology of these developmental learning disorders is unknown, but there is evidence of familial aggregation, indicating a potential genetic basis. Although these children respond to remediation, longitudinal studies have shown that the symptoms often persist into adulthood (see Tallal, 1988, for a more detailed discussion).