Neurobiology of developmental dyslexia: Part 1: A review of evidence from autopsy and structural neuro-imaging studies

Developmental dyslexia (DD) is a language-based neurological disorder which impairs readingability but does not result from low intelligence,lack of motivation, sensory impairment, or inadequate instruction. Although the neurological basisof dyslexia has long been assumed, the exact natureof the altered brain structure associated with DD remains unknown and has been a subject of autopsyand neuro-imaging research.  Autopsy studies provide consistent evidence of symmetry of the planum temporale (PT), thalamus and cortical malformations, whereas results from structural imaging studies such as computed tomography (CT) and magnetic resonance imaging (MRI) are inconsistent. To address the possible etiology of DD, this paper reviews evidence from autopsy and structural imaging studies on developmental dyslexia and discusses possible methodological sources of some inconsistent results. The role of the optometrist in the multidisciplinary management of dyslexia is highlighted. (S Afr Optom 2011 70(4) 191-202)

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