alexia/dyslexia

n. The terms alexia and dyslexia both denote the presence of a reading disorder that impairs production or comprehension of language. Dyslexia is a class of reading disorders resulting from brain damage or learning disability; alexia is a more specific deficit in word or letter reading resulting from brain damage. There are several types of dyslexia, each presenting with a different cause and etiology. At the highest level there exists the distinction between the acquired dyslexias and the developmental dyslexias. Four types of acquired dyslexias have been identified: pure alexia, surface dyslexia, phonological dyslexia, and deep dyslexia. Each of these acquired forms is caused by a particular type of cortical damage and has distinctive symptoms. Developmental dyslexia is a developmental learning disability that is characterized by specific difficulty in reading and spelling despite average or above-average intellectual ability. Children with developmental dyslexia are thought to have a core deficit in phonological coding or processing. - NL