Walsh & Hoyt: Acquired Alexia

Acquired alexia is the inability to read in previously literate individuals despite adequate visual acuity. The severity of the reading disorder and the pattern of accompanying neurologic defects vary depending on the location and extent of the underlying brain lesions. Reading is a complex behavior involving form perception, spatial attention, ocular fixation, scanning saccadic eye movements, and linguistic processing. Not surprisingly, many types of cerebral or visual dysfunction can disrupt the reading process; while other clinical signs may accompany the alexia, impaired reading is sometimes the chief or the only complaint. The severity of reading difficulty can range from a mild defect with slow reading and occasional errors, which requires comparison with normal controls matched for educational level, to a complete inability to read even numbers and letters. Analysis of the severity and type of reading errors can help differentiate between the various forms of reading disorders and their causes. Acquired alexia and milder forms of acquired reading disturbance must be distinguished from ""dyslexia,"" a developmental defect that results in much less severe reading difficulties characterized by slow reading, letter or word reversals, and other inefficiencies. The label ""dyslexia"" has also been applied in acquired reading disturbance where the reading defect is incomplete (analogous to the use of the term ""dyschromatopsia"" in cases of incomplete color vision loss).