Dyslexia

Abstract

Dyslexia is a neurodevelopmental disorder characterized by difficulty learning to read and spell.[a][3][4][5] Underlying deficits typically include impaired phonological awareness (an awareness of the sound structure of words) and processing; difficulty with verbal working memory; and slow verbal processing speed.[6] Observable problems include frequent spelling errors that same-age children do not exhibit; difficulty learning how to decode individual words, including "sounding out" words; and struggling to pronounce words correctly and fluently when reading aloud. Deficits in reading comprehension often occur as a secondary consequence.[7] Dyslexia is a heterogeneous disorder, which means that not all people with dyslexia have the same signs, symp-toms, underlying deficits, or functional impairment. Children and adults with dyslexia exhibit higher rates of comorbid conditions such as developmental language disorders; attention-deficit/hyperactivity disorder (ADHD);[8][9][10] and difficulties with motor coordination, mental calculation, concentration, and personal organi-zation, but these are not, by themselves, markers of dyslexia. Dyslexia manifests on a continuum of severity—it is a dimensional disorder.[11][12] People with this disorder have a normal desire to learn.[13][14][15][16] Dyslexia is believed to be caused by both genetic and environmental factors, and their interaction.[16] Dyslexia often runs in families.[15] Dyslexia that develops subsequent to a traumatic brain injury, stroke, or dementia is usually called acquired dyslexia.[13] The underlying mechanisms of dyslexia are problems within the brain's language processing.[15] Dyslexia is diagnosed through a series of tests of memory, spelling, and reading skills.[17] Dyslexia is separate from reading difficulties caused by hearing or vision problems or by insufficient teaching or opportunity to learn.[16] Treatment involves adjusting teaching methods to meet the person's needs.[13] While not curing the underlying problem, it may decrease the degree or impact of symptoms.[18] Treatments targeting vision are not effective.[19] Dyslexia is the most common learning disability and occurs in all areas of the world.[20] It affects 3–7% of the pop-ulation,[16][21] however, up to 20% of the general population may have some degree of symptoms.[22].