Deep dyslexia

Deep dyslexia  is a form of Alexia (acquired dyslexia) that disrupts reading processes that were functioning normally before the individual suffered a head trauma to the left hemisphere. Deep dyslexia may occur as a result of a head injury, stroke, disease, or operation (Harley, 2001 ).

The term dyslexia comes from the Greek words ‘dys’ meaning ‘impaired’, and ‘lexis’ meaning ‘word’ and is used to describe disorders of language concerning reading and spelling.

Deep dyslexia is mainly characterised by the occurrence of semantic reading errors or semantic paralexias when reading aloud (eg. view → “scene). Other characteristics of deep dyslexia include visual errors (eg. thing → “think”) and deviational errors (eg. alcohol → alcoholic) as well as poor reading of function words, more difficulty reading abstract than concrete and highly imaginable words, a complete inability to read non-words, severe impairments when writing to diction and writing spontaneously, and in many cases an impairment in short term memory, or digit span (Plaut & Shallice, 1993 ;Klein et al., 1994; Weekes et al., 1997; Harley, 2001 ; Kolb & Whishaw, 2003).

While the symptoms of deep dyslexia are different and independent impairments of reading, it is rare to find an individual who only displays some of the characteristics of it; indeed, most patients presenting with semantic paralexias also demonstrate all of the other symptoms. This has resulted in deep dyslexia being considered a symptom-complex and has led to much research into why this variety of symptoms may co-occur in so many patients (Coultheart, Marshall & Patterson, 1986; Weekes et al., 1997).