May Different Subtypes of Dyslexia Exist? A Literature Review
Enrico Ghidoni
The common clinical evidence of significant differences between people with dyslexia has stimulated research to define reference subtypes for the classification of individual cases. During thirty years of research, different classifications have been proposed, often on a dichotomous basis, e.g. dyseidetic vs dysphonetic dyslexia, linguistic (L) vs perceptive (P) dyslexia, phonological vs surface dyslexia. A separate discussion deserves to be made of cases with a rapid naming disorder. The most sophisticated analyses come to a finer description of the cognitive sub-components of the processes involved in individual cases. The evolution of taxonomy (DSM-5 and ICD-11) has remarked the difficulty in identifying well-defined profiles and now proposes a framework that provides for a single category of specific learning disorder, which then in individual cases is articulated with a different involvement of the main instrumental functions (reading, writing, calculation). This is the current solution, after a lot of research on the clinical and neuropsychological levels, to which in recent years have been added also studies on the neurobiological basis. Despite the inconclusive results, the search for a definition of both clinical and neurobiological subtypes is still an active area of investigation, from which a lot of data, discoveries and hypotheses have been accumulated.
Keywords
Dyslexia, Specific learning disorder, Subtypes, Functional profile.