Allographia
Definition and Clinical Features
Allographia is a specific type of peripheral agraphia (writing disorder). It is characterized by difficulty in correctly forming letters, specifically in selecting the correct letter shape or "allograph" (e.g., 'a' vs. 'A', or cursive vs. print).
The hallmark of this syndrome is the presence of "case change errors," where upper and lower case letters are mixed inappropriately within words. Sometimes, upper and lower case versions of the same letter are even superimposed on one another. These errors tend to increase in frequency with longer words. General spelling of both words and nonwords can also be impaired.
Allographia is characterized by errors in letter formation, such as incorrect or mixed letter casing (e.g., 'wRItiNg').
Pathophysiology and Clinical Significance
The deficits in allographia are interpreted as a disturbance in the selection of specific letter shapes (allographs). According to cognitive models of writing, this breakdown occurs after the abstract identity of the letter (the grapheme) has been correctly retrieved. The brain fails at the subsequent step of converting this abstract letter identity into a specific motor plan for a written form (e.g., upper case, lower case, or cursive). This makes allographia a useful sign for pinpointing a specific level of impairment within the complex process of writing.
References
De Bastiani P, Barry C. A model of writing performance: evidence from a dysgraphic patient with an "allographic" writing disorder. Bollettino della Società italiana di biologia sperimentale 1985; 61: 577-582
Cross References
