Peripheral dysgraphia characterized by the co-occurrence of case substitutions in uppercase and letter substitutions in lowercase writing

Patients with peripheral dysgraphia due to impairment at the allographic level produce writing errors that affect the letter-form and are characterized by case confusions or the failure to write in a specific case or style (e.g., cursive). We studied the writing errors of a patient with pure peripheral dysgraphia who had entirely intact oral spelling, but produced many well-formed letter errors in written spelling. The comparison of uppercase print and lowercase cursive spelling revealed an uncommon pattern: while most uppercase errors were case substitutions (e.g., A – a), almost all lowercase errors were letter substitutions (e.g., n – r). Analyses of the relationship between target letters and substitution errors showed that errors were neither influenced by consonant–vowel status nor by letter frequency, though word length affected error frequency in lowercase writing. Moreover, while graphomotor similarity did not predict either the occurrence of uppercase or lowercase errors, visuospatial similarity was a significant predictor of lowercase errors. These results suggest that lowercase representations of cursive letter-forms are based on a description of entire letters (visuospatial features) and are not – as previously found for uppercase letters – specified in terms of strokes (graphomotor features).