Progressive Dysgraphia: Co-occurrence of Central and Peripheral Impairments

Abstract

We studied two patients with a novel focal neurodegenerative syndrome: a progressive dysgraphia in which both central (linguistic) and peripheral aspects of the writing process were affected. In one patient the dysgraphia was remarkably pure. Longitudinal testing over roughly 4 years showed that the dysgraphia evolved in a broadly similar pattern for both patients. At presentation, SC and FM exhibited (central) surface dysgraphia on both oral and written spelling. Over time, nonphonologically plausible spelling errors increased, and eventually became the dominant response type for both patients in both response modes. The peripheral dysgraphia consisted of difficulty with producing letters, particularly in lower case, without a model to copy. Examination of a further 28 dysgraphic patients with cortical dementia revealed a strong concordance between spelling and letter production problems, indicating that the association is more common than previously recognised. Although this association may simply reflectpathological involvementof functionally and anatomically closely related brain regions, we also sketch a proposal for a principled relationship amongst the disorders observed in these cases. Damage to an interactive system with wordand letter-based levels of representation could plausibly result in initial surface dysgraphia, together with the progressive emergence of nonphonologically plausible spelling errors, and a deficit in letter production.