PROGRESSIVE DYSGRAPHIA - COOCCURRENCE OF CENTRAL AND PERIPHERAL IMPAIRMENTS

We studied two patients with a novel focal neurodegenerative syndrome: a progressive dysgraphia in which both central (linguistic) and perip heral aspects of the writing process were affected. In one patient the dysgraphia was remarkably pure. Longitudinal testing over roughly 4 y ears showed that the dysgraphia evolved in a broadly similar pattern f or both patients. At presentation, SC and FM exhibited (central) surfa ce dysgraphia on both oral and written spelling. Over time, nonphonolo gically 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 stron g concordance between spelling and letter production problems, indicat ing that the association is more common than previously recognised. Al though this association may simply reflect pathological involvement of 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 word- an d letter-based levels of representation could plausibly result in init ial surface dysgraphia, together with the progressive emergence of non phonologically plausible spelling errors, and a deficit in letter prod uction.