Agraphia in Alzheimer's disease.

Writing disorders are an early manifestation of Alzheimer's disease (AD), often more severe than language difficulties. AD patients produce shorter and less informative written descriptions of a complex picture than controls. These abbreviated texts also include many intrusions, semantic substitutions, and misspellings. Syntactic difficulties are characterized by a reduction of subordinate clauses rather than by the occurrence of grammatical errors. Lexical spelling is systematically more impaired and affected earlier than phonological spelling. With disease progression, the deficits of central writing processes extend to graphic difficulties and alteration of handwriting spatial organization. In the context of a semiotic hierarchy, an inverse relationship is suggested between writing acquisition during childhood and subsequent writing degradation in AD. The writing disturbance in AD is evidently related to a disruption in the anatomicofunctional cerebral network designed for writing processes, mainly in the parietal regions.