Spatial or afferent agraphia without left-sided neglect

Abstract

We report the case of a 72-year-old right-handed man, M. B., who, after a right posterior parietal infarction, developed a spatial or afferent agraphia. Language function and limb praxis were normal. The patient had no left-sided neglect but a mild visuo-constructional disorder. Spelling knowledge was preserved in oral spelling and block letter writing. Writing errors were present only in cursive handwriting, and were part of those usually observed in afferent agraphia: spatially malformed letters, repetitions or omissions of strokes, failure to dot i's or to cross t's. Furthermore, he significantly increased his error rate when his capacity to use visual or kinaesthetic feedback to control his writing movements was impaired, confirming that the shape and the number of strokes and letters are partially controlled by visual and kinaesthetic feedback. However, M. B. had no wide left margin, no wandering lines, and no unnecessary gaps between words or letters. Thus, he showed a dissociation characterized by the presence of stroke and letter errors in the absence of symptoms of left-sided neglect agraphia. Combined with patients V. B. and S.P., M. B. confirmed (1) that symptoms of spatial agraphia can be fractionated into two dissociable clusters, one related to left-sided neglect and the other related to letter and stroke errors because of feedback impairments; and (2) that different functional deficits underlie the different types of writing error noted in afferent or spatial agraphia.