Interpreting spatial dysgraphia after stroke: Straight ahead or straight above?

Abstract

Spatial dysgraphia, frequently observed after a right hemisphere stroke, associates signs of spatial compression in relation to spatial neglect, and a tilted writing which remains to be explained. Here we present a case study suggesting that tilted writing is due to a tilted representation of the vertical. JW, a 75-year-old patient who underwent a right hemisphere hemorrhage showed a pusher syndrome and a writing tilted 11.1° upwardly, consistent through many tests, without other signs of spatial dysgraphia. We comprehensively assessed and followed most aspects of spatial cognition, until nine months post-stroke. For writing assessments, head and trunk were kept upright, and JW was instructed to write with the right (non-paretic) hand, on a paper sheet affixed onto a graphic tablet (to quantify writing orientation and time) positioned in front him on a slanted table (30°). The writing was tested with or without visual clues, and after a modulation of verticality perception. One month post-stroke, spatial neglect was severe with predominant signs of body neglect. Subjective straight-ahead was normal. Visual (VV) and postural (PV) perceptions of the vertical were tilted of 11°, counterclockwise. This transmodal tilt was similar both in direction and magnitude to the tilt found congruent on all features of writing: margin, lines, and letters. At 3 months the writing was found slower than a control subject when JW was instructed to write on blank paper (1.67 vs. 0.82 s/letter; P < 0.001), and faster when writing on lines inclined 24° upwardly (1.11 s/letter; P < 0.05). Then JW was himself tilted, in sitting for 10 min at 30° to right side, in the dark using the wheel paradigm. As expected this normalized PV for several min. This PV modulation significantly reduced the writing tilt, measured 20 min later (6.2°; P = 0.001) and increased the writing speed (0.89 s/letter; P = 0.002). Nine months post-stroke we found a dissociation between signs of spatial neglect, which disappeared, and a tilt remaining both in verticality perception and writing (5° and 8.8°, respectively). After a right hemisphere stroke, a tilted writing is likely a sign of a tilted verticality representation.