Neglect dyslexia: frequency, association with other hemispatial neglects, and lesion localization.

Patients with right hemisphere injury often omit or misread words on the left side of a page or the beginning letters of single words (neglect dyslexia). Our study involving a large sample of acute right hemisphere stroke investigated (1) the frequency of neglect dyslexia (ND), (2) the association between ND and other types of contralesional hemispatial neglect (CN), (3) the effect of visual field defect (VFD) on ND, and (4) the anatomical substrates for ND. Participants were 138 consecutive patients with right hemisphere stroke who underwent a neglect test battery including a test for ND. ND was considered present if the patient misread or omitted the left portion of the word in three or more of the 25 target words. CN was noted in 80/138 (58.0%) patients while ND was found in 31/138 (22.5%) patients. Of the 80 patients with CN, the frequency of neglect based on ND test was only 37.5% while the frequency of neglect based on other neglect tasks ranged from 51.3% to 86.3%. The severity of neglect was a significant predictor for ND. VFD was also a significant predictor for the occurrence of ND but this effect disappeared when the severity of neglect was controlled. Patients with CN had lesions in the superior and middle temporal gyri, inferior parietal lobule, and posterior insular cortex; patients with ND had additional lesions in the lingual and fusiform gyri. In summary, ND was dissociated from other types of neglect and was most often associated with severe neglect. VFD contributed to the occurrence of ND. ND resulted from lesions of temporoparietal junction areas (inferior parietal/superior temporal gyri) combined with those of lingual/fusiform gyri.