The Neural Basis of Anosognosia for Spatial Neglect After Stroke

Abstract

Background and Purpose-The present study investigated the lesion anatomy of anosognosia for visuospatial neglect resulting from right hemispheric stroke. Methods-In 63 patients, self-ratings of performance in paper-and-pencil tests were contrasted with external performance ratings. Lesion analysis was conducted on patient subgroups with different degrees of anosognosia but comparable visuospatial impairment. Results-Independent of the severity of visuospatial neglect per se, damage to the right angular and superior temporal gyrus was associated with higher levels of anosognosia. Conclusions-Using a novel assessment of anosognosia for spatial neglect, the present study relates stroke-induced self-awareness deficits to inferior parietal and superior temporal brain damage. Key Words: lesion analysis Ⅲ neglect Ⅲ self-awareness D espite the severe impact of stroke-induced impairments on daily life, some patients remain unaware of their deficits, that is, show anosognosia. 1 Previous studies demonstrated that the majority of patients with reduced self-awareness for hemiplegia/hemiparesis have right hemispheric brain damage. 2,3 No study has yet focused on the lesion anatomy of self-awareness deficits for visuospatial neglect, although these are even more prevalent than for hemiplegia. 4 The present study investigated anosognosia for spatial neglect and its neuroanatomy in patients with different degrees of impaired self-awareness but comparable visuospatial impairment. Patients and MethodsSixty-three patients with unilateral right hemispheric stroke (22 females) and 18 healthy control subjects (7 females) gave written informed consent. Lesions were confirmed by CT or MRI. The study had been approved by the local ethics committee.Participants performed 6 paper-and-pencil tests from the Behavioral Inattention Test 5 (star and line cancellation, line bisection, figure copying, clock drawing, text reading). Subsequent to each subtest, the patients rated their performance on a 5-point scale (ranging from 1, severe difficulties to 5, no difficulties). An equivalent rating was performed by one of the investigators (P.E.) to evaluate the patient's difficulties during task performance. This external rating was moreover used to relate the patients' performance to that of healthy control subjects (patients performing Ͼ3 SDs below the mean of control subjects were regarded to have substantial visuospatial deficits; Table 1). Interrater agreement with 2 additional raters (evaluating the performance of 39 patients who gave their consent to video recordings) and correlations with objective performance measures (line bisection deviation and cancellation laterality quotients) were determined to ensure the reliability and validity of the external ratings.To quantify the degree of unawareness for visuospatial neglect, the following index was calculated:

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