Anosognosia (Babinski, 1914) is usually associated with widespread right-hemispheric lesions involving the parietal lobe. We studied the clinical features of anosognosia for mild hemiplegia without any sensory deficits. Subjects in this study were four patients (two males and two females, 47-60 years old, all right-handed) exhibiting anosognosia for mild hemiplegia, who were selected from 31 consecutively admitted patients presenting anosognosia due to acute cerebrovascular disease between January 1991 and December 1995. On admission all four patients denied their hemiplegia, whereas they became aware of their motor deficits with improvement of their hemiplegia. All four revealed unilateral spatial neglect, and three of the four showed sensory extinction and frontal lobe syndromes such as instinctive grasping phenomenon and imitation behavior. Regarding lesion location as detected by cranial MRI or CT, one patient had right-sided lesions involving the anterior cingulate gyrus, callosal genu and body, and putamen ; two had a right dorsolateral frontal lesion including the middle and inferior frontal, prefrontal and insular cortices ; and one had a right hemorrhagic lesion involving the putamen and globus pallidus. Heilman (1985) pointed out that four cerebral regions, including the inferior parietal, cingulate-limbic, dorsolateral frontal and mesencephalic-reticular areas, provide an integrated network for the modulation of directed attention, and lesions in only one component yield partial neglect syndromes. Anosognosia in our cases is considered to be based on similar mechanisms of frontal lobe neglect associated with general inattention due to frontal lobe and/or basal ganglia lesions. These findings support the feed-forward or inattentional hypothesis of anosognosia.

View full abstract