[Neuropsychological disorders in minor hemisphere damage].

Damage to the minor hemisphere or the right hemisphere of most right-handed subjects produces various neuropsychological disorders. Unilateral spatial neglect is the deficit to respond or orient to stimuli on the left side. The inferior parietal lobule is most frequently involved in the lesions of neglect patients, but lesions confined to the lobule may not cause chronic neglect. Severe and lasting neglect is frequently found in patients with an infarction in the territory of the middle cerebral artery or the anterior choroidal artery. Neglect is usually mild or moderate after frontal lesions. The most important mechanism of neglect seems to be disorders in spatial attention: rightward attentional bias, and impairment in disengagement and shift of attention from the right side. Directional hypokinesia is rarely observed in the chronic stage. Non-spatial factors, such as motivational deficit, insufficient compensation with verbal intelligence, or disuse of an appropriate spatial strategy may also contribute to the appearance of neglect. Anosognosia for hemiplegia is found in about half of patients with acute cerebrovascular accidents in the right hemisphere. Generalized attentional and intellectual deficits, diffuse brain atrophy or hypometabolism, and presence of multiple infarction may result in chronic anosognosia. Constructional disability is observed in about 30% patients with either hemisphere damage. Dressing apraxia is more frequent in right hemisphere damage. These two disorders, however, rarely appear as isolated neuropsychological deficits. Most patients show some of the accompanying disorders, such as unilateral spatial neglect, anosognosia, anosodiaphoria, and generalized attentional and intellectual impairment. By contrast, motor neglect may occur independently of the other disorders. Motor neglect follows damage to either hemisphere, although it occurs more frequently after right hemisphere damage. Neuropsychological deficits characteristic of right hemisphere damage may be unilateral spatial neglect in the acute and chronic stages and anosognosia for hemiplegia in the acute stage.