Remission of anosognosia for right hemiplegia and neglect after caloric vestibular stimulation.

Neglect and related phenomena, as anosognosia for hemiplegia and somatoparaphrenia, are often associated to right-hemisphere lesions. These deficits can be alleviated by caloric vestibular stimulation, but little is known about the efficacy of this physiological intervention on neglect following left-hemisphere lesions. Here we report the case of an ambidextrous left brain-damaged patient with severe right personal and extrapersonal neglect, anosognosia for right hemiplegia and somatoparaphrenia. These symptoms co-occurred with more typical manifestations of left-brain damage, such as aphasia and apraxia. Neurological examination revealed right hemiplegia, hemianesthesia and hemianopia. Visuo-spatial tests for personal and extrapersonal neglect, as well as an anosognosia questionnaire, were submitted before and after caloric vestibular stimulation. Results showed a dramatic improvement of anosognosia for hemiplegia and neglect; no change was observed for the remaining deficits. The results confirm the notion of the selectivity of vestibular stimulation for neglect and related disorders and extend this notion by showing that similar effects can be obtained after lesion of the left hemisphere, suggesting that similar mechanisms are responsible for left- and right-sided neglect. Such a peculiar association of language and visuo-spatial disorders jointly present after a left-sided lesion opens the question of the link between handedness and lateralization of cognitive functions.