Anosognosia for motor and sensory deficits after unilateral brain damage: a review

The syndrome of unawareness (anosognosia) for sensory and motor neurological deficits (hemiplegia, hemianaesthesia, and hemianopia), contralateral to the side of a hemispheric lesion, is reviewed.

Main topics include: basic historical facts; the types of patient's interview and specific questions used to reveal the deficits; the clinical patterns of presentation; the associations and dissociations of the different anosognosic manifestations, and their relationships with associated disorders of sensory, memory, and executive-intellectual functions; the hemispheric asymmetry of anosognosia, that, as the syndrome of unilateral spatial neglect, is more frequent and severe after damage to the right cerebral hemisphere; the relationships between spatial neglect and the anosognosias, and their neural correlates; the effects of lateralized sensory stimulations on defective awareness of neurological impairments.

The argument is made that anosognosia for sensory and motor neurological deficits should be considered as a multi-component syndrome, including a number of specific disorders that are due to the impairment of discrete monitoring systems, specific for the different supervised functions. The putative causal role of associated deficits of other parts of the sensory-motor or cognitive (e.g., memory, general intelligence) system is critically discussed. These specific control processes may be physically implemented in brain areas anatomically (and functionally) close to those subserving the monitored function.