[Spatial delusion: sign of lesions of the non-dominant hemisphere]

Two cases with respectively an ischemic and a tumoral lesion of the right hemisphere showing a striking and isolated delusional belief to be relocated elsewhere are reported. Delusion had the remarkable intrinsic coherence of a paranoid delirium but was limited to the localization in space. In contrast these patients had no mental clouding or hallucinations and were well orientated for time and persons. Associated findings were a misrepresentation of space in drawing in the first case, and a left hemiparesis, a left sensory extinction, a left hemianopsia, a left visual neglect, a constructional apraxia and a misrepresentation of space in the second case. Such a spatial delirium has been described after severe head injury but rarely after unilateral cerebral lesions. The latter involve constantly the right hemisphere, either in the frontal, temporo-parietal or thalamic region. Usual neurobehavioral correlates in these cases were a disorder of visual memory, a topographical disorientation, a lack of representation and use of visuospatial data, and an anosognosia. The putative role of a 'release' of the left hemisphere is discussed.