[Loss of mental images].

The authors report a case of loss of mental imagery in a 35 year old male patient who was operated on for an intraventricular meningioma in the region of the left trigonum collaterale. The symptomatology and its evolution are described. Discussion of the pathophysiologic hypotheses is focused on the possible role of a selective memory disturbance, of a functional disconnection between language- and visual representation-areas of the brain, and of visual agnosia. In the reported case, the underlying pathophysiologic mechanism seems to be very close to the one responsible for visual agnosia, and could be explained as a partial dissolution of visual memories. Analysis of 35 cases of loss of mental imagery reported in the literature shows that the investigation of this peculiar disturbance is in many cases incomplete. It nevertheless reveals that visual agnosia, or a particular form of visual agnosia, is present in all cases of unilateral posterior lesion of the dominant hemisphere.