[Right hemiasomatognosia and sensation of amputation caused by left subcortical lesion. Role of callosal disconnection].

A 72-year-old right-handed hypertensive man presented with a right brachial monoplegia, and hypesthesia of the right half of the body to touch and pricking, sparing the face. A CT scan 2 weeks later showed a spontaneous hyperdense area corresponding to a left subcortical parietal hematoma. The patient used his spontaneous language to express body image disturbances: intense prolonged feeling of amputation related to the upper limb and foot on the right side, hemiasomatognosia without anosognosia, autotopagnosia. Also associated were a right-sided visual negligence and a more general inability to handle spatial data leading to a temporospatial disorientation. Mild language disorders were suggestive of subcortical aphasia: normal incitation and repetition; with semantic paraphasias, poor verbal fluency. Furthermore comprehension of orders or propositions concerning spatial data were poor. Finally, there were signs suggestive of callosal disconnection: paradoxical extinction of the left ear during dichotic listening, agraphia and anomia of the left hand, ideomotor apraxia of the left upper limb, difficulty in visual transfer. The lesion interrupted thalamic tracts to parietal regions and callosal fibers linking parieto-occipital association areas. This twofold lesion was analyzed for each of the neuropsychological disturbances observed. Certain aspect of cerebral function in this patient were reminiscent of "split-brain" disorders. The left hemisphere which "speaks" fails to understand the feelings of the right hemisphere: unfamiliarity of places, sensations of illness, resulting in an unadapted speech. The pathophysiology of feeling of amputation is discussed.