Abstract
We reported a unique patient who showed inattention to the left hand during bimanual movements following a right parietal lobe lesion despite absence of unilateral neglect and motor extinction. The patient was a man in his late forties who suffered from cerebral infarction at watershed area of the right middle and posterior cerebral arteries, which was followed by subsequent subarachnoid hemorrhage secondary to a ruptured right internal carotid artery aneurysm. Eight months after the onset, neuropsychological examination disclosed that he had left side visual/auditory/tactile extinction, left hand clumsiness, and impairments of higher somotosensory functions including two-point discrimination and stereognosis, while his touch, pain, temperature and position senses on the left hand were intact. The patient presented with a unique failure on his left hand during bimanual movements despite absence of unilateral neglect and motor extinction. Although he performed as if his left hand could manipulate an object, the left hand caught only the air and missed the object. Re-examination following 4 years demonstrated that higher somatosensory disturbances and left hand clumsiness remained unchanged. However, his left hand movements during bimanual activities improved and multimodal extinctions dissolved as well. Although limb-kinetic apraxia following a deficit in the higher order sensory system is well known, there has been no report that the apraxia coincided with deterioration of contralesional hand clumsiness during bimanual activities. We conclude that his multimodal extinctions affected bimanual movements. Furthermore, we suggest that his unique left hand failure is accounted by inattention to somatosensory information that could arise intrinsically or spontaneously within active and voluntary bimanual movements, resulting from lesions involving the right parietal lobe posterior to primary sensory area.
