[Left unilateral apraxia].

A 32-year-old right-handed man suffered a traffic accident with head injury, resulting in loss of spontaneity, right hemiparesis, severe aphasia, and unilateral apraxia, which was noticed on his non-paralyzed left hand. An MRI scan conducted 11 months after onset revealed a large lesion in the left frontal lobe, a small lesion in the right frontal lobe and a striking thinning of the trunk of the corpus callosum with remarkable dilatation of the lateral ventricles. An IMP-SPECT scan, performed 1 year after onset, showed a diffuse hypoperfusion extending to the left temporo-parietal area further than the MRI verified abnormal density areas. The patient's praxic abilities were precisely evaluated 1 year after onset. The performance on the object use task was characterized by content errors. For example, when using a match with his left hand, he always treated with it like a cigarette. The right hand performance of this task was clumsy due to his right hemiparesis but successful. The performance on his left hand did not improved even when the patient was given visual examples. The term "ideational apraxia" proposed by Liepmann, which was characterized by content errors, implies a conceptual deficit. Morlaas defined ideational apraxia as a agnosia of usage. Ideational apraxia has been so far investigated mainly on patients with these difficulties in both hands. On the other hand, left unilateral apraxia has been explained by callosal disconnection. Liepmann and Maas thought that a lesion of the corpus callosum would prevent the space-time engrams in the left hemisphere from reaching the right sensorimotor area necessary to carry out the skilled act with the left hand, thereby inducing apraxia.(ABSTRACT TRUNCATED AT 250 WORDS)