[Releasing phenomenon of well learned praxis with right hand]

We report a case with "releasing phenomenon of well learned praxis" with right hand caused by cerebral infarction in the territory of left anterior cerebral artery. A 71-year-old right-handed woman suddenly developed motor paralysis in right lower and upper limbs associated with mutism. Motor paralysis of the right upper limb and speech disturbance improved gradually. At this period it was noted that she grasped and used an object in front of her with right hand against her own will. The neurological findings about one month after the onset of the disease revealed very mild weakness of the right upper extremity and severe motor paralysis of the right lower limb. In addition, tendon reflex was exaggerated in the right lower limb and sensory disturbance was noted in the region distal from the right knee. Neuropsychologically, ideomotor apraxia was observed in the left hand. Pathological gasping of the right hand was also noted. When the patient saw and touched an object, she used it with her right hand against her own will, and her left hand voluntarily hindered the right hand. This behavior is apparently similar with the "compulsive manipulation of tools" reported previously. However, the following hitherto unknown phenomena were observed in the present patient: Her right hand performed pantomimic movement for the use of objects orally described by the examiner without visually presenting them. The right hand also tended to imitate the gestures of the examiner automatically, even if the patient was not asked for imitating the gestures. These behavioral abnormalities of the right hand was thought to be liberated from the inhibition system.(ABSTRACT TRUNCATED AT 250 WORDS)