[A case of hemifacial hyperhidrosis on the opposite side of the pancoast tumor].

An 82-year-old man was referred to our pain clinic for the relief of pain arising from Pancoast tumor on the right side. The pain was controlled well by cervical epidural morphine, but one month after admission, he complained of unilateral hyperhidrosis on the face, head and neck on the left side. Massive sweating occurred only during the sleep. At this stage Horner's sign on the right side was recognized. Cervical epidural block diminished sweating. Massive sweating was observed until his death two months after admission. We speculate that paralysis of the right cervical sympathetic system caused by invasion of Pancoast tumor elicited sympathicotonia of the opposite side, resulting in left hemifacial hyperhidrosis, which was exaggerated during the sleep when the activity of perspiration center increased. We recommend that the presence of hemifacial sweating should be closely evaluated, because it can be caused not only by irritation of the ipsilateral sympathetic nervous system, but also by the paralysis of the contralateral sympathetic nervous system due to malignant tumors or other diseases in the neck and upper mediastinum.