Evidence for hypohydrosis as clinical clue to diagnosis of Horner's syndrome.

A 59-year-old man presented with hypohydrosis in his left upper extremity and left hand, and experienced difficulty in gripping the steering wheel while driving. One year prior to admission, he had felt pain and/or paresthesias in his left anterior chest, left shoulder area and left periaxillar area, which corresponded to involvement of dermatomes in T1-T3. He was diagnosed with Horner's syndrome caused by lung tumour, which was located at the apical posterior wall along with the second to fourth ribs. The tumour interrupted sympathetic neurons at the T1-T4 level. The degree of hypohydrosis was successfully evaluated by the starch-iodine technique, dermal thermography and a skin surface hygrometer. After radiation therapy, hypohydrosis and pain or paresthesias improved partially, and he was discharged uneventfully.