Sympathetic skin responses in the face by magnetic stimulation of the neck

: We studied the sympathetic skin responses (SSRs) in the face with magnetic stimulation of the neck, in 10 normal healthy subjects. The SSRs were recorded with surface electrodes placed on the forehead, the lower eyelid, the apex nasi, two points of cheek (one is near the ear, and another is near the mouth), the upper lip, and the lower jaw. Reproducible SSRs were obtained easily at the forehead and the upper lip compared to the other parts of the face. The SSRs on the forehead and upper lip were constantly evoked after drinking of hot water. Mean latencies are 0.98 +/- 0.22 sec. (mean +/- 1SD) at the forehead, and 0.89 +/- 0.12 sec. (mean +/- 1SD) at the upper lip. In the cervical sympathetic pathway, one part of postganglionic fibers runs along the internal carotid artery to innervate the eyelids and forehead, whereas another part runs along the external carotid artery to innervate other parts of the face. It suggests that the forehead and the upper lip are representative parts of those different innervations SSRs in the forehead and the upper lip could be useful for evaluating the sympathetic function of the face in various diseases.