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Three-Dimensional Topography of the Supratrochlear Nerve With Reference to the Lacrimal Caruncle, and Its Danger Zone in Asians

BACKGROUND The supratrochlear nerve (STN) is relatively superficial and therefore vulnerable to iatrogenic injury. OBJECTIVE To elucidate the course of STN with reference to the lacrimal caruncle, with the aim of preventing nerve injury during surgery in the forehead region. MATERIALS AND METHODS Thirty-four hemifaces from 18 Korean cadavers were dissected. The vertical line through the apex of lacrimal caruncle and the horizontal line through the supraorbital margin were used as horizontal and vertical reference lines, respectively. The course of STN in the frontal view and the point at which it pierced the overlaying musculature were examined. RESULTS After exiting the corrugator muscle cushion, the STN enters the subcutaneous plane by piercing the frontalis muscle. These piercing points occurred at mean horizontal and vertical distances relative to the medial branch of the STN of 9.2 and 9.6 mm, respectively; the corresponding distances for the lateral branch of the STN were 1.1 and 15.3 mm, respectively. CONCLUSION When performing surgery in the medial forehead region, the surgeon must ensure that the dissection plane of forehead tissue is more superficial: superiorly within 1.5 cm from the supraorbital margin and medially within 1.0 cm from the vertical line through the apex of lacrimal caruncle.