An anatomical study of the cutaneous branches of the mental nerve.

Minor surgical procedures to the inner (mucosal) aspect of the lower lip may occasionally cause numbness of the overlying skin. This study was designed to find, by means of dissection and computerized three-dimensional reconstruction, why surgical interference with nerve fibres in the deep aspect of the lip can cause neurological deficit in the superficial layers. Thirteen cadaveric lips were examined by dissection under a surgical microscope (9 lips) or serial sectioning and computerized three-dimensional reconstruction (4 lips). Muscle mass, minor labial salivary glands and nerve fibres were identified and traced. Three patterns of mental nerve distribution were seen on dissection and two on computerized reconstruction; these latter corresponded to two of the patterns seen on dissection. Fibres passing close to the labial minor salivary gland mass were seen to travel towards the superficial aspect of the lip, terminating in the dermis. It is clear that there is no safe anatomical space for minor surgical procedures to the inner (mucosal) aspect of the lower lip if avoidance of cutaneous numbness is an important consideration. However, we describe a technique that may minimize the possibility of cutaneous numbness.