SOMATOTOPY OF THE FACIAL NUCLEUS: A COMPARATIVE ANALYSIS WITH CLINICAL REMARKS

Stemming from our previous studies regarding somatotopy of the spinal cord, oculomotor complex and trigeminal complex, we developed this study of the somatotopy of facial nuclei to compare the musculotopic organization of the facial nucleus in different mammals. The results suggest that a basic pattern of muscle representation exists in the cranial nerve VII that is common to all mammals: the subnuclei innervating the nasolabial musculature are located in the lateral portions of the nucleus, while the auricular musculature is innervated by motor neurons located in the medial parts of the nucleus. In humans, it was identified that the facial motor nucleus has a dorsal and a ventral region: the neurons in the dorsal region innervate the muscles of the upper face, and the neurons in the ventral region innervate the muscles of the lower face. Interestingly, the neurons in the dorsal portion of the facial motor nucleus receive input from both sides of the cortex, while those in the ventral aspect mainly receive controlateral input. The result is that both cerebral hemispheres control the muscles of the upper face, and each controls the controlateral lower face. The study and knownledge of the somatotopy of the facial nucleus can be useful for greater precision on the damaged part of the nucleus and the nerves originating from it, and therefore a more precise surgery and monitoring of maxillo-facial tumors.