Facial nerve pathology in leprosy: searching for the proximal extent of the lesion in facial nerve biopsies

A light and electron microscope study was made of resin embedded facial ner ves in three cases of leprosy involving the facial nerve. The patients had irreversible facial nerve palsies and had requested facial reconstruction. No consistent pattern of nerve fibre damage was found. In one case the temp orozygomatic was affected, but the cervical branch was normal, suggesting t he damage begins distally. In two cases the loss of nerve fibres in the tru nk and all branches was similar, and is likely to emanate from damage at a more proximal site. The presence of increased numbers of unmyelinated axons , often in clusters, is evidence of regeneration. These axons probably have the potential to develop into functional myelinated fibres provided that t hey can innervate a viable distal target such as a muscle graft. These rege nerating axons are distal to the stylomastoid foramen suggesting that the m ost proximal level of involvement of the facial nerve could be intracranial . The finding of a more proximal level of nerve involvement, implies that t he mis-reinnervation seen in partially recovered facial nerve palsies in le prosy, could be due to some regenerating axons being mis-directed at the le vel of the main trunk bifurcation.