Ct-based intraoperative navigation for quick identification of the stylomastoid foramen during hypoglossal-facial nerve anastomosis

Facial nerve palsy is a highly invalidating condition, possibly complicating surgery for cerebellopontine angle lesions, other skull base tumours and trauma. In this context, hypoglossal-facial nerve anastomosis, with hypoglossal axons re-directed into the extracranial facial nerve to reinnervate the denervated facial muscles, is a reconstructive technique, which guarantees the best functional results. While several variations of this classical technique have been reported, the crucial point of this procedure is the correct identification of the facial nerve at the stylomastoid foramen. In fact, a few months after the injury, the nerve structure is transformed, with changes in external appearance as well as consistency, thereby hampering its correct identification. Standard intraoperative neuronavigation has the ability to reliably identify the stylomastoid foramen, thus providing a quick and effective recognition of the facial nerve at its exit from the skull base.We describe the technical nuances of this procedure by presenting two surgical cases who underwent hypoglossal-facial nerve anastomosis for complete facial nerve palsy occurring post removal of a giant vestibular schwannoma 6 months earlier.CT-based neuronavigation allowed a quick and reliable identification of the stylomastoid foramen and of the facial nerve at its exit from the skull. The entire procedure lasted for 3 hours. Three months after the anastomosis, the first signs of facial muscle reinnervation were visible.The use of neuronavigation during hypoglossal-facial nerve anastomosis is a simple and cost-effective strategy to decrease operative duration and increase surgical effectiveness.