Hypoglossal Facial Nerve Transfer (XII-VII Transfer)
The hypoglossal nerve is responsible for moving the tongue, and we each have a pair of hypoglossal nerves, one for each side of the tongue. On each side, the nerve exits from the skull and travels in the upper neck behind the submandibular gland before entering the tongue, where it provides innervation to the tongue’s muscles. Some fibers of the hypoglossal nerve can be re-purposed toward the facial muscles to help patients with facial palsy when there minimal to no chance for recovery of the native facial nerve.
Historically, the hypoglossal nerve was often used for smile reanimation in patients with facial palsy. Specifically, part or the entire hypoglossal nerve was cut, and connected to all or a branch of the facial nerve which innervates the smile muscles. Often, a nerve graft would be harvested to bridge the gap between the hypoglossal nerve and smile nerve. While the hypoglossal nerve can still be used to help patients smile, many surgeons typically use the masseteric nerve for this purpose as it avoids having to use a nerve graft, has less morbidity from sacrifice of the donor nerve, and may provide an even better smile for patients (5-7 Nerve Transfer).
However, we still use a part of the hypoglossal nerve to restore tone in patients’ faces. Patients are candidates for this procedure if they have flaccid facial paralysis, without a chance for recovery of the native facial nerve. If a patient is a candidate for hypoglossal-facial nerve transfer, we typically perform this procedure at the same time we perform other procedures such as cross facial nerve grafting and 5-7 nerve transfer procedures. It is performed under general anesthesia. A facelift incision is made on the affected side extending into a natural crease in the neck, to allow the hypoglossal nerve to be identified. We also identify the facial nerve through this incision. Approximately 40% of the fibers of the hypoglossal nerve are then connected to the facial nerve, using a nerve graft or a natural branch of the hypoglossal nerve. After suturing the nerves together using a microscope, the incision is closed and a small drain is placed. Patients usually stay one night in the hospital and go home the next morning after the drain is removed. The stitches are all dissolvable, so nothing that requires patients to come back in for removal. Patients can expect to see improved tone on the affected side of their face beginning 9-12 months after surgery.