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Resting Symmetry without Morbidity: The Descendens Hypoglossi - Hypoglossal Nerve Transfer for Facial Palsy
Nate Jowett, MD, Harvard Medical School / Mass Eye and Ear, Boston, MA

Introduction: Restoration of mimetic muscle tone in flaccid facial paralysis yields considerable advantages over static suspensions. Hypoglossal-facial nerve transfer reliably restores facial tone, but past approaches carried considerable risk of donor-site morbidity and facial hypertonicity. Herein is described concomitant descendens hypoglossi transfer to mitigate sequelae of hypoglossal nerve interposition graft transfer in the management of facial palsy.
Methods: The descendens hypoglossi is dissected to its juncture with the inferior root of the ansa cervicalis through a Blair incision, transected distally, and reflected superiorly. The extratemporal main trunk facial nerve is dissected to the stylomastoid foramen, transected proximally, and reflected inferiorly. A neurotomy is made through 30% of hypoglossal main trunk fibers. The distal 3-4 cm of the descendens hypoglossi is employed as an interposition nerve graft for transfer of axotomized hypoglossal fibers, while the proximal stump is employed for direct transfer to the extratemporal main facial nerve trunk.
Results: Fourteen patients underwent the procedure. The first four patients were admitted overnight for observation; the remainder were performed as day surgery. There were no intraoperative complications. One patient developed transient hemi-tongue atrophy, dysarthria and dysphagia, with full recovery of tongue bulk and function within three months. The remainder of patients suffered no transient or long-term tongue atrophy, dysarthria, or dysphagia. Of patients with 9 months follow-up (N = 8), all demonstrated evidence of neurotization. Of patients with 12 months follow-up (N = 4), all had recovered to House-Brackmann Grade III function without facial hypertonicity. Decisional regret was absent in all cases.
Conclusions: Initial results suggest this novel nerve transfer technique for dynamic reanimation of facial tone minimizes risk of donor site morbidity. Descendens hypoglossi - hypoglossal nerve transfer to the main facial nerve trunk may be paired with targeted cross-facial or masseteric nerve-transfers to select distal facial nerve branches for reanimation of volitional expressions.
Fig. 1: Descendens hypoglossi (DH) + hypoglossal (CN XII) - facial (CN VII) nerve transfer. (A) Right CN XII is shown at the juncture with the DH. The internal jugular vein (IJV) and external carotid artery (ECA) are labelled. (B) CN VII and DH reflected deep to the posterior belly of the digastric (PBD) muscle. (C) The proximal DH is coapted to the facial nerve in end-to-end fashion with an interposition nerve graft comprising the distal aspect of the DH (igDH) to a neurotomy through CN XII.
Fig. 2: Pre- (top) and 12 months post-op (bottom).


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