Intrafacial Nerve Transfer for Facial Synkinesis: An Anatomical Feasibility Study
David Jensson, MD1; Wolfgang Johann Weninger, MD2; Chieh-Han John Tzou, MD, PhD3; Lars Jonsson, MD, Phd1; Stefan Meng, MD4; Andrés Rodriguez-Lorenzo, MD, PhD5
1Uppsala University Hospital, Uppsala, Sweden, 2Center for Anatomy and Cell Biology, Medical University of Vienna, Vienna, Austria, 3Division of Plastic and Reconstructive Surgery, Department of Surgery, Hospital of Divine Savior, Vienna, Austria, 4Center for Anatomy and cell biology, Vienna, Austria, 5Department of Plastic and Maxillofacial Surgery, Uppsala University Hospital, Uppsala, Sweden
Abstract Background: Selective neurectomy of nerve branches to the orbicularis oculi is one treatment option to treat synkinetic movements in the eye. Patients with severe oral-ocular synkinesis often present with inefficient smile excursion. We propose a novel idea on intrafacial nerve transfer and coaptation of these affected nerve branches to the buccal branches innervating the zygomaticus major muscle. In theory, by redirecting nerve fibers to their native muscle by intra-facial nerve transfer, synkinetic movements may be reduced and voluntary smile improved. Aim of the Study: To explore the anatomical and technical feasibility of selective intra-facial nerve transfer between branches innervating the orbicularis oculi and the zygomaticus major muscle. Methods: Ten adult fresh cadavers (18 hemi-faces) were dissected. Measurements included number of nerve branches to the orbicularis oculi and zygomaticus major muscle, maximal length of nerve dissection and reach for direct coaptation between nerve branches. Histomorphometric analysis for axonal count was performed. Results: The average number of sub-branches to the orbicularis oculi muscle were 3.1 branches (1-5) and 4,7 (2-8) to the zygomaticus major muscle. The average maximal length of dissection of the most caudal orbicularis oculi nerve branch was 28.3 (15-40) mm and 23,8 (15-37) mm for the most cranial zygomaticus major nerve branches. Transection and a tension free coaptation was possible in all cases except one. Histomorphometric analysis of the coaptated nerves demonstrated an average of 5173 myelinated fiber counts per mm2 from the orbicularis oculi branch and 5256 myelinated fiber counts per mm2 for the zygomaticus major branch. Conclusion: In patients suffering from severe oral-ocular synkinesis, selective facial nerve transfer is an anatomically feasible procedure. In theory, intra-facial nerve transfer may decrease synkinesis and improve smile by redirecting nerve fibers to their target muscle.
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