Is the function of the donor nerve in facial reanimation more important than the axonal load?
Miranda Chacon, B.S., University of Rochester Medical Center, Rochester, NY, Michael Catanzaro, MD, URMC, Rochester, NY, Daniel Butler, MBBS, FRCS(Plast), Imperial College Healthcare NHS trust, London, United Kingdom, Adriaan Grobbelaar, MB ChB, FRCS(Plast), Inselspital, Bern, Switzerland and Jonathan I Leckenby, MD, PhD, Department of Plastic and Hand Surgery, URMC, Rochester, NY; University College of London, London, United Kingdom
Introduction: In order to re-animate the paralysed face, the gold-standard treatment is to combine a cross-facial nerve graft with a functional muscle transfer to the face that is undertaken in two stages; the goal is to restore the patient with a spontaneous symmetrical smile. Despite recent advances only 60% of patients obtain an excellent outcome and it is not possible to determine which patients will do well. We report the findings from a sequential series of twenty-five facial reanimation patients, coupling the clinical findings with histomorphological data. To understand the lack of predictability, a laboratory investigation manipulating the facial nerve in mice was undertaken to shed light on how the facial nerve regenerates across a graft and reinnervates the muscle target. Methods: Nerve biopsies were taken from 25 patients undergoing facial reanimation procedures. As a clinical outcome measure, all patients were evaluated using the eFACE tool pre-operatively and at 2-years post-operative follow-up in combination with the Harrison clinical outcome score. 15 patients underwent a two-stage procedure and nerve biopsies were taken from the contra-lateral donor buccal nerve, the sural nerve, the cross-facial nerve graft and the recipient lateral-pectoral nerve from the pectoralis minor muscle. 10 patients underwent a single stage procedure obviating the need for a cross-facial nerve graft. Biopsies in these cases were taken from the donor masseteric nerve and the recipient thoraco-dorsal nerve of the latissimus dorsi muscle. Results: In the two-stage group, the average eFACE score improved from 44 (32 Ð 56) to 78 (63 Ð 97) of which 64% were deemed an excellent outcome. On average, 58% of axons regenerated up to the distal end of the nerve graft. Patients with a higher graft axonal count had significantly improved eFACE scores (p=0.03). In the one-stage group, the eFACE score improved from 41 (36 Ð 56) to 78 (61 Ð 88). The masseteric (MN) donor count was significantly higher than the buccal nerve (BN) (MN 378, BN 243, p<0.05) despite the clinical outcome scores being lower than the two-stage group. Conclusion: Traditionally the donor nerve axonal count has been attributed to better outcomes in facial reanimation procedures. This study suggests the function of the donor nerve is more important than the axonal load reinnervating a transplanted muscle for improved clinical outcomes..
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