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Original Investigation
Jan/Feb 2019

Functional and Anatomical Outcomes of Facial Nerve Injury With Application of Polyethylene Glycol in a Rat Model

Author Affiliations
  • 1Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis
  • 2Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky
  • 3Department of Otolaryngology, Indiana University School of Medicine, Indianapolis
  • 4Research and Development Service, Richard L. Roudebush Veterans Affairs Medical Center, Indianapolis, Indiana
  • 5Department of Biomedical and Applied Sciences, Indiana University School of Dentistry, Indianapolis
JAMA Facial Plast Surg. 2019;21(1):61-68. doi:10.1001/jamafacial.2018.0308
Key Points

Question  Does the application of polyethylene glycol in addition to facial nerve neurorrhaphy improve functional and anatomical outcomes after facial nerve injury?

Findings  In this animal experiment, the right facial nerve of 36 rats was cut and immediately repaired using neurorrhaphy with or without the addition of polyethylene glycol. Compared with suture alone, the addition of polyethylene glycol showed no significant benefit in functional outcomes, motoneuron survival, or specificity of regrowth to target at any time points.

Meaning  The addition of polyethylene glycol to suturing may not be warranted in the surgical repair of facial nerve injury.

Abstract

Importance  Functional and anatomical outcomes after surgical repair of facial nerve injury may be improved with the addition of polyethylene glycol (PEG) to direct suture neurorrhaphy. The application of PEG has shown promise in treating spinal nerve injuries, but its efficacy has not been evaluated in treatment of cranial nerve injuries.

Objective  To determine whether PEG in addition to neurorrhaphy can improve functional outcomes and synkinesis after facial nerve injury.

Design, Setting, and Subjects  In this animal experiment, 36 rats underwent right facial nerve transection and neurorrhaphy with addition of PEG. Weekly behavioral scoring was done for 10 rats for 6 weeks and 14 rats for 16 weeks after the operations. In the 16-week study, the buccal branches were labeled and tissue analysis was performed. In the 6-week study, the mandibular and buccal branches were labeled and tissue analysis was performed. Histologic analysis was performed for 10 rats in a 1-week study to assess the association of PEG with axonal continuity and Wallerian degeneration. Six rats served as the uninjured control group. Data were collected from February 8, 2016, through July 10, 2017.

Intervention  Polyethylene glycol applied to the facial nerve after neurorrhaphy.

Main Outcomes and Measures  Functional recovery was assessed weekly for the 16- and 6-week studies, as well as motoneuron survival, amount of regrowth, specificity of regrowth, and aberrant branching. Short-term effects of PEG were assessed in the 1-week study.

Results  Among the 40 male rats included in the study, PEG addition to neurorrhaphy showed no functional benefit in eye blink reflex (mean [SEM], 3.57 [0.88] weeks; 95% CI, −2.8 to 1.9 weeks; P = .70) or whisking function (mean [SEM], 4.00 [0.72] weeks; 95% CI, −3.6 to 2.4 weeks; P = .69) compared with suturing alone at 16 weeks. Motoneuron survival was not changed by PEG in the 16-week (mean, 132.1 motoneurons per tissue section; 95% CI, −21.0 to 8.4; P = .13) or 6-week (mean, 131.1 motoneurons per tissue section; 95% CI, −11.0 to 10.0; P = .06) studies. Compared with controls, neither surgical group showed differences in buccal branch regrowth at 16 (36.9 motoneurons per tissue section; 95% CI, −14.5 to 22.0; P = .28) or 6 (36.7 motoneurons per tissue section; 95% CI, −7.8 to 18.5; P = .48) weeks or in the mandibular branch at 6 weeks (25.2 motoneurons per tissue section; 95% CI, −14.5 to 15.5; P = .99). Addition of PEG had no advantage in regrowth specificity compared with suturing alone at 16 weeks (15.3% buccal branch motoneurons with misguided projections; 95% CI, −7.2% to 11.0%; P = .84). After 6 weeks, the number of motoneurons with misguided projections to the mandibular branch showed no advantage of PEG treatment compared with suturing alone (12.1% buccal branch motoneurons with misguided projections; 95% CI, −8.2% to 9.2%; P = .98). In the 1-week study, improved axonal continuity and muscular innervation were not observed in PEG-treated rats.

Conclusions and Relevance  Although PEG has shown efficacy in treating other nervous system injuries, PEG in addition to neurorraphy was not beneficial in a rat model of facial nerve injury. The addition of PEG to suturing may not be warranted in the surgical repair of facial nerve injury.

Level of Evidence  NA.

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