Brief Electrical Stimulation Enhances Axon Regeneration Through a Nerve Graft
Kevin J. Zuo, MD1,2, Golsa Shafa, BSc2, Katelyn Chan, B.Eng2, Kira Antonyshyn, BSc2, Tessa Gordon, PhD1,2, Gregory H. Borschel, MD, FACS1,2.
1Division of Plastic & Reconstructive Surgery, Department of Surgery, University of Toronto, Toronto, ON, Canada, 2Division of Plastic & Reconstructive Surgery, The Hospital for Sick Children, Toronto, ON, Canada.
PURPOSE: Nerve graft reconstruction of gap defects may result in poor outcomes, particularly with long regeneration distances. Electrical stimulation (ES) of nerves may improve outcomes in such patients. A single session of ES at 20 Hz for 1 hour significantly enhances axon regeneration in animals and human subjects after nerve crush or nerve transection and repair. However, few studies have examined the effect of ES with nerve grafting. Furthermore, it is not known if a second, delayed session of ES has added benefit to an initial session of ES in staged surgical procedures such as cross face nerve grafting for facial reanimation. The objectives of this study were to evaluate if ES enhances axon regeneration through nerve grafts and if there is added benefit of a second, delayed session of ES (serial ES) on axon regeneration as compared to a single session only of ES.
METHODS: Female Sprague Dawley rats were randomized to control (sham ES + sham ES), single ES (ES + sham ES), or serial ES (ES + ES). A 10 mm nerve gap defect in the right common peroneal (CP) nerve was reconstructed with a reversed 20 mm left CP nerve autograft. Bipolar stainless steel electrodes connected to a Grass SD9 stimulator were placed proximal to the autograft for either 1 hour of ES (20 Hz, 0.1 ms pulse duration, 3-5 V) or sham ES (stimulator not turned on) prior to wound closure. After 4 weeks, the right CP nerve autograft was re-exposed and rats received a second 1 hour session of either ES or sham ES of the CP nerve. At 6 weeks after initial surgery, CP neurons that had regenerated axons 5 mm distal to the autograft were retrograde labeled for enumeration and the CP nerve distal to the autograft was harvested for histomorphometry.
RESULTS: The number of motoneurons (mean ± SD) that regenerated axons through the autograft was significantly higher after single ES (314 ± 70, p<0.01) or serial ES (292 ± 60, p<0.01) as compared to sham ES (182 ± 72). There were significantly more sensory neurons that regenerated their axons after single ES (754 ± 144, p<0.05) or serial ES (769 ± 188, p<0.05) as compared to sham ES (544 ± 165). There was no significant difference in the number of regenerated motor or sensory neurons between rats receiving either single ES or serial ES (p>0.05). There were no significant between group differences for myelinated axon counts on histomorphometry or muscle mass ratios of tibialis anterior or extensor digitorum longus (p>0.05).
CONCLUSION: A single session of ES enhances axon regeneration following immediate nerve autografting with no added effect of a second, delayed session of ES. These findings support previous studies in animals and humans of the robust effect of a single session of ES in promoting nerve regeneration following injury and repair. ES is a clinically translatable technique that may enhance outcomes following nerve gap reconstructions.
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