PURPOSE: Trigeminal nerve stimulation has been shown to improve functional outcomes of nerve injury, but little is known about the mechanism of this therapy. The aim of this study is to compare the histologic architecture of repaired nerves in a rodent forelimb model to gain better insight on the mechanism of this therapy.
METHODS: After being trained to proficiency in a reach and grasp task, 45 adult male Lewis rats were randomized into four groups: (1) sham injury, (2) nerve injury with sham ES, (3) nerve injury with peripheral ES, and (4) nerve injury with trigeminal ES. The rats were then retrained on the reach and grasp task, and the median and ulnar nerves were harvested for analysis at 12 weeks post-injury. The nerves were stained wioth Gomori's Trichrome and compared qualitatively and quantitatively for ratio of total fascicular area.
RESULTS: The repaired nerve cross-sectional fascicular area was similar between the sham ES, peripheral ES, and trigeminal ES groups (P > 0.05). Qualitative analysis noted more intra fascicular collagen in the sham ES and trigeminal ES groups.
CONCLUSION: Trigeminal ES improves functional outcomes of nerve injury and repair without affecting the architecture of the regenerating peripheral nerve in accordance with the proposed mechanism of primary cortical neuroplasticity. These findings in combination warrant more invasive studies to better determine mechanism.