Vitamin D3 potentiates myelination and recovery after facial nerve injury.

Roles of vitamin D on the immune and nervous systems are increasingly recognized. Two previous studies demonstrated that ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3) induced functional recovery and increased myelination in a rat model of peroneal nerve transection. The current report assessed whether cholecalciferol was efficient in repairing transected rabbit facial nerves. Animals were randomized into two groups of rabbits with an unilateral facial nerve surgery: the vitamin D group included animals receiving a weekly oral bolus of vitamin D3 (200 IU/kg/day), from day 1 post-surgery; the control group included animals receiving a weekly oral bolus of vehicle (triglycerides). Contralateral unsectioned facial nerves from all experimental animals were used as controls for the histological study. The facial functional index was measured every week while the inner diameter of myelin sheath and the G ratio were quantified at the end of the 3 month experiment. The current report indicates that cholecalciferol significantly increases functional recovery and myelination, after 12 weeks of treatment. To the best of our knowledge, this is the first study investigating the therapeutic benefit of vitamin D supplementation in an animal model of facial paralysis. It paves further the way for clinical trials based on the administration of this steroid in individuals with injured facial nerves.