Changes In Various Hormone Levels In The Rabbit Traumatic Facial Nerve Injury Model

Abstract

Objectives: We aimed to look into potential associations between specific biomarkers and trauma to Cranial Nerve VII (CNVII) in a rabbit model, focusing on whether endocrine studies have potential as biomarkers in this context. Methods: 30 adult New Zealand rabbits with intact facial muscles were used for the research. Each animal underwent identical surgery by the same surgeon. The facial nerve divisions were exposed by incising below the level of the mandible. After dissection of the skin and subcutaneous layers, the buccal division of CNVII was located with the nerve stimulator and microscopic dissection and a section of nerve 10mm long was excised in each case from the buccal branch of CNVII. Blood samples were drawn 8 weeks and 12 weeks after nerve injury had been surgically induced. The samples from day 1, week 4 and week 8 were tested for the following levels: Testosterone, oestrogen, progesterone, free T3 and T4, Cancer antigen 19-9 (Ca19-9), folate, TPSA, FPSA, FSH, LH, CA15.3, CAE, AFP and prolactin. Results: The levels of free T3 and T4 as well as testosterone, were down at 4th week, but at 8 weeks each had increased. Ca19-9 levels were also above the baseline. At 4 weeks, whilst oestrogen had markedly risen, progesterone had fallen. The statistical significance of the change in levels of free T3 and T4, testosterone, oestrogen, progesterone and FPSA was evaluated. For the group of animals with induced paralysis, the association between the lesion and testosterone, oestrogen, progesterone, free T3 and T4, Ca19-9, and folate levels were strong and at the level of statistical significance. Conclusion: There were statistically significant alterations in the serum levels of free T3 and T4, testosterone, oestrogen, progesterone and FPSA at the 4 and 8 week intervals post surgically-induced CN-VII injury. It is likely that rabbit pathophysiology resembles human pathophysiology in nervous injury, hence these six biomarkers may be of value in managing trauma or idiopathic degeneration of CNVII in humans. The authors hope this study will pave the way for future research in this area