Biomechanical and Microstructural Response of Recurrent Laryngeal Nerve in Pigs

Abstract

Tensile loading is a common physiological condition of peripheral nerves but can induce pathologic effects. Significant defects in nerve conduction have been reported for strains as low as ∼6% greater than the in situ strain [1]. In order to better understand the functional deficits resulting from tensile loading of nerve tissue, biomechanical testing is performed. The long-term goal of this research is to develop a constitutive and a computational model of the biomechanical properties of the “packaging,” or connective tissues of the recurrent laryngeal nerve (RLN) to investigate their role in the onset of unilateral vocal fold paralysis (UVP). The vocal folds are important for protection of the airway during swallowing, the regulation of breathing, and for voice production. Although surgery is most often linked to onset of UVP, the cause remains unknown in a large percentage of those with this disorder. Recent research has suggested that individuals with idiopathic UVP may have damage to the RLN at the level of the aortic arch related to a thoracic aneurysm. Our preliminary work has resulted in the conclusion that connective tissues of the RLN exhibit different biomechanical properties in the region of the aortic arch [2]. An aneurysm would impose increased stress and strain on the RLN where it is adjacent to the aorta resulting in impaired nerve function. The primary goal of this study is to identify the relationship between the biomechanical response of RLN tissue and how it response is governed by load dependent underlying extracellular matrix (collagen) organization. We hypothesize that regional differences exist in the microstructure and/or biomechanical response of the RLN and that these differences play a role in the onset of idiopathic UVP.