The accessory posterolateral nerve: An immunohistological analysis

Background: Recent endoscopic dissection studies have redefined the postganglionic pterygopalatine autonomic pathways suggesting that neurovascular rami, termed accessory posterolateral nerves, project directly through the palatine bone to innervate the posterolateral nasal mucosa rather than traveling with trigeminal arborizations. The goal of this study was to characterize these accessory posterolateral nerves by immunohistochemistry to determine their morphology and composition. Methods: This is an Institutional Review Board approved study in seven patients in whom the presence of accessory posterolateral nerves were surgically identified exiting the perpendicular plate of the palatine bone and sampled. The presence of neural tissue was confirmed by hematoxylin and eosin and S-100 protein staining. Nerves were then stained with anti-human choline acetyl-transferase (ChAT; 1:100) and anti-human dopamine beta-hydroxylase (DBH; 1:100) followed by a fluorescein isothiocyanate-labeled secondary antibody to test for the presence of peripheral parasympathetic and sympathetic fibers, respectively. Human cadaveric sensory nerves were used as a negative control. Results: All seven samples contained neural elements. Two specimens were also associated with arteries. All nerves were comprised of a single fascicle containing an approximately equal distribution of ChAT(+) and DBH+ fibers. Conclusion: This histological study supports prior descriptions defining a newly recognized neural pathway for innervation of the nasal mucosa. Our data confirm that these accessory posterolateral nerves project directly through the perpendicular plate of the palatine bone and are composed of autonomic fibers. Recognition of this pathway may be exploited in the treatment of sinonasal disease resulting from autonomic dysregulation. (Am J Rhinol Allergy 26, 271-273, 2012; doi: 10.2500/ajra.2012.26.3804)