13 - Exploring the Origin of Catecholaminergic Fibers in Orbital Cranial Nerves

Poster Board Number: 13
There are separate poster presentation times for odd and even posters.
Odd poster #s – first hour
Even poster #s – second hour

Co-authors:

Alla Barry - Missouri Southern State University; Grace Chang - Missouri Southern State University; Amil Dudhia - Missouri Southern State University; Tanner Fehrenbach - Missouri Southern State University; Mary Kilmer - Missouri Southern State University; Shelby Kuhnert - Missouri Southern State University; Elizabeth Martin - Missouri Southern State University; Tarunya Mayil Vahanan - Missouri Southern State University; Farida Mehrhoff - Missouri Southern State University

Abstract Body : INTRODUCTION. Sympathetic outflow in the orbit significantly influences various eye functions, such as accommodation, blood flow, and aqueous humor regulation. While existing literature indicates sympathetic innervation originating from superior cervical ganglion (SCG), recent studies using anti-Tyrosine Hydroxylase (TH) antibody suggest the presence of catecholaminergic fibers (CF) in all orbital cranial nerves. However, a comprehensive quantitative analysis of these fibers is lacking, and their origin remains debated. Our study aims to clarify distribution, quantity, and origin of CF in orbital cranial nerves.



METHODS. 6 formalin-preserved adult human cadavers (3 males and 3 females) underwent craniotomy followed by dissection of the orbits and cavernous sinuses (CS). The oculomotor, trochlear, trigeminal, and abducent nerves (AN) with their respective branches were traced from the brain to their orbital termination. Tissue samples were gathered for histological analysis from three locations: near the brain, within the CS, and in the orbit. Samples were stained using Luxol Fast Blue and Anti-TH antibody. Trigeminal ganglia were collected for antibody staining to explore their potential as a source of CF. The SCG was assessed for TH-reactivity to validate the accuracy of TH detection. Slides were photographed. Quantitative analysis was conducted with ImageJ software.



RESULTS. TH+ fibers near the brain were identified bilaterally within the AN in 2 out of 6 whole body donors, varying from 0.42% to 7%. A significant difference was observed when comparing TH+ fibers within AN across all three locations (p=0.012). There was a trend indicating an increase in TH+ fibers from the brain towards the CS (p=0.078), followed by a subsequent drop within the orbit (p=0.005). CF were not found in the trigeminal nerves at the brain location. However, they were diffusely interspersed in all collected ophthalmic nerves (ON) within the CS and frontal nerves in the orbit, ranging from 0.2% to 36.22%. TH+ activity was detected within the trigeminal ganglia.



CONCLUSION. CF exhibit a consistent presence within the ON and its orbital branches. However, given the observed TH activity within the trigeminal ganglia and distribution pattern of the fibers, we conclude that these fibers originate from the trigeminal ganglia rather than CS. Moreover, our findings indicate that the TH+ fibers within the AN most likely arise from the brain nuclei rather than being acquired within the cavernous sinus, contrary to previous assumptions.



SIGNIFICANCE. Our study has advanced our comprehension of the nature and origin of CF within the ON and AN. Further investigations with a larger sample size are warranted to bolster the strength of our findings.