2025 Proffered Presentations
S218: PARASYMPATHETIC INNERVATION OF THE LACRIMAL GLAND: A MICROSURGICAL CADAVER STUDY
Hassan A Fadel, MD; Jacob Pawloski, MD; Karam P Asmaro, MD; Jack Rock, MD; John Craig, MD; Henry Ford Hospital
Introduction: Keratoconjunctivitis sicca, or dry eye syndrome, is a potentially debilitating condition that arises secondary to a lack of tear production from the lacrimal gland. Tear production of the lacrimal gland is thought to be controlled by parasympathetic innervation from the lacrimatory nucleus of the facial nerve by way of the greater superficial petrosal nerve (GSPN) and vidian nerve. However, it has been repeatedly shown that symptomatic keratoconjunctivitis sicca rarely results from vidian neurectomy during expanded endonasal surgery. Therefore, we propose that the lacrimal gland receives parasympathetic innervation from outside the vidian nerve, potentially via the lacrimanl nerve. Therefore, we designed a study to examine the degree of extra-vidian parasympathetic innervation to the lacrimal gland in fresh cadavers.
Methods and Materials: 10 fresh, non-formalin-fixed adult cadaver heads were used to complete 10 microsurgical dissections. An extended pterional craniotomy was used to expose the greater superficial petrosal nerve (GSPN), Gasserian ganglion, ophthalmic division of the trigeminal nerve (V1), and the entire length of the lacrimal nerve until it entered lacrimal gland. 1-cm sections of the lacrimal nerve as it entered the lacrimal gland were harvested to determine the histopathologic presence of parasympathetic and sympathetic innervation to the lacrimal gland. Specimens were placed in formalin and then histopathologically processed and stained for parasympathetic (choline acetyltransferase) and sympathetic (tyrosine hydroxylase) nerve fibers. Digital density analysis was then completed by quantifying degree of stain per 0.00225 mm2 at 100x histological magnification.
Results: Of the 10 sets of specimens harvested, five specimens had positive parasympathetic histopathological staining in the lacrimal nerve and/or the ophthalmic division of the trigeminal nerve. Parasympathetic staining of the GSPN was used as a positive control.
Conclusions: Based on human qualitative analysis, the lacrimal nerve uncommonly demonstrated histopathologic evidence of parasympathetic fibers. Our findings indicate that there may be parasympathetic innervation to the lacrimal gland outside the accepted pathway via the vidian nerve. Our findings may explain why vidian neurectomy during expanded endonasal endoscopic surgery does not routinely lead to keratoconjunctivitis sicca.