Olfactory Anatomy and Surgical Implications for the Preservation of Its Function

Background: Despite the fact that olfaction has been considered a secondary sense, its loss has a great impact on the quality of life. For an optimal olfaction, various anatomical and histological structures have to be well functioning to maintain a healthy nasal environment. The olfactory mucosa is located on the superior and posterior regions of the nasal cavity.

Objective: There have been studies about the localization of the olfactory mucosa showing that it is not only limited to the superior posterior aspect of the nasal cavity. The olfactory mucosa projects the chemoreception through group of axons “fimbria.” The aim of this study is to localize the olfactory fimbria (OF) projection and distribution in the nasal cavity and to describe the vascular supply of the olfactory mucosa.

Methods: Twenty fresh cadaveric specimens injected with colored latex were used for dissection. Using high definition rigid endoscope of 0 to 45 degrees (Karl Storz, Tuttlingen, Germany) we dissected the nasal mucosa following all the nerves projections that reach the cribriform plate. We ruled out other kinds of innervation coming from V1 and V2. After localizing the fimbria distribution we described the density of OF in each zone and the path that the OF undertook before reaching the olfactory bulb.

Preliminary Results: The highest density of Fimbria was found on the mucosa covering the fovea and superior turbinate. The average quantity of fimbria found in the roof was 9.05 on the fovea versus the 4.9 on the septum.

We found an average of 1.33 crossing fimbria from one olfactory bulb to the contralateral nasal cavity. (27% of fimbria are found crossing the septum).

In 12 of 20 specimens, we found some fibers covering the lateral wall of the nose over the bulla ethmoidalis and posterior to it.

In 7 of 20 specimens, we found fimbria between the ostium sphenoidale and the choana.

In all the specimens, the areas comprising the highest density of fimbria were mostly supplied by the anterior and posterior ethmoidal arteries.

In 18 of 20 specimens, the major vascular supply was the anterior ethmoidal artery.

In all specimens, the mucosa of the lateral wall and the one between the choana and the ostium sphenoidale are supplied by the sphenopalatine arteries.

After entering the cribriform plate, the olfactory nerve trajectory is from medial to lateral starting at the level of the anterior ethmoidal artery in all specimens.

Conclusion: As mentioned before, anosmia has a great impact on the quality of life. Thus, a thorough understanding of the anatomy related to the olfactory mucosa, tract, and bulb, allow for preservation of olfaction.

During anterior cranial fossa surgery, coagulation of the ethmoidal arteries is performed to devascularize the tumors, however, this may lead to permanent anosmia.

The trajectory of the olfactory nerve should be considered while drilling the bone of the cribriform plate and the planum, to avoid its damage.