Endoscopic Study of the Distribution of Olfactory Filaments: A Cadaveric Study.

OBJECTIVE: Provide a detailed anatomical description of the olfactory filaments (OF) and their distribution in the nasal cavity through endoscopic endonasal dissection. METHODS: Four cadaveric specimens (8 sides) were used in this study. Nasoseptal (NSM), middle (MTM) and superior turbinate (STM) mucosa dissection was performed to identify the OF and follow them superiorly to the cribriform plate (CP). Measurements of the OF were taken on the NSM, MTM, STM under direct endoscopic visualization. A Student's T-Test was performed to compare means. RESULTS: The NSM contained a mean of 11 OF, distributed over surface area (SA) of 173 ± 31 mm2 with the highest density of OF being found at the posterior NSM. The MTM contained a mean 6 OF, covering a mean SA of 77 mm2, with the first OF found 5 mm from the anterior border of the MTM, on average. The STM had a mean 9 OF, with the OF covering a mean SA of 96 mm2. Overall mean OF length was 6 mm. The STM OF were significantly greater in number, with a greater distance from the first OF to last OF (p < 0.05) than the MTM OF. SUMMARY: The STM and MTM combined were found to have a greater density of OF than the NSM. The STM contains a significantly greater number of OF covering a greater area than the MTM OF. Preservation of the STM and MTM in skull base defect repair, and in routine sinus surgery, can be as beneficial for olfactory function as preservation of the NSM; particularly in CP defect repair. Moreover, our findings indicate that nasoseptal flap harvest performed at least 6 mm from the skull base preserves OF in the NSM. To our knowledge, this is the first anatomical study of the OF through direct endoscopic observation and measurements.