Reversible obstruction of the olfactory cleft: impact on olfactory perception and nasal patency

Abstract

Background: Temporary disruption of sensory input can be studied relatively easily for vision or hearing by covering the eyes or ears. In contrast, closing the nostrils affects not only the sense of smell, but also the ability to breathe through the nose and humidify and warm inhaled air. We hypothesized that filling the olfactory cle (OC) with dissolvable nasal dressing (foam) would temporarily block olfaction while respecting nasal airflow. Methods:In 30 healthy volunteers, the OC was unilaterally obstructed in a back-to-front fashion. Orthonasal and retronasal olfactory function were tested before and after foam application. Ratings of odors and subjective nasal patency (SNP) were collected. Peak nasal inspiratory flow (PNIF) was used to measure nasal patency. Results:Foam was safely applied in every case using minimal instruments. No complications were reported. Orthonasal and retronasal test results decreased significantly in overall participants (all p < 0.0008). Indicating temporary anosmia, 3 subjects reached the lowest possible score for odor-threshold testing, with corresponding drops in retronasal test scores. PNIF values before and a er foam application were not significantly different (p = 0.11). SNP ratings decreased slightly, but not significantly (p = 0.052). Odor-intensity ratings dropped significantly (all p < 0.05). Conclusion:The OC can be safely obstructed with dissolvable nasal dressing, resulting in a decrease in odorintensity and orthonasal and retronasal olfactory function test scores. This procedure may serve as a hyposmia model that maintains normal nasal airflow.

Olfaction: Sensitive indicator of inflammatory burden in chronic rhinosinusitis

“…Recently, Besser et al effectively established a hyposmia model obstructed the OC with dissolvable nasal dressing. 44 In keeping with this, nasal polyps can affect orthonasal olfactory function more strongly than retronasal olfactory function, emphasizing conductive mechanisms in smell dysfunction. 64 While there is no doubt that nasal patency is essential for olfactory perception, observations in patients with CRS show that smell loss is possible even when the OC is nonobstructed and no changes in nasal airflow are present.…”

“…43 Completely obstructing the olfactory cleft (OC) can significantly decrease orthonasal and retronasal olfactory function. 44 However, retronasal olfaction is more often preserved to a higher degree in CRSwP compared to orthonasal olfaction, supporting the idea that polyps mechanically change airflow to the OC. 45 A significant correlation was reported between retronasal olfaction and olfactory-specific QOL which was not found to the same degree for orthonasal function.…”

“…Retronasal and orthonasal odor identification are correlated in CRS patients 43 . Completely obstructing the olfactory cleft (OC) can significantly decrease orthonasal and retronasal olfactory function 44 . However, retronasal olfaction is more often preserved to a higher degree in CRSwP compared to orthonasal olfaction, supporting the idea that polyps mechanically change airflow to the OC 45 .…”

“…It has traditionally been assumed to be of a conductive origin, with the OC being mechanically obstructed by polyps/edematous mucosal tissue, leading to impaired airflow, and reduced odorant access to the olfactory epithelium. Recently, Besser et al effectively established a hyposmia model obstructed the OC with dissolvable nasal dressing 44 . In keeping with this, nasal polyps can affect orthonasal olfactory function more strongly than retronasal olfactory function, emphasizing conductive mechanisms in smell dysfunction 64 .…”

Olfactory Dysfunction in the COVID-19 Outbreak

“…Two possibilities seem likely: during an upper respiratory infection, it is common to experience some smell loss as a result of nasal inflammation, mucosal edema, and obstruction of airflow into the olfactory cleft, or a postviral anosmia syndrome with direct infection and inflammation of the olfactory mucosa and neurodegeneration of the olfactory sensory neurons. Damage to the peripheral nervous system and its dysfunction, with anosmia or hyposmia, could be a relevant indicator of disease progression [66,67].…”