Inﬂuence of the location of nasal polyps on olfactory airﬂow and olfaction
Hironobu Nishijima, MD, PhD
, Kenji Kondo, MD, PhD
, Takahisa Yamamoto, PhD
, Tsutomu Nomura, MD,
, Shu Kikuta, MD, PhD
, Yuya Shimizu, MD
and Tatsuya Yamasoba, MD, PhD
Background: Chronic rhinosinusitis with nasal polyps (CR-
SwNP) oen results in decreased olfaction. In this study,
we examined the relationship between nasal polyp location
and olfactory airﬂow and odorant transport changes using
virtual nasal polyp models at diﬀerent locations and compu-
tational ﬂuid dynamics (CFD) analysis. We also compared
olfactory airﬂow and olfaction between patients with nasal
polyps at diﬀerent locations using CFD analysis and an
Methods: Nasal computed tomography images were used
to generate a normal model and 4 virtual nasal polyp mod-
els based on polyp locations, including the olfactory re-
gion (all-olfactory model), the region anterior to the ol-
factory region (preolfactory model), the middle meatus
(middle-meatus model), and the superior meatus (superior-
meatus model). Various airﬂow parameters were compared
between these models and a normal model without polyps.
We then performed a similar comparison between the
3-dimensional (3D) reconstruction models of patients with
nasal polyps, and retrospectively investigated the correla-
tion between olfaction and nasal polyp location in those
Results: Virtual nasal polyp analysis revealed dispersion
of olfactory airﬂow in the all-olfactory model. Olfactory
airﬂow and odorant transport showed maximum decrease
in the preolfactory model and a slight decrease in the
superior-meatus model. Olfactory airﬂow by polyps was
further decreased by blockade of the olfactory airﬂow inlet
than of the outlet. The ﬁndings obtained by patients corre-
sponded well to those of the virtual polyp analysis.
Conclusion: Olfactory airﬂow and olfaction are diﬀeren-
tially aﬀected by nasal polyp location. This ﬁnding is im-
portant for planning polyp-removal surgeries from the per-
spective of improving patient olfaction.
Endoscopic sinus surgery; chronic rhinosinusitis with nasal
polyps; orthonasal airﬂow; retronasal airﬂow; olfaction;
How to Cite this Article:
Nishijima H, Kondo K, Yamamoto T, et al. Inﬂuence of the
location of nasal polyps on olfactory airﬂow and olfaction.
Int Forum Allergy Rhinol. 2018;8:695–706.
Department of Otolaryngology, The University of Tokyo, Tokyo,
Department of Mechanical Engineering, National Institute of
Technology, Gifu College, Gifu, Japan;
Otolaryngology, Saitama Medical Center, Saitama Medical University,
Correspondence to: Hironobu Nishijima, MD, PhD, Department of
Otolaryngology, The University of Tokyo, Tokyo, Japan; 7-3-1 Hongo
Bunkyo-ku, Tokyo 113–8655, Japan; e-mail: firstname.lastname@example.org
Additional Supporting Information may be found in the online version of this
Funding sources for the study: JFE (The Japanese Foundation for Research
and Promotion of Endoscopy) Grant and Grants-in-Aid for Scientiﬁc
Research from the Japanese Ministry of Health, Labour and Welfare (H26-,
H27-Research on measures for intractable disease-general-004).
Potential conﬂict of interest: None provided.
Received: 20 July 2017; Revised: 12 December 2017; Accepted:
4 January 2018
View this article online at wileyonlinelibrary.com.
hronic rhinosinusitis with nasal polyps (CRSwNP) of-
ten results in decreased olfaction. Up to 80% patients
with CRSwNP experience conductive and/or sensorineu-
ral olfactory loss.
The former occurs because of airﬂow
blockage by nasal polyps, while the latter occurs because
of inﬂammation of the nasal mucosa. There are 2 types
of olfactory airﬂow: orthonasal and retronasal. Orthonasal
airﬂow is deﬁned as airﬂow entering the nasal cavity during
inspiration. Orthonasal airﬂow is related to orthonasal ol-
faction, which is the sense of smell that is acquired through
the anterior nare. Retronasal airﬂow is deﬁned as airﬂow
circulating up to the nasal cavity during expiration. It is
related to retronasal olfaction, which is important for ap-
preciating food ﬂavors.
Nasal polyps occurring at various locations in the nasal
cavity may differentially impair olfactory airﬂow. For ex-
ample, a previous study reported that better retronasal
695 International Forum of Allergy & Rhinology, Vol. 8, No. 6, June 2018