The Effect of the Nasal Structure on the Olfactory Cleft Airflow: A Systematic Review

Abstract

Objective

Conductive olfactory losses mainly involve obstruction of the olfactory cleft (OC) and diminished OC airflow. This study investigated the association between abnormal nasal structure and OC airflow.

Methods

A systematic search was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis to identify studies on the effect of the nasal structure on the OC airflow and olfaction.

Results

A total of 11 studies were included. Nasal vestibule morphological variabilities directly impact the transport of molecules in odorant-laden air to the OC. A greater airflow vortex and a narrower vestibule region intensified the airflow vortex toward the olfactory region. Middle turbinectomy significantly increased the average flux to the OC. The location of the major airflow and airflow velocity maxima shifted towards the OC in patients with septal deviation. The airflow has been redirected into the upper part of the nasal airway in patients with inferior turbinate hypertrophy. For patients with unilateral cleft lip, unilateral nasal airflow on the cleft side has a lower rate and flow. The mean velocity in the posterior OC correlated well with olfaction compared to that in the anterior OC. The nasal polyps (NP) within the middle meatus increased the olfactory airflow but did not enhance the olfaction. NP in the olfactory region or anterior to the olfactory region significantly decreased the olfactory airflow and olfaction. Furthermore, obstruction of the OC did not change the nasal patency. When the OC shape presented with a stenotic slit or lumen structure among patients with conductive olfactory dysfunction without NP, the inspiratory velocity and flow rate within OC were significantly lower than in the healthy control group.

Conclusion

Various nasal structural factors affect patterns of OC airflow and olfaction. Identifying the related airflow-limiting structures may promote the comprehensive evaluation of conductive olfactory losses in patients with olfactory dysfunction.

Keywords

conductive olfactory losses olfaction olfactory cleft olfactory airflow nasal structure obstructive factors nasal cavity.

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