ACOUSTIC RHINOMETRY - INFLUENCE OF PARANASAL SINUSES

The influence of the maxillary sinuses in acoustic rhinometry (AR) has not been evaluated, and this is the aim of the present study. We exam ined six subjects with AR and magnetic resonance imaging (MRI) after n asal decongestion to compare the area-distance relationships determine d by the two methods. From the MRI data we obtained copies of the nasa l cavities with and without maxillary sinuses, which were made in plas tic by a stereolithographic method. AR curves from models without maxi llary sinuses differed from AR curves with sinuses included but were i n agreement with MRI curves without inclusion of sinuses. A similar di fference in AR was seen in two subjects before and after the nasal cav ities were flushed with saline to fill up the maxillary sinuses. The m easured volume in the first 50 mm of the nasal cavity models was unaff ected by the sinuses, but the volume in the first 70 mm corresponding to the length of the nasal cavity septum was increased slightly but si gnificantly (from 10.8 to 11.3 cm(3); P = 0.05). The presence of maxil lary sinuses increased the volume of the epipharynx (70-100 mm from th e nostril) from 12.2 to 21.3 cm(3) (P < 0.01), and this increase was n ot due to the influence from the contralateral nasal cavity. We conclu de that the maxillary sinuses may significantly contribute to the acou stically determined areas in the posterior part of the nasal cavity an d the epipharynx, especially during decongestion, and may explain a pa rt of the difference between area-distance curves obtained by AR and M RI, whereas contribution from the contralateral nasal cavity does not.