Changes of visualised Eustachian tube lengths by age and position: Radiologic study in sitting and supine positions using cone beam and conventional CT

Abstract

ObjectivesPatulous eustachian tube (ET) has been characterised by the visualisation of full‐length ET on computed tomography (CT) results. We wanted to investigate the changes of visualised ET lengths by age in supine and sitting positions.DesignRetrospective study.SettingTertiary care academic referral centre.ParticipantsOne hundred subjects who underwent cone beam CT (CBCT) in a sitting position and conventional CT in a supine position for non‐otitis‐related or dental complaints.Main outcome measuresVisualised ET lengths from the nasopharyngeal orifice measured by different positions and ages.ResultsSubjects did not show visualisation of full‐length ET throughout the study. The visualised ET lengths (9.0 ± 2.5 mm) of the CBCT group were significantly larger than those (6.8 ± 2.3 mm) of the conventional CT group (P < 0.0001).Women showed longer visualised ET lengths than men in CBCT group (P < 0.001). The visualised ET lengths of the CBCT group were consistent or slightly increasing as a function of age (P = 0.06); however, the visualised ET lengths of the conventional CT group decreased as a function of age (P = 0.001). The slopes of regression lines of the two groups were significantly different.ConclusionsWhen in the supine position, the ET lengths gradually shortened as the subjects got older, most likely due to venous engorgement and the collapse of surrounding tissues; this finding thus suggests that CT in a supine position is an inappropriate method to diagnose patulous ET. The visualised ET lengths by CBCT in a sitting position were consistent throughout the different ages of the subjects and may be used as a diagnostic test for patulous ET.

A new “practical" plane for Eustachian tube measurements and its application in predicting middle ear dysfunction in patient with acquired cholesteatomas

“…The ET lumen path length can be measured from cadaveric specimens, which were finely sectioned and 3D reconstructed to account for the curvature of the ET at the bony cartilaginous junction [ 6 ]. The measurement of ET lumen path length is not possible on CT scans unless under special circumstance such in patients with patulous ET [ 11 ], or with invasive injection of contrast media into the middle ear cleft [ 10 ].…”

“…The increased availability of high-resolution temporal bone computed tomography (CT) and the use of cone-beam CT, combined with the advent of multiplanar reconstruction (MPR) has made it possible for ETs to be measured on imaging studies [ 1 – 3 , 10 , 11 ]. A review of the literature revealed a range of methods in measuring ET angle and lengths, as summarised in Table 1 .…”

“…Dinç et al [ 3 ] used the Frankfort plane as a reference point, which was defined as the left infraorbital margin and the upper margins of the external auditory canals. Other authors only measured the length of the ET and did not measure the ET angle [ 1 , 11 ].…”