This article discusses the authors’ approach to the assessment of the eustachian tube using opening pressure measurement, endoscopic assessment of the protympanic segment of the eustachian tube, and Valsalva computed tomography. A possible algorithm for the evaluation of eustachian tube obstructive disorders is detailed both preoperatively and intraoperatively.
Key points
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Mechanical obstruction of the eustachian tube is a common finding in chronic ear surgery and needs to be assessed preoperatively for the purpose of informed consent and for making a plan of action.
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Valsalva computed tomography of the temporal bone is helpful in assessing the patency of the distal end of the eustachian tube.
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Intraoperative inspection of the protympanic segment of the eustachian tube is possible and might lead to clear determination of the site of obstruction.
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Measurement of the opening pressure of the eustachian tube is a useful determinant of the presence of obstruction and the effect of possible interventions.
Video content accompanies this article at http://www.oto.theclinics.com .
Introduction
Surgery for chronic ear disease has always centered on disease removal and restoration of hearing without paying much attention to the underlying eustachian tube disorder. Because much of the eustachian tube is out of reach of traditional instruments, it is always assumed that time and age have resolved the disorder. Failures in surgery for chronic ear disease have been shown to correlate with persistent eustachian tube dysfunction. So far, there is no reliable, reproducible, and simple way of assessing the function of the eustachian tube. The anatomic patency of the tube can be assessed by testing for opening pressure and further localization of possible obstruction obtained by Valsalva computed tomography (CT) and endoscopic evaluation of protympanum. Endoscopic technique and its excellent access to the tympanic cavity allows the identification and assessment of other sites of segmental failure of ventilation within the temporal bone. This article discusses the authors’ algorithm for both preoperative and intraoperative evaluation of patency of the eustachian tube and assessment of any segmental ventilation failures in patients with chronic ear disorders.
Valsalva Computed Tomography
Many of the testing methods that have been devised for eustachian tube function are not anatomically based and are indirect methods that do not locate the site of obstruction. Indirect evidence of the tube status on CT is usually derived from the status and pneumatization of the middle ear cleft. There has been some success at MRI visualization of eustachian tube structure and related muscles, as well as the depiction of submucosal tumors, but the lumen and physical obstruction could not be visualized in the naturally collapsed tube.
In normal physiologic conditions, the eustachian tube opens as a result of a combination of direct muscle action and indirect action by increased nasopharyngeal pressure beyond the opening pressure of the tube. Improved CT technology with spiral CT has resulted in a very short imaging time that allows patients to maintain Valsalva maneuver throughout the examination. In addition, multiplanar reconstruction allows orientation of the plane in the desired way to match the sloping position of the eustachian tube. Valsalva CT of the temporal bone is performed while the patient is actively performing the Valsalva maneuver (concurrent with the examination). Upright positioning of the patient (as is possible in cone beam CT) enhances the patient’s ability to dilate the tube. Technologists are instructed to ask the patient to perform forceful exhalation against a closed nose. Primary image acquisition is made with the patient in the supine position using helical mode and a 0.6 mm (thickness) by 0.5 mm (increment) overlapping axial data set is usually obtained. Multiplanar reconstruction of the images in the axis of the eustachian tube is then performed. Different makers have proprietary software on the CT scanner workstation that use the following methodology: the rotation center (crosshair) is positioned at the fundus of the nasopharyngeal end of the eustachian tube on axial sections. Then, looking at the sagittal view, the axial plane is tilted anteroinferiorly until the whole length of the tube is visualized ( Fig. 1 ). Visualization of the whole length of the cartilaginous tube with Valsalva is usually observed in almost a third of the normal population. This phenomenon tends to be bilateral in patients who have it. In almost all patients, Valsalva maneuver increases the length of the visualized segment and extends it to include the distal one-third of the tube. Therefore, a collapsed distal tube despite adequate performance of Valsalva maneuver during CT indicates distal eustachian tube obstruction. In clinical practice, this is consistently observed in association with enlarged adenoids filling the fossa of Rosenmüller and collapsing the torus tubarius anteriorly ( Fig. 2 ). This finding represents an unusual cause of eustachian tube obstruction in patients with chronic otitis media.
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Valsalva CT distends and visualizes the full length of the eustachian tube in one-third of the normal population; it is usually bilateral in patients who have it. The distal one-third of the tube is open on Valsalva CT in most normal patients.
Case discussion
This adult male patient presented to our clinic for left-sided middle ear effusion and retraction with a previous history of left ear blockage throughout his life and no nasal symptoms. His Valsalva CT confirmed the collapse of the distal eustachian tube secondary to enlarged adenoids that obliterated the fossa of Rosenmüller on the left side (see Fig. 2 ). Placement of tympanostomy tubes in the left ear was done in the clinic and middle ear effusion was evacuated. Using an endotracheal tube pressure pump, the pressure in the ear canal and the middle ear (through the tympanostomy tube) were increased to 50 cm H 2 O while performing CT scan. Fig. 3 shows the tube and the pressure pump in the axial plane. Fig. 4 shows an anteroinferiorly angled view matching the position of the eustachian tube. Visualization of the protympanic segment of the eustachian tube and the isthmus area with air was obtained, showing patency of the proximal eustachian tube. The patient underwent microscopic adenoidectomy and decompression of the fossa of Rosenmüller, as seen in [CR] . Follow-up after 1 year shows the extrusion of tympanostomy tube, the healing of the tympanic membrane and the resolution of middle ear effusion.
Introduction
Surgery for chronic ear disease has always centered on disease removal and restoration of hearing without paying much attention to the underlying eustachian tube disorder. Because much of the eustachian tube is out of reach of traditional instruments, it is always assumed that time and age have resolved the disorder. Failures in surgery for chronic ear disease have been shown to correlate with persistent eustachian tube dysfunction. So far, there is no reliable, reproducible, and simple way of assessing the function of the eustachian tube. The anatomic patency of the tube can be assessed by testing for opening pressure and further localization of possible obstruction obtained by Valsalva computed tomography (CT) and endoscopic evaluation of protympanum. Endoscopic technique and its excellent access to the tympanic cavity allows the identification and assessment of other sites of segmental failure of ventilation within the temporal bone. This article discusses the authors’ algorithm for both preoperative and intraoperative evaluation of patency of the eustachian tube and assessment of any segmental ventilation failures in patients with chronic ear disorders.
Valsalva Computed Tomography
Many of the testing methods that have been devised for eustachian tube function are not anatomically based and are indirect methods that do not locate the site of obstruction. Indirect evidence of the tube status on CT is usually derived from the status and pneumatization of the middle ear cleft. There has been some success at MRI visualization of eustachian tube structure and related muscles, as well as the depiction of submucosal tumors, but the lumen and physical obstruction could not be visualized in the naturally collapsed tube.
In normal physiologic conditions, the eustachian tube opens as a result of a combination of direct muscle action and indirect action by increased nasopharyngeal pressure beyond the opening pressure of the tube. Improved CT technology with spiral CT has resulted in a very short imaging time that allows patients to maintain Valsalva maneuver throughout the examination. In addition, multiplanar reconstruction allows orientation of the plane in the desired way to match the sloping position of the eustachian tube. Valsalva CT of the temporal bone is performed while the patient is actively performing the Valsalva maneuver (concurrent with the examination). Upright positioning of the patient (as is possible in cone beam CT) enhances the patient’s ability to dilate the tube. Technologists are instructed to ask the patient to perform forceful exhalation against a closed nose. Primary image acquisition is made with the patient in the supine position using helical mode and a 0.6 mm (thickness) by 0.5 mm (increment) overlapping axial data set is usually obtained. Multiplanar reconstruction of the images in the axis of the eustachian tube is then performed. Different makers have proprietary software on the CT scanner workstation that use the following methodology: the rotation center (crosshair) is positioned at the fundus of the nasopharyngeal end of the eustachian tube on axial sections. Then, looking at the sagittal view, the axial plane is tilted anteroinferiorly until the whole length of the tube is visualized ( Fig. 1 ). Visualization of the whole length of the cartilaginous tube with Valsalva is usually observed in almost a third of the normal population. This phenomenon tends to be bilateral in patients who have it. In almost all patients, Valsalva maneuver increases the length of the visualized segment and extends it to include the distal one-third of the tube. Therefore, a collapsed distal tube despite adequate performance of Valsalva maneuver during CT indicates distal eustachian tube obstruction. In clinical practice, this is consistently observed in association with enlarged adenoids filling the fossa of Rosenmüller and collapsing the torus tubarius anteriorly ( Fig. 2 ). This finding represents an unusual cause of eustachian tube obstruction in patients with chronic otitis media.
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Valsalva CT distends and visualizes the full length of the eustachian tube in one-third of the normal population; it is usually bilateral in patients who have it. The distal one-third of the tube is open on Valsalva CT in most normal patients.
