Endoscopic technique allows visualization of the protympanic segment of the eustachian tube in patients undergoing chronic ear surgery. Balloon dilatation of the area can be undertaken with clear widening of the obstructed areas. This article discusses the authors’ approach and experience with transtympanic dilatation of the eustachian tube. It includes case selection, technique, immediate postprocedure evaluation, and results, with multiple case presentations and videos.
Key points
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The proximal cartilaginous eustachian tube is the most common site of anatomic obstruction in chronic otitis media.
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Access to that area is provided for inspection and intervention through the transtympanic route using a 30° angled endoscope.
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The carotid canal can be identified endoscopically and the anatomy of the protympanum is variable.
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The protympanum is the only area of the eustachian tube with close proximity to the carotid, and safe endoscopic access to the proximal cartilaginous tube is possible beyond this dangerous segment.
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Dilatation of the proximal segment of the eustachian tube is safely undertaken through the transtympanic route during chronic ear surgery after visualization of the carotid canal.
Video content accompanies this article at http://www.oto.theclinics.com .
Introduction
Balloon dilatation of the eustachian tube has been reported with a significant degree of success and patient safety. Instrumentation of the eustachian tube is performed by introducing the balloon catheter through the nasopharyngeal opening of the tube and subsequently dilating the cartilaginous segment of the tube. Safety consideration with regard to avoiding possible injury to the carotid artery has limited the area of instrumentation to the distal end of the tube, which is probably the least likely obstructed segment. Other sites of obstruction in the proximal area of the eustachian tube have been reported in patients undergoing chronic ear surgery. Endoscopic ear surgery allows access to and visualization of the protympanic segment of the eustachian tube, including the carotid canal. Transtympanic introduction of the balloon catheter beyond the carotid canal into the cartilaginous eustachian tube ensures the safety of the dilatation along with the dilatation coverage of a wider segment of the cartilaginous tube.
Technique
All patients undergoing surgery for chronic otitis media (perforations/cholesteatoma/retraction/drainage) should be assessed for the source of ventilation failure as per the previous article. Intraoperatively, a measurement of the opening pressure of the eustachian tube is performed up to 50 cm of water using the setup in Fig. 1 . If the air pressure is not released through the eustachian tube at 50 cm of water, then endoscopic evaluation of the protympanic segment of the eustachian tube is performed using a 30°, 3-mm, 15-cm rigid endoscope that is introduced anterior to the handle of malleus after detaching the tympanic membrane remnant from the handle of the malleus.
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Evidence of obstruction in the proximal cartilaginous tube is required before proceeding with transtympanic dilatation. It is usually a combination of Valsalva computed tomography (CT) showing open distal tube and inability to open up the tube at 50 cm of water or direct endoscopic evidence of blockage.
The protympanic segment is then assessed for clear impression of the carotid artery canal, presence of blind pouches, and for evidence of obstruction beyond that ( Fig. 2 ). An eustachian tube balloon dilatation catheter (Spiggle & Theis, Germany) is used. The catheter is usually shipped with a metal stylet that runs within the catheter. A 30° deflection is bent at the distal 1 cm of the stylet. The proximal end of the stylet is looped to allow for rotating and orienting the deflection at the distal end toward the opening of the eustachian tube ( Fig. 3 ). The stylet functions like a guidewire and the catheter is fed into the eustachian tube over the stylet until it is well within the distal tube. The stylet is then removed. Then the balloon is inflated by infusing saline to 10 cmH 2 O as indicated by the inflating device. At this point, the catheter should be easily moving within the eustachian tube because the distal end of the tube is much larger than the inflated balloon catheter. Then, with the balloon inflated, the catheter is pulled out until it is lodged at the isthmus, which is much smaller than the inflated balloon catheter and does not allow it to be pulled out. Then the balloon is deflated and pulled by 0.5 cm and inflation is performed again. Given the V shape of the tube, the surgeon experiences catheter pull-in to the nasopharynx as it is inflated. This pull-in confirms to the surgeon that it is located within the eustachian tube ( Fig. 4 ).
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The presence of catheter pull is a clear evidence of cannulating the eustachian tube. It happens because of the V-like shape of the tube with the distal segment being much larger than the proximal part. It also confirms that the distal segment is not involved in the obstruction.
The catheter is then pulled out until the balloon area is barely visualized using the 30° scope. Another approach is to pull the tube in small increments and attempt inflation of balloon, checking for the point where the balloon is lodged and stable within the isthmus without the need to hold on to keep it from advancing as it is being inflated ( Fig. 5 ).
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The lodging of the tube and the lack of catheter pull as the catheter is pulled out confirms that the balloon is engaging the isthmus of the eustachian tube.
The pressure is maintained at 10 bar for 2 minutes and then deflated and pulled out. Reinspection of the area with a 3-mm 30° endoscope is performed to assess for change of aperture of the eustachian tube in that area ( Fig. 6 ). Then the opening pressure is tested again to verify its decrease beyond 50 cm of water. [CR] shows the procedure.
Case study
This involves a woman who presented with chronically discharging ear. Multiple attempts at local treatments with combinations of steroid and antibiotic ear drops were made without any response ( [CR] ). Valsalva CT was performed and showed visualization of the whole length of the eustachian tube on the right and patent distal eustachian tube on the left with obstruction of the proximal cartilaginous segment ( Figs. 7 and 8 ). The patient had exploration of the ear, which showed intact ossicular chain, no cholesteatoma, granulation tissue posteriorly and anteriorly, and thick mucus. Transtympanic balloon dilatation was performed with simple tympanoplasty. Postoperatively the patient did well and the eardrum healed with no discharge and normal hearing. Valsalva CT was performed 3 months postprocedure and showed visualization of the whole length of the eustachian tube on the left side ( Figs. 9 and 10 ).
Anatomic Considerations: Relationship of the Carotid to the Eustachian Tube
Given the limited microscopic access to the protympanum, it has been the common wisdom in the otology community to avoid any interventions involving the proximal eustachian tube. Further confirmation of that close relationship is found on the axial plane CT images, in which the carotid is very prominent and appears in close proximity to the whole length of the eustachian tube ( Fig. 11 ). However, all of the cartilaginous tube is well away from the carotid artery because it turns downward toward the nasopharynx (see Fig. 9 ). Fig. 12 shows a parasagittal multiplanar reconstruction of the CT taken in the plane of the eustachian tube defining the downward slope of the cartilaginous tube. Fig. 13 is the same image as Fig. 12 but with an overlay of the carotid artery course obtained from a parallel section just medial to Fig. 12 . It confirms that the carotid artery takes a different direction and intersects with only a limited segment of the medial aspect of the protympanic bony segment of the tube. If the protympanic segment is visualized endoscopically and instrumentation is directed anterior to it, carotid artery safety should be ensured.
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Contrary to common perception, the carotid only engages the eustachian tube in a limited segment of the posterior protympanum. The whole cartilaginous tube slopes downward away from the carotid anatomically.
Anatomic Considerations: Anatomy of Protympanum
The lack of access to the protympanum has resulted in a distorted view of the anatomy of the eustachian tube. For endoscopic observers of that area, the idea of a bony eustachian tube seems to be counterintuitive. The existing definition of the bony eustachian tube is based on lack of access when using the microscope. Once visualized with the 30° scope, that part of the anatomy ceases to be an eustachian tube and becomes just an anterior extension of the mesotympanum, or the anterior part of the protympanum. The proximal cartilaginous tube opens up into that bony extension of the mesotympanum in a similar way that the distal end opens up into the nasopharynx: with a cufflike protrusion of the tube with an opening in the middle of that cuff ( Fig. 14 ).
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The common orthodoxy of a bony and cartilaginous tube does not stand up to endoscopic inspection. The bony tube is part of the protympanum and the cartilaginous part is the whole eustachian tube.
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