Abstract
Background
Not many imaging techniques have been reported in Eustachian tube imaging.
Purpose
To investigate the role of selective Eustachian tubography (SET) and Valsalva computed tomography (CT) in patients who underwent Eustachian tube balloon dilation (ETBD).
Material and Methods
Eligible patients were aged 18 years and older with chronic Eustachian tube dysfunction who had failed medical treatment. On the day of the procedure, Valsalva CT and SET were performed. Participants underwent fluoroscopic ETBD with a 6×20-mm balloon catheter. Clinical examinations to check for the ability to perform the Valsalva maneuver and ETDQ-7 score change were conducted at one week and then at one, two, and six months. Follow-up Valsalva CT was performed in the one-month follow-up.
Results
A total of 30 ears in 23 patients (16 right ears, 14 left ears; 10 women, 13 men) underwent ETBD from August 2018 to November 2019. Positive CT patency was higher in follow-up Valsalva CT than baseline Valsalva CT (40% and 23.3%, respectively) (P = 0.006). In SET, positive patency was observed in 13 of 25 ears. Response to balloon dilation was observed in 18 of 25 patients. Clinical success was achieved in 16 of 27 ears. Response to balloon dilation was the only significant predictor of clinical success (P = 0.012).
Conclusion
SET depicted the lumen of the Eustachian tube; thereby, it could be a potentially valuable tool in ETBD. Valsalva CT provides additional information about the cartilaginous portion of the Eustachian tube.
Introduction
The Eustachian tube (ET) connects the middle ear cavity with the nasopharynx. It ventilates the middle ear cavity and clears fluid from the middle ear. ET dysfunction (ETD) may occur when the mucosal lining of the ET is swollen or does not open or close properly. Persistent dysfunction of the ET results in chronic ETD causing chronic otitis media, long-term inner-ear pain, and hearing difficulty (1). If chronic ETD does not respond to medical treatment, ventilation of the middle ear cavity is needed to prevent permanent damage to middle ear organs. Tympanostomy with a ventilation tube or balloon dilatation of the ET are methods of middle ear ventilation (2).
Endoscopic Eustachian tube balloon dilation (ETBD) has been reported as a promising treatment for chronic ETD. The safety and efficacy of endoscopic ETBD have been proven in a number of studies since its first report in 2010 (3–8). However, visualization of the whole ET lumen is not possible during endoscopic ETBD. Thus, only subjective symptomatic changes and non-imaging functional tests, such as tympanometry, have been used to evaluate procedural outcomes. Moreover, it is hard to obtain pathologic specimens in the ET. Due to the absence of imaging and pathologic outcomes, structural change to the ET after balloon dilation has not been described in previous studies.
Not many imaging techniques have been reported in ET imaging. Recently, selective Eustachian tubography (SET) has been reported (9). SET is possible during ETBD if the procedure is performed under fluoroscopy guidance. Valsalva computed tomography (CT) is another novel technique that could visualize the ET lumen (10). In Valsalva CT, a CT image is obtained just after applying the Valsalva maneuver, using air as a negative contrast media. To our knowledge, these imaging techniques have not been used for assessing the ET lumen in patients who underwent ETBD. Therefore, the aim of the present study was to investigate the role of SET and Valsalva CT in patients who underwent ETBD.
Material and Methods
Patients
This single-center prospective study was approved by our institutional review board. During the period from August 2018 to November 2019, patients were prospectively enrolled from the otolaryngology practice at our tertiary referral center. All patients provided written informed consent before enrollment. Eligible patients were aged 18 years and older with chronic ETD who had failed medical treatment within three months. Chronic ETD was defined by patient-reported symptoms with at least one of two findings on an otoscope: tympanic membrane retraction or middle ear effusion. The diagnosis was confirmed with abnormal tympanometry, otomicroscopy, and symptomatic dysfunction, as documented by the Eustachian Tube Dysfunction Questionnaire-7 (ETDQ-7).
Valsalva CT
Pre-procedural temporal bone CT scans were obtained on the day of balloon dilation to rule out anatomical anomalies of the ET or cranial base. CT was performed while the patient performed the Valsalva maneuver (Valsalva CT). Patients were asked to close their mouth and nose, then perform forceful exhalation against a closed airway. If the patient noticed a popping sound in the ear, it was regarded as a successful Valsalva maneuver. Individual patient instructions were given by the technician just before the CT examination. Primary image acquisition was obtained in the supine position in the helical mode. An overlapping, 0.4 mm (thickness) × 0.5 mm (increment) axial dataset was obtained. Multiplanar reconstruction of the images in the axis of the cartilaginous portion of the ET was performed as described elsewhere (10). Briefly, the axial plane was tilted anteroinferiorly until the whole length of the ET was visualized (Fig. 1a). For the cartilaginous portion of the ET, the anterior limit was considered to be the lateral lip of the nasopharyngeal orifice, and the posterior limit was considered to be the starting point of the bony portion. The distance between the lateral lip of the nasopharyngeal orifice and most proximal point of the dilated tube was considered to be a visualized segment, and the distance between the most proximal point of the dilated tube and the starting point of the bony portion was considered to be a non-visualized segment (Fig. 1b). The visualized segment ratio (VSR) for the ET was calculated as follows: visualized segment/(visualized segment + non-visualized segment). For the bony portion of the ET, luminal diameters were measured in the middle of the bony portion (Fig. 1c). The presence of a bony spur protruded to the cartilaginous portion (Fig. 1d), and the presence of air inside the bony portion was evaluated.
Valsalva CT. (a) Screenshot of the CT workstation. Multiplanar reconstruction of temporal bone CT. The rotation center was positioned at the fundus of the nasopharyngeal orifice of the ET on the axial plane. The axial plane was tilted anteroinferiorly on the sagittal plane until the whole length of the cartilaginous portion and bony portion were visualized. (b) Visualized segment (asterisks) and non-visualized segment (arrowheads). (c) Measurement of bony portion diameter. (d) Bony spur formation toward the cartilaginous portion at the orifice of the bony portion. CT, computed tomography.
Fluoroscopy
All procedures were performed on an outpatient basis. Topical anesthesia of the nasal mucosa around the ET orifice by the injection of 4% lidocaine, 1:1000 epinephrine was performed under endoscopic guidance. Each patient was placed on the fluoroscopy table in the supine position with shoulders and trunk elevated and with the head and neck extension. The X-ray tube was caudally tilted according to the extension angle to gain a skull submentovertical view (11).
Pre-balloon dilation SET
SET was performed by manually injecting approximately 2 mL of non-diluted iodinated contrast media (Visipaque 270; GE Healthcare, Cork, Ireland) into the ET. Reference images of pre-balloon dilation (pre-BD) SET were obtained using a digital subtraction technique. Using contrast media in the passage to the middle ear cavity, any blunt lesion inside the ET was evaluated in pre-BD SET (Fig. 2a and b) .
Findings of selective Eustachian tubography. (a) Contrast media passage through slit-like ET (arrow) to the middle ear cavity (asterisk) is observed. (b) Blunt lesion in the ET is shown (arrow). No contrast media passage was observed in the middle ear cavity. (c) Post-balloon dilation image of the same patient. The ET has a response to the balloon dilation. The diameter of the slit-like ET has increased (arrow). ET, Eustachian tube.
Balloon dilation
A metallic guiding sheath and 6×20-mm balloon catheter (Genoss, Suwon, Republic of Korea) were used in this study. The sheath had an inner diameter of 2.5 mm, outer diameter of 3.45 mm, and length of 190 mm. The distal tip of the sheath was curved in a J-shape to access the nasopharyngeal orifice of the ET. Under endoscopic guidance, the guiding sheath was introduced through the nose, and the tip of the sheath was rotated toward the orifice of the ET. The balloon catheter was then passed through the sheath to locate its tip at the orifice of the ET. A 0.035-inch flexible guidewire (RadiofocusM; Terumo, Tokyo, Japan) was inserted through the balloon catheter, then manipulated to negotiate it into the ET under fluoroscopic guidance. After confirming the guidewire had successfully passed through the cartilaginous portion and bony portion of the ET, the balloon catheter was slightly advanced along the guidewire to locate its tip in approximately 0.5–1 cm inside the cartilaginous portion. After pre-BD SET, the guidewire was passed through the cartilaginous portion again. The balloon catheter was then advanced under fluoroscopy guidance through the cartilaginous portion of the ET until its tip reached the isthmus of the ET. Typically, the operator could feel resistance when the tip of the balloon catheter reached the isthmus. The balloon was inflated up to 12 atm for 2 min. After deflation of the balloon catheter, it was retracted until its tip was located at the orifice of the ET.
Post-balloon dilation SET
The guidewire was removed, and post-balloon dilation (post-BD) SET was obtained. The response to the balloon dilation was evaluated by comparing the pre-BD and post-BD diameters of the ET (Fig. 2c). After the balloon catheter and sheath were removed together, the ET orifice was examined by endoscopy to assess complications.
Follow-up
The patients were asked to record a 10-point visual analog scale (VAS) score of pain immediately after the procedure. Clinical examinations were performed one week, one month, two months, and six months after the procedure. Valsalva CT was performed at the one-month follow-up. Changes in symptoms were documented by the ETDQ-7 score on each visit. The ability to perform a Valsalva maneuver was assessed on each visit. Otomicroscopic inspection of a tympanic membrane was performed during the Valsalva maneuver.
Definitions and statistical analysis
The outcomes were assessed with reference to the following variables: technical success; clinical success; complications; ETDQ-7 score; and ability to perform the Valsalva maneuver. Technical success was defined as successful balloon dilation through the ET. Clinical success was defined as normalization of the ability to perform the Valsalva maneuver with an improvement of ETDQ-7 score by at least 1 point at the one-month follow-up. Major complications were defined according to the Society of Interventional Radiology clinical practice guidelines (12).
If the VSR was ≥0.5, it was defined as a positive CT patency. If the bony portion diameter was ≥2.5 mm, it was defined as an enlarged bony portion, and if the diameter was <1 mm, it was defined as a narrow bony portion. If the flow of contrast media through the ET and/or contrast media pooling in the middle ear cavity was observed in digital subtraction images, it was defined as a positive ET patency.
Statistical analysis was performed using MedCalc Version 19.7 (MedCalc Software, Ostend, Belgium). Numerical variables were expressed as mean ± SD. Pre- and post-procedural ETDQ-7 scores were compared using the paired t-test. Pearson's chi-square or Fisher's exact test was used to compare proportions of categorical variables. All P values were two-sided with a statistical significance evaluated at the 0.05 alpha level.
Results
Enrolled patient data
A total of 30 Eustachian tubes (16 right and 14 left; 7 bilateral) from 23 patients (10 women, 13 men; mean age = 48 years; age range = 18–73 years) were enrolled in this study. The mean duration of ETD was 11.7 ± 10.9 years (range = 1–39 years). The mean number of previous tympanostomies was 3 (range = 0–10). The mean ETDQ-7 score was 18.7 ± 7.1 (range = 8–44).
Valsalva CT
Valsalva CT was successfully performed in all patients. For the cartilaginous portion, the mean baseline VSR was 0.42 ± 0.28 in 30 Eustachian tubes. Positive CT patency was observed in 7 of 30 Eustachian tubes. Among them, the VSR was 1.00 in five Eustachian tubes, which means the whole ET was the visualized segment (Fig. 3). For the bony portion, an enlarged bony portion was observed in one, a narrow bony portion in two, a bony spur in 10, and air in the bony portion in 20 Eustachian tubes. Valsalva CT findings are summarized in Table 1. There was no statistical significance in mean VSR between baseline and one-month follow-up (P = 0.357). However, the rate of positive CT patency was higher at the one-month follow-up Valsalva CT compared with the baseline Valsalva CT (40% and 23.3%, respectively) (P = 0.006). No change was found in the findings of the bony portion between pre-procedural and post-procedural Valsalva CT.
Quantification of Valsalva CT. (a) Valsalva CT image shows visualized segments and non-visualized segments of both Eustachian tubes. Visualized segment ratio on the right side is calculated as follows: 1.66/(1.66 + 0.69). (b) Whole ET was the visualized segment in five cases of pre-procedural Valsalva CT. Visualized segment ratio is 1.00 in these cases.
Valsalva CT data.
Values are given as n (%) or mean ± SD.
CT, computed tomography; VSR, visualized segment ratio.
SET
SET was successfully performed in 25 of 30 treated Eustachian tubes. In five patients, appropriate digital subtraction images could not be obtained due to poor cooperation. Positive ET patency was observed in 13 of 25 (52%) patients. A blunt lesion was found in 8 of 25 (32%) patients. Response to balloon dilation was observed in 18 of 25 (72%) patients.
Clinical outcomes of ETBD
Balloon dilation was technically successful in all 30 E-tubes. The mean time required for the procedure was 11.0 ± 3.9 min (range = 5–22 min). The mean VAS score was 6.7 ± 2.2 (range = 1–10). Clinical success was achieved in 16 of 27 (59.3%) E-tubes. A cumulative Valsalva maneuver improvement rate of 65.5% was achieved after six months. Valsalva ability and ETDQ score at each visit is summarized in Table 2.
Valsalva ability and ETDQ scores at each visit.
Values are given as n (%) or mean ± SD.
ETBD, Eustachian tube balloon dilation; ETDQ-7, Eustachian Tube Dysfunction Questionnaire-7.
Predictors of clinical success
Relationships between the clinical success and Valsalva CT and SET findings are summarized in Table 3. The response to balloon dilation (P = 0.012) was the only significant predictor of clinical success. Clinical success was obtained in 11 of 16 (68.8%) patients with the presence of response to balloon dilation.
Predictive factors of clinical success.
Values are given as n (%).
CT, computed tomography; ET, Eustachian tube; SET, selective Eustachian tubography.
Discussion
Obtaining pre- and post-procedural images is important in the evaluation of balloon dilation. In a pre-procedural image, the location and luminal diameter of a stenotic lesion can be measured. In a post-procedural image, dilatory response and immediate complications such as mural dissection can be identified. The present study revealed that SET can be safely performed during ETBD. The narrowest portion and patency of the ET could be identified on pre-BD SET. SET provided information related to clinical outcomes. Patients with the presence of a response to balloon dilation on post-BD SET showed higher clinical success compared to patients without a response. The rate of positive CT patency was higher at the one-month follow-up Valsalva CT compared with the baseline Valsalva CT. However, Valsalva CT did not show any findings significantly related to clinical outcomes.
Adding fluoroscopy guidance enables Eustachian tubography during an ETBD session (9). In previous Eustachian tubography, the nasopharyngeal cavity should be completely filled with contrast media (13). It is time-consuming and uncomfortable for patients; as a result, it cannot be applied during the ETBD. In the present study, only 2–3 mL of contrast media was directly injected into the ET. Better resolution of Eustachian tubography could also be gained by means of a digital subtraction technique. The presence of an obstructive lesion and the patency of the ET are easily identified on pre-BD SET. One concern is that contrast media injection can induce barotrauma. However, no adverse event related to contrast media injection was observed in the present study, probably due to tympanostomy in all the patients. If SET is performed in patients without tympanostomy, a meticulous injection of contrast media is needed to prevent tympanic membrane damage.
Unlike vascular or gastrointestinal stenosis, finding a clear obstruction lesion is hard in Eustachian tubography. Only 32% of patients showed a blunt lesion that looked like stenosis in the current study. However, it was not related to clinical outcomes. We evaluated imaging findings that might be related to obstructive ETD. Negative ET patency on SET may reflect the poor function of the ET; thus, patients with negative ET patency might obtain a good therapeutic response by ETBD. In the present study, there was a trend toward significance in a relationship between negative ET patency and clinical success. Eight of 11 patients with negative ET patency showed clinical success after ETBD compared to findings that only 3 of 11 patients with positive ET patency showed clinical success. The presence of response to balloon dilation on post-BD SET implies balloon dilation actually works in the ET lumen. Eleven of 16 patients with a presence of response showed clinical improvement. However, no clinical improvement was observed in all six patients without the presence of response. Secondary intervention, such as repeated balloon dilation or changing balloon catheters, can be applied in response to balloon dilation, though these strategies were not used in this study.
Valsalva CT is an emerging technique in ET imaging (10,14). Valsalva CT seemed to be a promising imaging technique since it does not need contrast media injection and provides multiplanar imaging containing discriminative information about soft tissue and bone. However, the lumen of ET could not be clearly depicted in Valsalva CT. A plausible explanation of this is that an ET can be easily closed by blood engorgement while patients lie in CT scanners. Another reason is that there were high individual differences in the ability to perform the Valsalva maneuver. In the present study, we used VSR for the quantification of an ET lumen; however, there was no significant Valsalva CT finding related to clinical outcome including VSR. Although an increase in positive CT patency ratio might imply balloon dilation induces a structural change in the cartilaginous portion of an ET, Valsalva CT has limitations in ET lumen imaging. Nevertheless, Valsalva CT could replace the role of conventional temporal bone CT, which has been used as routine pre-procedural examination in most studies to screen patients who are not suitable for ETBD (e.g. carotid canal dehiscence), as well as to detect middle ear pathology. Further studies on Valsalva CT are warranted to establish a standardized method for qualitative and quantitative assessment of the ET.
Adding fluoroscopy guidance in ETBD has several advantages. Fluoroscopy-guided ETBD has been reported to increase the safety of the procedure, as guidewire passage and balloon location could be visualized (11,15). In the present study, fluoroscopy guidance enables pre- and post-procedural SET, which offers information about the status of ET. It is possible that Valsalva CT could be performed in the same session if a cone-beam CT fluoroscopy machine is used. However, a fluoroscopy-alone procedure is still hard to perform, as there are no dedicated instruments or established techniques. In addition, nasopharyngeal mucosa is highly vulnerable and sensitive. Thus, friction of the catheter applied to the mucosal wall can induce bleeding and may not be tolerated under local anesthesia. For these reasons, fluoroscopy alone is realistically difficult, so fluoroscopy guidance could be used as a supplementary method in ETBD practice.
The present study has some limitations. First, the number of cases was small and therefore the power of statistical analysis was limited. Second, all patients had tympanostomy at the time of ETBD; thus, imaging findings in patients without tympanostomy were not analyzed in this study. Third, patients should be in a recumbent position during SET and Valsalva CT scanning. Blood engorgement around the ET can induce narrowing of an ET lumen and thereby may affect imaging findings. For these reasons, further prospective studies with larger sample sizes are warranted to investigate the role of ET imaging in ETBD. Our results indicated that the findings of SET have relevance to clinical outcomes. SET depicted the lumen of the ET; thereby, it could be a potentially valuable tool in patients with ETD. Valsalva CT provides additional information about the cartilaginous portion of the ET as well as temporal bone status. Therefore, Valsalva CT can be useful as a pre-interventional screening and planning tool, and could even replace conventional temporal bone CT. However, a standardized protocol for the evaluation of ETBD should be developed in the future.
In conclusion, although only preliminary results were provided in our study, SET and Valsalva CT may become useful tools in ETBD.
Footnotes
Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Fund of Biomedical Research Institute, Jeonbuk National University Hospital (grant no. CUH2018-0016).
