Transnasal Placement of a Balloon-Expandable Metallic Stent: Human Cadaver Study of the Eustachian Tube

First Investigation of a Eustachian Tube Stent in Experimentally Induced Eustachian Tube Dysfunction

Unmet needs in the treatment of chronic otitis media and Eustachian tube dysfunction (ETD) triggered the development of stents for the Eustachian tube (ET). In this study, for the first time, stents were placed in an artificially blocked ET to evaluate stent function. Eight adult female sheep were injected with stabilized hyaluronic acid (HA) on both sides to induce ETD. Subsequently, a tapered nitinol ET stent was inserted on one side, and animals were examined bilaterally by endoscopy, tympanometry, cone beam computed tomography, and final histology. Seven of the stents were placed in the desired cartilaginous portion of the ET. At the end of the study, one stented side appeared slightly open; all other ET orifices were closed. Tympanometry revealed re-ventilation of the middle ear in four out of seven correctly stented animals within 3 to 6 weeks after stent insertion. The major amount of HA was found at the pharyngeal orifice of the ET anterior to the stent. Thus, the stent position did not completely align with the HA position. While a functional analysis will require refinement of the experimental setup, this study provides first promising results for stent insertion in a sheep model of ETD.

Long-Term Preclinical Evaluation of a Permanent Stent Developed for the Human Eustachian Tube

The Eustachian tube (ET) is a bottleneck when it comes to middle ear (ME) health. If its function is impaired, this can lead to serious consequences for the patient, such as hearing problems or deafness. Therefore, this study investigated a tapered nitinol stent (3-5 mm × 14 mm) for the human ET as a potential new permanent treatment for chronic Eustachian tube dysfunction (ETD) and thus ME ventilation disorders. The self-expanding stent was inserted unilaterally into the ET of 24 sheep with observation periods of 3, 6, and 12 months. Local tissue effects and the safety of the stent insertion were analyzed based on regular endoscopic checks, weekly tympanometry measurements, final imaging, and histological examinations. The animals showed no stent-related health restrictions. However, the individual anatomy and stenting procedure had an influence on the results. The tissue reaction in the endoscopic examinations was mild even though no concomitant antibiotics were administered. After all three monitoring periods, stented ETs had a significantly larger ET lumen than the non-stented contralateral ETs. However, tissue growth was detected in the stent. Overall, the first long-term study on an ET stent showed that the tapered ET stent could be a promising treatment option for ETD.

A Study of the Anatomy of the Eustachian Tube for Its Surgical Approach in Otorhinolaryngology

BACKGROUND

The eustachian tube (ET) is a connection between the nasopharynx and the middle ear behind the inferior nasal concha. It plays an important role in regulating air pressure across the tympanic membrane for proper transmission of sound. The pharyngeal opening of the tube is an important landmark for endoscopic evaluation in patients suffering from chronic otitis media and is also an important anatomical landmark for the transnasal approach to the infratemporal fossa. Hence, the study was done to locate the position of the pharyngeal opening of the ET in relation to various important anatomical landmarks.

METHODOLOGY

Hundred (50 right and 50 left sides) adult (60-80 years) formalin-fixed sagittal sections of head and neck specimens were taken for the study, which was obtained during the undergraduate teaching program. The shape, size, and position of the pharyngeal opening of the ET were noted. The distance between the pharyngeal opening of the ET and various anatomical landmarks was measured with the help of the digital Vernier caliper. The mean and standard deviation of all the parameters were calculated and tabulated.

RESULTS

In the present study, a slit-like shape was the most common shape of the pharyngeal opening, present in 62 out of 100 specimens. The difference between the anteroposterior length and vertical height of the two sides showed a statistically significant difference.

CONCLUSION

The present study will help to locate the position of the pharyngeal opening of the ET during otorhinolaryngological evaluation for performing various surgeries in the middle ear.

The rat eustachian tube: Anatomical, histological, and radiological features

Purpose

This study investigated the anatomical and histological characteristics of the rat Eustachian tube (E-tube) and the feasibility of Eustachian tubography in a rat model.

Materials and methods

Fifteen male Wistar rats were used in this study, and the bilateral E-tubes of each rat were examined. Ten E-tubes were used for anatomical studies, another ten for histological analysis, and the other ten for Eustachian tubography. Five rats were euthanized and decapitated, and ten E-tubes were dissected to describe the anatomy of the E-tube. Ten E-tube specimens obtained from five other rats were sectioned to investigate E-tube histology. Eustachian tubography was performed on the bilateral E-tubes of the other five rats using the trans-tympanic approach.

Results

The rat E-tubes consisted of bony and membranous parts. Cartilage and bone tissue covered only the bony part. The E-tubes' mean diameter and overall length were 2.97 ​mm and 4.96 ​mm, respectively. The tympanic orifices' mean diameter was 1.21 ​mm. The epithelium of E-tubes was mainly composed of pseudostratified ciliated and goblet cells. Eustachian tubography was successfully performed on both sides of the E-tube for each rat. The technical success rate was 100%, the average running time was 4.9 ​min, and no procedure-related complications occurred. On tubography images, the E-tube, tympanic cavity, and nasopharynx could be identified because of the visualization of bony landmarks.

Conclusion

In this study, we described the anatomical and histological features of rat E-tubes. With the aid of these findings, E-tube angiography was successfully performed using a transtympanic approach. These results will facilitate further investigation of E-tube dysfunction.

Preliminary results of absorbable magnesium stent for treating eustachian tube dysfunction in a porcine model

Absorbable magnesium (Mg) stents have an attractive biocompatibility and rapid degradation rate, but their degradable behavior and efficacy in the Eustachian tube (ET) have not yet been investigated. In this study, the degradable behavior of the Mg stent in artificial nasal mucus was evaluated. The Mg stents in the porcine ET model were also investigated to evaluate their safety and efficacy. Four Mg stents were placed into the four ETs of two pigs. The mass loss rate of the Mg stents gradually decreased over time. The decrease rates were 30.96% at one week, 49.00% at two weeks, and 71.80% at four weeks. On the basis of histological findings, the thickness of submucosal tissue hyperplasia and the degree of inflammatory cell infiltration significantly decreased at four weeks compared with two weeks. Biodegradation of the Mg stent occurred before tissue proliferative reactions, and the ET patency was successfully maintained without stent-induced tissue hyperplasia at four weeks. The Mg stent that biodegrades rapidly seems to be effective and safe in porcine ET. Further investigation is required to verify the optimal stent shape and indwell period in the ET.

Tapered self-expandable metallic stent optimized for Eustachian tube morphology in a porcine ET model

Several investigations on the feasibility of stent placement into the Eustachian tube (ET) are being conducted. However, stents optimized for the anatomical structure of the ET have not yet been developed. In this study, the efficacy and safety of a self-expandable metallic stent (SEMS) optimized for porcine ET morphology was investigated. Silicone was injected into a cadaveric porcine ET to analyze the ET morphology. The three-dimensional-reconstructed porcine ET phantom images obtained after a computed tomography scan were measured to determine the dimensions of the porcine ET. The SEMS was designed as a tapered structure on the basis of the morphological findings of the porcine ET. The tapered SEMS (T-SEMS) and conventional SEMS (C-SEMS) were placed into the porcine ET to compare the safety and efficacy of the two types of SEMSs. Stent-induced tissue hyperplasia in the T-SEMS group was significantly lower than that in the C-SEMS group (p < 0.001). The T-SEMS optimized for the porcine ET was effective in maintaining stent patency. T-SEMS seems to be better than C-SEMS in suppressing stent-induced tissue hyperplasia, owing to the reduced stent-mediated mechanical injuries and maintaining ET patency.

Endoscopic vs. microscopic stapes surgery: An anatomical feasibility study

Objectives

To investigate the feasibility of the endoscopic approach vs. microscopic approach during stapes surgery, focusing on the visualization of the important anatomical structures of the middle ear, the volume of the resected scutum and chorda tympani (CT) injury.

Methods

Fresh frozen human cadaveric heads underwent two stapes surgeries using an operating microscope on one ear and an endoscope on the other ear. The surgeon documented the visualization of critical landmarks, as well as exposure and injury of the CT. The volume of resected scutum was evaluated using cone beam computed tomography scanning and three-dimensional imaging.

Results

We performed endoscopic stapes surgery in 10 ears and microscopic stapes surgery in 11 ears. A stapes prosthesis was placed in all ears. The volume of bony scutum resection was significantly lower in the endoscopic group (median = 2.20 mm³, IQR = 4.17) than in the microscopic group (median 13.25 mm³, IQR = 8.71). No scutum was removed in two endoscopic ears, while scutum was removed in all microscopic ears. The endoscopic and microscopic group had similar CT injury.

Conclusions

This study showed that the endoscopic stapes surgery procedure is feasible and might be less invasive than microscopic stapes surgery. Future clinical prospective and functional studies will be needed to support our findings.

The Eustachian Tube Dysfunction in Children: Anatomical Considerations and Current Trends in Invasive Therapeutic Approaches

The eustachian tube (ET) has a crucial role in the physiology of the middle ear. Thus, any condition that renders the tube dysfunctional is directly implicated with middle ear pathophysiology, like in the case of acute otitis media and otitis media with effusion. Children are more vulnerable to pathologies of the middle ear, primarily due to the immature development of their eustachian tubes. Otitis media with effusion, apart from being a burden for hearing, with direct consequences for speech development, may also be implicated in cholesteatoma formation. Medical therapy is not practically effective for the treatment of effusion. Moreover, the established surgical approaches, like grommets and adenoidectomy, deal only indirectly with the problem since they are not addressing the dysfunctional ET itself. An emerging interventional approach that intends to restore the function of the tube is the transnasal balloon dilation of the cartilaginous part of the ET. Growing international experience indicates that this promising technique is safe and effective. In the current review, we aim to provide background information on the anatomy, physiology, and pathophysiology of the ET and to present the progress of the balloon dilation technique with emphasis on pediatric patients.

Sirolimus-eluting cobalt-chrome alloy stent suppresses stent-induced tissue hyperplasia in a porcine Eustachian tube model

Various preclinical studies with developed Eustachian tube (ET) stents are in progress but have not yet been clinically applied. ET stent is limited by stent-induced tissue hyperplasia in preclinical studies. The effectiveness of sirolimus-eluting cobalt–chrome alloy stent (SES) in suppressing stent-induced tissue hyperplasia after stent placement in the porcine ET model was investigated. Six pigs were divided into two groups (i.e., the control and the SES groups) with three pigs for each group. The control group received an uncoated cobalt–chrome alloy stent (n = 6), and the SES group received a sirolimus-eluting cobalt–chrome alloy stent (n = 6). All groups were sacrificed 4 weeks after stent placement. Stent placement was successful in all ETs without procedure-related complications. None of the stents was able to keep its round shape as original, and mucus accumulation was observed inside and around the stent in both groups. On histologic analysis, the tissue hyperplasia area and the thickness of submucosal fibrosis were significantly lower in the SES group than in the control group. SES seems to be effective in suppressing stent-induced tissue hyperplasia in porcine ET. However, further investigation was required to verify the optimal stent materials and antiproliferative drugs.

Morphological Analysis of the Adult Eustachian Tube: A Fresh-Frozen Human Cadaver Study

OBJECTIVES

To evaluate the dilated Eustachian tube (ET) anatomy configuration using fresh human cadavers.

METHODS

Fourteen ears from human cadavers were used to identify the ET configuration. The cadaver head was cut in the sagittal plane parallel to the nasal septum, dividing it into right and left sides. Silicone was then inserted into the ET through the nasopharyngeal orifice (NO). The volume and length of the impression were measured using 3D computed tomography imaging.

RESULTS

The ET lumen was found to narrow from the NO to the isthmus, and the ET surface was concave anteriorly and convex posteriorly. The lower portion of the ET lumen was the most dilated and displayed a narrow top. The average volume of the ET impression was 1.4 ± 0.5 ml. The total length of the posterior side was 30.5 ± 3.6 mm, and that of the anterior side was 26.3 ± 3.4 mm. The widest ET area of the NO was 10.1 ± 0.9 mm in height and 8.0 ± 1.5 mm in width. The preisthmus was 2.4 ± 0.4 mm in height and 1.3 ± 0.5 mm in width. The height and width were 8.37 and 5.33 mm at the 5 mm point from the NO, and 5.51 and 1.94 mm at the 20 mm point from the NO, respectively.

CONCLUSION

We evaluated the configuration of the cartilaginous ET lumen, which is the main target of balloon dilation, and our findings may give insights into this dilation process and assist with the further development of ET balloons and stents.

Fluoroscopic Balloon Dilation Using a Flexible Guide Wire to Treat Obstructive Eustachian Tube Dysfunction

PURPOSE

To prospectively evaluate the midterm outcomes of fluoroscopic eustachian tube (E-tube) balloon dilation by using a flexible guide wire in patients with obstructive E-tube dysfunction.

MATERIALS AND METHODS

From October 2016 to September 2017, adult outpatients with persistent otitis media who were unable to perform the Valsalva maneuver were prospectively enrolled. The analysis included 32 E-tubes from 31 patients (18 women, 13 men; mean age, 47 years old, range 25-72 years). Participants underwent fluoroscopic E-tube balloon dilation with a 0.035-inch flexible guide wire and a 6- × 20-mm balloon catheter. Clinical examinations to check for the ability to perform the Valsalva maneuver and otomicroscopy were conducted at 1 week and then at 1, 3, 12, and 18 months after the procedure.

RESULTS

Balloon dilation was technically successful in all E-tubes. The mean time required for the procedure was 6.9 minutes (range, 5.8-10.3 minutes). The Valsalva maneuver was successful in opening 25 of 32 E-tubes (78.1%) at 3 months after balloon dilation. During the median follow-up of 15.9 months, failure of the Valsalva maneuver occurred in 4 of 25 improved E-tubes (16%), yielding a 2-year patency rate of 84%.

CONCLUSIONS

The fluoroscopic balloon dilation results were encouraging, and using a flexible guide wire for E-tube balloon dilation did not cause a false passage.