Dimensions and position of the Eustachian tube in Humans

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.

Anatomical Analysis of the Eustachian Tube in the Temporal Bone Through the Middle Fossa Window

PURPOSE

This cadaveric anatomical study aimed to explore precise morphometric measurements of the eustachian tube (ET) and adjacent structures in the middle cranial fossa, focusing on identifying reliable surgical landmarks when traditional markers are compromised due to tumors or trauma.

METHODS

Twenty-two temporal bones from 11 adult cadavers (mean age: 75.70 ± 13.75 yr, range: 40-90 yr; sex: 5 females and 6 males) were dissected bilaterally. Surgical tools, including an operation microscope, endoscope, and digital caliper, were used for meticulous measurements. Parameters such as ET dimensions, distances between key points, and relevant angles were quantified, ensuring precise anatomical data.

RESULTS

ET width at the foramen spinosum (FS) level, the midline level, and the eustachian orifice level were measured as 2.18 ± 0.68, 2.42 ± 0.70, and 2.30 ± 0.74 mm, respectively. The distances from the zygomatic root (ZR) to FS, ET, superior semicircular canal (SSC), and internal carotid artery (ICA) were 29.61 ± 2.56, 23.28 ± 2.61, 26.53 ± 2.56, and 32.61 ± 3.69 mm, respectively. The angles between SSC-ZR-ICA and FS-ZR-ICA were measured as 36.57 ± 10.32 and 13.63 ± 3.72 degrees, respectively. No statistical difference was found between right-left or male-female measurements ( p > 0.05).

CONCLUSION

The present study offers invaluable insights for neurotological surgeons performing middle fossa approaches. ET and ZR may serve as crucial reference points, enhancing surgical orientation and minimizing risks during complex procedures. These precise anatomical data may empower surgeons, ensuring safer and more confident middle cranial fossa operations, even in challenging clinical scenarios.

Age-related morphological change in bony segment and cartilage segment of Eustachian tube

Background

Eustachian tube dysfunction (ETD) is the predominant cause of otitis media with effusion in children and adults. Balloon dilatation of the Eustachian tube (BDET) provides a new method for restoring the ventilatory function of Eustachian tube (ET). However, the differences in age-related morphological changes in the dimensions and positions of ET in children and adults are unclear.

Purpose

This study aimed to examine age-related morphological changes in bony and cartilage segments of the ET in a three-dimensional space in normal population.

Methods

A total of 71 randomly selected computed tomography (CT) images of the temporal bones of 46 people were retrospectively studied in four age groups: A (0-3 years old); B (4-8 years old), C (9-18 years old), and D (19-65 years old). Space analytic geometry was assessed to calculate the dimensions and positions of ET.

Results

The bony segment of ET lengthened from infancy to adulthood with age in groups A, B and C (r = 0.562**/0.000). The cartilage segment of ET mostly extended with age from infancy to 8 years old in children (r = 0.633**/0.000), but with bending close to the sagittal plane and away from the horizontal plane with age in groups A, B and C (P < .05), and with a constant angle to the coronal plane among the four groups (P > .05).

Conclusion

The bony and cartilaginous segments of ET exhibit distinct morphological changes in space with age. The bony segment of ET extends in a constant position from infancy to adulthood. In contrast, the cartilaginous segment of the ET indicates multidimensional positional changes until adulthood, in addition to the elongation from infancy to children. This may provide an accurate morphological basis for comparing the differences in ETD pathogenesis and surgical treatment between children and adults.

When Can Children Perform Valsalva and Toynbee Maneuvers? An Exploratory Study

OBJECTIVES

Barochallenge-induced Eustachian tube dysfunction (ETD) is difficult to diagnose because the examination is often normal during clinical assessment. In adults, functional tympanometry testing, performed by asking the patient to Valsalva and Toynbee while measuring the pressure shift, can aid in the diagnosis of ETD. However, standardized values do not exist in children. We aim to determine the age at which children can perform these maneuvers and the normative values in this population.

METHODS

Patients with a normal basic ear examination 4 years and older, presenting to the pediatric Otolaryngology clinic, were recruited. Otoscopy, baseline tympanometry, followed by Valsalva and Toynbee maneuvers were performed. Because there are no pediatric norms, we hypothesized that children would achieve the same minimum normal pressure shift as cited in the adult literature (+20 daPa or higher for Valsalva and -20 daPa or lower for Toynbee). The data were analyzed using receiver operating characteristic curves and logistic regression.

RESULTS

One hundred sixty-eight children (276 ears) were assessed. Participants as young as 4 years old were able to perform a Valsalva and Toynbee. Age cut-offs at which children achieved adult norms were 12.5 years ( p = 0.016) and 8.5 years ( p = 0.071) for Valsalva and Toynbee maneuvers, respectively. Mean pressure shift ranged from +29 to -36 daPa, and males were 2.5 times more likely to achieve Toynbee compared with females ( p = 0.006).

CONCLUSIONS

Functional tympanometry testing may be used to help diagnose barochallenge-induced ETD in older children.

Evaluation of Eustachian tube dimensions by temporal bone computed tomography in patients with chronic otitis media

OBJECTIVE

To clarify the relationship between Eustachian tube dimensions and chronic otitis media aetiology using temporal bone computed tomography.

METHODS

The data of 231 adults who had undergone surgery for unilateral chronic otitis media were reviewed retrospectively. Diseased and healthy ears were enrolled in groups 1 and 2, respectively. Group 1A included chronic otitis media with cholesteatoma (n = 28) and group 1B included chronic otitis media without cholesteatoma (n = 203). The Eustachian tube dimensions of groups 1 and 2 were compared, to clarify the relationship between the Eustachian tube dimensions and chronic otitis media aetiology. Groups 1A and 1B were compared to assess the effect of Eustachian tube dimensions on cholesteatoma development.

RESULTS

The Eustachian tube was shorter, narrower and located more horizontally in ears with chronic otitis media. No significant difference was found between groups 1A and 1B.

CONCLUSION

Eustachian tube dimensions are closely related to chronic otitis media aetiopathology, but are not related to cholesteatoma development.

Investigation of Stent Prototypes for the Eustachian Tube in Human Donor Bodies

Chronic otitis media is often connected to Eustachian tube dysfunction. As successful treatment cannot be guaranteed with the currently available options, the aim is to develop a stent for the Eustachian tube (ET). Over the course of this development, different prototypes were generated and tested in ex vivo experiments. Four different prototypes of an ET stent and one commercially available coronary stent were implanted in the ET of seven human donor bodies. The position of the stents was verified by cone beam CT. The implanted ETs were harvested, embedded in resin and ground at 200 µm steps. Resulting images of the single steps were used to generate 3D models. The 3D models were then evaluated regarding position of the stent in the ET, its diameters, amount of squeezing, orientation of the axes and other parameters. Virtual reconstruction of the implanted ET was successful in all cases and revealed one incorrect stent placement. The cross-section increased for all metal stents in direction from the isthmus towards the pharyngeal orifice of the ET. Depending on the individual design of the metal stents (open or closed design), the shape varied also between different positions along a single stent. In contrast, the cross-section area and shape remained constant along the polymeric prototype. With the current investigation, insight into the behavior of different prototypes of ET stents was gained, which can help in defining the specifications for the intended ET stent.

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.

Radiological dimensions of the Eustachian tube in patients with adhesive otitis media

OBJECTIVE

This study aimed to analyse the computed tomography parameters for effective ventilation in patients with adhesive otitis media.

METHODS

Twenty-six patients with unilateral adhesive otitis media were included in the study. The patients' temporal bone computed tomography images were retrospectively reviewed. Eustachian tube length and diameter were measured. Mastoid pneumatisation and middle-ear size were evaluated by measuring petroclival and Eustachian tube-tympanic cavity ventilation angles.

RESULTS

The average Eustachian tube length was 38.4 mm and 38.9 mm in adhesive otitis media and healthy ears, respectively. The Eustachian tube diameter of the adhesive otitis media ears (1.47 mm) was significantly narrower than that of the healthy ears (1.83 mm). There were no significant differences in the angles between adhesive otitis media and healthy ears.

CONCLUSION

A narrow Eustachian tube diameter was associated with developing adhesive otitis media. Measuring Eustachian tube diameter is simple and can be routinely performed when examining temporal bone computed tomography images for Eustachian tube function evaluation.

Enlargement of Eustachian Tube Lumen in Patulous Eustachian Tube Patients Compared to that by Aging

OBJECTIVE

To evaluate the Eustachian tube (ET) dimensions in patulous ET (PET) patients compared with that by aging using sitting 3D computed tomography (CT).

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

SUBJECTS AND METHODS

A retrospective survey of medical records in Sen-En Rifu Hospital identified 105 ears of 76 PET patients and 65 ears of 34 patients without ET dysfunction findings (non-PET). Subjects in both PET and non-PET groups were then divided into two age groups. Groups A and C defined as non-PET and PET subjects respectively, who were under the age of 60 years, while Groups B and D defined of non-PET and PET subjects respectively, who were 60 years and above. 3D CT (Accuitomo; Morita, Kyoto, Japan) was performed on all subjects in the sitting position. The ET lumen from the ET pharyngeal orifice to 15 mm was analyzed.

RESULTS

No significant difference in the ET lumen near the pharyngeal orifice was found between Group A and C; however, there was a significant difference in the ET at points lateral to the pharyngeal orifice. The ET lumen was significantly larger at the site close to the pharyngeal orifice in Group B as compared to that of Group A. For the two groups of PET classified according to the size of the pharyngeal orifice and area close to the isthmus, age was only significantly different between two groups of pharyngeal orifice. On the contrary, sonotumometry and Ohta method were significantly different between the two groups of the area close to the isthmus.

CONCLUSION

The lumen of the ET is enlarged in both PET and aging. However, the responsible site was found to be different. While the enlargement of the ET lumen in 60 years and above subjects without PET mainly occurred near the pharyngeal orifice of the ET, it was near the isthmus in under 60 years PET patients. Further study of possible clinical implications of these findings as well as treatment strategy are required.

Transeustachian Middle Ear Endoscopy Using a Steerable Distal-Camera Tipped Endoscope

OBJECTIVE

Demonstrate the ability of a novel steerable distal chip endoscope to traverse the Eustachian tube and provide diagnostic quality images of the human middle ear.

PATIENTS

Three cadaveric temporal bone specimens were used in this work.

INTERVENTION

Diagnostic transeustachian endoscopy of the middle ear was performed.

MAIN OUTCOME MEASURE

Diagnostic image quality.

RESULTS

A novel 1.62 mm steerable endoscope successfully cannulated the Eustachian tube of three human cadaveric temporal bone specimens to reveal intact middle ear anatomy with high optical clarity.

CONCLUSIONS

A steerable endoscope can be designed to traverse the human Eustachian tube and provide diagnostic quality images of middle ear anatomy.

Developmental Anatomy of the Eustachian Tube: Implications for Balloon Dilation

OBJECTIVE

To describe the developmental anatomy of the eustachian tube (ET) and its relationship to surrounding structures on computed tomography.

STUDY DESIGN

Case series with chart review.

SETTING

A tertiary care hospital.

METHODS

ET anatomy was assessed with reformatted high-resolution computed tomography scans from 2010 to 2018. Scans (n = 78) were randomly selected from the following age groups: <4, 5 to 7, 8 to 18, and >18 years. The following were measured and compared between groups: ET length, angles, and relationship between its bony cartilaginous junction and the internal carotid artery and between its nasopharyngeal opening and the nasal floor.

RESULTS

The distance between the bony cartilaginous junction and internal carotid artery decreased with age between the <4-year-olds (2.4 ± 0.6 mm) and the 5- to 7-year-olds (2.0 ± 0.3 mm, P = .001). The ET length increased among the <4-year-olds (32 mm), 5- to 7-year-olds (36 mm), and 8- to 18-year-olds (41 mm, P < .0001). The cartilaginous ET increased among the <4-year-olds (20 mm), 5- to 7-year-olds (25 mm), and 8- to 18-year-olds (28 mm, P < .0001). The ET horizontal angle increased among the <4-year-olds (17°), 5- to 7-year-olds (21°), and 8- to 18-year-olds (23°, P≤ .003), but the ET sagittal angle did not statistically change after 5 years of age. The height difference between the nasopharyngeal opening of the ET and the nasal floor increased among the <4-year-olds (4 mm), 5- to 7-year-olds (7 mm), and 8- to 18-year-olds (11 mm, P < .0001).

CONCLUSION

The ET elongates with age, and its angles and relationship to the nasal floor increase. Although some parameters mature faster, more than half of the ET growth occurs by 8 years of age, and adult morphology is achieved by early adolescence.