The Eustachian tube, also termed the pharyngotympanic or auditory tube, is a vital structure in regulating middle ear homeostasis, with complex anatomy designed for achieving this function. It travels medially from the middle ear, directing down and forwards to open just posterior to the end of the inferior turbinate. The bony lateral third travels past both squamous and petrous portions of the temporal bone. The medial two-thirds is fibrocartilaginous, opening out into the nasopharynx as a mucosal elevation known as the torus tubarius. The tube opens on positive pressure, e.g., yawning, sneezing, swallowing, and the Valsalva maneuver, by contraction of the levator veli palatini and tensor veli palatini muscles.
Through the Eustachian tube's complex structure, it can carry out its three main functions:
Firstly, by having a patent and open Eustachian tube, the pressure of the middle ear is equalized to that of the nasopharynx (i.e., towards atmospheric pressure). This has assistance from active mucosal gas exchange within the middle ear. With the maintenance of middle ear pressure, tympanic membrane compliance is optimized for hearing.
Secondly, it contains tube mucociliary transport. This consists of ciliated cells that clear inflammatory products and secretions from the middle ear and Eustachian tube, transporting them towards the direction of the nasopharynx for elimination.
Lastly, a functioning Eustachian tube protects the middle ear from loud sounds and potential hazards, including pathogens and secretions from the nasopharynx
Eustachian tube dysfunction (ETD) is the failure of the Eustachian tube in maintaining any of the three roles mentioned above. This categorizes as either acute (less than three months presentation) or chronic ETD (more than three months). ETD affects 1% of the population, with symptoms including aural fullness or 'popping sounds,' reduced hearing, tinnitus, autophony, otalgia, and imbalance. It can be broadly categorized into baro-challenged induced, patulous, and dilatory ETD.
Baro-challenge induced Eustachian tube dysfunction describes the failure of the Eustachian tube to open with the surrounding pressure changes, thereby inhibiting the regulation of middle-ear pressure. Patients will have normal otoscopy and tympanometry findings, as the failure of tube opening is situation-specific, and arise with increased atmospheric pressure e.g. deep-sea diving, or descent from altitude. The stress imposed on the mucosal surfaces of the Eustachian tube by repetitive equalization maneuvers from the increased atmospheric pressure leads to localized inflammation and mucosal edema. This affects the ability for subsequent attempts at opening and clearance. By applying oral or topical decongestants for the treatment of baro-challenge induced ETD, it is thought that mucosal edema and local tissue hyperemia is reduced, thereby shrinking the nasopharyngeal mucosa and improving Eustachian tube patency.
Patulous ETD is caused by an overtly patent Eustachian tube, whereby the failed tube closure at rest provides continuous communication between the nasopharynx and the middle ear. This creates the reported symptom of autophony, with habitual ‘sniffing’ to help alleviate self-vocalization.
Physiological causes of dilatory ETD involve the development of inflammation and mucosal edema, caused by episodes of rhinitis, upper respiratory tract infection or gastro-oesophageal reflux disease, which lead to blockage of the orifice and dysfunction. Malignancy such as nasopharyngeal carcinoma can present with unilateral obstruction and must be excluded, with benign causes of obstruction including adenoidal hypertrophy and sequelae following adenoidectomy. Aural fullness is a common symptom due to the build-up of negative middle ear pressure.
Prevalence is greater in children than in adults with recent studies demonstrating 0.77 adult visits to every 1 pediatric clinic visit for Eustachian tube dysfunction. An estimated 90% of children develop otitis media with effusion, a recognized sequela of ETD, prior to starting school. Approximately 1% of the adult population is diagnosed with ETD. Males are more likely to be diagnosed before the age of 20, with females more likely affected at older ages. No statistically significant difference between seasons has been proven.
History includes determining any precipitating factors that may lead to inflammation or edema of the mucosal surfaces, leading to reduced patency of the Eustachian tube, including gastro-oesophageal reflux disease, rhinosinusitis, Samter’s triad, allergies, and recent upper respiratory tract infections. A history of adenoidectomy is a risk factor, and it is important to establish a family history of Eustachian tube dysfunction or diseases of reduced mucociliary clearance e.g., Kartagener syndrome and cystic fibrosis. Down syndrome and cleft palate disorders have an association with ETD.
Irritants that lead to inflammation include exposure to cigarette smoking and environmental allergens. Has the patient participated in activities such as diving or hiking at high altitudes? Ensure that the use of intranasal medication, including oxymetazoline and corticosteroids, is explored.
The examination involves a head and neck examination, with otoscopy required to visualize for tympanic membrane retractions and evidence of negative middle ear pressures. Occasionally, hemotympanum is present in baro-challenge-induced ETD.
Visualize the oropharynx and perform anterior rhinoscopy. Flexible nasoendoscopy (FNE) should be included to directly examine the nasal mucosa for signs of inflammation or edema, and the larynx for evidence of gastro-oesophageal reflux disease. FNE provides access to the postnasal space, including a view of the contralateral nasopharyngeal orifice of the Eustachian tube. The valve mucosa is S-shaped when closed at resting state and becomes rounded when dilated. Dilation should occur with swallowing.
Tympanic insufflation is performed to demonstrate active negative pressure, and a type C Tympanogram suggests negative resting middle ear pressures. Audiological tests need to be completed with pure tone audiometry and Rinne’s and Weber’s tuning fork tests.
The Eustachian Tube Dysfunction Patient Questionnaire (ETDQ-7) is aimed at screening for patient-reported severity of ETD using a scoring system. It consists of 7 separate questions, scored between 1 (no problem) and 7 (severe problem). A mean overall score of more than 2.0 indicates the presence of ETD.
Treatment of Eustachian tube dysfunction is dependent on the likely cause of dysfunction:
Gastro-oesophageal reflux disease is addressed with lifestyle changes including losing weight and dietary modifications to reduce acid production. Anti-acid medication e.g. proton pump inhibitors may be considered.
Lifestyle changes to avoid potential allergens, if possible, should be tried. Medical interventions include antihistamines and nasal corticosteroid medication.
Treatment of rhinosinusitis should be commenced if indicated. Immunosuppressive agents will be required for granulomatous disease e.g. Sarcoidosis, granulomatosis with polyangiitis (Wegener disease).
Surgical dilatation of the Eustachian tube is performed using a Eustachian tube balloon catheter, with studies demonstrating improvement of the ETDQ-7 score at 12 months follow-up. ETD from otitis media with effusion is commonly managed with tympanostomy tube insertion
Patients should be considered for adenoidectomy if adenoid hypertrophy is thought to be the main contributing factor to ETD. This is more common in children, who may present with middle ear effusion. The use of auto-inflation devices for reopening the Eustachian tube by raising the pressure in the nose has shown favorable results for correcting of middle ear pressure and fluid clearance.
Autophony is not limited to patulous Eustachian tube dysfunction- symptoms may present in conditions including superior canal dehiscence and the presence of a foreign body within the external ear canal. Temporomandibular joint dysfunction may present with ‘popping’ noises and associated reduced hearing; however, it is also associated with discomfort upon jaw movement.
The outcome is dependent on the underlying cause and compliance with treatment. However, pediatric Eustachian tube dysfunction will generally improve and resolve with the maturation of the Eustachian tube and its surrounding muscles, aiding air ventilation- this usually occurs at seven years of age.
Complications of untreated Eustachian tube dysfunction include conductive hearing loss, chronic otitis media, otitis media with effusion (glue ear) and its sequelae, and eardrum retraction.
Deterrence and patient education are focused around information regarding healthy lifestyle changes e.g., smoking cessation and dietary changes, that can reduce the recurrence of inflammation and disease and identify cases that require medical review and intervention.
Eustachian tube dysfunction, although present at any stage in life, is more prevalent in children due to the need for further growth of the Eustachian tube. Compared to adults, pediatric Eustachian tubes have a shallow angle to the horizontal plane, increasing the risk of poor middle ear secretion and, therefore, otitis media with effusion.
Sequalae of ETD include episodes of acute otitis media or otitis media with effusion- with subsequent progression towards speech and hearing problems, disturbances in attention, limited vocabulary, and sleep deprivation. This reduces the child’s overall quality of life, in addition to causing stress and concern for the parent/caregiver.
Often schoolteachers or parents may highlight initial concerns regarding the child's hearing or disruptive behavior within the class setting, which should prompt the family physician to perform a thorough otology examination and subsequent referral for further investigations.
Audiologists perform a pivotal role by determining the severity, type, and laterality of hearing loss in the patient, enabling clinicians to appropriately counsel families with regards to reduced hearing and the potential impact. Speech and language pathologists may discuss strategies for minimizing the impact within the home and learning environment (e.g., preferential seating in the front of the classroom, facing the child and speaking clearly, using visual cues, etc.).
With this holistic care between different health professionals, the physician can focus on patient-based care and appropriately decide between conservative, medical, or surgical (e.g., adenoidectomy and tympanostomy tube insertion) management based on the patient’s own needs. [Level 1]
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