Health-care providers working in primary care, allergy, pediatrics, and otolaryngology frequently encounter both acute and chronic eustachian-tube dysfunction (ETD). This common condition can be challenging to treat, particularly in patients with a lifelong history of ETD. A properly functioning eustachian tube allows gas diffusion which equalizes middle-ear pressure with that of the environment. An improperly functioning eustachian tube can result in negative middle-ear pressure. Left untreated, this condition may lead to complaints of hearing loss, tinnitus, otalgia, vertigo (and subsequent tympanic membrane atelectasis), fulminate cholesteatoma formation, and otitis media.1
The eustachian tube
The narrow eustachian tube is part of the contiguous system that includes the nose, palate, and nasopharynx.2,3 The nasopharynx is proximal to the eustachian tube, and the middle ear and mastoid are located at its distal end.4 Directed downward, forward, and medially from the middle ear, the eustachian tube opens approximately 1.25 cm behind and just below the posterior end of the inferior turbinate.2 The eustachian tube of an adult sits at a 45° angle, while the angle is approximately 10° in infants.4 Additionally, an infant’s eustachian tube measures approximately 18 mm in length; the tube grows rapidly during childhood, reaching its adult length of 3-4 cm by age 7 years.2,4 The lumen of the tube will also increase with physical maturity.
The eustachian tube drains or clears middle-ear secretions into the nasopharynx, protects the middle ear from nasopharyngeal pressure changes and secretions, and ventilates the middle ear so that the pressure within is equal to atmospheric pressure.1-6 Drainage of normal secretions from the middle ear to the nasopharynx via the eustachian tube is aided by mucociliary transport and repeated active tubal opening and closing.2 The four muscles associated with the eustachian tube (tensor veli palatini, levator veli palatini, salpingopharyngeus, and tensor tympani) are all are either directly or indirectly related to tubal function.4 Normally closed at rest, the eustachian tube opens when we yawn, sneeze, swallow, or chew,1,2,4 allowing air to enter the middle ear and mucus to flow out. This also promotes proper tympanic membrane function by enabling the equalization of middle-ear and atmospheric pressures.4 With normal function, middle-ear pressure is maintained between +50 mm and -50 mm H2O.2,4 The Ostmann fat pad, located in the inferolateral aspect of the eustachian tube, is thought to play a role in closing the tube to prevent backflow of nasopharyngeal secretions and likely contributes to protection of the tube.1
ETD occurs when the tube fails to open properly or becomes blocked, thereby preventing the normal flow of air into the middle ear.3 This results in higher air pressure outside the tympanic membrane than in the middle ear, a condition that may cause long-term pathologic changes to the tube. Eustachian-tube pathology is strongly related to mucosal disease and associated hypertrophy, which can be precipitated by reactive disease (e.g., allergy) as well as other causes.1 Such anatomic abnormalities as cleft palate and other craniofacial abnormalities may lead to inflammation of the eustachian tube.5 Damage to the tube lining also can be directly related to viral infection, which is thought to result in decreased mucociliary clearance. Gastroesophageal reflux is thought to play a role in the development of middle-ear and eustachian-tube inflammation and may play a role in ETD as well. Nasopharyngeal pH has been noted to be lower in some patients with otalgia and adenoiditis.6