The patulous eustachian tube is a rare disorder of the Eustachian tube. In this disorder, the tube, which is usually closed under normal conditions, stays intermittently open. Patients complain of fullness and autophonia – the abnormal perception of their bodily sounds such as voice and breathing in the ear. A slight hearing loss may be present.
What is the Eustachian tube
The Eustachian tube is a delicate anatomical structure that connects the middle ear to the nasopharynx, the part of the throat above the palate. It is not visible through the open mouth.
Two-thirds of its length from its opening in the middle ear is bony and formed by the temporal bone. The other third, which opens in the nasopharynx at its pharyngeal orifice, is made out of cartilage. The Eustachian tube furthermore contains muscles and is lined on the inside by respiratory epithelium, partly able to secrete mucous.
The Eustachian tube acts as a pressure regulator of the air in the middle ear and the throat. Equalising the ambient air pressure in the throat with the air pressure in the middle ear is an essential function. This occurs automatically due to the muscle attachments when we swallow and talk. The act of equalising can be initiated by performing certain manoeuvres, such as the Valsalva manoeuvre or by simply blowing our noses.
Eustachian tube dysfunction
Eustachian tube dysfunction occurs in less than 1 % of the general population. This condition is often misdiagnosed. It is divided into two main types, namely the Patulous Eustachian Tube or PET (where the tube is inadequately open) and eustachian tube blockage (where the tube is blocked or not opening adequately).
Long-standing Eustachian tube blockage may lead to retractive disorders of the middle ear such as chronic secretory otitis media, adhesive chronic otitis media and cholesteatoma. It may also lead to pain, ear damage, dizziness, vertigo, and hearing loss when equalising the middle ear with the changing ambient pressure needs to occur immediately. Barotrauma, including tympanic membrane rupture and perilymph fistula (may occur during scuba diving and less commonly during flying. Even patients with normal Eustachian tubes may experience temporary dysfunction during a cold or upper respiratory infection.
Eustachian tube function in children
From an anatomical and functional viewpoint, the Eustachian tube is still immature in babies and smaller children, only reaching maturity over eight years. The Eustachian tube is shorter and more horizontally oriented in children. This, coupled with a higher incidence of allergies, food intolerance and upper respiratory infections, is more commonly associated with ear infections. The passive inhalation of parents’ exhaled cigarette smoking is a major contributing factor.
How is the function of the Eustachian tube assessed
There is currently no universally accepted gold standard for testing Eustachian tube function.
The clinical examination may show different stages of tympanic membrane retraction, secretory otitis media and even cholesteatoma in patients with eustachian tube dysfunction of the blocked variety.
PET may present with tympanic membrane movements synchronous with the patient’s breathing.
In most cases, though, mild, recently onset, and intermittent dysfunction reveals nothing with the examination. The inability to perform a successful Valsalva manoeuvre during examination is not necessarily a sign of chronic dysfunction.
It is vital to examine the nasopharynx to rule out allergies, infections, enlarged adenoids and tumours that may cause obstruction. Smoking can negatively affect mucous transportation by the respiratory epithelium.
Immittance testing of the middle ear, including different forms of tympanometry, is an indirect method of measuring Eustachian tube function at a specific given moment. Abnormal results should, however, be evaluated with great care and be misleading. Another sensitive yet underutilised test is nasally delivered masking noise during a hearing assessment. This test is considered highly sensitive for PET.
Imaging in the form of computed tomography and magnetic resonance imaging helps to visualise overt abnormalities of the bony and soft tissue aspects of the tube, respectively. It does not measure function, however.
The Patulous Eustachian Tube
PET is a disorder in which the Eustachian tube, closed under normal conditions, intermittently stays open. Patients present with autophonia (hearing bodily sounds in their ears). Breathing can be heard and sometimes be escorted by the visual movement of the tympanic membrane during the examination. Lying down often decreases the sensations. Patients often complain of hearing their heartbeat, chewing, breathing and voice in their ears.
The exact cause is not known. Sudden weight loss is often a precipitation factor in over a third of patients. It is explained based on the reducing fat in the wall of the eustachian tube, increasing its lumen. Dehydration, alcohol, caffeine, nasal spray and exercise can lead to temporary PET. Radiation and certain chronic muscular disorders may lead to chronic PET problems. The effect of high oestrogen in pregnancy and rarely autoimmune diseases may also be to blame.
Another potential cause is the presence of liquid secretions in the Eustachian tube. This occurs with middle ear infections (otitis media)
Superior semicircular canal dehiscence syndrome (SCDS) is a condition where the superior canal of the vestibular organ is open. SCDS may mimic PET as it also presents with autophonia.
Treatment of Patulous Eustachian Tube
Overly aggressive surgical treatment should be avoided. A patulous Eustachian tube may readily be converted into a blocked, non-functional tube if damaged. Saying that, however, does not mean that treatment should be withheld if the problem can be identified with certainty.
Nasal drops or nasal spray reach the pharyngeal opening of the Eustachian tube. Using saturated potassium iodide, diluted hydrochloric acid, chlorobutanol, and benzyl alcohol, the lumen of the eustachian tube is temporary and, in some cases, permanent reduced. Unfortunately, not all of these are approved by the South African Health Products Regulatory Authority (SAHPRA). Some nasal decongestants can worsen the situation by removing the tenacious secretions in the tube.
Other attempts in narrowing the Eustachian tube include cauterisation of the opening with resultant scarring, the injection of fat, absorbable gelatin powder(Gelfoam), hyaluronic acid or Teflon paste in the wall of the canal. Some of these injections work only temporary, and some may lead to severe complications. Eustachian tube balloon dilatation for PET is widely used and may yield favourable results.
Another approach is to address the tympanic membrane. Myringotomy and placement of grommets equalise the pressure and may be of value in patients with PET who is “habitual sniffers”. Reinforcing the tympanic membrane with thinned cartilage harvested from the same ear is another option. In some cases, excellent results are obtained by placing sterile sigaret paper patches on the outside of the tympanic membrane. This may have to be repeated but does avoid surgery.
Further reading
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6849362/