Patulous Eustachian Tube (PET) is a condition where the Eustachian tube, a narrow passageway connecting the middle ear to the back of the nose and throat, remains abnormally open. This persistent patency creates a direct conduit for sound and pressure from the nasopharynx to the middle ear space. The most defining and disruptive symptom of this disorder is autophony, a phenomenon where a person hears their own voice, breathing, and even heartbeat amplified to a loud, distracting volume. Understanding why this tube fails to close properly is the first step toward finding relief.
How the Eustachian Tube Normally Functions
The Eustachian tube, also known as the pharyngotympanic tube, is typically a closed structure, opening only briefly to perform specific tasks. Its primary functions are to equalize air pressure between the middle ear and the external environment, and to drain normal secretions from the middle ear cavity. This pressure equalization is accomplished by the tube opening during actions like swallowing, yawning, or chewing.
The tube is partially bony and partially fibrocartilaginous; the cartilaginous portion is normally collapsed at rest. The active opening is controlled primarily by the tensor veli palatini muscle, which contracts to pull the tube open. When this muscle relaxes, the tube is held closed by the surrounding soft tissue, the surface tension of the mucosal lining, and a protective cushion of fatty tissue.
This resting, closed state prevents excessive sound transmission and protects the middle ear from nasopharyngeal secretions. In Patulous Eustachian Tube, this protective closure mechanism fails, allowing a constant, unfiltered connection between the upper airway and the middle ear space.
Causes Related to Tissue and Weight Changes
A major physiological cause of PET involves the loss of supportive tissue surrounding the cartilaginous portion of the tube. The Eustachian tube is encased in a protective layer of fat known as Ostmann’s fat pad. This peritubal adipose tissue is a physical cushion that helps maintain the tube’s collapsed state when the opening muscles are relaxed.
When a person experiences rapid or significant weight loss, the body mobilizes fat stores, including the delicate fat pad surrounding the Eustachian tube. The sudden reduction in this fatty tissue removes the external physical pressure needed to keep the tube wall firmly closed. Studies, particularly involving patients who undergo bariatric surgery, show that this acute loss of tissue pressure can trigger PET symptoms, sometimes after losing as little as 10 to 20 pounds.
Changes to the muscles controlling the tube can also contribute to patency. While the tensor veli palatini muscle is an opener, atrophy or weakness in the associated muscles, often due to certain neurological conditions, can disrupt the overall muscular tension required for proper tubal function. Conditions like multiple sclerosis, stroke, or post-polio syndrome have been implicated in this muscular weakening.
Radiation therapy directed at the head and neck area is another factor that causes direct tissue change. High-dose radiation, often used to treat nasopharyngeal cancers, can lead to atrophy or fibrosis of the mucosal lining and surrounding soft tissues. This scarring and loss of tissue elasticity can structurally prevent the tube from collapsing fully, resulting in a persistently open or patent state.
Systemic and Iatrogenic Contributors
Dehydration is a significant factor, as a reduction in overall body water volume can cause the mucosal lining of the Eustachian tube to shrink. When the normally plump, moist mucosal tissues dry out and contract, the tube’s lumen becomes wider, facilitating the persistent opening.
Medications that promote fluid loss, specifically diuretics, can induce this state of mucosal shrinkage. Similarly, long-term or excessive use of certain nasal decongestant sprays can have a paradoxical drying effect on the nasopharyngeal mucosa. This drying and thinning of the tissue lining the tube can remove the necessary surface tension and bulk that helps keep the tube walls adhered and closed at rest.
Hormonal fluctuations, particularly those involving estrogen, are frequently associated with PET. Pregnancy is often cited as the second most common cause after weight loss, where the elevated hormone levels are thought to alter the surface tension of the mucosal lining. Oral contraceptives and estrogen replacement therapy can also create a similar effect on the delicate tissues of the tube.
While the exact mechanism is complex, the hormonal influence is believed to affect the production of surfactant, a substance that normally helps the tube walls adhere to each other. This change in surface tension, rather than physical shrinking, reduces the force required to keep the tube closed. Other systemic factors, such as extreme fatigue, stress, and vigorous exercise, can also temporarily induce or worsen PET symptoms, often by causing transient dehydration or hyperventilation.