The Eustachian tube is a narrow tube which links the back of the nose to the middle ear. It is normally closed but opens when we swallow, yawn or chew. The Eustachian tube has three main functions: to protect the middle ear from pathogens; to ventilate the middle ear, which can help to keep the air pressure equal on either side of the eardrum, enabling the eardrum to work and vibrate properly; and to help drain secretions from the middle ear cleft.
Eustachian tube dysfunction (ETD) is the inability of the Eustachian tube to adequately perform these functions. However, the precise function and mechanisms of the Eustachian tube and the underlying causes of dysfunction are complex and not fully understood. From a diagnostic perspective, ETD is also poorly defined.
Eustachian tube dysfunction may occur when the mucosal lining of the tube is swollen, or does not open or close properly. If the tube is dysfunctional, symptoms such as muffled hearing, pain, tinnitus, reduced hearing, a feeling of fullness in the ear or problems with balance may occur. Long-term ETD has been associated with damage to the middle ear and the eardrum. Complications include otitis media with effusion (glue ear), middle ear atelectasis (retraction of the eardrum), and chronic otitis media.
However, the role of the Eustachian tube in the development of other middle ear conditions is not fully understood. Middle ear ventilation is increasingly seen as being associated with other mechanisms, such as those relating to gaseous exchange through the middle ear mucosa. Therefore, it may be that problems with middle ear ventilation (and therefore symptoms and signs previously attributed to ETD) may not all be associated with problems with or dysfunction of the Eustachian tube. Abnormal patency (patulous Eustachian tube) is a separate condition, in which the Eustachian tube remains intermittently open, causing an echoing sound of the person’s own heartbeat, breathing, and speech.