The round window is part of the internal anatomy of the ear. It consists of a small opening between the ear canal and the inner ear, covered in a flexible membrane. When pressure builds up inside the ear, the round window can bulge out to create an outlet, relieving the pressure. When pressure is normal or low, the window snaps back into place. This is an important part of the function of the ear, and problems with the round window can lead to hearing loss.
Hearing occurs as sound moves through the ear and vibrates the oval window or ear drum, another opening to the inner ear. This causes bones inside the ear known as the auditory ossicles to move, vibrating hairs inside the ear. The brain uses input from these vibrations to process and understand sound. The fluid-filled inner ear relies on pressure fluctuation. If the pressure inside the ear is too high, the auditory ossicles cannot move and no sound is transmitted.
The flexible membrane of the round window can bulge with increasing pressure, allowing pressure buildups to disperse. Pressure increases whenever the auditory ossicles move, and this membrane must be able to snap back and forth with a high degree of elasticity to allow people to hear reliably. In some congenital conditions, the membrane is stiff and does not move as readily, contributing to hearing loss. In this case the structure of the rest of the ear may be fine, but the vibrations in the inner ear cannot occur because there is no outlet for pressure.
People with ear infections can sometimes experience thickening and irritation of this membrane, and may develop temporary hearing loss. The round window can also have trouble coping with high pressure caused by a buildup of excess fluid with poor drainage, leading to a muffled sense of hearing, as only very loud noises are strong enough to fight the pressure and vibrate the structures inside the ear. As the infection resolves, hearing should return.
Congenital disorders involving the round window may be accompanied with other structural abnormalities in the ear. In these cases, surgery can be used to address a problem with the round window but the patient may not experience a noticeable improvement in hearing. A surgeon can evaluate a patient to see if the hearing loss can be treated with surgery and to discuss surgical options. Risks of surgery can include further damage to the ear, making restoration of hearing even less likely.