A cholesteatoma is an abnormal growth of skin trapped behind the eardrum, inside the middle ear. Despite the name, it is not a cancer or a tumor. It is a pocket of skin cells that sheds layers of dead tissue (keratin) that accumulate and expand over time. As it grows, it releases enzymes that dissolve bone, which is what makes it dangerous. Left untreated, a cholesteatoma can destroy the tiny bones responsible for hearing, erode into the inner ear, and in rare cases damage the nerve that controls facial movement.
Cholesteatoma affects roughly 3 to 15 people per 100,000 each year, with a slight male predominance. It occurs in both children and adults, though the underlying cause can differ.
What a Cholesteatoma Is Made Of
The growth itself is structurally identical to the outer layer of your skin. It has the same four layers found in normal thin skin: a base layer that produces new cells, a middle layer, a granular layer, and a tough outer layer of dead, flattened cells called keratin. In healthy skin, those dead cells flake off naturally. Inside a closed space like the middle ear, they have nowhere to go. They pile up into a growing mass.
Surrounding this skin-like core is a layer of connective tissue packed with immune cells, particularly white blood cells and macrophages. This inflammatory lining is a key part of the problem. It produces enzymes (a family of proteins that break down the structural scaffolding of tissues) that actively dissolve the surrounding bone. The balance between these destructive enzymes and the body’s natural inhibitors of those enzymes determines how aggressively the cholesteatoma erodes into nearby structures.
Congenital vs. Acquired Types
Cholesteatomas fall into two broad categories. Congenital cholesteatomas are present from birth. They form when skin cells become trapped behind an intact, normal-looking eardrum during fetal development. A doctor examining the ear may see a white mass sitting behind the eardrum, sometimes pushing it outward. These are less common and tend to be discovered in young children, often during a routine ear check or when a parent notices hearing trouble on one side.
Acquired cholesteatomas are far more frequent and develop later in life, usually connected to repeated ear infections or poor function of the tube that ventilates the middle ear (the eustachian tube). When this tube doesn’t equalize pressure properly, the eardrum can get sucked inward, forming a pocket. Skin cells collect in that pocket and begin to grow. Chronic infections can also cause the eardrum to perforate, allowing skin from the ear canal to migrate inward. Acquired cholesteatomas recur after surgery more often than congenital ones: about 12% versus 7%.
Symptoms to Recognize
Cholesteatomas are almost always one-sided. The hallmark symptom is persistent, foul-smelling ear drainage that doesn’t clear up with standard ear drops or antibiotics. The odor is distinctive and comes from the breakdown of accumulated dead skin and bone debris, often complicated by bacterial infection.
Progressive hearing loss in the affected ear is the other major symptom. As the growth erodes the three tiny bones that transmit sound from the eardrum to the inner ear, hearing gradually worsens. Many people live with these symptoms for months or even years before getting a diagnosis.
Less commonly, dizziness or balance problems develop if the cholesteatoma erodes into the inner ear structures responsible for equilibrium. Facial weakness or paralysis is an uncommon but serious sign, occurring in roughly 1% to 3.4% of cases. This happens when the growth erodes the thin bony canal that houses the facial nerve, compressing it or exposing it to toxic inflammatory substances. Sudden facial weakness tends to result from chemical irritation of the nerve and often recovers well after treatment. Gradual facial weakness, on the other hand, usually indicates physical compression from bone erosion and can mean more extensive nerve damage.
How It Is Diagnosed
An ear, nose, and throat specialist can often identify a cholesteatoma by looking in the ear with a microscope or otoscope. A white, pearly mass or a deep retraction pocket filled with debris behind or involving the eardrum is the classic finding. But imaging is needed to understand how far the growth extends and to plan surgery.
CT scans show bone detail well, revealing which structures have been eroded. For detecting whether cholesteatoma has come back after surgery, a specialized type of MRI called non-echoplanar diffusion weighted imaging has become the preferred tool. It can detect cholesteatoma as small as 2 millimeters and has largely replaced the need for “second look” surgeries that were once routine just to check whether any disease remained. Growths smaller than about 3 millimeters can be missed on a single scan, so doctors typically monitor with repeat imaging over time to catch anything that may be growing.
Surgical Treatment
Surgery is the only effective treatment. Cholesteatomas do not resolve on their own and will continue to grow and erode bone if left in place. The goal is to completely remove the growth, prevent recurrence, and preserve or restore as much hearing as possible.
Two main surgical approaches exist, distinguished by what happens to the bony wall of the ear canal:
- Canal wall up: The surgeon removes the cholesteatoma while preserving the natural anatomy of the ear canal. Recovery is more straightforward, and you can generally get the ear wet once healed. The trade-off is a higher chance that disease comes back, with pooled recurrence rates around 16%.
- Canal wall down: The surgeon removes part of the bony ear canal wall to get a wider view and more complete removal. This approach has a lower recurrence rate (around 7%) but creates an open cavity that needs periodic cleaning and must be kept dry, which can limit activities like swimming.
The choice between these depends largely on how much bone the cholesteatoma has already destroyed. When the ear canal wall is intact, surgeons generally prefer the canal wall up approach. When the disease has already eroded that wall, canal wall down becomes necessary.
Additional techniques during surgery can significantly improve outcomes. Filling the mastoid cavity with tissue (obliteration) drops the recurrence rate from about 29% to 9%. Rebuilding the chain of hearing bones during the same procedure lowers it further, to around 6%.
Recurrence and Long-Term Monitoring
Cholesteatoma has a notable tendency to come back. The overall recurrence rate after surgery is about 11%, but that number climbs with time. At one year post-surgery, roughly 7% of patients show signs of recurrent disease. By five years, that rises to 18%. Over 15 years, it can reach as high as 39%. Children have a somewhat higher recurrence rate than adults (13% versus 10%), likely because their cholesteatomas tend to be more aggressive and their eustachian tube function is less mature.
This is why long-term follow-up matters. Regular MRI scans can catch regrowth early, often when it is still small enough for a simpler revision surgery. Most specialists recommend imaging at intervals for several years after the initial operation, particularly for canal wall up procedures where residual disease is harder to detect on physical exam alone.
Potential Complications
The damage a cholesteatoma causes is driven by its slow, relentless expansion and the enzymes it releases. The tiny hearing bones are the most vulnerable targets, leading to conductive hearing loss that may be partially reversible with reconstructive surgery. Erosion into the inner ear can cause permanent nerve-type hearing loss and chronic balance problems.
Facial nerve paralysis, while uncommon at 1% to 3.4% of cases, results from erosion of the thin bony channel that protects the nerve. The facial nerve fills 35% to 65% of this channel, with the rest occupied by blood vessels and connective tissue. There is essentially no spare room, so even modest swelling from infection or slight compression from the growing mass can impair nerve function. Surgery to remove the cholesteatoma and decompress the nerve is urgent in these cases.
In the most severe scenarios, a cholesteatoma can erode through the bone separating the ear from the brain, potentially causing meningitis or brain abscess. These complications are rare today because most cholesteatomas are caught and treated before they progress that far, but they underscore why persistent, foul-smelling ear drainage and worsening hearing should not be ignored.