Chronic mastoiditis is a long-standing infection and inflammation of the mastoid bone, the honeycomb-like structure of air cells sitting just behind your ear. It develops when a middle ear infection persists or recurs without fully resolving, gradually eroding the bony walls of the mastoid and sometimes giving rise to a cholesteatoma, a growth of trapped skin cells that slowly destroys surrounding structures. Unlike acute mastoiditis, which strikes suddenly with fever and swelling, the chronic form tends to smolder for weeks to months, making it easier to overlook and harder to treat with antibiotics alone.
How Chronic Mastoiditis Develops
The mastoid bone is not a solid block. It contains a network of air-filled pockets that connect directly to the middle ear through a narrow passage. In a healthy ear, air circulates freely through these cells. When a middle ear infection (otitis media) lingers or keeps coming back, the lining of these air cells swells, fluid and pus accumulate, and the normal ventilation pathway gets blocked. Over time, the trapped infection eats into the thin bony partitions between the air cells, a process called coalescence. In the chronic form, this destruction unfolds gradually rather than explosively, driven by persistent inflammation that never fully clears.1Cureus. Mastoiditis Now Affects Adults: A Case Report of an Occurrence of the Disease in an 82-Year-Old Male
One reason the infection keeps going is that bacteria in chronically inflamed ears form biofilms, dense colonies encased in a protective slime that shields them from both antibiotics and your immune system. Research on middle ear tissue from patients with chronic otitis media found biofilms in nearly all patients who had active ear discharge, while healthy control tissue was completely free of them.2PubMed Central. Bacterial biofilm formation in the middle-ear mucosa of chronic otitis media patients These biofilms help explain why oral antibiotics so often fail to stamp out chronic ear infections: the drugs reach the bloodstream just fine, but the bacteria inside a biofilm are shielded from concentrations that would kill them in open tissue.
The bacteria involved in chronic mastoiditis also differ from those in a straightforward acute ear infection. A prospective study of chronic mastoiditis patients found that Pseudomonas aeruginosa was the single most common organism, recovered from over half the patients. Anaerobic bacteria, types that thrive without oxygen, were also isolated from the majority of cases, and most patients harbored a mix of aerobic and anaerobic species at once.3Microbiology Society (JMM Case Reports). A prospective study of seven patients with chronic mastoiditis This mixed-organism profile is one reason chronic mastoiditis is trickier to treat than acute infections, which are more commonly caused by a single bacterium.
The Cholesteatoma Connection
Cholesteatomas come up frequently in discussions of chronic mastoiditis because the two conditions feed each other. A cholesteatoma is essentially a pouch of skin that grows in the wrong place, typically the middle ear or mastoid, and slowly expands. As it grows, it produces enzymes that dissolve bone. Untreated, it can erode through the temporal bone and damage structures far beyond the ear, including the skull base.4PubMed Central. Recurrent Cholesteatoma with Skull Base Erosion: A Case Report The growth tends to progress quietly, which often delays diagnosis until the damage is already significant.5International Journal of Surgery Case Reports. Cholesteatoma-induced cerebellopontine abscess; a misdiagnosed case of chronic otitis media with temporal bone erosion: A case report and literature review
Not every case of chronic mastoiditis involves a cholesteatoma, and not every cholesteatoma leads to mastoiditis. But when a cholesteatoma sits in the mastoid, it provides a constant source of debris and infection that antibiotics alone cannot eliminate. The growth needs to be physically removed. This is why the surgical approach to chronic mastoiditis depends heavily on whether a cholesteatoma is present: if it is, surgery becomes a question of when, not if.
Symptoms That Often Get Missed
Chronic mastoiditis does not announce itself the way acute mastoiditis does. There is usually no dramatic swelling behind the ear, no high fever. Instead, the hallmark is persistent or recurrent ear discharge, often foul-smelling, that does not resolve with standard treatment. Many people live with it for months or even years, attributing it to a stubborn ear infection or swimmer’s ear. Other symptoms can include a dull ache or pressure deep in the ear, and gradual hearing loss that worsens over time.
Hearing loss in chronic mastoiditis typically starts as a conductive type, meaning sound is physically blocked from reaching the inner ear, usually because the eardrum has a perforation or the tiny middle ear bones have been damaged. A five-year clinical overview of patients with chronic otitis media and mastoid involvement found conductive hearing loss in about a third of audiometric recordings. In more advanced cases, the damage extends deeper and produces mixed hearing loss, a combination of conductive and inner ear damage, which carries a worse prognosis.6PubMed Central. Audiometric Outcomes in Chronic Otitis Media with Mastoid Involvement: A Five-Year Clinical Overview Mixed hearing loss signals that the infection or erosion has reached the cochlea, and the inner ear damage from that is often permanent.
Headache is another symptom that can be deceptively misleading. In one documented case, a man with chronic otitis media developed a persistent headache that met all the clinical criteria for chronic migraine. He underwent mastoidectomy and multiple courses of antibiotics, but the headache continued. Imaging eventually revealed petrous apicitis, an infection that had spread from the mastoid into the dense bone at the base of the skull. His headache resolved completely only after a prolonged antibiotic course targeted at that deeper infection.7PubMed Central. Headache in Petrous Apicitis: A Case Report of Chronic Migraine-like Headache Due to Peripheral Pathology The takeaway for anyone with chronic ear problems and unexplained headache: the two may well be related.
How It Is Diagnosed
Diagnosis usually starts with a physical exam. An ear, nose, and throat specialist will look into the ear canal with a microscope or endoscope, checking for a perforated eardrum, discharge, granulation tissue, or visible cholesteatoma. But the physical exam alone cannot show what is happening inside the mastoid bone. That requires imaging.
High-resolution CT scanning is the standard first step for evaluating the mastoid. It gives excellent detail of the bony architecture, showing which air cells have broken down, whether the bony walls between them have eroded, and how far any damage extends.8PubMed Central. Role of High Resolution Computed Tomography of Mastoids in Planning Surgery for Chronic Suppurative Otitis Media Surgeons rely on these scans to plan the operation, because the anatomy of the mastoid varies from person to person and the scan reveals exactly where critical structures like the facial nerve and the brain’s covering membrane sit relative to the disease.
CT has a limitation, though: it cannot reliably distinguish a cholesteatoma from scar tissue or simple inflammation. Everything looks like soft tissue density on a CT scan. This is where MRI, specifically a technique called diffusion-weighted imaging (DWI), becomes valuable. DWI exploits the fact that cholesteatoma tissue restricts the movement of water molecules differently than scar tissue or granulation tissue does. A study evaluating this approach found it could tell cholesteatoma from granulation tissue with very high accuracy, and it is particularly useful in patients who have already had surgery, where post-operative scarring can mimic recurrent disease on CT.9American Journal of Neuroradiology. The Utility of Diffusion-Weighted Imaging for Cholesteatoma Evaluation Research measuring the specific diffusion values confirmed that cholesteatoma tissue behaves measurably differently from inflammatory granulation tissue on MRI, with near-perfect sensitivity and specificity when using an optimized threshold.10PubMed. Cholesteatoma vs granulation tissue: a differential diagnosis by DWI-MRI apparent diffusion coefficient
Hearing tests round out the workup. Pure tone audiometry documents the type and degree of hearing loss, and the pattern often hints at what structures are involved. Conductive loss suggests the problem is in the middle ear. Mixed loss suggests the inner ear is also affected. Baseline hearing data is essential before surgery, both for planning what procedure to do and for measuring whether hearing improves afterward.
Medical Treatment and Its Limits
Antibiotics are part of the management of chronic mastoiditis, but they are rarely the whole solution. Where they matter most is in controlling active infection and ear discharge. The evidence here is clear: topical antibiotic eardrops work better than oral antibiotics for chronically discharging ears with an eardrum perforation. A Cochrane systematic review found that topical quinolone antibiotics were roughly three times more effective at stopping discharge within one to two weeks compared to oral antibiotics, whether the oral drug was a quinolone or not. Adding an oral antibiotic on top of the topical one did not produce any detectable additional benefit.11Cochrane Database of Systematic Reviews. Systemic antibiotics versus topical treatments for chronically discharging ears with underlying eardrum perforations
This makes intuitive sense when you consider the biofilm problem. A topical antibiotic delivers a high concentration of drug directly to the infected surface, which is more likely to penetrate a biofilm than the relatively dilute concentration that arrives through the bloodstream after swallowing a pill. In practice, most ENT specialists prescribe a fluoroquinolone eardrop (ciprofloxacin or ofloxacin) and reserve oral antibiotics for situations where the infection has spread beyond the ear or the patient is showing signs of systemic illness.
The catch is that medical treatment alone usually cannot cure chronic mastoiditis, especially when there is significant bone erosion or a cholesteatoma. Antibiotics can quiet the infection temporarily, but the underlying structural damage, blocked drainage, or trapped skin growth means the infection tends to return once the drops are stopped. This is why surgery enters the conversation for most chronic cases.
Surgical Options
Mastoidectomy, the surgical removal of diseased mastoid bone, has been performed in various forms since before antibiotics existed. In the pre-antibiotic era, draining mastoid abscesses was a common and often life-saving procedure.12PubMed Central. A brief history of mastoidectomy Modern techniques have refined the surgery considerably, and the debate today is less about whether to operate than about which approach to use.
The two traditional techniques are canal wall up (CWU) and canal wall down (CWD) mastoidectomy. In a CWU procedure, the surgeon removes the diseased air cells but leaves the back wall of the ear canal intact, preserving more normal anatomy. The downside is that leaving the wall intact can create hidden pockets where cholesteatoma can recur. A CWD procedure takes down the ear canal wall, creating a single large cavity (called a mastoid bowl) that is easier to inspect and keep clean, but it requires lifelong ear canal maintenance and carries a higher rate of persistent drainage from the open cavity.
A more recent approach combines CWD with mastoid obliteration, filling the cavity with tissue or bone material to eliminate the open bowl. A systematic review and meta-analysis comparing these strategies found that CWD with obliteration had significantly lower rates of persistent ear discharge compared to CWD without obliteration, while maintaining comparable recurrence rates. And compared to the CWU technique, the obliteration approach carried a significantly lower risk of cholesteatoma recurrence.13American Journal of Otolaryngology. Mastoid obliteration versus canal wall down or canal wall up mastoidectomy for cholesteatoma: Systematic review and meta-analysis This combination appears to offer something close to the best of both worlds: less recurrence than CWU, less drainage than a standard open cavity.
When the tiny bones of the middle ear (the ossicular chain) have been damaged by chronic disease, hearing reconstruction is often performed at the same time or as a staged second procedure. Ossiculoplasty involves placing a prosthetic replacement for the eroded bones. A study of over 180 patients who underwent ossiculoplasty for chronic otitis media with severe hearing loss found that air conduction, bone conduction, and the air-bone gap all improved significantly at 12 months after surgery.14PubMed Central. Efficacy of ossiculoplasty in patients with chronic otitis media with severe to profound hearing loss That said, hearing outcomes tend to be somewhat better in patients whose chronic ear disease did not involve a cholesteatoma, compared to those whose disease did.15PubMed Central. Factors influencing audiologic outcomes in ossiculoplasty for chronic otitis media: a prospective multicentre study The presence of a cholesteatoma often means more extensive middle ear damage that is harder to fully reconstruct.
What Happens When It Goes Untreated
Left to progress, chronic mastoiditis can produce complications that extend well beyond the ear. The mastoid sits immediately next to the brain, the large venous sinuses that drain blood from the brain, and the facial nerve. Once infection erodes through the thin bone separating these spaces, the consequences can be severe. A case report of a child with chronic otitis media and cholesteatoma documented a cascade of complications: bacterial meningitis, a cerebellar abscess, an abscess around the sigmoid sinus, and thrombophlebitis (infection and clotting) of that sinus, all from the same chronic ear process.16PubMed. Intracranial complications of acute and chronic mastoiditis: report of two cases in children
These catastrophic complications are uncommon, but they are not historical curiosities. They still occur, particularly in settings where access to ENT care is limited or when patients and clinicians underestimate the seriousness of chronic ear discharge. Facial nerve paralysis is another feared complication, since the nerve runs through a bony canal that passes directly through the middle ear and mastoid. Bone erosion from infection or cholesteatoma can expose and damage the nerve.
Life After Surgery and Quality of Life
For patients who have been living with a chronically draining ear, persistent pain, or the social embarrassment of foul-smelling discharge, successful surgery can be genuinely life-changing. A study measuring health-related quality of life using a validated questionnaire found that patients who underwent mastoid cavity obliteration experienced a large and statistically significant improvement in their quality-of-life scores after surgery, with mean scores nearly halving from before to after the procedure.17PubMed Central. Mastoid cavity obliteration leads to a clinically significant improvement in health-related quality of life
Recovery after mastoidectomy typically involves several weeks of restricted activity, keeping the ear dry, and follow-up visits for cleaning and monitoring. Patients who had an open-cavity (CWD) procedure without obliteration will likely need periodic ear cleaning by a specialist for the rest of their lives, because the large cavity accumulates debris and wax that a normal ear canal would handle on its own. This long-term maintenance burden is one of the main reasons the obliteration technique has gained popularity.
Mastoid Size and Why Anatomy Varies
One underappreciated factor in chronic mastoiditis is that the size and development of the mastoid air cell system varies enormously from person to person and across populations. The mastoid air cells start forming in childhood, and their growth depends on both genetics and the presence or absence of ear infections during development. A child with recurrent otitis media tends to develop a less well-pneumatized (less airy, more solid) mastoid, which may itself predispose to further problems because the smaller air cell system does not ventilate as effectively. A scoping review of the literature confirmed that mastoid air cell size differs across populations of different origins and that the relationship between air cell development, age, and ear disease is still not fully mapped out.18PubMed Central. Temporal bone pneumatization: A scoping review on the growth and size of mastoid air cell system with age Surgeons take this anatomical variation into account when planning mastoidectomy, because a small, sclerotic mastoid is technically different to operate on than a large, well-pneumatized one.
This variability also means there is no universal threshold for how much bone erosion is “too much” on a CT scan. What counts as abnormal depends partly on what the patient’s mastoid looked like before the disease started, and that baseline is usually unknown. Interpreting imaging in chronic mastoiditis requires experience and clinical context, not just a checklist of measurements.
Who Gets Chronic Mastoiditis
Historically, mastoiditis of any kind has been thought of as a childhood disease, since children get far more middle ear infections than adults. But chronic mastoiditis occurs in adults too, and there is some evidence that clinicians are seeing it in older adults more than they used to. A case report describing mastoiditis in an 82-year-old man highlighted how unusual this presentation was considered, and how the condition may be underrecognized in elderly patients, whose ear complaints are sometimes attributed to age-related hearing decline rather than active infection.1Cureus. Mastoiditis Now Affects Adults: A Case Report of an Occurrence of the Disease in an 82-Year-Old Male
People with weakened immune systems, diabetes, or a history of prior ear surgery are at higher risk. Individuals who had chronic ear infections as children but never received definitive surgical treatment may carry low-grade mastoid disease into adulthood, only seeking help decades later when hearing loss becomes disabling or a complication develops. In parts of the world where access to ENT surgery is limited, chronic suppurative otitis media and its mastoid complications remain a significant cause of preventable hearing loss and occasionally life-threatening infection.