Chronic suppurative otitis media (CSOM) is a long-lasting middle ear infection characterized by a hole in the eardrum and persistent drainage from the ear lasting longer than six weeks. It affects an estimated 297 million people worldwide, with about 85% of cases occurring in low- and middle-income countries. Unlike a typical ear infection that clears up on its own or with a short course of treatment, CSOM lingers, and without proper care it can cause permanent hearing loss and serious complications.
How CSOM Differs From a Regular Ear Infection
Most ear infections (acute otitis media) are short-lived. The middle ear fills with fluid, pressure builds, and you feel pain. Within days to a couple of weeks, the infection resolves. Sometimes the eardrum ruptures briefly, fluid drains out, and the perforation heals on its own in roughly 80% of cases.
CSOM is what happens when that process fails. The eardrum stays perforated, the infection persists, and the ear continues to drain pus or mucus for six weeks or longer. The defining features are the non-healing hole in the eardrum and the ongoing discharge. Pain is not always present, which is part of the reason some people live with the condition for months or years before seeking treatment.
Symptoms to Recognize
The hallmark symptom is persistent ear discharge, which can range from thin and watery to thick and foul-smelling. In some cases, the ear may go through “dry” periods where drainage temporarily stops before returning. Other symptoms include:
- Hearing loss: the most common complication, which can be conductive (caused by the damaged eardrum and disrupted middle ear bones) or sensorineural (caused by damage spreading to the inner ear)
- Tinnitus: ringing or buzzing in the affected ear
- A feeling of fullness or pressure in the ear
Hearing tests in people with CSOM typically show a gap between what the inner ear can detect and what actually reaches it through the damaged middle ear. At lower pitches, this gap averages around 40 decibels, roughly the difference between a quiet room and normal conversation. At higher pitches the gap is smaller, around 27 to 29 decibels, but still enough to make speech sound muffled or unclear. In children, this level of hearing loss can affect language development and school performance.
What Causes It
CSOM usually begins as an acute ear infection that either goes untreated or doesn’t fully resolve. The bacteria involved tend to differ from those in a standard ear infection. The two most commonly found organisms are Pseudomonas aeruginosa (a bacterium that thrives in moist environments) and Staphylococcus aureus, including antibiotic-resistant strains like MRSA. A range of other bacteria and sometimes fungi can also be involved, which is one reason the infection can be stubborn to treat.
Risk factors include repeated acute ear infections in childhood, poor access to healthcare, crowded living conditions, and lack of breastfeeding in infancy. A history of ear tube placement that leaves a persistent perforation can also lead to CSOM.
The Cholesteatoma Complication
One important distinction doctors make is whether CSOM involves a cholesteatoma, which is an abnormal growth of skin cells that collects behind the eardrum. It is not a tumor, but it behaves aggressively. A cholesteatoma expands over time, eroding the tiny bones of the middle ear and potentially breaking into surrounding structures.
Imaging studies show a stark difference between CSOM with and without a cholesteatoma. Bone erosion occurs in about 36% of standard CSOM cases, but in 96% of cases with a cholesteatoma. The small hearing bones are especially vulnerable: the incus (the middle bone in the chain) shows erosion in 88% of cholesteatoma cases compared to just 14% without one. This distinction matters because a cholesteatoma almost always requires surgery, while standard CSOM can often be managed with medical treatment first.
How It Is Treated
Treatment typically starts with two things done together: cleaning the ear and applying antibiotic drops directly into the ear canal.
Cleaning, often called aural toilet, involves carefully suctioning out discharge and debris so that medication can actually reach the infected tissue. This is done by a clinician using a small suction tip inserted gently into the ear canal. In ears that are heavily blocked, a medicated wick (a small strip of compressed material) may be placed in the canal to deliver antibiotic drops more effectively. The wick is usually replaced or removed after 24 to 48 hours.
For the antibiotic drops themselves, a large Cochrane review found that topical quinolone antibiotics (drops applied directly into the ear) are slightly more effective at resolving ear discharge than antibiotics taken by mouth. Drops delivered directly to the infection site achieve higher concentrations where they’re needed most, with fewer whole-body side effects. This is why ear drops are generally the first-line approach.
When Surgery Becomes Necessary
If the ear does not respond to medical treatment, or if a cholesteatoma is present, surgery is the next step. The most common procedure is tympanoplasty, a reconstruction of the eardrum with or without repair of the tiny hearing bones behind it. The goals are straightforward: close the perforation to stop recurring infections and restore as much hearing as possible.
When the infection has spread into the mastoid bone (the bony bump you can feel behind your ear), a mastoidectomy may be performed alongside tympanoplasty to remove infected bone and create a cavity that is easier to keep clean. Recovery from these surgeries typically involves several weeks of avoiding water in the ear and follow-up visits to monitor healing.
Serious Complications
Left untreated over months or years, CSOM can cause problems well beyond hearing loss. Complications fall into two categories based on where they occur.
Outside the skull, the most common complications are mastoid abscess (a collection of pus in the bone behind the ear), labyrinthitis (infection of the inner ear causing severe dizziness), and facial nerve palsy, where the nerve running through the middle ear becomes damaged, causing weakness on one side of the face.
Inside the skull, the risks are more serious. Brain abscess and meningitis are the two most frequently reported intracranial complications. Lateral sinus thrombosis, a blood clot in one of the large veins draining the brain, can also occur. These complications are uncommon with proper treatment but remain a real concern in settings where care is delayed. Other potential outcomes include scarring of the eardrum (tympanosclerosis) and the formation of ear polyps, which are inflammatory growths that can further block drainage and worsen the cycle of infection.
Who Is Most Affected
The global prevalence of CSOM sits at about 3.8% of the world’s population. That translates to roughly 297 million people, with an estimated 252 million of them living in low- and middle-income countries where access to ear care specialists is limited. Children are disproportionately affected because their ear anatomy makes them more prone to infections, and because untreated acute infections in childhood are the most common pathway to chronic disease. In these populations, CSOM is one of the leading preventable causes of hearing disability.