Otosclerosis: What Causes Abnormal Bone Growth in the Middle Ear and How It Affects Hearing

Imagine sitting across from your spouse at dinner, and they’re talking normally - but you can’t make out what they’re saying. You ask them to repeat it. They speak louder. Still nothing. You start blaming yourself: Am I going deaf? Then you notice something stranger: you hear the dog barking clearly, but you miss the low rumble of the TV. That’s not just aging. That’s otosclerosis.

Otosclerosis is a condition where abnormal bone grows in the middle ear, specifically around the stapes - the smallest bone in your body, about the size of a grain of rice. This bone normally vibrates like a tiny piston to send sound from your eardrum to the inner ear. But when it gets stuck in place by extra bone, sound can’t travel. The result? Progressive hearing loss that sneaks up slowly, often starting in your 30s or 40s.

How Otosclerosis Actually Works

Your middle ear has three tiny bones: the malleus, incus, and stapes. They work like a chain, passing vibrations from your eardrum to the cochlea. In otosclerosis, the stapes becomes fused to the oval window - the entrance to the inner ear. Instead of moving freely, it’s locked in place. That’s why you lose the ability to hear low-pitched sounds first - whispers, bass tones, men’s voices. High-pitched sounds like birds chirping or children’s voices often stay clear longer.

This isn’t just random bone growth. It’s a malfunction in bone remodeling. Healthy bone is constantly being broken down and rebuilt. In otosclerosis, the process goes haywire. New bone forms too quickly and doesn’t harden properly, creating spongy, porous areas that later calcify. Over time, the stapes becomes immobile. Audiograms show this as an air-bone gap - usually between 20 and 40 decibels - meaning your ear can’t conduct sound the way it should, even though your inner ear is still working fine.

It’s not just the stapes. In about 1 in 10 cases, the abnormal bone spreads to the cochlea. That’s when hearing loss becomes mixed - part conductive, part sensorineural. Once it hits the inner ear, it’s harder to fix. That’s why early detection matters.

Who Gets Otosclerosis - And Why?

Otosclerosis doesn’t pick on everyone equally. It’s most common in people of European descent. About 0.3% to 0.4% of Caucasians have it. In African and Asian populations, the rate drops to 0.1% or lower. Women are twice as likely to develop it as men, and it often flares up during pregnancy - likely due to hormonal changes that speed up bone remodeling.

Genetics play a huge role. If one parent has otosclerosis, your risk jumps to about 25%. If both parents have it, your chances climb to nearly 50%. Scientists have identified at least 15 genes linked to the condition, with the RELN gene on chromosome 7 being the strongest predictor. That’s why it often runs in families - even if no one ever got diagnosed.

It’s also not rare. Around 3 million Americans have otosclerosis. That’s nearly 1 in 100 people. And because symptoms start slowly, many go years without knowing what’s wrong. Some think they’re just losing hearing with age. Others blame earwax or stress. The average delay in diagnosis? 18 months.

What It Feels Like - Real Patient Stories

People with otosclerosis don’t wake up deaf. They notice things slipping away.

One woman in her late 30s kept asking her husband to repeat himself. She thought he was mumbling. Then she realized: she couldn’t hear the hum of the refrigerator, or the bass in music. Her audiogram showed a 45 dB loss at 500 Hz - the exact frequency range otosclerosis hits hardest.

A teacher in Florida couldn’t hear students whispering in the back of her classroom. She thought they were being disrespectful. Turns out, her hearing had dropped 30 dB in two years. After surgery, she said: “I finally heard a student say ‘I love this class’ - quietly, from the back. I cried.”

But it’s not just about hearing. About 80% of people with otosclerosis also get tinnitus - a ringing, buzzing, or hissing in the ears. For 35% of them, it’s bad enough to ruin sleep. That’s often the most frustrating part. The hearing loss can be fixed. The noise? Not always.

How It’s Different From Other Hearing Losses

Otosclerosis isn’t the same as noise damage or aging-related hearing loss.

Noise-induced hearing loss hits high frequencies first - you lose the ability to hear birds, alarms, or the “s” and “th” sounds in speech. Otosclerosis? It hits low frequencies. You miss the rumble of a car engine, the bass in music, or your partner’s voice.

Age-related hearing loss (presbycusis) usually starts after 65. Otosclerosis hits in your 30s to 50s. And unlike Meniere’s disease, it doesn’t come with spinning dizziness or sudden hearing drops. It’s steady. Slow. Silent. That’s why it’s so easy to ignore.

And unlike congenital hearing problems, otosclerosis is treatable - often with near-perfect results. Surgery fixes the problem in 90% to 95% of cases. That’s higher than most other ear surgeries.

How Doctors Diagnose It

There’s no blood test. No scan you can do at home. Diagnosis starts with a hearing test - pure-tone audiometry. If you have a clear air-bone gap of at least 15 dB, and your speech recognition is still above 70%, otosclerosis is the top suspect.

Next, a doctor will use an otoscope to look inside your ear. If the eardrum looks normal (which it usually does), and you don’t have fluid or infection, they’ll suspect otosclerosis. A CT scan of the temporal bone can show the early spongy bone changes - small, dark spots about 0.5 to 2 mm wide around the stapes.

But here’s the catch: many primary care doctors don’t know what to look for. They hear “hearing loss” and think “age.” That’s why so many people wait years. If you’re under 50 and your hearing’s getting worse - especially if low voices are harder to hear - ask for a referral to an ENT specialist. Don’t wait.

Treatment Options: Hearing Aids vs. Surgery

You have two real choices: hearing aids or surgery.

Hearing aids are the first step for many. They amplify sound - especially low frequencies - and work well for mild to moderate loss. About 65% of people start here. But they don’t fix the problem. They just mask it. And as the bone grows, you’ll need stronger aids over time.

Surgery - specifically, a stapedotomy - is the gold standard. It’s not a big operation. The surgeon uses a microscope, makes a tiny hole in the stapes footplate, and inserts a prosthetic (often made of titanium or platinum). The new prosthesis restores vibration. The procedure takes under an hour, usually done under local anesthesia. Most people go home the same day.

Success rates? 90% to 95% of patients regain near-normal hearing. A 2024 FDA-approved prosthesis called StapesSound™ has a 94% success rate at one year - better than older models. The average cost? $8,500 to $12,000 out-of-pocket, though insurance often covers it if it’s deemed medically necessary.

But it’s not risk-free. In about 1% of cases, patients lose significant hearing in the operated ear. That’s rare, but devastating. That’s why every surgeon spends hours explaining the risks before you sign anything.

What’s New in Otosclerosis Treatment

There’s promising research beyond surgery and hearing aids.

A 2024 study in the Journal of Otology showed sodium fluoride - a mineral used for osteoporosis - can slow bone growth in otosclerosis. Patients who took it for two years had 37% less hearing loss than those who didn’t. It’s not a cure, but it might delay the need for surgery.

Genetic testing is coming fast. Within five years, doctors may be able to screen high-risk people - especially those with family history - before symptoms even appear. Polygenic risk scores could identify who’s likely to develop otosclerosis in their 30s. That means earlier intervention, better outcomes.

But there’s a problem: fewer surgeons are doing stapedectomies. Since 2018, the number of procedures has dropped 15%. Why? Younger ENTs are focusing on cochlear implants and other high-tech fields. Stapedotomy is old-school. It’s precise. It’s tricky. And it takes years to master. Mount Sinai requires 50 supervised cases before letting a surgeon do one alone.

What to Do If You Suspect Otosclerosis

If you’re under 50 and your hearing is slipping - especially if:

• You struggle to hear low voices or whispers
• You hear better in noisy rooms than quiet ones
• You’ve had ringing in your ears for months
• Family members have had hearing issues

Then get tested. Don’t wait. Schedule a hearing evaluation with an audiologist. Ask for a referral to an otolaryngologist who specializes in ear surgery. Bring your family history. Mention otosclerosis by name. Most doctors haven’t seen many cases - but they’ll listen if you’re informed.

And if you’re diagnosed: know this - you’re not alone. About 3 million Americans have it. And 9 out of 10 of them get their hearing back. Whether through a hearing aid or a tiny metal implant, most people go on to live full, connected lives.

Don’t let silence steal your conversations. Get checked. Find out. Take back your hearing.