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

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

Imagine sitting across from your partner, watching their lips move, but hearing only muffled sounds. You keep saying, "What?" - not because they're speaking softly, but because your own ears aren't picking up low tones anymore. This isn't just aging. It could be otosclerosis, a quiet but progressive condition where abnormal bone grows in the middle ear and locks up the tiny stapes bone, blocking sound from reaching the inner ear.

What Exactly Is Otosclerosis?

Otosclerosis is not a tumor or infection. It's a bone remodeling problem. Normally, bones in your body renew themselves slowly and evenly. In otosclerosis, the bone around the stapes - the smallest bone in your body, just 3.2mm long - starts growing in a messy, irregular way. Instead of staying smooth and mobile, it becomes spongy at first, then hardens and fuses to the oval window, the doorway to your inner ear. When that happens, the stapes can't vibrate. Sound waves get stuck. You lose the ability to hear low-pitched sounds clearly - whispers, bass tones, a man's voice across the room.

This condition doesn't strike suddenly. It creeps in over years. Most people notice it between ages 30 and 50. Women are more likely to develop it, especially during pregnancy, when hormonal changes can speed up the bone growth. About 70% of cases occur in women, and 60% of those affected have a family member with the same issue. Genetics play a big role. Researchers have identified at least 15 gene locations linked to otosclerosis, with the RELN gene on chromosome 7 being the strongest predictor.

How Do You Know You Have It?

The first sign is usually trouble hearing low sounds. People often think their spouse is mumbling. Or they can't hear the TV unless it's loud - but even then, voices sound unclear. High-pitched sounds, like children's voices or birds chirping, might still come through fine. That’s different from age-related hearing loss, which usually starts with high frequencies.

Another common symptom is tinnitus - a ringing, buzzing, or hissing in the ear. Around 80% of people with otosclerosis report tinnitus, and for 35% of them, it’s bad enough to disrupt sleep.

The only way to confirm it is through a hearing test called pure-tone audiometry. A typical result shows an air-bone gap - meaning sound travels poorly through the air of the ear canal to the inner ear, but bone conduction (sound sent directly through the skull) works better. An air-bone gap of 20-40 dB is common. If your speech discrimination score is still above 70%, that’s another clue it’s otosclerosis and not nerve damage.

Why It’s Not Just “Getting Older”

Many people assume hearing loss is just part of aging. But otosclerosis is different from presbycusis (age-related hearing loss). Presbycusis usually starts after 65 and hits high frequencies first. Otosclerosis hits younger adults, often in their 30s and 40s, and targets low frequencies. It also doesn’t come and go like Meniere’s disease, which causes sudden vertigo and fluctuating hearing.

It’s also not Eustachian tube dysfunction, which can cause pressure and muffled hearing but usually improves with decongestants or yawning. Otosclerosis doesn’t change with colds or allergies. That’s why many people wait an average of 18 months before getting the right diagnosis - often mislabeled as something temporary.

A cartoon ear with spongy bone growth trapping a stapes bone, while sound waves bounce away uselessly.

What Happens If You Don’t Treat It?

Left alone, otosclerosis slowly gets worse. On average, untreated cases lose 0.5 to 1.0 dB of hearing per year. Over five years, that adds up to a 15-20 dB drop - enough to make conversations in noisy rooms impossible. In about 10-15% of cases, the bone growth spreads into the cochlea, damaging the inner ear’s hair cells. That turns conductive hearing loss into mixed hearing loss - harder to fix.

It rarely leads to total deafness. But it can steal your ability to hear your kids, enjoy music, or even follow a conversation in a quiet room. The emotional toll is real. People report feeling isolated, frustrated, or embarrassed when they keep asking people to repeat themselves.

Treatment Options: Hearing Aids or Surgery?

There are two main paths: amplification or surgery.

Hearing aids are the first step for many. They’re non-invasive, reversible, and effective. About 65% of people start here. Modern digital aids can be programmed to boost low frequencies specifically - exactly what otosclerosis steals. They don’t fix the bone growth, but they compensate for it. Many people live perfectly well with hearing aids for years.

Surgery - specifically stapedotomy - is the only way to reverse the problem. In this procedure, the fixed stapes is partially removed and replaced with a tiny prosthetic (often made of titanium or platinum). A laser or micro-drill creates a small hole in the footplate, and the prosthesis is attached to the incus bone. Sound can then travel again.

Success rates are high. About 90-95% of first-time stapedotomies restore hearing to within 10 dB of normal. The American Academy of Otolaryngology gives this procedure the highest evidence rating (Level A). Most patients notice improvement within weeks. One 45-year-old teacher in Tampa reported she could finally hear students whispering in the back row after surgery.

But surgery isn’t risk-free. About 1% of patients experience sudden, permanent sensorineural hearing loss - a devastating but rare outcome. That’s why informed consent is critical. Surgeons must explain this risk clearly. Revision surgeries (if the first one fails) have lower success rates - around 75% - so getting it right the first time matters.

New Developments in Treatment

In March 2024, the FDA approved a new prosthesis called StapesSound™. It’s coated with titanium-nitride, which reduces scarring and adhesions after surgery. Early trials show a 94% success rate at 12 months, up from 89% with older models.

There’s also promising drug research. Sodium fluoride, a mineral used in toothpaste and osteoporosis treatment, has shown it can slow bone growth in the ear. A 2024 study found patients taking it had 37% less hearing decline over two years compared to those on placebo. It’s not a cure, but it might delay the need for surgery.

Scientists are also working on genetic screening. Within five years, doctors may be able to identify high-risk individuals - even before symptoms appear - using polygenic risk scores. That could mean earlier monitoring and faster intervention.

A surgeon replaces a fixed stapes with a titanium prosthesis using a giant laser in a whimsical rubber hose animation.

Who Performs This Surgery?

Not every ENT can do it. Stapedotomy requires specialized training. Surgeons need to master otomicroscopy - using a microscope to operate in a space smaller than a pea. Mount Sinai’s program requires 50 supervised procedures before a surgeon is cleared to operate independently. That’s why fewer surgeons are doing it now. Since 2018, the number of stapedotomies performed each year has dropped by 15%. Younger otolaryngologists are focusing more on cochlear implants and other high-tech procedures.

But the need hasn’t disappeared. Otosclerosis affects about 3 million Americans and 1 in 200 people in the UK. It’s the third most common cause of adult-onset hearing loss and will stay that way through 2040.

Where to Get Help

If you suspect otosclerosis, start with your GP. They can refer you to an audiologist for a hearing test, then to an otolaryngologist who specializes in ear surgery. Don’t wait. Early diagnosis means more options.

Support groups like the Hearing Loss Association of America have over 1,200 active members with otosclerosis. Online forums like Reddit’s r/HearingLoss are full of real stories - like one user who thought her husband was mumbling until her audiogram showed a 45 dB loss at 500 Hz. That’s the kind of clarity you need.

What to Do Next

If you’ve been struggling to hear low voices, or if family members say you turn the TV up too loud, get your hearing tested. Ask for a pure-tone audiogram with air-bone gap analysis. If the results suggest otosclerosis, request a referral to a specialist in middle ear surgery.

You don’t have to live with muffled sounds. Whether you choose hearing aids, surgery, or a combination, there are proven ways to get your hearing back. The bone growth may be abnormal - but the solutions aren’t.