A vestibular schwannoma is a benign tumor that grows on the balance nerve connecting your inner ear to your brain. It develops from Schwann cells, the specialized cells that wrap around and insulate this nerve. Despite being noncancerous, the tumor can cause significant hearing loss, ringing in the ear, and balance problems as it presses on nearby structures. About 1.14 people per 100,000 are diagnosed each year in the United States, with the highest rates among adults aged 65 to 74.
Where the Tumor Grows
The eighth cranial nerve, also called the vestibulocochlear nerve, has two branches: one for balance (vestibular) and one for hearing (cochlear). Vestibular schwannomas almost always start on the balance branch, typically in the narrow bony channel called the internal auditory canal where the nerve passes from the inner ear toward the brain. The tumor grows from Schwann cells, which produce the insulating sheath around nerve fibers.
Here’s what makes the early symptoms confusing: even though the tumor originates on the balance nerve, the first noticeable problem is usually hearing loss, not dizziness. That’s because as the young tumor expands within that tight canal, it compresses the neighboring hearing nerve and can obstruct the tiny blood vessels that supply the inner ear’s hearing structures. This is why the condition was historically called “acoustic neuroma,” a name still widely used even though it’s technically inaccurate.
Common Symptoms
The hallmark symptom is one-sided hearing loss. It typically develops gradually, though some people notice it suddenly. The hearing loss is almost always worse on one side, which distinguishes it from age-related hearing decline that tends to affect both ears.
Other early signs include:
- Tinnitus: a persistent ringing, buzzing, or hissing in the affected ear
- Dizziness or imbalance: a vague unsteadiness rather than the room-spinning vertigo people often associate with inner ear problems
- Facial numbness: less common, but can occur if the tumor grows large enough to press on the facial nerve, which runs alongside the vestibulocochlear nerve
Small tumors may produce no symptoms at all and are sometimes found incidentally on brain imaging done for unrelated reasons.
Who Gets It and Why
Most vestibular schwannomas are sporadic, meaning they occur without a clear inherited cause. The tumor develops when Schwann cells lose a protein called merlin, which normally keeps cell growth in check. Without merlin, Schwann cells multiply unchecked and form a slow-growing mass. The average growth rate is about 1.4 millimeters per year, roughly the thickness of a credit card.
Incidence is roughly equal between men and women. It peaks in the 65 to 74 age group, where the rate climbs to about 3.18 per 100,000. Rates are highest among white non-Hispanic individuals and lowest among Black non-Hispanic individuals, though the reasons for this disparity aren’t fully understood.
A small percentage of cases are linked to a genetic condition called neurofibromatosis type 2 (NF2), caused by a mutation on chromosome 22. People with NF2 typically develop vestibular schwannomas on both sides, often at a younger age. NF2 follows an autosomal dominant inheritance pattern, meaning a child of someone with the mutation has a 50% chance of inheriting it. Some cases arise from new, spontaneous mutations with no family history. Among children diagnosed with vestibular schwannomas, nearly 29% have bilateral tumors, a strong indicator of NF2.
How It’s Diagnosed
If you report one-sided hearing loss, the first step is usually a hearing test (audiogram). Asymmetric hearing loss, particularly poor speech discrimination in one ear, raises suspicion. Good high-frequency hearing and strong speech discrimination at the time of diagnosis also turn out to be useful predictors of whether hearing will hold up over time if the tumor is monitored rather than treated immediately.
The gold standard for confirming the diagnosis is an MRI with a contrast agent called gadolinium. The contrast lights up the tumor on the scan, making even small growths visible within the internal auditory canal. This imaging also reveals the tumor’s size and its relationship to the brainstem and surrounding nerves, which directly shapes treatment decisions.
Observation: The Wait-and-Scan Approach
Not every vestibular schwannoma needs immediate treatment. For small to medium tumors that aren’t compressing the brainstem or affecting nerves beyond the hearing and balance nerve, observation with regular imaging is a reasonable first step. A large retrospective analysis found that tumor control with observation alone was about 65%, and 71% of patients maintained useful hearing at two years.
The standard monitoring schedule typically looks like this: a first follow-up MRI six months after diagnosis, another scan a year after that, then imaging every two years for up to ten years, assuming the tumor stays stable or grows minimally. Serial imaging during the first year is especially important because that’s when faster-growing tumors tend to reveal themselves. If the tumor shows significant growth or new symptoms develop, the conversation shifts toward active treatment.
Radiation Therapy
Stereotactic radiosurgery delivers highly focused beams of radiation to the tumor in one or a few sessions. Despite the name, it doesn’t involve cutting. The goal is to stop tumor growth rather than remove it. For large vestibular schwannomas treated with a single session, pooled data from 13 studies covering 483 patients showed radiographic control (meaning the tumor stopped growing or shrank) in 92% of cases and clinical control in 89%.
Doses have come down significantly over the years. Early treatments used higher doses that controlled tumors in over 95% of cases but caused more nerve damage. Current protocols rarely exceed 14 Gy, balancing strong tumor control with fewer side effects. Some patients receive the radiation split across multiple sessions (fractionated treatment), which showed clinical control in about 91% of patients in a smaller pooled analysis.
Surgical Removal
Surgery aims to remove the tumor partially or completely. Three main surgical approaches exist, and the choice depends on tumor size, location, and how much hearing remains in the affected ear.
- Translabyrinthine: goes through the bone behind the ear and through the inner ear structures. It provides good access to the tumor but sacrifices any remaining hearing on that side.
- Retrosigmoid: approaches from behind the ear through the skull, allowing the surgeon to see both the tumor and the hearing nerve. It offers a chance of preserving hearing.
- Middle fossa: accesses the tumor from above, through a small opening in the skull above the ear. It’s typically used for smaller tumors when hearing preservation is a priority.
One of the main risks of surgery is damage to the facial nerve, which controls the muscles of facial expression and runs right alongside the tumor. Delayed facial nerve paralysis, which develops days to weeks after surgery rather than immediately, occurs in about 12% of patients who undergo microsurgical removal. Most cases of delayed paralysis improve over time, but it remains a significant consideration when weighing surgery against other options.
Recovery and Rehabilitation
After surgery or radiation, many people experience a period of dizziness and imbalance as the brain adjusts to changed input from the inner ear. Vestibular rehabilitation, a specialized form of physical therapy, helps speed this adjustment. Programs typically include several types of targeted exercises performed multiple times daily.
Head-turning exercises (sometimes called Cawthorne-Cooksey exercises) involve moving the head forward, backward, and side to side with increasing speed, repeated four to five times per day. These help reduce dizziness and vertigo symptoms. Eye-tracking exercises train the connection between head movement and vision, minimizing the blurry vision that often accompanies vestibular damage. These are typically done five times a day. Balance work progresses from simple standing exercises to tandem walking (heel to toe), side-stepping, Swiss ball balancing, and eventually normal gait training with postural correction.
The timeline for recovery varies widely. Some people feel steady within weeks, while others need months of consistent rehabilitation. The brain’s ability to compensate for one-sided vestibular loss is generally strong, particularly in younger and more active individuals, but the process requires repetition and patience.