An acoustic neuroma is a slow-growing, noncancerous tumor that develops on the nerve connecting your inner ear to your brain. Despite the name, the tumor doesn’t actually grow from the acoustic (hearing) nerve itself. It originates from the cells that wrap around and insulate the vestibular nerve, which controls balance. About 76% of these tumors start on the vestibular nerve branches, while roughly 24% arise from the cochlear (hearing) nerve branch. The medical community increasingly uses the more accurate name “vestibular schwannoma,” but both terms refer to the same condition.
These tumors occur at a rate of about 1.1 per 100,000 people per year, with an average age at diagnosis of 53. They affect men and women equally and appear on the left and right sides at similar rates.
How Symptoms Develop
The hallmark symptom is hearing loss in one ear, reported by over 90% of people with acoustic neuromas. This hearing loss typically develops gradually, sometimes over months or years, making it easy to dismiss. It usually affects your ability to understand speech clearly rather than simply reducing volume. You might first notice it when holding a phone to the affected ear or struggling to follow conversations in noisy rooms.
Tinnitus, a ringing or buzzing sound in one ear, is also very common. Nearly half of people with acoustic neuromas experience unsteadiness or balance problems, which tend to worsen as the tumor grows. True vertigo, the spinning sensation, is less typical. Because the tumor grows slowly, the brain often compensates for the gradual loss of balance signals from one side, which is why many people don’t feel dramatically dizzy even as the tumor enlarges.
Larger tumors that press on surrounding structures can cause facial numbness, facial weakness, headaches, or difficulty swallowing. These symptoms are uncommon at initial diagnosis since most tumors are caught before they reach that size.
How It’s Diagnosed
The process usually starts when a hearing test reveals asymmetric hearing loss, meaning one ear performs significantly worse than the other for no obvious reason. A standard audiogram measures both how well you detect tones at different pitches and how clearly you understand spoken words. When results are noticeably different between ears, imaging becomes the next step.
The definitive diagnostic test is an MRI with a contrast agent that highlights abnormal tissue. This scan can detect tumors as small as a few millimeters and gives doctors a detailed picture of the tumor’s size, shape, and position relative to the brainstem and surrounding nerves. CT scans are occasionally used when MRI isn’t an option, but they’re far less sensitive for small tumors.
The Three Management Options
Treatment depends on tumor size, your age, hearing status, and how fast the tumor is growing. There are three main paths: observation, radiation, and surgery.
Observation (Watch and Wait)
Many acoustic neuromas grow slowly enough that immediate treatment isn’t necessary. The average growth rate across all tumors is 1 to 2 millimeters per year. Among tumors that do actively grow, the rate is 2 to 4 millimeters per year. Some tumors stop growing entirely.
During observation, you’ll get periodic MRI scans, typically every 6 to 12 months initially, then less frequently if the tumor remains stable. Hearing tests track any changes over time. This approach avoids the risks of surgery or radiation while keeping close tabs on the tumor. If scans show meaningful growth, you and your doctor can shift to active treatment.
Stereotactic Radiosurgery
Despite the name, this isn’t surgery at all. It delivers highly focused beams of radiation to the tumor in one session (or a small number of sessions), with the goal of stopping growth rather than removing the tumor. Large studies report tumor control rates of 90 to 100% at five years and 91 to 98% at ten years, meaning the vast majority of treated tumors stop growing or shrink.
Radiation has become increasingly popular for smaller tumors. Among tumors under 2 centimeters, about 27% are now treated with radiation rather than surgery, a rate that has risen significantly over time. The procedure is typically done as an outpatient, and most people return to normal activities within a few days.
Surgery
Surgery aims to remove the tumor partially or completely. About 60% of acoustic neuroma patients nationally are treated surgically. The specific approach depends largely on tumor size, location, and whether preserving hearing is realistic.
For small tumors (under 2 centimeters) that haven’t reached the brainstem, surgeons can use an approach through the skull above the ear that offers the best chance of preserving hearing. This option works best for younger patients with functional hearing still intact.
For tumors pressing against the brainstem, or in patients who have already lost useful hearing, an approach through the bone behind the ear is often preferred. This route sacrifices any remaining hearing on that side but provides excellent access to the tumor and the facial nerve.
A third approach, through the back of the skull, is used for large tumors that sit mostly inside the skull cavity rather than deep in the ear canal. It offers some possibility of hearing preservation but requires more manipulation of brain tissue.
The most significant surgical risk across all approaches is damage to the facial nerve, which runs directly alongside the tumor. Surgeons use real-time nerve monitoring during the procedure to minimize this risk. Hearing preservation rates vary widely depending on tumor size and the surgical approach used.
Recovery After Surgery
The initial recovery period involves a hospital stay of several days. Dizziness is expected immediately after surgery because removing the tumor also eliminates the remaining balance signals from that ear. Within a few days, the intense spinning sensation typically transitions to a vaguer, more manageable dizziness as your brain starts compensating.
Outpatient physical therapy focused on balance retraining usually starts within two to three weeks after surgery, assuming no complications. These exercises help your brain recalibrate using signals from your other ear, your vision, and sensors in your joints and muscles. Most people see steady improvement over weeks to months, though the timeline varies. Some residual imbalance in challenging situations, like walking in the dark or on uneven surfaces, can persist longer.
Living With One-Sided Hearing Loss
Whether from the tumor itself or as a result of treatment, many people with acoustic neuromas end up with significant hearing loss in one ear. Single-sided deafness creates specific challenges: difficulty telling where sounds come from, trouble following conversations when noise is coming from your deaf side, and increased listening fatigue in group settings.
Several technologies can help. Routing devices pick up sound on the deaf side and transmit it to the hearing ear. Bone-anchored hearing devices accomplish something similar through vibrations in the skull. For some people, a cochlear implant on the affected side may be an option, though candidacy depends on whether the hearing nerve is intact after treatment. An audiologist can help determine which approach fits your situation best.