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What is acoustic neuroma (vestibular schwannoma)?
An acoustic neuroma — more accurately called a vestibular schwannoma — is a benign (non-cancerous) tumor that grows from the Schwann cells, the cells that form the insulating sheath around the vestibulocochlear nerve, the nerve that carries hearing and balance signals from the inner ear to the brain. It develops in the narrow canal and angle where this nerve passes from the inner ear toward the brainstem. Because it sits on the hearing-and-balance nerve and lies close to the facial nerve (which moves the muscles of the face), its symptoms usually involve those functions: gradual hearing loss in one ear, ringing in that ear (tinnitus), unsteadiness or balance problems, and sometimes facial numbness or, with larger tumors, facial weakness. These tumors are almost always benign and slow-growing, and they do not spread to other parts of the body. Most occur on one side and have no clear cause; a small number occur in people with an inherited condition called neurofibromatosis type 2, which can cause tumors on both sides. Because they grow slowly and many barely grow at all, a very common and reasonable first approach — especially for small tumors with good hearing — is careful monitoring with periodic MRI scans and hearing tests. When treatment is needed, the two main options are surgery and focused radiation, and the choice depends on the tumor's size, the person's hearing, age, and preferences. The central goals of treatment are to control the tumor while preserving hearing and protecting the facial nerve, and modern radiation techniques are very good at doing exactly that for appropriately sized tumors.
The main types
Doctors group acoustic neuroma (vestibular schwannoma) by where it starts and how it behaves:
| Type | What it means, simply |
|---|---|
| Sporadic (one-sided) vestibular schwannoma | The usual form — a single tumor on one side with no inherited cause; the vast majority of cases. |
| Neurofibromatosis type 2 (NF2)-related | An inherited condition that can cause vestibular schwannomas on both sides along with other nervous-system tumors; managed by a specialized team with hearing preservation as a central concern. |
| Intracanalicular tumor | A small tumor confined to the bony canal of the nerve; often watched, and well suited to focused radiation if it grows. |
| Tumor extending to the cerebellopontine angle | A larger tumor that has grown out of the canal toward the brainstem; size and pressure on nearby structures guide whether surgery or radiation is best. |
Staging, in plain terms
Acoustic neuromas are benign and do not spread, so they are not staged like a cancer. Instead, doctors describe them mainly by size and how far they extend, often using the Koos grading scale, which runs from grade I (a small tumor limited to the bony nerve canal) up to grade IV (a large tumor that reaches and presses on the brainstem). They also pay close attention to two functional measures that drive decisions: the person's hearing in the affected ear, and the health of the nearby facial nerve. Growth over time is important too — because many of these tumors grow very slowly or not at all, doctors frequently obtain a baseline MRI and then repeat it to see whether the tumor is actually enlarging before recommending treatment. Putting these together — tumor size and extent, current hearing, facial nerve function, the person's age and overall health, and whether the tumor is growing — determines whether the best path is to watch it, treat it with focused radiation, or remove it surgically. For small and medium tumors, radiation and surgery offer similar tumor control, so the decision often comes down to preserving hearing and facial function and to patient preference.
| No cancer staging — classified by size and location (Koos grade I–IV) and by hearing status | What it generally means |
|---|---|
| Small, stable, good hearing | A small tumor that isn't growing in someone with useful hearing; usually managed with active surveillance — periodic MRI and hearing tests — since many never need treatment. |
| Small-to-medium, growing or symptomatic | A tumor that is enlarging or causing symptoms but is still a suitable size for focused radiation; single-session radiosurgery offers high control with good hearing and facial-nerve preservation. |
| Large tumor pressing on the brainstem | A bigger tumor causing pressure on the brainstem or other structures; usually treated with surgery to relieve the pressure, sometimes followed by radiation to any remaining tumor. |
| NF2-related (both sides) | Tumors on both sides in someone with neurofibromatosis type 2; managed by a specialized team balancing tumor control with preserving any remaining hearing, sometimes with a targeted medicine. |
The standard of care
Acoustic Neuroma (Vestibular Schwannoma) is almost always treated by a team that may include a surgeon, a medical oncologist, and a radiation oncologist, combining therapies for the best result. The usual building blocks are:
Active surveillance
For small, stable tumors — especially with useful hearing — periodic MRI scans and hearing tests are often the best first step, since many of these tumors grow little or not at all.
Stereotactic radiosurgery (SRS)
A highly focused, usually single-session radiation treatment that controls small-to-medium tumors with high success while aiming to preserve hearing and protect the facial nerve, without any incision.
Fractionated stereotactic radiotherapy
Precise radiation divided into several smaller sessions, an option for somewhat larger tumors or when extra care is taken to protect hearing.
Microsurgical removal
An operation to remove the tumor, preferred for larger tumors pressing on the brainstem; the surgical approach is chosen to protect the facial nerve and, when possible, hearing.
Targeted medicine for NF2
In neurofibromatosis type 2, a drug that blocks tumor blood-vessel growth (bevacizumab) can shrink tumors and sometimes improve hearing in selected patients.
How radiation treatment works
Radiation therapy controls an acoustic neuroma by delivering precisely targeted energy that damages the DNA inside the tumor's cells, halting their ability to grow and divide. Because these tumors are benign and slow-growing, success is measured as long-term control — the tumor stops enlarging and frequently shrinks over the following years — rather than a quick disappearance. The technique that makes this possible is stereotactic radiosurgery, in which many radiation beams are aimed from different directions so that they all intersect precisely at the tumor. Each individual beam is weak, but together they deliver a strong, conformal dose right at the target, while the dose falls off so steeply at the edges that the structures packed in around the tumor receive very little. That precision is the whole point here, because the tumor sits within millimeters of the facial nerve, the hearing nerve and cochlea, and the brainstem. Sparing those structures is what allows radiation to control the tumor while protecting facial movement and, in many cases, preserving useful hearing. Treatment is often given in a single session without any incision, and for somewhat larger tumors or for extra protection of hearing, the dose can instead be divided into several smaller sessions (fractionated radiotherapy), giving sensitive tissues time to recover between treatments. Careful planning keeps the dose to the cochlea low, which is linked to a better chance of keeping hearing. For small and medium acoustic neuromas, focused radiation achieves tumor control in roughly 90–95% of cases over the long term, with rates of facial-nerve preservation that are very high, making it an effective alternative to surgery — particularly for tumors that are not large enough to require an operation to relieve pressure on the brainstem.
The main ways radiation is delivered for acoustic neuroma (vestibular schwannoma):
Stereotactic radiosurgery (SRS)
Many finely aimed beams converge on the tumor to deliver a precise dose in a single session, with the dose dropping off sharply so the nearby facial nerve, brainstem, and cochlea are largely spared — well suited to small and medium tumors.
Fractionated stereotactic radiotherapy (FSRT)
The same precise targeting delivered as several smaller daily treatments, used for somewhat larger tumors or to give sensitive structures like the cochlea extra protection in hopes of preserving hearing.
Cochlea-sparing planning
Treatment is planned to keep the radiation dose to the cochlea (the hearing organ) as low as possible, since limiting that dose is linked to a better chance of keeping useful hearing.
Proton therapy in selected cases
Proton beams stop after reaching the target, reducing dose to surrounding brain and structures — an option in selected cases, particularly in younger patients.
Latest studies shaping care
Care keeps improving — often toward getting the same excellent results with less burden on patients. A few developments:
Radiosurgery offers high long-term tumor control: Long-term studies of stereotactic radiosurgery for small-to-medium vestibular schwannomas report tumor control rates around 90–95% with high preservation of facial-nerve function, establishing it as a standard alternative to surgery for appropriately sized tumors.[1]
Long-term vestibular schwannoma radiosurgery series
Lower cochlear radiation dose linked to better hearing preservation: Research shows that keeping the radiation dose to the cochlea low during radiosurgery is associated with a higher chance of preserving useful hearing, leading to treatment planning that specifically protects the hearing organ.[2]
Hearing-preservation radiosurgery analyses
Targeted therapy for NF2-related tumors: In neurofibromatosis type 2, the anti-angiogenic drug bevacizumab can shrink vestibular schwannomas and improve hearing in some patients, offering a non-surgical, non-radiation option in this challenging inherited condition.[3]
NF2 systemic therapy studies
Common questions
Is an acoustic neuroma cancer? No. An acoustic neuroma (vestibular schwannoma) is a benign, non-cancerous tumor, and it does not spread to other parts of the body. The reason it needs attention is its location — it sits on the hearing-and-balance nerve and close to the facial nerve and brainstem, so as it grows it can affect hearing, balance, and facial movement.
Will treatment affect my hearing or my face? Protecting hearing and facial movement is the central goal of treatment. Focused radiation is planned to keep the dose to the hearing organ and facial nerve as low as possible, and facial-nerve preservation rates are very high. Hearing is harder to guarantee with any treatment, but careful, cochlea-sparing radiation gives many people a good chance of keeping useful hearing, especially for smaller tumors.
Should I just watch it instead of treating it? Often, yes — at least at first. Many acoustic neuromas grow very slowly or not at all, so for small tumors, especially with good hearing, doctors frequently recommend active surveillance: a baseline MRI and hearing test, then repeat scans to see whether it changes. Treatment is recommended if the tumor grows or symptoms worsen, which spares people unnecessary treatment for a tumor that may stay stable.
References
Numbered sources for the studies cited above. Links open the primary publication on PubMed or the publisher’s site.