Acoustic neuroma

A slow-growing growth on the nerve between the inner ear and the brain. Why it has two names. Why your hearing counts in the decision alongside the size. What the three choices are, and the one sign that should be looked at fast.

The short version

An acoustic neuroma is a growth on the nerve that runs between your inner ear and your brain. It is not cancer, and it usually grows very slowly.

It sits in a narrow space where the cerebellum meets the brainstem. Because of where it is, the first signs are almost always on one side: hearing that fades in one ear, ringing in that ear, or trouble with balance.

You will see two names for it. Your report may say vestibular schwannoma, which is the more exact one. Both names mean the same growth.

Most people do not need an operation right away. The three choices are watching it, focused radiation, and surgery. Your hearing is part of this decision, not just the size on the scan.

One sign here is worth knowing before you need it: hearing that drops suddenly in one ear should be looked at fast. It is in the symptoms section, below the general list of when to call.

What is an acoustic neuroma?

It grows from the cells that wrap a nerve, not from the nerve itself.

The eighth of the nerves that come straight off the brain carries two things from your inner ear. One branch carries sound. The other carries balance.

Around every nerve are cells that wrap it, the way the skin of an onion wraps what is inside. They support the nerve and insulate it. This growth starts when too many of those wrapping cells are made in one spot.

It sits in a tight corner. It begins in the narrow bony channel the nerve runs through, and it can widen out into the narrow corner where the brainstem meets the cerebellum, low down at the back of your head. That corner is why balance, and later the face, can be involved.

It grows beside the brain, not inside it. That is a real difference and not a form of words. It also does not settle everything, because a growth in that corner can still press on what is next to it.

Is it cancer? What does its grade mean?

No. It is not cancer, and it does not spread to other parts of the body.

The word benign will turn up, in a letter or in conversation. It tells you what this growth will not do. It says nothing about your hearing, and hearing is what it usually costs people. So the word is true, and it is not an answer to the question you are actually asking.

Where a grade is given at all, this one sits at the bottom of the scale. Clinical references describe this growth as a grade 1 tumor, which is the slowest-growing kind. Older paperwork writes that same grade as grade I, in Roman numerals.

Two things about that grade are worth keeping apart, because your report may show either style. The convention changed in 2021, when ordinary digits took over from Roman numerals, which is why two letters about one growth can look unalike. The grade itself comes from the clinical references rather than from that 2021 document, which lists this growth without printing a grade beside it at all.

What matters more is which nerve it is sitting on, and how your hearing is doing. Both come further down.

Where does it grow, and why does it cause these symptoms?

Nearly everything on this page follows from one fact: it grows on the nerve that carries hearing and balance from the inner ear to the brain.

The growth usually starts on the balance branch. That is the first reason the old name is a poor fit, and there is a second: it is made of the wrapping cells, not of nerve cells. So acoustic neuroma names the wrong branch and the wrong cell. Your team may still use it, because it is the name most people know.

Trouble arrives in a few ways.

It presses on the hearing branch. Hearing fades on one side. Most often it goes slowly, over years. Speech can start to sound muffled on that side, especially on the phone or in a noisy room.

It irritates the same nerve. Ringing, buzzing or hissing in that one ear is common, and for some people it is the first thing they notice.

It presses on the balance branch. This one often causes less than people expect. Because the growth is so slow, the other side has time to take over, and the body compensates. So unsteadiness here is more often a vague thing than a spinning attack.

If it grows, it can reach what is next door. Numbness or tingling in the face can come from the nerve that sits nearby. Weakness of the face is unusual with this growth, and worth saying plainly, because it is what people fear when they read about a tumor near the face.

Before you read the next part. What comes below describes growths sitting inside the brain itself. Two of the things it lists are not how this one behaves: it does not set off seizures the way a growth inside the brain does, and it does not make the brain around it swell. If you ever did have a seizure, the ambulance rule below applies to you as much as to anyone. Two others do apply, but only if a growth gets large: pressure building up inside the head, and fluid being blocked on its way out. In the map of brain areas after that, the entry about the skull base, below and behind the ear, is the closest fit of the three that are about this growth. One thing in it is uncommon here: facial weakness, which this growth usually causes only once it is large. If it is new, the same-day list further down is the one to go by. The cerebellum entry is this growth's territory too, balance and walking. The brainstem entry describes what can happen only once a growth is big enough to press on it.

Most people are told what they have long before anyone explains what it is doing. These are the ways a tumor in the brain causes symptoms. They overlap, and most people have more than one going on at once. Which of them apply to you depends on what your tumor is and where it sits.

It takes up room. The skull is a closed box. It cannot stretch. So anything new inside it has to push on something. The tumor and any swelling around it together take up space and press on nearby parts of the brain.

It can make the brain around it swell. This one surprises people, and it is worth understanding. Fluid builds up in the brain tissue near the tumor. That swelling plays a major part in deciding what symptoms you get. Some of what you are feeling may not be the tumor itself. It may be the swelling around it. That is why medicines that bring swelling down can change how somebody feels, without the tumor being any different than it was.

Pressure can build up inside the head. When the pressure inside the skull rises, there is a pattern doctors watch for: headaches that are worse in the morning, feeling sick to your stomach and throwing up, odd eye movements, seizures, and being confused or very drowsy. Not everybody with raised pressure has all of it, and some people have almost none of it. If this pattern is new for you, it is worth a phone call rather than a wait. If you have a shunt, it means getting help right away.

It can set off seizures. A tumor and the irritated brain around it can upset the normal electrical activity of that part of the brain. For some people a seizure is the first sign that anything is wrong.

It can block the flow of fluid. The brain makes a fluid that circulates around it and drains away. A tumor sitting in the wrong place can block that flow, so the fluid backs up and the pressure goes up. This is more likely with tumors near the narrow channels the fluid passes through. It can be treated, and the usual treatment is a shunt. That is a thin tube that carries the fluid to another part of the body, where it is absorbed. It is the word your team will use. Shunts and hydrocephalus covers what having one is like, and the signs it has stopped working.

Why your symptoms are the ones you have

The short rule: the symptom tells you where, the scan tells you what. A tumor disturbs whatever job the brain does in that spot, so where it sits decides what you notice.

There is one exception, and it is the fluid. When the flow is blocked, what you notice is the pressure rather than the spot: headaches worse in the morning, throwing up, double vision, and feeling unsteady. Those signs are much the same wherever the blockage sits, so they tell you the pressure is up, not where the tumor is. If that is your pattern, the part above called It can block the flow of fluid is the one about you, and it says what can be done. If the pattern is new, the phone call above applies.

• Front of the brain. Personality, behavior, planning, motivation, and on one side, producing speech.
• Side of the brain, near the temple. Seizures, memory, and understanding what people say.
• Upper back part of the brain. Sensation, knowing where your body is in space, reading, writing and arithmetic.
• Back of the brain. Vision, and losing part of your field of view.
• Cerebellum, low at the back. Balance, coordination and walking.
• Brainstem. Double vision, facial weakness, and trouble swallowing.
• Deep in the middle, near the spaces the fluid runs through. A tumor here can block the flow, so what you notice is often the pressure rising rather than anything that points to the spot.
• The floor of the skull, below and behind the ear. Hearing, balance, and the nerves to the face. So hearing loss or ringing in one ear, dizziness, and numbness or weakness down one side of the face. Your team may call the whole floor of the skull the skull base. This spot is one part of it.
• Behind the eyes, at the base of the brain. Vision, and the hormones that set energy, weight, thirst and periods. In a child, growth and puberty too. Side vision is what usually goes first, so things start disappearing at the edge. Your team may call this the pituitary or the sellar region.

If something on this list matches what you have noticed, it is worth writing down and taking to your next appointment. Your team can tell you whether it fits where your tumor actually is.

This list is about what the place explains. The other half of the question is what the place changes: whether an operation is offered, how much of it can come out, and when the place makes something urgent on its own. Where your tumor is, and what that changes is that half.

What symptoms does it cause?

Almost always on one side, and almost always the ear first.

The three that bring most people to a doctor are hearing loss in one ear, ringing in that ear, and trouble with balance.

The reason it is often found late is that none of those is alarming on its own. Hearing that slips over years gets put down to age. Ringing gets ignored. Balance that is slightly off gets blamed on tiredness. One-sided is the part that matters. Hearing that is worse in one ear than the other is worth mentioning, even when it seems small.

If it grows, it can add numbness or tingling on that side of the face. Headache, throwing up, and trouble with walking come later and only with larger growths.

One sign here has a rule of its own. It comes after the lists below.

When to call for help right now

Some things should not wait for the next appointment.

Call an ambulance for any of these. Call 911, or your local emergency number:

• A first ever seizure.
• A seizure that lasts more than five minutes.
• One seizure right after another, with no waking up in between.
• Someone who cannot be woken.
• Trouble breathing, or someone who seems to be choking.
• Suddenly not being able to speak, move one side, or see.

A seizure like the ones you usually have, that stops on its own, is not an ambulance call. What to do during a seizure draws the line.

Call your team the same day for any of these:

• A headache much worse than usual, or one that wakes you from sleep.
• Throwing up again and again.
• New weakness in the face, an arm or a leg.
• New trouble speaking, or understanding what people say.
• New confusion.
• Sleeping much more than being awake.
• A sudden change in your vision.

If you are having chemotherapy, a fever is its own rule. It means calling your team right away, at any hour, not waiting for the morning. An infection during chemotherapy can get dangerous fast, and it is treatable when it is caught early. The fever rule explains why, and what number your team will give you.

In the weeks after brain surgery, a fever is its own rule too, especially with a stiff neck or a bad headache. What comes after a craniotomy has the rest of that list.

If you have a shunt, the signs it has stopped working are their own rule. For you, everything on the same-day list above is a right-away call instead, and so are a few other signs. Get help right away, at any hour: call your team, or go to the emergency department. Signs a shunt is not working has the full list.

If you are not sure whether to call, call. Nobody on that team minds a phone call that turns out to be nothing.

Same day means today, not the next clinic appointment. Ask your team now for the after-hours number, and put it somewhere you will find it at two in the morning rather than somewhere sensible.

What to do during a seizure has the step-by-step, and getting help now is the short version to keep on a phone.

This growth has one rule the list above does not carry. There is only one, and it is worth reading today rather than at the moment you need it.

If the hearing in one ear drops suddenly, get it looked at fast. Sudden means over a few days, or all at once, rather than over months. It is not the same as the slow fade described above.

Ask to be seen quickly rather than waiting for an appointment. Your own doctor, an urgent care clinic, or an ear, nose and throat specialist are all places that can start this. The National Institute on Deafness and Other Communication Disorders calls sudden hearing loss a medical emergency and says to see a doctor immediately, and a national hearing-loss charity says the same and names those three places to go.

Most sudden hearing loss is not caused by a growth like this one. The specialist guideline for sudden hearing loss says a growth on this nerve is only rarely behind it. The reason to move fast is that treatment for sudden hearing loss works better the sooner it starts, whatever the cause turns out to be.

If you already know you have one of these, a sudden change is a reason to contact your team rather than wait for your next scan. What to report between scans sets out that rule, and it applies to any new change, not only to hearing.

What is NOT on this page is a checklist for a growth that has got large. The general list above covers pressure signs for brain tumors as a whole, and it applies to you as much as to anyone. What this page does not add is a separate set of signs for this growth in particular. That is deliberate. The reports describing pressure on the brainstem are written for surgeons deciding on an operation, and none of them tells a patient what to do or when to call. The patient organizations say the opposite of act now: for most people this growth is not something that has to be treated urgently. So this page does not invent a rule its own sources do not give. What your team watches for is size and change, and that is what the scans are for.

How do doctors find out it is this?

A hearing test first, then a scan.

The hearing test is the one that raises the question. It is not the check you have for glasses or the one at a work physical. It measures each ear on its own, across a range of pitches, and it looks for a difference between the two sides. A one-sided pattern is what leads to the scan.

An MRI scan is what shows it, and it is what tells this apart from other reasons for one-sided hearing loss. The scan shows where the growth sits, how big it is, and what it is touching.

Balance testing is sometimes added, because the balance branch can be affected without you noticing much.

Tissue is not usually taken to make the diagnosis. The scan and the hearing test are enough to say what this is. That is unlike most of the tumors on this site, and it is why a report may describe the growth without a piece of it ever having been looked at under a microscope.

What do the words on my report mean?

Two names for this growth can appear in your paperwork, and both of them are correct.

Acoustic neuroma, and vestibular schwannoma. These are the same thing. The second is more exact, for the two reasons above: the growth usually starts on the balance branch rather than the hearing one, and it is made of the cells that wrap the nerve. Many doctors prefer the newer name. The older one is still used more often in writing, so you will meet both.

Grade 1, and grade I on older paperwork. One grade, written two ways. Ordinary digits replaced Roman numerals when the convention changed in 2021, and a great many letters were never rewritten.

Schwann cells. The cells that wrap and insulate nerves. They are what this growth is made of, and they are where the name schwannoma comes from.

NF2-related schwannomatosis. This is the name of an inherited condition, and it is not a diagnosis of the growth you have. It is here because you may meet the name while reading, and because the name itself changed recently. Older letters use neurofibromatosis type 2. An international group retired that older name in 2022, to make the diagnosis more exact. A reference for doctors records that the newer name was proposed by that group, to fit what the condition actually causes.

What that condition means for you depends on two things: whether there is a growth on both sides, and your age. Growths on both nerves are the mark of that condition, and they are uncommon. The large majority of these growths are on one side only and are not inherited. The reference above puts the rest plainly: someone under thirty with a growth on one side is watched more closely, because there is a real chance of one appearing on the other side, while someone over thirty with a growth on one side has a very low chance of having the condition at all.

If it is in your family, ask. About half of the people who have that condition inherited it from a parent. The other half are the first in their family to have it. Your team can say whether anyone else should be checked.

Your pathology report goes through a report made from tissue, though yours may not be one.

How is it usually treated?

There are three choices, and doing nothing for now is one of them. A federal health institute lists them as watching, radiation, and surgery.

Watching. For a small growth that is not causing much trouble, a plan of scans and hearing tests is often the first choice rather than a delay. The European guideline puts the clearest case for it where a growth was found by chance and is causing no symptoms. Many of these never need treating at all. Watching a tumor with scans is the page for that plan, and it carries a passage on this growth in particular.

Focused radiation. The aim is usually to control the growth rather than to take it out. Doctors call this stereotactic radiosurgerystereotactic radiosurgery: Radiation aimed at a small target, in one visit or a few. There is no cutting, despite the name. See the glossary. The day itself, and what it is like is a page of its own.

Surgery. An operation to take the growth out. It is the usual choice when a growth is large, and for the largest ones it is the only way to take pressure off the brainstem. What an operation involves, and the weeks after has the general aftercare.

How the choice gets made, honestly. Size matters, and so does your hearing, your balance, your age and what you want. No one option is better at everything. One comparison found that dizziness and ringing tended to do better after surgery, while the nerve to the face came out about the same whichever route was taken. The European guideline reaches a different conclusion about that nerve for smaller growths. The reports disagree, and both sets of authors say why: nobody has ever run the kind of study that would settle it, so all of it comes from watching what happened rather than from a trial.

Two things are genuinely unsettled, and it is fair to ask about both. There is no agreed point at which watching should turn into treating. And for growths in the middle range of sizes, there is no settled best answer.

What is treatment actually like, and what is normal afterwards?

What happens to hearing

This is the part people most want a straight answer about, and the honest answer has two halves.

Hearing on that side tends to get worse over time whatever is done, including when the growth is only being watched. It can get worse even in a year when the growth has not grown at all. That is worth knowing, because "we are just watching it" can sound like "nothing is changing".

The other half is that treatment does not protect hearing from that. A review of the evidence found that surgery and focused radiation both appear to speed up a decline that was already happening, and the same sentence says more research is needed, because the evidence is weak. Every recommendation in that review sits at its lowest level of confidence. Both halves belong together: it is not a reason to refuse treatment, and it is not a promise that waiting keeps your hearing.

So ask what your own hearing is now, and ask what each choice is expected to do to it. That question, asked early, is worth more than any figure.

Balance, the face, and the first weeks

Balance often settles. The other ear takes over the work, and most people adjust, though it can take weeks and it is worse in the dark or on uneven ground. Ask whether balance therapy would help you.

The nerve to the face runs right beside this growth, which is why it comes up in every conversation about treatment. Weakness of the face is not a common way for this growth to show up in the first place. After treatment it is a real risk, and it is bigger with larger growths.

Ringing does not always go. It can stay after successful treatment, and for some people it is the symptom that bothers them most afterwards. Say so if it does, because it can sometimes be treated in its own right.

Tiredness after an operation is heavier than people expect, and it lifts slowly.

Everyday life

Hearing on one side changes some ordinary things, and none of them is obvious until it happens. Working out which direction a sound came from gets harder. So do noisy rooms, restaurants and group conversations.

Small things help more than they sound like they will. Sit with your better ear toward the room. Ask people to move to that side. Tell the people you see often, so they stop repeating themselves into the wrong ear.

Ask about a hearing aid or another device, including for the ear that has lost the most. It is worth raising rather than waiting to be told.

If your balance is off, be careful on stairs and in the dark, when your eyes cannot help you.

Tiredness is real here, and it is not only about sleep. Straining to hear all day is work, and it is a common reason people feel wiped out by the evening.

Follow-up scans, and what to do while you wait

Here, follow-up means scans and hearing tests side by side, carrying on for years whether or not you have had treatment.

Follow-up scans explains how one scan gets read against the last. Waiting for results covers the stretch before anyone calls you, which many people find worse than the appointment.

Get your own plan written down: when the next scan is, what would bring it forward, and who to tell if something changes in between.

If it comes back

After an operation, some of these can grow again. That can happen when a piece was deliberately left behind to protect a nerve, which is a recognized choice rather than a mistake, and one of the things to ask about beforehand.

After focused radiation, the aim was to control the growth rather than remove it, so a scan that shows it unchanged is the result that was wanted.

If something does change, the choices are the same as before, and which of them fits depends on what was done the first time.

Did I cause this?

Almost everybody asks this, usually in the first week, usually in private. It is worth answering plainly.

For most brain tumors, nobody knows the cause. That is the honest state of it. The exact cause of most brain and spinal cord tumors is not fully understood, and there are very few well established risk factors. Tumors start when genes that control how cells grow and divide are changed, and in most cases those changes happen by chance during a person's life. Not because of something done or not done.

Cell phones. They give off a kind of radiation called radiofrequency. It is not the same as the radiation in an x-ray. The energy is too low to damage DNA, and it is not known to cause cancer. The evidence so far is that using a cell phone does not cause brain tumors.

Stress. There is no scientific evidence that stress causes brain tumors, and no data linking stress to a higher chance of getting one. A hard year before a diagnosis is a hard year. It is not a cause.

Something you ate, or did not eat. No food and no diet is an established cause of a brain tumor. It is not on the list of known risk factors at all.

Something you passed on, or caught. Brain tumors are not contagious. Most are not inherited either. A small number of people do have an inherited condition that raises the risk, and if that applies to you, your team will raise it and offer to talk it through.

If you are turning this over at three in the morning, that is ordinary and it happens to nearly everyone. It is also worth saying out loud to somebody on your team, because they have answered it many times and they would rather you asked.

For this growth there is one thing worth adding. The old story that cell phones cause growths on this nerve has been looked at specifically, and it is not supported. Nothing you did with a phone brought this on.

What might happen over time

For the person caring for someone with this

If you are the one driving to the appointments, keeping track of the pills, and lying awake at night worrying about them, this part is for you.

You are allowed to ask questions. In one study, families said they were afraid of annoying the doctor by asking too much. One of them was told by a doctor to stop playing doctor. Ask anyway. Write your questions down before you go, and bring a notepad. Two people in the room hear more than one.

Ask who your first call is. Care comes from a lot of people at once, and it is easy to end up as the only one holding it together. Ask the team: who do I call first? Some teams have one person whose job this is, often a nurse. Get the name and the number.

Get two numbers, and know which one to use. One for work hours, one for nights and weekends. Then ask what counts as "call us today" and what counts as "call an ambulance" for this tumor, and write the answer down where you can see it. If you are not sure which it is, call. Nobody on that team will mind.

If they have seizures, read about them before you need to. What to do when someone has a seizure is the one to know by heart. Living with seizures is about the rest of the time: what is safe, what to change, and driving.

Ask to be shown anything you are sent home to do. In that same study, families were sent home to change dressings and give medicines with no training at all. That is not fair to you. Before you leave the hospital, ask someone to show you. Then do it once while they watch.

Say what you notice. You may see a change before they do. Changes in thinking, mood and behavior can show up to the people close by first. Telling the team is not going behind their back. It is something the team cannot learn any other way.

Look after yourself, and let people help. Eat, sleep, and keep your own appointments. Take a little of the day back for yourself. When someone asks what they can do, give them a real job: a meal, a ride, an hour with the kids. Most people want to help and do not know how to offer.

You can talk to somebody about all of this today. See where to get help.

Three things belong to this one in particular.

One-sided hearing loss is invisible, and it gets read as rudeness. Not answering, answering the wrong question, going quiet in a group: all of that looks like inattention and is not. Sit on their better side, and say their name before you start.

Learn the one urgent rule with them. If the hearing in one ear drops suddenly, it should be looked at fast, by their own doctor, an urgent care clinic or an ear specialist. You may be the one who notices they have stopped using the phone on that side.

Watching is not doing nothing, and it is tiring to live with. A plan of scans can look like being left alone with it, and the wait around each scan is its own kind of hard. The worry that comes with being watched covers what has been studied about that, including for this growth.

What to ask your team

• Which side is it on, and which nerve is it sitting on?
• What is my hearing like now on that side, compared with the other?
• Are we watching it, treating it, or deciding? Why that one?
• What would make you want to treat it rather than keep watching?
• What is each choice meant to achieve: stopping growth, or removing it?
• What is each choice likely to do to my hearing?
• What is the risk to the nerve that moves my face, and how does size change it?
• If the plan is watching, when is my next scan and my next hearing test?
• What should I tell you about between appointments?
• Could a hearing aid or another device help me now?
• Is balance therapy worth trying?
• Is there any reason to think this is the inherited kind?

Where to get support

• Getting help now, for when reading is not what you need and a human voice is.
• The Acoustic Neuroma Association publishes patient material on this growth and on living with the hearing loss it causes.
• The Vestibular Disorders Association covers balance problems and what can be done about them.
• The specialist nurse or the audiologist looking after you. Either can get you a straight answer faster than almost anyone.