Medulloblastoma

A fast-growing tumor that starts at the back of the brain. It is most often found in children. What grade 4 does and does not mean here. Why the whole spine is checked, and what craniospinal radiation is. And what posterior fossa syndrome is.

The short version

A medulloblastoma is a fast-growing tumor that starts at the back of the brain. It is the most common cancerous brain tumor in children, and adults get it too. It can spread through the fluid around the brain and spine, so the whole spine is checked at the start. Treatment is usually surgery, then radiation to the brain and spine, then chemotherapy, with the radiation left out for the youngest children. This tumor is grade 4, and that word means something different here than it does for some other brain tumors.

What is a medulloblastoma?

It starts in the cerebellum, at the back and bottom of the brain, most often in the middle of it beside a fluid space called the fourth ventricle. The cerebellum handles balance and coordination, which is why balance is often the first thing that changes.

It is an embryonal tumor. That means it grows from early forms of nerve cells, not from the supporting cells that gliomas come from.

It is most common in children under 16. Adults get it, and in adults it is rare.

The name on older paperwork

Doctors used to call this tumor a primitive neuroectodermal tumor, or PNET. That name is no longer used. You may still see it in an older letter, or in a paper written some years ago.

You may also see PNET5, PNET4 or PNET3 with a number after them. Those are names of research studies, not names of the tumor.

Is it cancer? What does its grade mean?

Yes. A medulloblastoma is cancer. The word your team will use is malignant.

It is grade 4, and every medulloblastoma is. Grade 4 is the top of the scale, and here it describes this type of tumor as a whole rather than sorting one child's tumor from another's.

Grade 4 does not mean the same thing for every tumor. The World Health Organization says so about this tumor in particular. It warns that calling the WNT kind grade 4, the same as brain tumors that cannot be treated, risks giving families a false picture when treatment is discussed. Every medulloblastoma is grade 4 whatever its kind, so the number cannot tell you how one child will do.

So the grade is not the part that tells you the most. The kind, and whether it has spread, matter more. Both are on your report, and the next sections explain them.

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

It grows at the back of the brain, beside the space the brain's fluid runs through, and most of the early symptoms come from that fluid backing up.

It can also travel in that fluid. Cells can settle further along the brain or down the spine. That is why the whole spine is scanned and the fluid is tested, and it is why treatment usually covers the whole brain and spine rather than one spot.

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?

Most of these come from the fluid backing up, and they often build over a few weeks:

• Headaches, often worse in the morning, sometimes better after throwing up.
• Throwing up, often in the morning.
• Trouble with balance or walking, or falling backwards.
• Clumsiness, or handwriting that has changed.
• Double vision, or eyes that do not move together.
• Being much more tired, or not seeming like themselves.

New or worse trouble with balance or walking is a same-day call, or a right-away call if there is a shunt or if the tumor has spread to the spine.

In a baby, the head can grow faster than it should and the soft spot on top can swell. If you see that in a baby with this tumor, call your team the same day, or right away if there is a shunt.

If the tumor has spread down the spine, there can be back pain, trouble walking, and trouble with the bladder or bowel. For a tumor that has spread to the spine, those signs have their own rule, at the end of the section on when to call for help, 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.

If the tumor is in the spinal cord, or has spread to the spine, new signs from the cord are their own rule. For you, an arm or a leg that is newly weak, or weaker than it was, is a right-away call, not a same-day one.

So are new trouble walking, new numbness or tingling, new or worse pain in the back or neck, and new trouble controlling the bladder or bowel. When cancer presses on the spinal cord, Cancer Research UK calls it an emergency that needs treating quickly. Call your team right away, at any hour, or go to the emergency department.

How do doctors find out it is this?

• An MRI scan of the brain, and one of the whole spine. The spine scan is best done before the operation, because after surgery the pictures can show marks that look like spread and are not.
• The operation. The tissue that names the tumor usually comes from the surgery to remove it.
• Gene tests on that tissue. They decide which kind it is, and the kind changes the treatment plan. One test reads a chemical pattern across the tumor's DNA, and it is the test that tells groups 3 and 4 apart.
• A test of the fluid. A thin needle in the lower back takes a small amount of the fluid, and the lab looks for tumor cells in it.

The fluid test waits, and that wait is deliberate. It is not done before surgery, because the pressure in the head makes it unsafe. In the first days after surgery, blood in the fluid makes the result hard to read. So the test is done about two weeks later. Guidance differs a little on the exact day: one national standard says at least 14 days in one place and 10 to 14 days in another. Ask your team when yours is planned.

What the result changes. Tumor cells in the fluid, or spread seen on a scan, put the tumor in the higher risk group, and that changes how much treatment is given. Your team may call this staging, or use an M and a number.

What do the words on my report mean?

The rules for naming brain tumors changed in 2021. If your paperwork was written before that, some of its words are no longer used.

This matters more than it sounds. People read an old report next to a new one, see two different names, and think somebody made a mistake. Usually nobody did. The tumor did not change. The way doctors write it down changed.

Three changes affect almost every report.

• Roman numeral grades, such as grade II or grade IV on an older report. These are now written with ordinary numbers instead: grade 2, grade 4. Nothing about the grade itself changed. Only the way of writing it did.
• Gene results are now part of the name. Older reports named a tumor mostly by how the cells looked. A name written now usually has a gene result built into it. That is why a newer report can look longer and more technical than an older one about the same tumor. You may also see NOSNOS: Short for "not otherwise specified". It means the gene tests needed to name the tumor fully were not done or could not be done. Ask your team whether they can be. See the glossary or NECNEC: Short for "not elsewhere classified". The tests were done, but the results do not match any named tumor type. Ask your team what it means for your plan. See the glossary written next to your diagnosis. These say something about the testing, not about how serious the tumor is. NOS means the tests needed to be more exact were not available. NEC means testing was done, but the results did not fit any defined group neatly.

Seeing an older name on your own report does not mean it was wrong. It means it was written under the old rules. If you are holding an old report and a new one and they do not match, that is a good thing to take to your team and ask about.

This report has two parts, and both matter. One says how the cells look. The other says which molecular group the tumor is in. Your team puts them together into one diagnosis.

How the cells look, one of four patterns:

• Classic.
• Desmoplastic or nodular.
• With extensive nodularity, seen in very young children.
• Large cell, or anaplastic.

Which group it is in, one of four:

• WNT-activated.
• SHH-activated, TP53-wildtype.
• SHH-activated, TP53-mutant.
• Non-WNT, non-SHH. Inside this one, your report may say group 3 or group 4. Both names are still used.

Which group it is in helps decide how much treatment is given, and which trials fit.

The two parts line up more often than not. Nearly all WNT tumors look classic, and the desmoplastic and nodular ones are nearly all SHH.

Below the four groups there are finer groupings, fourteen of them, used mostly in research. A report may name one.

Your pathology report walks through the document itself.

How is it usually treated?

A tumor board is a meeting where specialists look at one person's case together: surgeons, cancer doctors, the lab, and the people who read scans. It tends to happen when a case is complicated or something is hard to read.

You do not go to the meeting. Afterwards, the doctor who knows you best explains what was said.

What they decide is advice, not an order. The choice is still yours. Because you are not in the room, tell your team what matters to you before it happens, so it is taken into account.

Surgery comes first, and the aim is to take all of it out. How much came out explains the words the team will use afterwards.

If the fluid is blocked, that may be treated first, and quickly. That can be a temporary drain, a shunt, or a small operation inside the brain that makes a new path for the fluid.

Radiation to the whole brain and spine usually follows, with an extra dose aimed at the place the tumor was. Treating the whole brain and spine is deliberate: this tumor travels in the fluid, so the treatment follows the fluid. Your team may call it craniospinal radiation.

• Not for the youngest children. St. Jude does not use radiation under age 3, and Cancer Research UK says every child under 3 is in the higher risk group and radiation to the whole brain and spine is usually avoided. Chemotherapy is used instead, to hold the tumor while the child grows. Where the line sits is changing: newer studies use age 4 or 5 in some plans. Ask your team where they draw it.
• Proton therapy is used for some children. When the spine is treated, it can keep more of the dose away from the chest and belly. It is not available everywhere.

Chemotherapy is usually given as well, after radiation, or on its own for the youngest children. The combination usually includes cisplatin, vincristinevincristine: A chemotherapy given into a vein. It is the V in PCV. It can cause numbness or tingling in the hands and feet, which is worth reporting early. See the glossary and cyclophosphamide, and some plans add lomustinelomustine: A chemotherapy you take as a capsule. You take it now and then, not every day. It lowers your blood counts weeks after a dose. That is why the doses are spaced out. See the glossary. Doses of each are held down on purpose: to protect the nerves, the hearing and the chance of having children later.

Risk groups decide how much treatment is given. A tumor is put in the higher risk group if it has spread, if the cells are the large cell or anaplastic kind, if certain gene results are there, or if the child is under 3. It also goes there if more than a certain amount is left behind: your team measures what is left on the scan after surgery, so ask which side of the line yours is on. Everyone else is in the average risk group, which gets less.

Ask about clinical trials. Several studies are testing whether children with WNT tumors can safely have less radiation. Those results are not published yet, so nobody can tell you today what they will show.

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

The library pages carry the detail: what an operation is like, what radiation is like and proton therapy.

After surgery at the back of the brain

This is common after surgery for a medulloblastoma. It can follow surgery for other tumors at the back of the brain too. Doctors call it posterior fossa syndromeposterior fossa syndrome: Something that can happen after an operation on the lower back of the brain. Some children cannot speak for a while. Swallowing, walking and mood can change too. It always starts in the first week after surgery. See the glossary.

A day or two after surgery low at the back of the brain, some children stop talking. It can also change swallowing, walking, mood and behavior. It always starts within the first week.

Suddenly not being able to speak is on the ambulance list above, and that rule still stands. What this section describes usually starts in the hospital, in the days right after the operation, where the team is watching for it.

It is frightening to see. Doctors know it as a complication of the operation itself. Most children slowly get better. Speech usually comes back over days or weeks, and for some it takes months. Most children walk on their own again. Some trouble with speech, movement or mood can last longer, even years. Speech therapy can help. If the swallowing, walking, mood or behavior changes start or get worse after you are home, call your team the same day, or right away if there is a shunt.

Some of it can last. A study that followed survivors for years found that children who had it were more likely to have lasting trouble with attention and with how fast thinking works, even after the early symptoms settled.

The risk is lower with a surgeon who does many of these operations, and it is higher the younger the child is. Asking how often your surgeon operates here is fair, and it is a question teams expect.

Everyday life: school, hearing, growth and tiredness

• School and learning. Radiation to a young brain, and this treatment as a whole, can affect memory, attention and how fast school work goes. Ask early who at the hospital helps with school, and ask what help can be put in place.
• Hearing. Cisplatin and radiation to the head can both affect hearing, more so in a young child. Hearing tests find it early, and they belong in the regular check-ups.
• Growth and hormones. Radiation near the gland at the base of the brain can change the hormones that run growth and other body systems. This is checked for years, and hormone levels are part of the regular blood tests.
• Tiredness can come from the treatment, and it can also come from the tumor or from fluid that is not draining. Sleeping much more than being awake is a same-day call, or a right-away call if there is a shunt.

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

Scans go on for years, and they spread further apart as time passes. Follow-up is not only scans: it includes hearing tests, eye tests, blood tests for hormones, and a check of balance and strength. A curve in the spine can develop after treatment, so that is watched too.

Follow-up scans goes through what each scan is compared with, and waiting for results covers the gap before the answer.

If it comes back, or changes

There is no single agreed plan for a medulloblastoma that comes back, and sources say so plainly. What is offered depends on what was given the first time.

Your team may talk about surgery again, radiation for a child who did not have it the first time, chemotherapy, or a clinical trial. The tumor can change, so your team may test a new sample rather than rely on the first result.

Ask what each option is for, and write the answers down.

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.

A small number are linked to an inherited condition. The ones linked with this tumor are Gorlin syndrome, Li-Fraumeni syndrome and familial adenomatous polyposis, which older letters may call Turcot syndrome. That name is not used now.

Which kind the tumor is decides who gets offered testing. Teams offer genetic counseling to families of children with SHH tumors whatever the family history, and to some others depending on the gene result. If your family has one of these conditions, say so early, because children with Gorlin syndrome are unusually sensitive to radiation and it can change which treatment is chosen. Tell your team before treatment is planned.

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 specific to this diagnosis.

Most people caring for someone with this tumor are parents of a child. Everything above still applies, and it is fine to ask the team to explain things more than once.

After surgery at the back of the brain, watch talking and swallowing. If your child comes home still having trouble swallowing, ask to be shown how to give food and drink before you leave. New or worse trouble swallowing after you are home is a same-day call, or a right-away call if there is a shunt. Choking, or trouble breathing, is an ambulance call.

Keep the check-up dates somewhere safe. Hearing, hormones, eyes and school support are all followed for years, by different people, and you may be the one holding the whole picture.

What to ask your team

• What kind is it, and what does the report say about the group and the cells?
• Has the whole spine been scanned, and when will the fluid be tested?
• Was all of it taken out? What did the scan after surgery show?
• Is this average risk or higher risk, and what does that change?
• Will radiation cover the brain and spine, and is proton therapy an option?
• If my child is very young, what is used instead of radiation?
• What is the chemotherapy for, and which side effects are watched for?
• Before surgery: how often do you do this operation?
• Who checks hearing, hormones and school progress, and how often?
• Should our family be offered genetic counseling?
• Is there a clinical trial for this kind?
• Who do we call after hours, and what number is it?

Where to get support

• Getting help now if you need somebody today.
• Together by St. Jude has pages for families of children and teens, including one on posterior fossa syndrome.
• The American Brain Tumor Association works to improve the understanding and treatment of brain tumors, and has support for people affected by one.
• The Brain Tumor Network helps adult patients and caregivers in the United States find treatment options and trials, at no cost.
• Your team's specialist nurse, who is usually the fastest way to get a question answered.