Brainstem tumor

Overview

A brainstem tumor is a growth in the midbrain, pons or medulla. These three areas connect the brain to the spinal cord and guide many essential functions.

Most brainstem tumors are gliomas. These include diffuse midline glioma and low-grade glioma in children. These tumors often grow along the brainstem's busy nerve pathways, which makes them hard to separate from nearby tissue.

In adults, brainstem tumors are less common and include a broader mix of gliomas and other tumors.

Even small tumors can cause significant issues. Because the brainstem is small and tightly packed, a brainstem tumor can affect movement, balance, coordination, sensation, speech or basic body functions. Some tumors grow slowly in one area while others spread more widely through nearby tissue. A tumor may appear as a single mass or as multiple spots.

Brainstem tumors can be noncancerous, also called benign. Or they can be cancerous, also called malignant. Even slow-growing tumors may be hard to remove because they sit close to nerves and nervous system pathways that guide movement, breathing, swallowing and other important functions. Whether a brainstem tumor can be removed depends on the tumor's type, how it grows and how closely it touches these critical structures.

Types

Brainstem tumors can begin in different kinds of cells. Most start in glial cells, which support nerve cells. These growths are called gliomas, and they are the most common type of brainstem tumor.

Gliomas

Gliomas include several subtypes that start in different parts of the brainstem and grow in different ways.

Diffuse midline glioma (DMG) is a common type of brainstem tumor. Diffuse midline gliomas are especially common in children, where they make up most malignant brainstem tumors. Historically, in children these tumors were referred to as diffuse intrinsic pontine gliomas (DIPGs). These high-grade gliomas grow quickly and usually begin in a part of the brainstem called the pons. They spread between cells in the brainstem rather than forming clear borders, which makes them difficult to remove with surgery.

Low-grade glioma grows more slowly and may stay in one place. Some low-grade gliomas grow outward from the brainstem surface. They are called exophytic tumors and can sometimes be easier to reach with surgery. Subtypes of low-grade gliomas found in the brainstem include:

• Pilocytic astrocytoma — a slow-growing tumor that can form in the midbrain, pons or medulla.
• Pilomyxoid astrocytoma — a less common variant of pilocytic astrocytoma that can also occur in the brainstem and is often more aggressive than pilocytic astrocytoma.

• Ganglioglioma — a rare tumor that contains both nerve cells and glial cells and may develop in the lower brainstem.

  These tumors can appear in any part of the brainstem, including the midbrain or medulla.

Rare tumor types

There are other rare types of gliomas that can occur. Angiocentric gliomas are linked to changes in the MYB gene.

Polymorphous low-grade neuroepithelial tumors of the young (PLNTYs) are linked to changes in genes that affect the MAPK pathway, such as BRAF or FGFR.

Many childhood-type diffuse low-grade gliomas have gene changes that affect the MAPK pathway. Adult-type diffuse low-grade gliomas usually have changes in the IDH gene.

Other rare tumors can form in the brainstem, although they are much less common than gliomas. These may occur in different parts of the brainstem or other parts of the brain. They are seen more often in adults. Some of these rare tumors include ependymomas and hemangioblastomas.

Causes

The exact cause of most brainstem tumors is not known. In many cases, a tumor forms when certain cells in the midbrain, pons or medulla begin to grow in an uncontrolled way. Most brainstem tumors start in glial cells, which support communication between nerve cells. Changes within these glial cells can lead to gliomas, the most common type of brainstem tumor.

Researchers have found that some gliomas develop because of gene changes that affect how glial cells grow and divide. These gene changes can happen on their own during cell development and are not usually linked to anything a person did or was exposed to.

For most people, there is no clear cause or trigger for a brainstem tumor. There is no evidence that diet, stress or environmental exposures cause brainstem tumors. Current research continues to study how gene changes and cell growth patterns contribute to these tumors.

Complications

A brainstem tumor can lead to complications when its growth blocks nearby spaces. The tumor can interfere with breathing, swallowing, fluid flow or long-term nerve function.

Possible complications include:

• Hydrocephalus. This condition happens when fluid builds up on the brain. A tumor can block the flow of cerebrospinal fluid, leading to increased pressure inside the skull. This may require treatment to relieve pressure.
• Breathing problems. Tumors in or near the medulla can affect breathing rhythm, which may become slowed or irregular over time.
• Long-term swallowing difficulty. Ongoing pressure on the nerves that control throat and tongue movement can make swallowing unsafe, increasing the risk of choking or breathing in food or liquid.
• Long-term weakness or loss of coordination. Continued pressure on nerves can lead to lasting problems with strength, balance or fine motor skills, even if early symptoms were mild.
• Ongoing vision or eye movement problems. Tumors involving cranial nerves can cause lasting changes in eye control or vision.
• Behavior or learning changes in children. As the tumor grows, children may develop ongoing challenges with attention, how quickly they can think and respond to information, or school performance.

These complications reflect the long-term effects a brainstem tumor can have on movement, breathing and other functions. Complications can be different from person to person, but many occur because the brainstem is small and controls many important body functions.

Diagnosis

Diagnosing a brainstem tumor begins with learning about symptoms and doing a physical exam. A neurological exam is used to check balance, eye motion, strength, coordination and swallowing. These findings help the care team understand which parts of the brainstem may be affected.

Imaging tests are then used to look closely at the brainstem. In some cases, a small sample of tissue or cerebrospinal fluid may be taken to learn more about the tumor's cells to establish a diagnosis.

Imaging tests

Magnetic resonance imaging (MRI). A brain MRI is the main test used to diagnose a brainstem tumor. It creates detailed pictures of the brainstem and can show whether a growth is present, where it is located, and how it affects nearby structures. MRI scans can show features that help identify:

• The expected type of tumor.
• How much of the brainstem is involved.
• Whether the growth stays in one area or spreads throughout other areas.

MRI with and without contrast can help identify common tumor types, including diffuse midline glioma (DMG) and other gliomas that can form in the brainstem.

MRI also can show whether the tumor stays in one area or spreads through brainstem tissue, which helps guide the next steps in diagnosis.

A mass that shows on brainstem MRI means there is an area that looks different from the surrounding tissue. This may be a tumor or another type of lesion. MRI helps show the size and position of the mass and how it affects nearby areas.

Some changes seen on brainstem MRI scans may be caused by conditions other than a tumor, such as inflammation, cavernous malformations, or other types of lesions including inflammatory or demyelinating conditions such as multiple sclerosis. Imaging tests help the care team understand the cause and guide other testing.

Other imaging. Depending on the situation, the care team may use additional imaging to better understand the growth or to rule out other conditions. These may include brain CT scans or specialized MRI techniques. These tests help confirm the tumor's position and its effect on surrounding areas.

Biopsy

In some cases, a small sample of tissue is taken with a needle to study the tumor's cells. This is called a needle biopsy. Modern techniques allow biopsies to be performed with high accuracy and a low rate of lasting side effects.

A biopsy is most helpful when MRI results are unclear or when several tumor types are possible based on imaging alone.

Lumbar puncture

In some situations, a lumbar puncture may be done to look at the spinal fluid for clues about the tumor. The fluid can be checked for cells that have moved from the tumor or for genetic changes that point to a certain type of tumor. This information can help confirm what type of tumor you have and help the care team plan next steps.

How results are used

After imaging and biopsy results are collected, the care team looks at the tumor's location, its pattern of growth and the features of the cells. These details help identify the tumor type and guide decisions in later steps of care.

Preparing for an appointment

If you have symptoms that worry you, make an appointment with a doctor or other healthcare professional. If you have a brainstem tumor, you'll likely be referred to specialists, such as:

• Doctors who specialize in brain conditions, called neurologists.
• Doctors who treat cancer with medicine, called medical oncologists.
• Doctors who use radiation to treat cancer, called radiation oncologists.
• Doctors who specialize in nervous system cancers, called neuro-oncologists.
• Surgeons who operate on the brain and nervous system, called neurosurgeons.
• Rehabilitation specialists.

Here's some information to help you get ready for your appointment.

What you can do

• Be aware of anything you need to do before your appointment. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as change your diet.
• Write down any symptoms you've been experiencing and how long you've had them.
• List your key medical information, including all conditions you have and the names of any medicines you're taking. Include prescription medicines and medicines you can buy without a prescription and the doses.
• Take a family member or friend with you. Sometimes it can be difficult to remember all of the information you get during an appointment. Someone who goes with you may remember something that you missed or forgot.
• Write down questions to ask your healthcare professional.

Questions to ask at your first appointment include:

• What may be causing my symptoms?
• Are there any other possible causes?
• What kinds of tests do I need? Do these tests require any special preparation?
• What do you recommend for the next steps in determining my diagnosis and treatment?
• Should I see a specialist?

Questions to ask an oncologist or a neurologist include:

• Do I have a brainstem tumor?
• How will the brainstem tumor grow over time?
• Where is the brainstem tumor located?
• How large is the brainstem tumor?
• What might happen because of the brainstem tumor?
• What are the goals of my treatment?
• Is surgery a treatment option? What are the risks?
• Is radiation therapy a treatment option? What are the risks?
• Will I need chemotherapy?
• What treatment approach do you recommend?
• If the first treatment doesn't work, what will we try next?
• What is the prognosis for my condition?
• Do I need a second opinion?
• Is there a clinical trial available for people with a brainstem tumor? Is it right for me?

In addition to the questions that you've prepared, don't hesitate to ask any other questions that may come up during your appointment.

What to expect from your doctor

Be prepared to answer questions about your symptoms and your health history. Questions may include:

• What are your symptoms?
• When did you first notice these symptoms?
• Have your symptoms gotten worse over time?
• If you have pain, where does the pain seem to start?
• Does the pain spread to other parts of your body?
• Have you participated in any activities that might explain the pain, such as a new exercise or a long stretch of gardening?
• Have you experienced any weakness or numbness in your legs?
• Have you had any difficulty walking?
• Have you had any changes in your bladder or bowel function?
• Have you been diagnosed with any other medical conditions?
• Are you currently taking any medicines, including prescription medicines and medicines that you can get without a prescription?
• Do you have any family history of noncancerous or cancerous tumors?