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.

Symptoms

Brainstem tumor symptoms can affect movement, balance, coordination, eye motion, facial control, breathing and swallowing. Because the brainstem is very compact and carries many message routes between the brain and body, people often notice several symptoms at once.

Symptoms can build over time or appear more quickly. Some tumors grow in a way that causes steady changes that get worse little by little. Others grow more slowly, which can lead to symptoms that develop over weeks or even months.

Common symptoms for brainstem tumors include:

Balance or coordination problems

• Trouble walking or standing.
• Clumsiness or dropping items.
• Difficulty with fine motor skills.
• Dizziness or feeling unsteady.

Changes in eye motion

• Double vision.
• Trouble moving the eyes in one or more directions.
• Eyes drifting or not lining up.

Speech or swallowing changes

• Slurred or slowed speech.
• Trouble swallowing food or liquids.
• Coughing or choking during meals.

Weakness on one side of the body

• Dragging a foot.
• Trouble with stairs.
• Weakness in the arm, leg or face.

Changes in facial movement or hearing

• Facial drooping or uneven facial expression.
• Ringing in one ear.
• Reduced hearing.

Headaches, morning nausea or vomiting

• Often worse when waking up or lying down.
• Caused by blocked fluid flow and pressure inside the skull.

Behavior or school changes

• Irritability or mood changes.
• Trouble focusing or keeping up with schoolwork.
• Changes in daily routine or activity level.

When to see a doctor

You should seek care if you notice new symptoms that affect movement, balance, eye motion, speech, swallowing or strength. These symptoms can appear suddenly or build over time and may be a sign that changes in the brainstem are affecting how signals travel between the brain and body.

Seek care right away for symptoms such as:

• Trouble walking or sudden loss of balance.
• New double vision or eyes that drift or do not move together.
• Slurred speech or trouble swallowing.
• Weakness in the face, arm or leg.
• Ongoing headaches, especially in the morning.
• Morning nausea or vomiting.
• Changes in breathing rhythm.
• Sudden changes in behavior or school performance in children.

You also should seek care if symptoms keep getting worse over days or weeks or if new symptoms appear. Even mild changes can be important when they involve the brainstem.

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.

Risk factors

There are very few known risk factors for brainstem tumors. For most children and adults, a brainstem tumor happens without any identifiable risk factor. The most well-known risk factor is having had a high dose of radiation earlier in life, for example, as treatment for other tumors or cancers.

There are no known links between brainstem tumors and lifestyle habits, environmental exposures or personal choices.

Age patterns

Brainstem tumors are more common in children than adults. Gliomas that begin in the pons occur most often in children.

Rare genetic conditions

A small number of people with inherited conditions, such as neurofibromatosis type 1 (NF-1), have a higher chance of developing certain brainstem tumors including pilocytic astrocytomas. Even in these conditions, brainstem tumors are still uncommon.

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.

Prevention

There is no known way to prevent a brainstem tumor. These tumors form when certain cells in the midbrain, pons or medulla begin to grow in an uncontrolled way. Most tumors start because of gene changes inside glial cells. These changes often happen on their own and are not linked to diet, lifestyle or environmental exposures.