Cancers of the brain and nervous system are the most common type of childhood cancer. When discovered early, these cancers often can be cured.

There are many different types of brain and nervous system cancers, and doctors categorize them based on where the tumors are, the type of cells involved, and how quickly they grow.

Here are some of the most common types of brain and nervous system cancers.

Brain Stem Glioma

The brain stem, located deep in the back of the brain, is made up of the midbrain, pons, and medulla. These parts of the brain control the body's autonomic nervous system (which is responsible for controlling body processes like breathing, digesting, sweating, and shivering).

A tumor that develops in any area of the brain stem is called a brain stem glioma. Tumors in the pons are called pontine gliomas (or diffuse intrinsic pontine gliomas, DIPG). Pontine gliomas are the most common brain stem gliomas, and also the most difficult to treat. Tumors in the midbrain and medulla are less common, but usually easier to treat.

Symptoms of a pontine glioma may start suddenly and get worse very quickly. These can include:

• double vision
• turning in of one eyeball
• drooping of the eyelid or one side of the face
• trouble swallowing
• trouble speaking and walking
• nausea and vomiting

Midbrain tumors may cause eye symptoms similar to pontine gliomas, along with headaches and vomiting. This is due to increased pressure in the head caused by the flow of cerebrospinal fluid being blocked. (Cerebrospinal fluid is a clear, colorless liquid that delivers nutrients to the brain and spinal cord and "cushions" them for protection.)

Tumors of themedulla cause swallowing problems and limb weakness.

Because the brain stem is an area of the brain where surgery can be difficult, brain stem gliomas are often treated with radiation therapy (high-energy X-rays that kill cancer cells) and/or chemotherapy.

Ependymoma

Ependymomas are tumors that develop in the brain cells that make cerebrospinal fluid. They often develop in children under age 5.

Ependymomas are classified according to their location, and most don't spread (metastasize) to other areas of the body. Those located in the top part of the brain are called supratentorial ependymomas. Supratentorial ependymomas can cause nausea, vomiting, and headaches from increased pressure within the brain, as well as weakness and vision problems.

Ependymomas also can be found in the spinal cord.

Tumors in the back of the brain are more common. These are called infratentorial ependymomas. They can cause nausea, vomiting, and headache, and trouble with coordination.

Supratentorial ependymomas sometimes can be cured by surgery alone. Infratentorial ependymomas usually need much more aggressive treatment with surgery, chemotherapy, and radiation.

Primitive Neuroectodermal Tumor (PNET)

PNETs are a group of tumors that can happen anywhere in the brain. Types of PNETs include medulloblastoma, posterior fossa PNET, supratentorial PNET, and pineoblastoma. All of these tumors can metastasize (spread) through the cerebrospinal fluid that surrounds the brain and the spinal cord.

PNET symptoms generally depend on their size and location, but common ones include:

• headaches, nausea, and vomiting (especially in the morning) caused by increased pressure in the head
• weakness in the arms and legs
• vision problems
• seizures
• trouble with balance and coordination

Even though PNETs require aggressive treatment (including surgery, chemotherapy, and radiation therapy), recent medical advances have made a cure possible for most children who have them.

Optic Pathway Glioma

The optic pathway sends signals to the brain about what the eye sees. A tumor that develops along this pathway is called an optic pathway glioma.

Optic pathway gliomas mostly affect kids under age 10. People with neurofibromatosis type 1 (a genetic condition that causes tumors to grow on nerve tissue) have an increased risk of developing them.

The most common symptom of an optic pathway glioma is progressive vision loss. With slow-growing tumors, this may be hard to spot at first — especially in younger children who can't describe what they're seeing. With fast-growing tumors (or less aggressive ones that have reached a large size), vision problems become apparent more quickly.

Kids also may start tilting their heads or having what appear to be developmental delays like clumsiness during walking, speech difficulties, or behavior changes. A condition called nystagmus (when the eyeballs appear to "jitter" involuntarily) also can happen. Sometimes, a tumor that's pressing on the pituitary gland can cause growth problems.

Optic pathway gliomas are usually treated with chemotherapy, although radiation also can be used. Most kids do well with treatment.

Astrocytomas

Astrocytomas develop from star-shaped brain cells known as astrocytes. Astrocytomas come in four major subtypes: pilocytic astrocytoma (grade I), fibrillary astrocytoma (grade II), anaplastic astrocytoma (grade III), and glioblastoma multiforme (grade IV).