Cancers of the brain and nervous system are the second most common type of childhood cancer, after leukemia (cancer of the blood or bone marrow).

With these types of cancer, clusters of cancer cells, or tumors, develop within the brain or spinal cord and can affect the entire nervous system.

When discovered early, cancers of the brain and nervous system are usually treatable. There are many different types, and doctors categorized them according to where the tumors are located, the type of cells involved, and how quickly they grow.

Discussed in this article 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, consists of the midbrain, pons, and medulla. These structures coordinate all of the brain's messages. They also control many of the body's autonomic functions (the autonomic nervous system is responsible for controlling many of the body processes we almost never need to think about, like breathing, digestion, sweating, and shivering).

A tumor that develops in any area of the brain stem is called a brain stem glioma. Tumors that occur in the pons (pontine gliomas) are the most common but are often the most difficult to treat. Tumors that occur in the midbrain and medulla are less common but usually more easily treated.

Symptoms of a pontine glioma may come on suddenly and worsen very quickly. These may include:

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

Midbrain tumors may cause similar eye symptoms, along with headaches and vomiting. This is due to increased pressure in the head caused by a blockage of cerebrospinal fluid, the fluid that surrounds and cushions the brain and spinal cord.

Tumors of the medulla are associated with swallowing problems and limb weakness.

Because the brain stem is an area of the brain that generally can't tolerate surgery, brain stem gliomas are usually treated with radiation (high-energy X-rays that kill cancer cells) and chemotherapy.

Ependymoma

Ependymomas are tumors that originate in brain cells that produce cerebrospinal fluid. They mostly develop in children under age 5.

Ependymomas are classified according to their location, and most do not spread (metastasize) to other areas of the body. Those located in the top part of the head are called supratentorial. This type of tumor is associated with symptoms such as nausea, vomiting, and headaches from increased pressure within the brain, as well as weakness and vision problems.

Tumors found in the back of the head are more common. These are called infratentorial, and are also associated with nausea, vomiting, and headache, as well as trouble with coordination.

Supratentorial ependymomas often can be cured by surgery alone, while infratentorial ependymomas usually require much more aggressive treatment with surgery, chemotherapy, and radiation.

Ependymomas can also be found in the spinal cord.

Primitive Neuroectodermal Tumor (PNET)

PNETs are a group of tumors that can occur anywhere in the brain, but whose cells look very similar under a microscope. Types of PNETs include medulloblastoma, posterior fossa PNET), supratentorial PNET, and pineoblastoma. All of these tumors are able to metastasize 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 the majority of children who have them.

Optic Nerve Glioma

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

These tumors mostly affect kids under age 10; those with the genetic condition neurofibromatosis type 1 (which causes tumors to grow on nerve tissue) have an increased risk.

The most typical symptom 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 will eventually become apparent.

Kids also may start tilting their heads or experiencing what appear to be developmental delays such as clumsiness during walking, speech difficulties, or behavior changes. A condition called nystagmus (when the eyeballs appear to "jitter" involuntarily) also might appear. Sometimes, if the tumor is pressing on the pituitary gland, growth problems can result.

Optic nerve gliomas are usually treated with chemotherapy, although radiation also can be used. Most kids do well with treatment, and further vision loss usually is prevented.

Astrocytomas

Astrocytomas originate from star-shaped brain cells known as astrocytes. They come in four major subtypes: pilocytic astrocytoma (grade 1), fibrillary astrocytoma (grade 2), anaplastic astrocytoma (grade 3), and glioblastoma multiforme (grade 4).