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About Brain Tumors

Any growth of abnormal tissue that forms a mass in the brain is a brain tumor. While there are many types of tumors — each with its own properties, likely locations, cell types and probable outcomes — all pose risks and should be carefully diagnosed and appropriately addressed. Recent years have seen tremendous progress in the treatment of brain tumors. Much of that progress has unfolded here at Lucile Packard Children’s Hospital Stanford, where some of the world’s best pediatric brain tumor specialists are dedicated to understanding and treating the condition.

Approximately 4,000 children in the United States are diagnosed with brain tumors each year. Because children’s brains are still developing, the tumors they get are different from adult tumors on both structural and molecular-biological levels. Fortunately for our young patients, children’s tumors are, on the whole, far more treatable than their adult counterparts. For one thing, whereas most adult brain tumors have spread (or metastasized) to the brain from somewhere else in the body, most children’s brain tumors originate there. That means that the treatment, too, can usually remain more localized. If their brain tumors are diagnosed early enough and treated appropriately, many young patients go on to lead normal lives. Because of the differences between childhood and adult tumors, it is preferable, if possible, for young patients to be treated at specialized pediatric brain tumor centers such as Packard Children’s.

All brain tumors arise from normal brain cells running amuck. Some types result from cellular changes that switch on genes that cause uncontrolled growth. Others result from changes that switch off genes that normally suppress growth. In both cases, the disease hacks into essential cellular code and causes it to malfunction. Some “hacked” tumor-causing genes can be passed down from a parent, but most of the code mistakes, called genetic mutations, occur spontaneously and for no known reason. They are called idiopathic.

Brain tumors can cause several different symptoms depending on which parts of the brain they affect. A tumor near the pineal gland, for instance, may disrupt the secretion of melatonin, a hormone that helps regulate the sleep cycle. A tumor growing near the nerves that connect the eyes to the brain may alter vision. Because brain tumors grow in a closed space inside the skull, many of them eventually cause an increase in intracranial pressure and the symptoms that can go along with it: headache, weakness, nausea, vomiting or seizures. In some cases, symptoms appear suddenly when a tumor reaches a certain size or enters a particular brain area. In other cases, symptoms appear and intensify gradually.  

The different types of children’s brain tumors

There are several kinds of childhood brain tumors. On the broadest level, all of them can be divided into two types: malignant and benign. The word “malignant” roughly means aggressively harmful. Tumors are malignant when they are composed of cancerous cells, when they occupy particularly dangerous areas or when they are fast growing. The word “benign” means gentle or harmless. Tumors with this classification usually pose less threat, but they still frequently require surgical removal.

  • Gliomas are malignant brain tumors that arise from glia, brain cells that provide support for neurons and act as insulation between them. Gliomas are categorized by where in the brain they are found and the specific type of glial cells — there are multiple types — that give rise to them.

  • Astrocytomas are derived from glial cells called astrocytes, which are found throughout the brain and spinal cord. Astrocytomas can occur throughout the central nervous system. They are generally subdivided into high-grade, medium-grade and low-grade tumors. High-grade astrocytomas are the most malignant of all childhood brain tumors. They may cause headache, vomiting, problems with coordination and walking, and double vision.   

  • Brain stem gliomas are derived from the glial cells of the brain stem and occur most commonly in children between 5 and 10 years old. A child with a brain stem glioma may experience double vision, problems with walking or coordination, or difficulty moving their face or even one entire side of their body.

  • Ependymomas, also glial cell tumors, usually develop in the lining of the brain’s ventricles (cavities in the brain filled with cerebrospinal fluid, or CSF) or in the spinal cord and are usually located in the back of the brain near the cerebellum. These tumors commonly block the flow of CSF, which causes increased pressure in the brain and can induce nausea, vomiting, headaches and vision problems. Although ependymomas usually grow slowly compared to other tumors, they are also more likely to return after a full round of treatment. When they do recur, it is often in a form that is more aggressive and treatment-resistant.

  • Optic nerve gliomas are found in or around the nerves that send messages from the eyes to the brain. They can cause blindness. Because they are usually located at the base of the brain near the hormonal control center, they can also cause hormone regulation problems such as poor growth and short stature. Because these tumors are surrounded by sensitive brain structures, they can be difficult to treat.

  • Medulloblastomas are the most common type of malignant brain tumor in children. They develop from the neural precursor cells (not glia) of the cerebellum and are usually found at that structure’s midline. These tumors grow rapidly and often block drainage of the CSF, causing symptoms associated with increased intracranial pressure. Medulloblastoma cells can metastasize to other areas of the central nervous system, especially around the spinal cord. A combination of surgery, radiation and chemotherapy are usually needed to treat these tumors.

  • Craniopharyngiomas are benign tumors that occur near both the nerves running from the eyes to the brain and the brain’s hormone centers. These tumors mostly occur in children and young adults, but they can develop at any age. Symptoms often include headaches and vision problems. Because they can cause hormonal imbalances, poor growth and short stature may also be problems. Although benign, these tumors are hard to remove without damaging the sensitive brain structures surrounding them.

  • Tumors that arise near the pineal gland, the pea-sized body that helps control sleep and wake cycles by producing melatonin, are called pineal region tumors. Gliomas are common in this region, as are the fast-growing pineoblastomas. Germ cell tumors can also be found there. Benign pineal gland cysts growing in this region can sometimes make diagnosis difficult, and a biopsy may be required to distinguish benign from malignant forms. Children with pineal tumors may experience headaches or other symptoms of increased intracranial pressure. Specific treatment, which can be complicated by the sensitive brain tissue in this area, also depends on the type and size of the tumor.

The keys to mapping treatment in every case are determining precisely what kind of brain tumor a child has and getting a high-resolution depiction of its dimensions and margins. Packard Children’s neurosurgeons, oncologists, neurologists, neuropathologists and neuro-radiologists are among the best in the world. They collaborate to deploy cutting-edge diagnostic imaging and surgical technology to identify and treat brain tumors quickly and thoroughly while navigating the safest and least disruptive route to the best possible outcome for each patient.