Pediatric Brain Tumors

Types

Regions of the brain

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Names of brain tumors can be confusing. There are many types of brain tumors and often different names for the same tumor. One large family of tumors — causing half of all brain tumors in children — is gliomas, which arise from glial cells (the supporting cells of the nervous system). Glial cells consist of astrocytes, ependymal cells and oligodendrocytes. Some tumors take their names from these cells.

Brain tumors are grouped according to their location within the brain and the appearance and behavior of the cells. The following groupings are used for childhood brain tumors.

Tumors Found in the Lower Part of the Brain

Medulloblastoma
This is the most common malignant brain tumor in children. Medulloblastomas are a subtype of primitive neuroectodermal tumors (PNETs). They occur in the cerebellum and are believed to arise from a very immature neuronal (rather than glial) precursor cell. This tumor occurs more frequently in boys than in girls. The peak incidence of medulloblastoma occurs in children 2 to 7 years old, although some occur in young adults.

Symptoms include loss of balance, lack of coordination, double vision, difficulty speaking, and signs of hydrocephalus (excess fluid in the brain), including headache, nausea, vomiting and instability in walking.

Surgery is often recommended to remove as much of the tumor as possible.

Surgery is not curative. Radiation to the craniospinal axis with a boost to the site of the primary tumor can cure some tumors. Adjuvant chemotherapy (after radiation therapy) has increased the cure rate compared with the use of radiation therapy alone. With appropriate initial therapy, long-term survival is achieved in 60 to 80 percent of patients with medulloblastoma.

Cerebellar Astrocytoma
This tumor of the cerebellum — the part of the brain that influences body movement, muscle tone and balance — usually grows slowly. It also is found in regions of the brainstem around the cerebellum. Astrocytomas arise from glial (non-neuronal) cells and can be low grade or high grade (see information on tumor grading).

Brainstem glioma (low grade astrocytoma) in a child

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For low-grade astrocytomas, a practical approach is to remove (resect) as much of the tumor as possible with as little neurologic injury as possible. Depending on the child's age and location of the tumor and extent of resection, radiation therapy may be used to treat any remaining tumor or new tumor. Often MRI scans are obtained at regular intervals to monitor whether tumor cells remain that are still growing.

For high-grade astrocytomas, the standard initial treatment is to remove as much of the tumor as possible. Radiation therapy has been shown to prolong survival and is a standard component of treatment. In general, median survival ranges from two to three years for adult patients. The long-term prognosis is generally better for pediatric patients.

Clinical trials have not shown adjuvant chemotherapy to be beneficial for these tumors.

Ependymoma
Ependymal tumors begin in the ependyma, the cells that line the hollow cavities within the brain (called ventricles) which are filled with cerebrospinal fluid. The growth of ependymal tumors can obstruct the flow of cerebrospinal fluid through the brain and spinal cord, a condition called hydrocephalus. This condition often requires urgent surgical intervention.

In children, these tumors are more commonly found in the posterior fossa and spinal cord. For low-grade lesions, surgical resection may cure the tumor. Low-grade resectable ependymomas in the spine are usually treated with surgery alone. High-grade or incompletely resected low-grade tumors are usually treated with radiation therapy after surgery.

Diffuse Intrinsic Brain Stem Glioma
This tumor occurs in the pons or the medulla (areas near the base of the brain). It accounts for approximately 15 percent of brain tumors in children. Surgery is difficult due to location, so radiation therapy and chemotherapy are generally used. The diagnosis is often made by a characteristic appearance on MRI scan and physical exam.

Tumors Found in the Upper Part of the Brain

Cerebral Astrocytoma

Giant cell astrocytoma

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These tumors arise from brain cells called astrocytes (a type of glial cell) and can occur in any part of the brain or spinal cord. However, they are most commonly found in the main part of the brain, the cerebrum. They can be low grade or high grade and have different features, such as the degree of invasiveness.

Glioblastoma Multiforme
Glioblastoma multiforme is the most common and most malignant primary brain tumors in adults. It is a very rare tumor in children. Surgical removal remains the mainstay of treatment, provided that unacceptable neurologic injury can be avoided.

Supratentorial Ependymoma
Supratentorial ependymomas begin in the upper part of the brain. They arise from ependymal cells that line the hollow cavities within the brain (called ventricles) filled with cerebrospinal fluid. These tumors may spread to other areas of the brain and spinal cord, depending on their grade. The growth of ependymal tumors can obstruct the flow of cerebrospinal fluid through the ventricles and cause increased pressure or hydrocephalus.

Craniopharyngioma
Craniopharyngiomas are tumors that generally occur just above the pituitary gland. Located at the bottom of the brain just behind the optic nerves, the pituitary gland is about the size of a pea and controls many vital and hormonal functions. Craniopharyngiomas can compress nearby structures causing vision and memory loss or alterations in wakefulness or appetite.

Central Nervous System Germ Cell Tumor
Germ cell tumors arise from the very primitive cells found in the brain that share characteristics with early embryonic cells (germ cells). Germ cell tumors include germinomas, embryonal cell carcinomas, choriocarcinomas and teratomas. These tumors usually occur in the center of the brain, and can spread through the spinal fluid to other parts of the brain and spinal cord.

Choroid Plexus Papillomas
These tumors occur in the part of the brain that produces cerebrospinal fluid. A tumor in this location accounts for 1 to 3 percent of pediatric brain tumors. This tumor usually arises in infants and often causes hydrocephalus.

Optic glioma in a child

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Optic Pathway and Hypothalamic Glioma
An optic pathway glioma occurs along the nerve that sends messages from the eye to the brain (the optic nerve). A hypothalamic glioma is a tumor in the hypothalamus, a portion of the brain that lies beneath the thalamus and governs hormone secretion, which influence the functions of the pituitary gland and regulates body temperature, water balance, blood sugar and fat metabolism.

Pineal or Suprasellar Tumors
These tumors arise from the pineal gland in the back part of the brain or may arise from the sella turcica, where the pituitary gland resides. These tumors may secrete active proteins or hormones. They are often treated by surgery, radiation and chemotherapy.

Meningiomas
Meningiomas are usually benign and originate in the dura that covers the brain and spinal cord. Meningiomas are extremely rare in children, except among childhood survivors of another type of tumor who received craniospinal radiation therapy. There is an increased incidence of meningiomas as a secondary malignancy in these children.

Oligodendrogliomas
Tumors that contain oligodendroglial elements are relatively uncommon, probably accounting for no more than 10 percent of primary brain tumors. Prognosis is not clear for pediatric patients due to the very low incidence of these tumors in children. Patients typically present with seizures.