Juvenile pilocytic astrocytoma (JPA) is a rare childhood brain tumor. In most cases, the tumor is a benign, slow growing tumor that usually does not spread to surrounding brain tissue. Symptoms of a JPA will vary depending upon the size and location of the tumor. Most symptoms result from increased pressure on the brain and include headaches, nausea, vomiting, balance problems and vision abnormalities.
A JPA develops from certain star-shaped brain cells called astrocytes. Astrocytes and similar cells form tissue that surrounds and protects other nerve cells found within the brain and spinal cord. Collectively, these cells are known as glial cells and the tissue they form is known as glial tissue. Tumors that arise from glial tissue, including astrocytomas, are collectively referred to as gliomas.
Astrocytomas are classified according to a grading system developed by the World Health Organization (WHO). Astrocytomas come in four grades based upon how fast the cells are reproducing and that likelihood that they will spread (infiltrate) nearby tissue. Grades I or II astrocytomas are nonmalignant and may be referred to as low-grade. JPA are Grade I tumors and, unlike the low grade astrocytomas of adults, rarely up-grade and become malignant. Grades III and IV astrocytomas are malignant and may be referred to as high-grade astrocytomas. Anaplastic astrocytomas are grade III astrocytomas. Grade IV astrocytomas are known as glioblastoma multiforme.
The symptoms associated with juvenile pilocytic astrocytomas vary depending upon the size and location of the tumor. A JPA can develop anywhere with the central nervous system (i.e., brain and spinal cord). Most cases arise in the lower area of brain near the back of the neck that controls movement and balance (cerebellum), the brainstem, the hypothalamic region or the optic nerve pathways.
The most common finding associated with a JPA is increased pressure within the brain, which may be caused by the tumor itself or by blockage of the fluid-filled spaces in the brain called ventricles, which results in the abnormal accumulation of cerebrospinal fluid (CSF) in the brain. Symptoms commonly associated with increased pressure on the brain include headaches, lethargy or drowsiness, vomiting, and changes in personality or mental status. In some cases, a JPA may also be associated with seizures, vision problems such as blurred vision or double vision (diplopia), gradual changes in behavior or mood, and weakness of the arms and legs resulting in coordination difficulties.
A JPA in the brainstem may be associated with nausea, vomiting, an impaired ability to coordinate voluntary movements (ataxia), and wryneck (torticollis). Ocular symptoms including swelling of the optic disc (papilledema) and involuntary rapid eye movements (nystagmus) may also occur. In some cases, paralysis (palsy) of the sixth and seventh cranial nerves may develop.
A JPA in the optic nerve pathways may be associated with loss of vision, degeneration (atrophy) of the optic nerve, papilledema, nystagmus, and protrusion of the eyeball (proptosis).
A JPA in the hypothalamic region may be associated with weight gain or loss, premature puberty or diencephalic syndrome, which is characterized by failure to thrive, abnormal thinness, irritability, and eye abnormalities.
The exact cause of juvenile pilocytic astrocytomas is unknown. Researchers speculate that genetic and immunologic abnormalities, environmental factors (e.g., exposure to ultraviolet rays, certain chemicals, ionizing radiation), diet, stress, and/or other factors may play contributing roles in causing specific types of cancer. Investigators are conducting ongoing basic research to learn more about the many factors that may result in cancer.
Astrocytomas occur with greater frequency with certain genetic disorders including neurofibromatosis type I, Li-Fraumeni syndrome, and tuberous sclerosis. The exact relationship between astrocytomas and these rare genetic disorders is unknown.
Juvenile pilocytic astrocytomas affect males and females in equal numbers. Most JPAs develop within the first two decades of life. JPAs are the most common cerebellar tumor in children. Astrocytomas as a whole are the most common brain tumor of childhood accounting for more than half of all primary childhood tumors of the central nervous system. The incidence rate is estimated at 14 new cases per million in children younger than 15 years of age. Most astrocytomas (approximately 80 percent) in children are low grade.
A diagnosis of juvenile pilocytic astrocytoma is made based upon a thorough clinical evaluation and a variety of specialized test, including various imaging techniques. Such imaging techniques may include computerized tomography (CT) scanning and magnetic resonance imaging (MRI). During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues such as the brain. CT scanning and MRIs may also be to help evaluate the size, placement, and extension of the tumor and to serve as an aid for future surgical procedures.
A diagnosis of JPA may be confirmed by surgical removal and microscopic evaluation (biopsy) of tissue from the tumor. In certain cases, a biopsy may not be performed because of the location of the tumor (e.g., tumors located in the optic pathway or the brainstem).
The therapeutic management of individuals with a JPA may require the coordinated efforts of a team of medical professionals, such as physicians who specialize in the diagnosis and treatment of cancer (medical oncologists), specialists in the use of radiation to treat cancer (radiation oncologists), surgeons, oncology nurses, and other specialists. Referral to a Children's Oncology Group center may be appropriate.
Specific therapeutic procedures and interventions may vary, depending upon numerous factors, such as primary tumor location, extent of the primary tumor (stage), and degree of malignancy (grade); whether the tumor has spread to lymph nodes or distant sites; an individual's age and general health; and/or other elements. Decisions concerning the use of particular interventions should be made by physicians and other members of the health care team in careful consultation with the patient, based upon the specifics of the case; a thorough discussion of the potential benefits and risks; patient preference; and other appropriate factors.
The main form of treatment for a JPA is surgical excision and removal of as much as the tumor as possible (resection). With cerebellar tumors, most cases can be completely removed by surgery, which is generally considered curative.
In some cases, only a portion of the tumor can be safely removed. In such cases follow-up (adjuvant) therapy is necessary with either certain anticancer drugs (chemotherapy) or radiation therapy. Various chemotherapeutic agents are being studied to determine their effectiveness in treating JPAs and for the potential for side effects.
The use of radiation therapy for the postoperative treatment of children with a JPA is controversial. Radiation therapy can destroy the cancer cells left over after surgery, yet, the potential for serious side effects exists. Radiation therapy is especially avoided in children less than 5 years of age because of the potential for serious side effects and the lack of proof that radiation therapy prevents recurrence.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
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Brauner R, Trivin C, Zerah M, et al., Diencephalic syndrome due to hypothalamic tumor: a model for the relationship between weight and puberty onset. J Clin Endocrinol Metab. 2006;91:2467-73.
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