 Thalamic/hypothalamic Astrocytoma
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A low-grade glioma of either the thalamus or hypothalamus is a tumor arising from a type of cell in the central nervous system known as a glial cell. These tumors originate from a specific type of glial cell known as an astrocyte. Astrocytes make up the supportive network of the brain. These cells are named for their star-like appearance.
Low-grade gliomas of the thalamus or hypothalamus (sometimes referred to as suprasellar astrocytomas or suprasellar low grade gliomas) are astrocytomas (grade I pilocytic astrocytomas or grade II fibrillary astrocytomas) of the thalamus (responsible for identification of sensation, such as temperature, pain, touch) or the hypothalamus (responsible for hormone functioning, body temperature, sleep and appetite). A low-grade glioma may invade both the thalamus and hypothalamus, or may involve only one of these deep-lying, central areas of the brain.
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Children with certain genetic syndromes, including neurofibromatosis and tuberous sclerosis, are at higher risk of developing tumors of glial origin, including thalamic and/or hypothalamic low-grade gliomas. The vast majority of children with these tumors however, develop them spontaneously, meaning there is no identifiable cause.
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Due to the relative slow growth rate of thalamic/hypothalamic low-grade gliomas, children with these tumors tend to present to the doctor with symptoms that have been occurring for many months. Some children, however, will have a more sudden onset of symptoms. The following are the most common symptoms of a thalamic/hypothalamic low-grade glioma, however, each child may experience symptoms differently. Common symptoms may include:
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- many present with symptoms of increased pressure within the brain. These symptoms include:
- headache (generally upon awakening in the morning)
- others may experience hormone imbalance (weight loss/gain, salt and water imbalance) and/or changes in vision (the thalamus and hypothalamus lie in close proximity to the visual pathway system of the brain)
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The symptoms of a brain tumor may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
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Diagnostic procedures for a thalamic/hypothalamic low-grade glioma may include:
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- physical examination - the child may demonstrate evidence of increased pressure in the brain
- computerized tomography scan (also called a CT or CAT scan) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. CT scans are more detailed than general x-rays. For a thalamic/hypothalamic low-grade glioma, a CT scan of the brain is usually done.
- magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body. For thalamic/hypothalamic low-grade gliomas, an MRI of the brain is usually done. An MRI of the spine may also be obtained to look for evidence of tumor in the spine (thalamic and hypothalamic low-grade gliomas very rarely spread to the spine).
- biopsy - a tissue sample from the tumor of either the thalamus or hypothalamus may be taken through a needle during a surgical procedure or an open biopsy, which is a layer operation performed by a neurosurgeon to confirm the diagnosis
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Specific treatment for a thalamic/hypothalamic low-grade glioma will be determined by your child's physician based on:
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- your child's age, overall health, and medical history
- type, location, and size of the tumor
- extent of the disease
- your child's tolerance for specific medications, procedures, or therapies
- how your child's doctors expect the disease to progress
- your opinion or preference
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Treatment may include (alone or in combination):
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- surgery - the initial treatment of a low-grade glioma of the thalamus and/or hypothalamus is maximum surgical removal. Surgery is often limited due to the deep, central placement of both the thalamus and hypothalamus within the brain.
- chemotherapy - a drug treatment that works by interfering with the cancer cell's ability to grow or reproduce. Different groups of chemotherapy drugs work in different ways to fight cancer cells and shrink tumors. Often, a combination of chemotherapy drugs is used to fight a specific cancer. Certain chemotherapy drugs may be given in a specific order depending on the type of cancer it is being used to treat.
A number of combinations of chemotherapy drugs, including vincristine with carboplatin and vincristine with CCNU, procarbazine and thioguanine, are thought to be effective in stabilizing and, in some cases, shrinking the size of the glioma.
While chemotherapy can be quite effective in treating certain cancers, the agents do not differentiate normal healthy cells from cancer cells. Because of this, there can be many adverse side effects during treatment. Being able to anticipate these side effects can help the care team, parents, and child prepare, and, in some cases, prevent these symptoms from occurring, if possible.
Chemotherapy is systemic treatment, meaning it is introduced to the bloodstream and travels throughout the body to kill cancer cells. Chemotherapy can be given:
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- as a pill to swallow
- as an injection into the muscle or fat tissue
- intravenously (directly to the bloodstream; also called IV)
- intrathecally - chemotherapy given directly into the spinal column with a needle
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- radiation therapy - shown to be effective in halting the growth of these tumors, however radiation therapy often has effects on hormone functioning and learning, so it is often avoided in the initial treatment. Radiation therapy uses high-energy rays (radiation) from a specialized machine to damage or kill cancer cells and shrink tumors
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Children with thalamic/hypothalamic low-grade gliomas may have side effects related to the tumor itself and its treatment. Symptoms at the time of diagnosis related to increased pressure within the brain, such as headache, vomiting and lethargy, are often relieved by surgical debulking of the tumor. In cases where only a limited surgical removal is achieved, symptoms related to increased pressure within the brain may not be adequately reduced. These children may undergo a surgical procedure to insert a device (a shunt) to drain excess fluid accumulating within the brain (cerebral spinal fluid).
Endocrine and/or visual functioning may or may not improve with surgical debulking.
Dexamethasone, an oral steroid, is often used, especially in the post-operative period, to assist in controlling systems of increased pressure within the brain, as well as any additional tissue swelling that may occur post-operatively.
Common side effects related to chemotherapy include nausea, vomiting and decreased blood counts (i.e. anemia). Anti-emetics (anti-nausea) medications are administered with the chemotherapy to control symptoms of nausea and vomiting. Occasionally, children receiving chemotherapy will require transfusion of red blood cells and/or platelets to replace these cells since chemotherapy temporarily decreases the body's ability to produce red blood cells and platelets. White blood cells are also reduced with chemotherapy, however these cells are not transfused. Occasionally, children will receive a medication to assist the body in producing white blood cells.
Radiation therapy may cause swelling related to tissue inflammation. This inflammation may lead to symptoms of headache or difficulty with coordination. These symptoms, if significant, may be treated with the oral medication dexamethasone.
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Low-grade gliomas of the thalamus and/or hypothalamus have a high rate of survival.
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The recommended treatment for progressive/recurrent low-grade glioma of the thalamus and/or hypothalamus is radiation therapy. Dana-Farber Cancer Institute is one of nine institutes in the nation belonging to the Pediatric Brain Tumor Consortium. The consortium is dedicated to the development of new and innovative treatments for children with progressive/recurrent brain tumors not responsive to standard therapies. Children with progressive/recurrent low-grade gliomas of the thalamus and/or hypothalamus would be eligible for a number of experimental therapies available through the consortium.
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Children's Hospital and Dana-Farber Cancer Institute are conducting numerous research studies that will help clinicians better understand and treat thalamic/hypothalamic low-grade gliomas. For more information on current research, see the Brain Tumor Program.
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