What is a medulloblastoma?
Medulloblastoma is the most common malignant central nervous system tumor of childhood. It accounts for 15-20 percent of pediatric brain tumors. These tumors are located in the cerebellum, the part of the brain that controls balance and other complex motor functions. Within the cerebellum, medulloblastomas are most often seen in the region of the fourth ventricle/vermis, or the central part of the cerebellum, and less frequently they arise within the cerebellar hemispheres.
As you read further below, you will find general information about medulloblastoma.
What causes a medulloblastoma?
There are no identified predisposing factors that lead to the development of medulloblastomas. Current research is focusing on understanding some of the possible genetic pathways that may be involved in the development of medulloblastomas, because there are rare genetic conditions in which medulloblastomas may arise with a slightly increased frequency.
What are the symptoms of a medulloblastoma?
The following are the most common symptoms of a medulloblastoma, however each child may experience symptoms differently. Medulloblastomas have a peak incidence between the ages of 3 and 8 but can be seen anywhere from the newborn/infant up into adulthood. Common symptoms may include:
increased pressure within the brain. These symptoms include:
headache (generally upon awakening in the morning)
The duration of these symptoms is relatively short, up to several weeks, and often children are diagnosed with the "flu" or a viral illness.
imbalance and lack of coordination
a neck tilt or double vision
rarely, medulloblastomas spread within the nervous system and/or within the spinal canal, causing loss of strength in the lower extremities or significant back pain
The symptoms of a brain tumor may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.
How is a medulloblastoma diagnosed?
Diagnostic procedures for a medulloblastoma may include:
neurological exam -a test of reflexes, muscle strength, eye and mouth movement, coordination, and alertness
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 medulloblastoma, a CT scan of the brain is 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 medulloblastoma, MRIs of the brain and spine are performed. It is important to obtain a spine MRI prior to surgery to evaluate the extent of disease and the presence/absence of spread of the tumor within the nervous system. This information helps determine the initial management of this tumor.
7 magnetic resonance spectroscopy (MRS) - a test done along with MRI at specialized facilities that can detect the presence of particular compounds produced by the body's metabolism within sample tissue that can identify tissue as normal or tumor, and may be able to distinguish between different types of brain tumors.
magnetic resonance spectroscopy (MRS) - a test done along with MRI at specialized facilities that can detect the presence of particular compounds produced by the body's metabolism within sample tissue that can identify tissue as normal or tumor, and may be able to distinguish between different types of brain tumors.
biopsy - in rare cases, a tissue sample from the tumor will be taken through a needle during a simple surgical procedure performed by a surgeon to confirm the diagnosis.
A lumbar puncture, or spinal tap, is never performed in patients with medulloblastoma because such a procedure can lead to catastrophic deterioration in the child's condition.
What are the treatments for medulloblastoma?
Specific treatment for a medulloblastoma will be determined by your child's physician based on:
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 expects the disease to progress
your opinion or preference
Treatment may include (alone or in combination):
ventriculoperitoneal shunt (also called a VP shunt) - a bypass, usually a type of tubing, that is placed in the head to drain excess cerebrospinal fluid (CSF) from inside the brain to space in the abdomen. A VP shunt helps control the pressure inside the brain. On rare occasions, it may be necessary to place a shunt or some other drain to relieve intracranial pressure prior to operating on the tumor. This is indicated in situations when the children are experiencing extreme symptoms from intracranial pressure problems and awaiting definitive surgery, which should be performed on an emergency basis.
surgery - the goals of surgery are to establish a diagnosis, relieve hydrocephalus (swelling on the brain) and remove the tumor. It has been shown through national studies that outcome is correlated with the degree of removal, and therefore an attempt is made to completely remove the tumor, without compromising the child's neurologic function.
Following surgery, lumbar puncture is performed to determine the presence/absence of tumor cells in the spinal fluid, which determines the grade of disease. An MRI of the brain will also be obtained to assess the degree of surgical removal. Typically, medulloblastomas are divided into three groups: infants (children under the age of 3), standard risk (no evidence of disease outside of the posterior fossa of the brain with a complete removal of the tumor) and high risk (evidence of incomplete removal or tumor spread elsewhere in the nervous system). Further treatment is then determined upon the grade of tumor.
radiation therapy and chemotherapy - radiation therapy uses high-energy rays (radiation) from a specialized machine to damage or kill cancer cells and shrink tumors. Chemotherapy is 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.
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:
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
Children with standard risk medulloblastoma are treated with craniospinal irradiation (radiation to the brain and entire spine) over a course of 4-6 weeks. This is followed by chemotherapy.
Children with high-risk medulloblastoma are treated with pre-irradiation chemotherapy followed by craniospinal irradiation, then more chemotherapy.
Infants are treated with chemotherapy until they reach the age of 3 at which time craniospinal irradiation is offered and given.
Throughout their therapy, children are monitored closely by their caregivers with frequent neurologic evaluations and routine MRIs of the brain and spine to monitor response to therapy. A multi-disciplinary team consisting of a neurosurgeon, neuro-oncologist, radiation therapist and neurologist coordinate the management of children with medulloblastoma. In addition to these physicians, there are specialized nurses and social workers that are part of the team managing the child's care. Post-operative care also involves closely physical, occupational and speech therapists.
Post-operatively some children may have difficulties related to coordination, weakness in their extremities and imbalance. These typically resolve over a course of several weeks with the help of physical and occupational therapy. A rare complication is that of "posterior fossa mutism" where children will awake from surgery appearing well but within 24 hours will develop an inability to speak and difficulty with swallowing. This is often associated with large tumors and recovers over several weeks up to several months. In approximately 15 percent of the children diagnosed with medulloblastoma hydrocephalus may develop, requiring the placement of a shunt to drain spinal fluid into the peritoneal cavity.
What is the expected outcome after treatment for medulloblastoma?
The outcome for children with medulloblastoma has improved dramatically over the past several decades. Children with standard risk medulloblastoma have an expected 5-year survival of 65-80 percent. For high-risk medulloblastoma, that number is slightly lower, at 60 percent 5-year survival. The results in infants are disappointing and many studies are being performed to evaluate treatment strategies in infants that will improve overall outcome. Some include administering aggressive chemotherapy and only local irradiation of the posterior fossa to minimize the deleterious effects of radiation on the developing brain.
The long-term effects of treatment include hearing loss related to chemotherapy, loss of height secondary to the radiation and, in some patients, endocrine dysfunction from irradiation of the pituitary gland/hypothalamus. In some patients, secondary tumors (most often high-grade gliomas) develop in areas of the body that received radiation therapy, usually 8-12 years after treatment. The follow-up of patients with medulloblastoma consists of yearly evaluations by the multidisciplinary team with detailed physical and neurologic examinations, audiologic evaluations, endocrine assessments, neuropsychologic testing and MRIs.
What about progressive or recurrent disease?
In the case of relapse, there has not been shown to be an effective curative therapy. However, radiosurgery and chemotherapy are used which can provide long-term comfort with few side effects.
Infromation Courtsey of : Children's Hospital of Bostson