What is medulloblastoma?
Medulloblastoma is the most common malignant brain tumor of childhood. The tumor arises in the area of the brain called the cerebellum. The cerebellum is located in the back and lower part of the brain. Like most cancers, medulloblastoma is a collection of abnormal cells that are rapidly dividing and growing out of control. Medulloblastoma most commonly spreads to other parts of the brain and spinal cord. Rarely, it can spread outside of the brain and spinal cord to bones and bone marrow. It is important to remember that medulloblastoma is not contagious. A person with medulloblastoma cannot spread the cancer to others who they are in contact with.
What causes medulloblastoma?
In most cases, it is not clear what causes medulloblastoma. For some reason, abnormal cells begin to rapidly divide and grow out of control leading to a tumor. In the case of medulloblastoma, these cells possess characteristics of normal brain cells, but they have become malignant and are rapidly dividing and growing out of control. There are a few rare instances where some patients may have a pre-disposition to developing medulloblastoma. Some patients and families have an abnormality in their genes that may predispose them to multiple types of cancers, including medulloblastoma. In general, however, we currently do not know what triggers the development of medulloblastoma in most patients.
What are the symptoms of medulloblastoma?
Often, the location of the medulloblastoma tumor may cause a blockage of cerebrospinal fluid flow. The cerebrospinal fluid (CSF) is a fluid produced in the brain that coats and cushions the brain and spinal cord. When the flow of the CSF is blocked, the build up of fluid cause increasing pressure on the brain. This increased pressure will cause patients to develop persistent headaches, nausea, and vomiting. Other symptoms include: sleepiness, changes in vision (blurred or double vision), loss of coordination, slurred speech, poor balance, dizziness, seizures, and confusion. In infants, the symptoms may be less obvious. Infants may present with symptoms such as increasing head circumference, decreased activity, poor appetite, and/or irritability.
How is the diagnosis made?
The diagnosis of medulloblastoma is often made when a patient develops one or more of the above symptoms that leads a physician to order a scan to look inside the patient’s head. Often times, the first scan ordered is a CT or CAT scan (Computed Tomography), a type of radiology photograph that can show that there is an abnormal mass within the cerebellum. Once a mass is identified, the patient will have an MRI (Magnetic Resonance Imaging) taken of the brain to better delineate the tumor’s size, extent, and location. Although a medulloblastoma often has certain common characteristics on MRI and CT scans, the diagnosis cannot be made by imaging studies alone. A Neuro-surgeon will remove the mass, or as much of the mass as possible, and the diagnosis is made by the Pathologist who reviews the tumor under a microscope. Medulloblastoma will have certain features under a microscope that will distinguish it from other brain tumors.
Once a diagnosis of medulloblastoma is made, it is important to identify if it has spread or not. To evaluate this further, an MRI of the spine will be performed. Also a lumbar puncture or spinal tap is performed. A spinal tap is a procedure that takes a sample of the cerebrospinal fluid (CSF). The fluid is then evaluated under a microscope to look for the presence of tumor cells. It is extremely rare for a medulloblastoma to spread beyond the brain and spinal cord when it is fist diagnosed. However, if a patient has a finding on physical exam or a complaint that may suggest the tumor has spread, the treating physician may choose to perform further tests, including a bone scan and/or bone marrow sample.
How do you treat medulloblastoma?
Treatment of medulloblastoma differs depending upon whether the disease has spread or not, but in general, therapy consists of a combination of the following: surgery, radiation therapy, and chemotherapy. One of the most important parts of therapy is the surgery. It is important for the Neuro-surgeon to remove as much of the tumor as possible. Medulloblastoma is very sensitive to radiation therapy. Unfortunately, there are often long term effects of radiation, particularly in very young children. For this reason, many newer therapies in children attempt to postpone or eliminate the need for radiation by utilizing chemotherapy. Some children will under go very high doses of chemotherapy followed by a bone marrow transplant in an effort to avoid radiation therapy.
Can medulloblastoma come back after it is treated?
Unfortunately, like most cancers, there is a possibility that medulloblastoma will return after treatment. For this reason, patients are followed with serial MRI scans after treatment in order to identify any recurrences. It is important to identify relapsed disease early in order to have a better chance at appropriate therapy. Although relapsed disease is often more difficult to cure, there are options and treatments available for relapsed patients that have proven successful.
Can adults get medulloblastoma?
Although most cases of medulloblastoma are seen in children, adult patients can develop medulloblastoma. They can develop the same symptoms as children including headache, nausea, vomiting, weakness, double vision, and seizures. In general, adults are evaluated and treated the same as children with medulloblastoma. An MRI of the brain and spinal cord are performed, and an evaluation of the patient’s spinal fluid is made. Adults should also have a complete surgical resection, if possible, and often they are treated with post- surgical radiation with or without chemotherapy.
What is PNET? Is it different from medulloblastoma?
PNETs or primitive neuro-ectodermal tumors are a group of tumors that appear to be derived from abnormal early brain and nervous system cells. Medulloblastoma is considered a member of this group of tumors, and sometimes, medulloblastoma will be referred to as a posterior fossa PNET, meaning it is a PNET within the lower back portion of the brain (in the cerebellum). The preferred term to help avoid confusion is medulloblastoma. In fact, many researchers and physicians believe that PNETs in other parts of the brain behave differently from medulloblastomas, and thus, the two should be considered separate types of tumors.