Medulloblastoma is a type of brain cancer in which the tumor is located in the cerebellum, an important structure located at the base of the brain. According to Children's Hospital Boston, medulloblastoma is the most common malignant tumor of the central nervous system (CNS) in children and accounts for approximately 15 to 20 percent of all pediatric CNS tumors.
Symptoms
The cerebellum primarily functions in balance and complex motor function control, such as speech, and damage to this structure by a tumor can lead to many problems. Early signs of medullablastoma include flu-like symptoms such as lethargy, fever and loss of appetite. Cerebellum damage leads to imbalance and loss of coordination, dizziness, and double vision. Depending on the location and size of the tumor, blockage of cerebrospinal fluid (CSF), a circulating fluid in the brain, can lead to hydrocephalus. Hydrocephalus is increased pressure in the brain which triggers headaches, vomiting, nausea and fatigue, especially upon waking in the morning.
Causes
The exact cause of medullablastoma is unknown, although it is suspected that it may be caused gene and chromosomal changes that occur during fetal development or after birth. Exposure to environmental toxins or viruses is also under investigation as the cause of medullablastoma. The majority of cases occur in children under the age of fifteen and are most common in children ages 5 to 6. Medullablastoma does not appear to run in families and is more common in boys than in girls.
Diagnosis
The first step in diagnosing medullablastoma is a complete medical and symptom history assessment along with the administration of a neurological exam. An MRI (magnetic resonance imaging) scan is generally administered to provide a more detailed image of the tumor. Confirmation of medullablastoma is by microscopic analysis of a small section of the tumor through a biopsy, which is generally removed during surgical treatment.
Treatment
Treatment of medullablastoma is dependent on the size and location of the tumor as well as the physical condition of the patient. The three main treatment approaches for medullablastoma include a ventriculoperitoneal (VP) shunt, surgery, and radiation and chemotherapy. VP shunting involves placing a tube in the head to drain the excess cerebrospinal fluid and is generally reserved for individuals with severe symptoms who are awaiting surgery for tumor removal. With surgery, the goal is for complete removal of the tumor without compromising brain function. Radiation and chemotherapy involves the use of high-energy rays and chemicals to destroy the tumor cells, respectively, and is can be administered in combination with surgery.
Prognosis
Post-operatively, physicians use a tumor recurrence assessment scale to place individuals into one of three groups--infant, standard risk or high risk--to assess degree of tumor removal. All individuals under the age of three are placed into the infant group. Standard risk individuals show no evidence of tumor outside of the cerebellum with complete surgical removal. High risk individuals exhibit evidence of incomplete tumor removal or signs that the tumor has spread elsewhere in the central nervous system (CNS). These assessments provide a basis for 5-year survival rates. The 5-year survival rate for children in the standard risk group is 70 to 80 percent and 60 to 65 percent for high risk individuals. The prognosis for infants with medullablastoma is not as good, with a 5-year survival rate of 30 to 50 percent, according to the Central Brain Tumor Registry of the United States. The 5-year survival rate for adults with medullablastoma is 65 to 70 percent following diagnosis.
