Embryonal tumors of the central nervous system are cancerous (malignant) tumors that start in the fetal (embryonic) cells in the brain. Embryonal tumors can occur at any age, but most often occur in babies and young children.

Types of embryonal tumors include:

• Medulloblastomas. The most common type of embryonal tumor, these fast-growing cancerous brain tumors start in the lower back part of the brain, called the cerebellum. The cerebellum is involved in muscle coordination, balance and movement. Medulloblastomas tend to spread through cerebrospinal fluid (CSF) to other areas around the brain and spinal cord, though they rarely spread to other areas of the body.
• Embryonal tumors with multilayered rosettes (ETMRs). Rare tumors that are cancerous, ETMRs typically occur in infants and young children. These aggressive tumors most often start in the largest part of the brain, called the cerebrum, which controls thinking and voluntary movement. ETMRs can also occur in other parts of the brain and are often characterized by a certain genetic change.
• Medulloepitheliomas. These rare, fast-growing cancerous tumors typically occur in the brain or spinal cord of infants and young children.
• Atypical teratoid/rhabdoid tumors. These rare, cancerous tumors are most often found in the cerebellum of infants and children under 3 years of age.
• Other embryonal tumors. A category called embryonal tumors not otherwise specified includes most cancerous tumors that were formerly called primitive neuroectodermal tumors (PNETs), occurring in the brain and spinal cord.

Signs and symptoms of embryonal tumors vary, depending on the type of tumor, location, severity and other factors, such as pressure buildup within the brain. Symptoms may include, for example, headaches, nausea, vomiting, unusual tiredness, dizziness, double vision, unsteady walk, seizures or other issues.

The process of diagnosis usually starts with a medical history review and a discussion of signs and symptoms. Tests and procedures used to diagnose embryonal tumors include those below, but additional tests may be needed to find out if the cancer has spread.

• Neurological exam. During this procedure, vision, hearing, balance, coordination and reflexes are tested. This helps determine which part of the brain might be affected by the tumor.
• Imaging tests. Imaging tests can help determine the location and size of the brain tumor. These tests are also very important to identify pressure or blockage of the CSF pathways. A computerized tomography (CT) scan or magnetic resonance imaging (MRI) may be done right away. These tests are often used to diagnose brain tumors. Advanced techniques, such as perfusion MRI and magnetic resonance spectroscopy, also may be used.
• Removal of tissue for testing (biopsy). A biopsy is usually not done before the tumor is surgically removed, but it may be recommended if the imaging features aren't typical of embryonal tumors. The sample of suspicious tissue is analyzed in a lab to determine the types of cells.
• Removal of cerebrospinal fluid for testing (lumbar puncture). Also called a spinal tap, this procedure involves inserting a needle between two bones in the lower spine to draw out cerebrospinal fluid from around the spinal cord. The fluid is tested to look for tumor cells or other abnormalities. This test is only done after managing the pressure in the brain or removing the tumor.

Treatment for embryonal tumors depends on the patient's age (typically babies and young children), tumor type and location, tumor grade and extent, and other factors. Options include:

• Surgery to relieve fluid buildup in the brain. Some embryonal tumors may grow to block the flow of cerebrospinal fluid, which can cause a buildup of fluid that puts pressure on the brain (hydrocephalus). ). Surgery to create a pathway for the fluid to flow out of the brain (external ventricular drain or ventriculoperitoneal shunt) may be recommended. Sometimes this procedure can be combined with surgery to remove the tumor.
• Surgery to remove the tumor. A pediatric brain surgeon (neurosurgeon) removes as much of the tumor as possible, taking care not to harm nearby tissue. Typically, all children with embryonal tumors should receive additional treatments after surgery to target any remaining cells.
• Radiation therapy. A pediatric radiation oncologist administers radiation therapy to the brain and spinal cord using high-energy beams, such as X-rays or protons, to kill cancer cells. Standard radiation therapy can be used, but proton beam therapy — available at a limited number of major health care centers in the United States — delivers higher targeted doses of radiation to brain tumors, minimizing radiation exposure to nearby healthy tissue.
• Chemotherapy. Chemotherapy uses drugs to kill tumor cells. Typically, children with embryonal tumors receive these drugs as an injection into the vein (intravenous chemotherapy). Chemotherapy may be recommended after surgery or radiation therapy, or in certain cases, at the same time as radiation therapy. In some cases, high dose chemotherapy followed by stem cell rescue (a stem cell transplant using the patient's own stem cells) may be used.
• Clinical trials. Clinical trials enroll eligible participants to study the effectiveness of new treatments or to study new ways of using existing treatments, such as different combinations or timing of radiation therapy and chemotherapy. These studies provide a chance to try the latest treatment options, though the risk of side effects may not be known. Talk with your doctor for advice.

To ensure correct diagnosis and treatment, children with embryonal tumors need to be seen at a center that has a team of pediatric specialists with expertise and experience in pediatric brain tumors, with access to the latest technology and treatments for children.