[2] Common symptoms of CNS tumors include vomiting, headache, changes in vision, nausea, and seizures.

The list is based on the WHO classification of CNS tumors and on the pediatric cancer register Deutsches Kinderkrebsregister | Übersicht[5] and Surveillance, Epidemiology, and End Results Program.

[10] A number of genetic disorders increase the risk of specific types of CNS tumors.

The first step in diagnosis is usually a neurological exam, including tests for reflexes, muscle strength, vision and eye movements, and balance and alertness.

In perfusion MRI a contrast agent, such as gadolinium compounds, may be used to study the structure of the blood vessels around the tumor that provide nutrients and remove waste.

An image guidance system is then used to provide assistance in directing a needle into the tumor to collect a small tissue sample.

Many tumors shed microscopic extracellular vesicles into the bloodstream that can be used to monitor the progress of a cancer or its response to therapy.

[18] Some tumors are deep-seated and unsafe to remove, and in these cases the role of surgery may be limited to obtaining a diagnostic biopsy.

Radiation therapy uses high energy rays to destroy cancer cells or to shrink tumors.

This may be done by placing a solid source of radiation adjacent to the tumor in the form of a seed, ribbon or capsule (brachytherapy)[1] or by giving the patient a liquid source of radiation that travels through the body and kills cancer cells (system therapy).

[citation needed] Chemotherapy is a treatment that uses a tumor-killing drug to prevent the growth of cancer cells by stopping them from dividing.

[1] Common side effects of chemotherapy include: [20] An increasing number of drugs are available that promise to target a tumor specifically, reducing harm to normal cells.

Targeted therapies may block enzymes or other proteins necessary for cancer cell proliferation, deliver toxic substances directly to cancer cells, help with immune system function, or prevent the tumor from obtaining the nutrients it needs.

[citation needed] Checkpoint inhibitors, which prevent the tumor from blocking the action of tumor-killing cells of the immune system.