To diagnose an oligodendroglioma brain tumor, a neurologist (a doctor with special additional training in the diagnosis and treatment of disorders of the brain, spinal cord and nerves) performs a complete examination, which may include a magnetic resonance imaging (MRI) scan or a computed tomography (CT or CAT) scan. An MRI usually finds low-grade tumors earlier than CT.
Depending on the patient's symptoms, specialized testing may be necessary, including tests of the field of vision, the sharpness of vision and hearing. If the results of other tests aren't conclusive, an examination of the fluid that surrounds the brain and spinal cord may be done. Cerebral angiography is rarely used to diagnose a brain tumor, but may be done before surgery. Chest X-rays may also be needed to determine if the tumor has spread from another part of the body.