Introduction: When to Seek Diagnostic Evaluation

If you experience certain warning signs, it’s important to seek medical evaluation promptly. The most common reason people discover they have an oligodendroglioma is when they experience a seizure, which is a sudden episode of abnormal electrical activity in the brain that can cause convulsions or loss of consciousness. In fact, up to 80 percent of people with this tumor will have a seizure at some point, and for many, this seizure occurs before they even know they have a tumor.^[1] This happens because oligodendrogliomas commonly develop in the outer surface of the brain, which controls many everyday functions like movement, language, and vision.^[3]

Other symptoms that should prompt you to see a doctor include persistent headaches that don’t respond to usual treatments, changes in your personality or behavior that your loved ones notice, weakness or numbness in your arms or legs, problems with speaking or understanding others, or vision changes.^[1] Because these tumors often grow slowly, especially the low-grade type, symptoms may develop gradually over months or even years. Some people only discover they have a tumor by accident when brain imaging is done for another reason, such as after a head injury or for investigation of severe headaches.^[3]

It’s worth noting that many of these symptoms can also be caused by conditions that are not brain tumors. However, only proper medical evaluation can determine the actual cause. If you have a family history of brain tumors, you should be especially attentive to any new neurological symptoms, though it’s important to know that only about 5 percent of brain tumors are genetic, so having a family member with a brain tumor doesn’t necessarily mean you’ll develop one.^[11]

Classic Diagnostic Methods

Initial Medical Examination

When you first visit your doctor with concerning symptoms, they will conduct a thorough neurological examination. During this exam, the doctor will ask detailed questions about your symptoms, including when they started, how often they occur, and whether they’re getting worse. They’ll also review your complete medical history to understand your overall health picture.^[10]

The neurological exam itself involves testing various aspects of your brain and nervous system function. Your doctor will check your vision and hearing, test your balance and coordination, evaluate your muscle strength, and examine your reflexes. They may also assess your ability to feel sensations like touch and temperature. Problems in any of these areas can provide important clues about which part of your brain might be affected by a tumor. For example, weakness on one side of your body might suggest the tumor is located in the opposite side of the brain, since brain signals cross over as they travel down the spinal cord.^[10]

Brain Imaging Studies

If your doctor suspects a brain tumor based on your symptoms and examination, the next step is usually brain imaging. The most commonly used test is magnetic resonance imaging (MRI), which creates detailed pictures of your brain using magnetic fields and radio waves rather than radiation. An MRI is particularly good at showing soft tissues like the brain and can reveal the location, size, and certain characteristics of a tumor.^[10]

During an MRI scan, you lie inside a large tube-shaped machine for about 30 to 60 minutes while images are taken. The machine makes loud knocking or thumping sounds, so you’ll usually be given earplugs or headphones. You need to stay very still during the scan so the images come out clear. Sometimes, a contrast dye called gadolinium is injected into your vein during the scan to make certain parts of the brain show up more clearly. This can help doctors see the borders of the tumor and whether there are any areas of active growth.^[6]

On MRI images, oligodendrogliomas typically appear as a single tumor with well-defined borders. They often show some swelling in the surrounding brain tissue. High-grade oligodendrogliomas are more likely to “enhance” with the contrast dye, meaning they appear brighter in certain areas, which suggests more aggressive growth.^[6] Oligodendrogliomas frequently contain calcium deposits called calcifications, which can also sometimes be seen on imaging.^[12]

Some medical centers may use specialized types of MRI called functional MRI. This advanced imaging technique shows which parts of your brain control critical functions like language, movement, and memory. This information is extremely valuable if surgery is being considered, because it helps surgeons plan how to remove the tumor while protecting the areas that control your most important abilities.^[10]

In some situations, doctors may order a computed tomography (CT) scan instead of or in addition to an MRI. A CT scan uses X-rays to create cross-sectional images of your brain. While not as detailed as MRI for soft tissue, CT scans are faster and can be particularly good at showing calcium deposits in tumors. Sometimes CT scans are used in emergency situations when quick imaging is needed, such as after a first seizure.^[12]

Tissue Sampling and Laboratory Analysis

While imaging can suggest the presence of a brain tumor, the only way to know for certain that it’s an oligodendroglioma is to examine actual tumor tissue under a microscope. This requires either a biopsy, where a small sample of tissue is removed, or surgery to remove the entire tumor. In most cases, doctors prefer to remove as much of the tumor as possible during surgery, which both treats the tumor and provides tissue for diagnosis.^[6]

Once tissue is obtained, a specialist doctor called a neuropathologist examines it under a microscope. They look at the shape and arrangement of the tumor cells. Oligodendroglioma cells have a distinctive appearance that pathologists describe as looking like “fried eggs” – the cells have a clear area around the nucleus that creates this characteristic look. The blood vessels in the tumor also have a particular pattern called “chicken wire” because of how they’re arranged around the cells.^[12]

However, looking at cells under a microscope is only part of the diagnosis. In 2016, the World Health Organization changed how brain tumors are classified to include genetic testing, not just appearance. For a tumor to be definitively diagnosed as an oligodendroglioma, it must have two specific genetic changes.^[12]

The first required genetic change is called 1p/19q co-deletion. Your genetic information is stored in structures called chromosomes, which are like instruction manuals for your cells. Each chromosome has a short arm (called “p”) and a long arm (called “q”). In oligodendrogliomas, pieces of chromosome 1’s short arm and chromosome 19’s long arm are missing. This specific pattern of missing genetic material is found only in oligodendrogliomas and not in other types of brain tumors.^[6]

The second required genetic change is a mutation in a gene called IDH (isocitrate dehydrogenase). This gene normally produces an enzyme that helps cells produce energy. When the gene is mutated, it produces an abnormal enzyme. Having this IDH mutation, along with the 1p/19q co-deletion, confirms that a tumor is an oligodendroglioma rather than another type of brain tumor.^[8]

After examining the tissue and completing the genetic tests, doctors assign the tumor a grade. Oligodendrogliomas are either grade 2 or grade 3. Grade 2 oligodendrogliomas grow slowly and are considered low-grade tumors. They may not cause symptoms for years. Grade 3 oligodendrogliomas, previously called anaplastic oligodendrogliomas, are malignant, meaning they grow faster and are more aggressive.^[6]

Diagnostics for Clinical Trial Qualification

If you’re considering participating in a clinical trial for oligodendroglioma, you’ll likely need to undergo several additional tests beyond the standard diagnostic procedures. Clinical trials have specific requirements to ensure that participants are suitable for the experimental treatment being tested and can be safely monitored throughout the study.

The most fundamental requirement for enrolling in an oligodendroglioma clinical trial is confirmation of your diagnosis through both microscopic examination and genetic testing. You’ll need documentation showing that your tumor has been tested for the IDH mutation and 1p/19q co-deletion. Many trials specifically require these genetic markers to be present, as they define true oligodendroglioma and indicate how the tumor might respond to treatment.^[2] If genetic testing wasn’t performed when you were first diagnosed, you may need to have it done before enrolling in a trial.

Clinical trials typically require recent imaging studies, usually an MRI scan taken within a few weeks or months before enrollment. This baseline scan allows researchers to accurately measure the tumor’s size and characteristics before treatment begins. During the trial, you’ll have additional scans at scheduled intervals so researchers can track whether the treatment is affecting the tumor. These repeated scans help determine if the experimental treatment is working better than, worse than, or the same as standard treatments.^[12]

Blood tests are another common requirement for clinical trial participation. These tests check your overall health status and ensure your organs are functioning well enough to handle the experimental treatment. Specific blood tests often include a complete blood count, which measures different types of blood cells, and tests of kidney and liver function. These baseline measurements are important because some treatments can affect blood cell production or organ function, and doctors need to know your starting point to detect any changes.^[12]

Your performance status will also be evaluated. This is a standardized way of measuring how well you can perform daily activities and how the disease is affecting your quality of life. Doctors use scales like the Karnofsky Performance Scale or the Eastern Cooperative Oncology Group (ECOG) scale. These assessments involve questions about your ability to care for yourself, work, and maintain your usual activities. Many clinical trials only accept patients who are relatively healthy and functional, as this helps ensure they can safely complete the trial and makes it easier to measure the effects of the treatment.

Some trials require additional specialized testing. For instance, if a trial is testing a treatment that might affect heart function, you may need an electrocardiogram (ECG), which records your heart’s electrical activity. If the treatment being studied could potentially affect thinking or memory, you might undergo cognitive testing before starting the trial to establish a baseline of your mental abilities.

Documentation of all previous treatments is essential. Researchers need to know exactly what therapies you’ve already received, including surgery, radiation, and chemotherapy. Many trials are specifically designed for people who haven’t been treated yet, while others are for people whose tumors have come back after previous treatment. The timing of previous treatments also matters – some trials require that a certain amount of time has passed since your last chemotherapy or radiation treatment.

Informed consent is a critical part of joining any clinical trial, though it’s not a diagnostic test itself. Before you can enroll, you must thoroughly understand what the trial involves, including all potential risks and benefits. You’ll receive detailed written information about the study and have opportunities to ask questions. This process ensures you’re making a fully informed decision about your participation. You always have the right to leave a clinical trial at any time, for any reason, without affecting your regular medical care.