The short answer
Glioblastoma is a grade 4 brain tumor that grows and spreads quickly. It is the most common malignant brain tumor in adults. Symptoms depend on where it is in the brain and can include headache, seizures, or changes in thinking. Some symptoms are medical emergencies. Treatment usually combines surgery, radiation, and chemotherapy.
Glioblastoma is a grade 4 brain tumor, the fastest-growing and most aggressive grade, and the most common malignant brain tumor in adults.
Symptoms depend on where the tumor is in the brain and can include headache, seizures, weakness, or changes in thinking or mood.
A first seizure, a sudden severe headache with vomiting, or sudden weakness or trouble speaking are emergencies — call 911 or go to the nearest emergency department right away.
Standard treatment combines surgery, radiation therapy, and chemotherapy, sometimes with a wearable device called tumor-treating fields.
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The simple version
Glioblastoma is a brain tumor that grows and spreads quickly. Doctors call it "grade 4," a grade that tends to grow quickly. It starts in astrocytes, the supportive cells that hold nerve cells in place. It is the most common cancerous (malignant) brain tumor in adults. Glioblastoma is sometimes called "glioblastoma multiforme," or GBM.
Symptoms — and which ones are an emergency
Symptoms depend on where the tumor sits in the brain and how big it is. Different areas of the brain control different things, such as movement, speech, and vision. Common symptoms include:
- Morning headache, or a headache that goes away after vomiting.
- Seizures.
- Nausea or vomiting.
- Vision, hearing, or speech problems.
- Other changes, such as weakness, balance trouble, or changes in thinking or mood, depending on where the tumor is.
Some of these are emergencies. Call 911 or go to the nearest emergency department right away for:
- A first-time seizure in someone who has never had one before.
- A sudden, severe headache, especially with vomiting.
- Sudden weakness, numbness, or trouble speaking or understanding speech.
These signs can point to a serious problem in the brain. Do not wait to "see if it gets better," and do not wait for a clinic call-back. This is a 911 situation, not a same-day one.
Two more warrant the same response: a seizure that lasts longer than five minutes or repeats without the person waking up in between, and someone who cannot be roused or does not return to normal after a seizure.
How glioblastoma is diagnosed
Doctors use an MRI scan of the brain, and a biopsy to study the tumor tissue. Ask your team about molecular tests on the tissue, such as MGMT and IDH, and how the results guide treatment.
Treatment
Most people are offered:
- Surgery to remove as much of the tumor as can be done safely, .
- Radiation therapy, given together with chemotherapy after surgery.
- Chemotherapy, usually a pill called temozolomide. It is given at the same time as radiation, then continued alone.
- Tumor-treating fields, a device worn on the scalp that creates electric fields. Your team can tell you if it fits your care.
NCI says clinical trials are studying other ways to treat glioblastoma. Clinical trials are therefore a normal part of the conversation, not a last resort. It is reasonable to ask about them at diagnosis, and again if the tumor comes back or grows.
Sources
- National Cancer Institute, Adult Central Nervous System Tumors Treatment (PDQ) – Patient Version, accessed August 3, 2026.
- American Cancer Society, Types of Brain Tumors and Spinal Cord Tumors in Adults, checked October 2, 2026.
- MedlinePlus, Seizures, checked October 2, 2026.
Common questions
What is glioblastoma?
Glioblastoma is a fast-growing, grade 4 tumor that starts in astrocytes, a type of supportive cell in the brain. It is the most common malignant (cancerous) brain tumor in adults.
What are the symptoms?
Symptoms depend on the tumor's location and size. Signs include morning headache or headache that eases after vomiting, seizures, nausea and vomiting, and vision, hearing, or speech problems. Other changes depend on where the tumor is.
Which symptoms mean I should call 911?
A first-time seizure, a sudden and severe headache with vomiting, or sudden weakness, numbness, or trouble speaking can point to a serious problem in the brain. These need emergency care immediately — call 911 or get to the nearest emergency department. Do not wait to see if they pass.
How is glioblastoma treated?
Treatment usually starts with surgery to remove as much of the tumor as can be done safely. This is followed by radiation therapy and chemotherapy (usually a pill called temozolomide) given together, then chemotherapy alone. A wearable device called tumor-treating fields, which creates electric fields, may be discussed by your team.
What should I ask about after treatment?
Ask your care team what to expect after treatment. NCI notes that clinical trials are studying new ways to treat glioblastoma, so many people ask about them at diagnosis or if the tumor grows again.
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Last updated: 2026-08-13Next planned review: 2027-08-03
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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