Brain Tumors: An Overview

What Patients and Referring Providers Need to Know

"There's a mass on your brain scan" is one of the most frightening sentences a person can hear, and the word tumor tends to arrive with a set of assumptions attached — that it is cancer, that surgery is inevitable, that the outlook is grim. For many patients, none of those assumptions turn out to be true. "Brain tumor" is not one diagnosis. It's an umbrella over dozens of very different conditions, ranging from slow-growing benign growths that may only ever need to be watched, to aggressive cancers that call for a coordinated, multi-specialty treatment plan.

This page is a broad introduction: what a brain tumor actually is, the major types, how they present, how we work them up, and the full menu of treatment options — including the option of not treating at all. It is deliberately general. In the coming months I'll be adding dedicated pages on individual tumor types (gliomas, meningiomas, metastatic tumors, acoustic neuromas, and others), and a separate page on pituitary tumors is already available. Think of this one as the map; those will be the street-level views.

What Is a Brain Tumor?

A brain tumor is any abnormal growth of cells inside the skull. That definition is broad on purpose, because the two questions that matter most aren't answered by the word "tumor" at all:

• Where did it come from? Primary brain tumors arise from cells that belong in the head — the brain's supporting glial cells, the meninges (the brain's covering), the cranial nerves, or the pituitary gland. Metastatic (secondary) brain tumors are cancers that started somewhere else in the body, most often the lung, breast, skin (melanoma), kidney, or colon, and spread to the brain through the bloodstream. Metastatic tumors are considerably more common than primary ones.
• Is it benign or malignant? Roughly 70% of primary brain tumors are non-malignant, according to the Central Brain Tumor Registry of the United States (CBTRUS). "Benign" means the tumor grows slowly, has clear borders, and doesn't invade surrounding brain or spread elsewhere. It does not mean harmless — a benign tumor in the wrong location can still press on critical structures and cause real problems. Malignant tumors grow faster and infiltrate the brain around them, which is why they are harder to remove completely.

To put the numbers in perspective: CBTRUS estimates around 94,000 new primary brain and other central nervous system tumors are diagnosed in the United States each year, of which roughly 26,000 are malignant. For comparison, brain metastases develop in an estimated 10–30% of adults with cancer, which translates to well over 100,000 patients per year.

Grading: How Aggressive Is It?

The World Health Organization assigns brain tumors a grade from 1 to 4 based on how the cells look under the microscope and, increasingly, on their molecular fingerprint. The 2021 WHO classification (often called "CNS5") reorganized many diagnoses around specific genetic markers, because two tumors that look identical under a microscope can behave very differently depending on their mutations.

Grade is the single most important predictor of how a tumor will behave over time, and it's why a biopsy or surgical specimen is so often necessary even when imaging strongly suggests a diagnosis. Imaging can tell us what a tumor probably is; only tissue can tell us what it definitely is and how it's wired.

The Major Types

Below are the tumor types I see most often. Each gets a fuller treatment in its own article; the aim here is orientation.

Meningiomas

The most common primary brain tumor in adults, accounting for roughly 40% of all primary tumors. Meningiomas arise from the meninges — the membrane covering the brain — not from brain tissue itself, which means they push brain aside rather than growing into it. About 80% are grade 1. They are more common in women, become more common with age, and are frequently discovered by accident on a scan ordered for something else. Many are simply watched; those that grow, cause symptoms, or sit in a concerning location are removed surgically or treated with focused radiation.

Gliomas

Gliomas arise from the brain's glial cells — the supporting cells that outnumber neurons — and are the most common malignant primary brain tumor. They span the full grading scale. On the slower end are IDH-mutant astrocytomas and oligodendrogliomas, which often occur in younger adults and can be managed over many years. On the aggressive end is glioblastoma, which accounts for about half of all malignant primary brain tumors and, despite steady progress, remains the most difficult tumor we treat. Because gliomas infiltrate normal brain, they generally can't be "cut out" the way a meningioma can; treatment is a combination of maximal safe surgery, radiation, and chemotherapy, and the molecular profile of the tumor (IDH status, 1p/19q co-deletion, MGMT methylation) directly shapes the plan.

Metastatic Brain Tumors

The most common brain tumor overall. Lung cancer is the leading source, followed by breast cancer, melanoma, kidney cancer, and colorectal cancer. Metastases may be single or multiple, and their management has changed dramatically in the past two decades: focused radiation (stereotactic radiosurgery) now treats most lesions without an incision, surgery is reserved for large or symptomatic tumors, and modern immunotherapy and targeted drugs increasingly cross into the brain. A brain metastasis is no longer the automatic end-of-the-road diagnosis it once was, and many patients live years with well-controlled disease.

Pituitary Adenomas

Benign tumors of the pituitary gland at the base of the brain, making up about 15–17% of primary tumors. They cause problems by overproducing hormones or by pressing on the optic nerves. Some are treated with medication alone, some are watched, and some are removed through the nose with no external incision. I've covered these in detail in the dedicated Pituitary Tumors article.

Vestibular Schwannomas (Acoustic Neuromas)

Benign tumors of the balance nerve, presenting with one-sided hearing loss, ringing in the ear, or imbalance. They grow slowly — often less than a millimeter or two a year — and observation, radiosurgery, and microsurgical removal are all legitimate options depending on tumor size, hearing status, age, and patient preference.

Other Tumors

A long list of less common tumors round out the picture: ependymomas (arising from the fluid-space lining), craniopharyngiomas (benign but stubborn tumors near the pituitary), primary CNS lymphoma (treated with chemotherapy rather than surgery), hemangioblastomas, chordomas of the skull base, and the pediatric tumors — medulloblastoma, pilocytic astrocytoma, and others — that are managed at dedicated children's centers.

Symptoms: How Brain Tumors Present

There is no single "brain tumor headache" and no symptom that is unique to brain tumors. Presentation depends on the tumor's size, its growth rate, and above all its location. The most common patterns are:

• Headache — present in about half of patients at diagnosis, but almost never the only symptom. The features that raise concern are a new headache pattern in someone over 50, headaches that are worse in the morning or wake a person from sleep, headaches that worsen with coughing, straining, or lying flat, or a headache accompanied by nausea and vomiting. The vast majority of headaches, including most severe ones, are not caused by tumors.
• Seizures — a first-time seizure in an adult is a tumor until proven otherwise and warrants an MRI. Seizures are especially common with slow-growing tumors in the cerebral cortex and are frequently the only symptom of a low-grade glioma.
• Focal neurological deficits — weakness or numbness on one side, trouble finding words or understanding speech, visual field loss, loss of coordination, or difficulty walking, depending on which region of the brain is involved. These typically develop gradually over weeks to months, which distinguishes them from the sudden onset of a stroke.
• Cognitive and personality changes — slowed thinking, memory difficulty, apathy, poor judgment, or a personality change that family notices before the patient does. Frontal lobe tumors are notorious for this and are sometimes initially mistaken for depression or dementia.
• Signs of raised intracranial pressure — nausea and vomiting, blurred or double vision, drowsiness. This is the pattern that needs urgent evaluation rather than routine scheduling.
• Cranial nerve symptoms — one-sided hearing loss or ringing (vestibular schwannoma), facial numbness, double vision, or swallowing difficulty with tumors at the skull base.

Diagnosis and Workup

MRI with and without contrast is the definitive imaging study for brain tumors and the one that should be ordered when there is real clinical suspicion. CT is faster and is what a patient usually gets first in an emergency room; it is good at detecting bleeding, large masses, and swelling, but it misses small tumors and gives far less information about tumor type. A normal CT does not rule out a brain tumor.

Beyond the standard MRI, several additional tools help me characterize a tumor before an operation:

• Advanced MRI sequences — perfusion imaging (how much blood the tumor is drawing), spectroscopy (the tumor's chemical signature), and diffusion imaging help distinguish tumor grade and separate tumor from infection, stroke, or radiation change.
• Functional MRI and tractography (DTI) — map the location of speech, motor, and vision areas and the white-matter pathways connecting them, so that a surgical approach can be planned around them.
• Systemic staging — when a metastasis is suspected, a CT of the chest, abdomen, and pelvis or a PET scan looks for the primary cancer and other sites of disease. In roughly 10–15% of patients, a brain metastasis is the first sign of a cancer that had not yet been diagnosed.
• Tissue diagnosis — either a stereotactic needle biopsy (a small sample obtained through a dime-sized opening using image guidance) or the specimen from a resection. Modern pathology combines the microscopic appearance with molecular testing, and for gliomas in particular the molecular result — IDH mutation, 1p/19q co-deletion, MGMT promoter methylation, and others — often matters more than the traditional grade.

Treatment: The Full Menu

My general philosophy in spine surgery — that the least invasive option that solves the problem is the right one — applies just as firmly to the brain. Not every tumor needs surgery, and not every tumor that needs treatment needs it right away. These are the tools, roughly in order of increasing intensity.

What Brain Tumor Surgery Involves

Most tumor operations are performed through a craniotomy — a temporary opening in the skull that is replaced and secured at the end of the operation. The procedure is done under general anesthesia (or, for tumors near speech or movement areas, with the patient awake for a portion of it), typically takes three to five hours, and follows a fairly consistent sequence:

1. Planning and navigation. The patient's MRI is loaded into a neuronavigation system — essentially GPS for the brain — and registered to the patient's head, so I can see in real time where an instrument sits relative to the tumor and the structures around it. The incision is planned to be as small as the tumor allows and is usually placed within the hairline.
2. Opening. A small section of bone is removed and the dura (the brain's covering) is opened to expose the tumor or the brain surface above it.
3. Mapping, when needed. For tumors near critical areas, electrical stimulation is used to identify exactly where speech, motor, or sensory function lives so it can be protected. In an awake craniotomy, the patient talks, names objects, or moves a hand during this portion; the brain itself has no pain fibers, and patients are comfortable.
4. Resection. Working under an operating microscope or exoscope, the tumor is removed piece by piece. For high-grade gliomas, a fluorescent dye taken by mouth before surgery (5-ALA) makes tumor cells glow under a special light, helping distinguish tumor from normal brain. Intraoperative ultrasound or MRI may be used to check how much tumor remains.
5. Closure. The dura is closed, the bone is replaced and fixed with small titanium plates, and the scalp is closed. The plates are permanent, MRI-safe, and generally not noticeable.

Some tumors are reached differently: pituitary and certain skull base tumors through the nose (endoscopic endonasal surgery), deep tumors through a small tubular corridor, and biopsies through an opening the size of a dime.

Recovery: What to Expect

Driving is restricted after any craniotomy and, by Georgia law, for a period of at least six months after a seizure. Most patients feel that their energy takes four to eight weeks to fully return, and a temporary worsening of any pre-operative deficit (weakness, word-finding trouble) in the first days after surgery is common and usually improves as swelling settles.

Risks and Complications

Every operation carries risk, and the risks of brain surgery depend enormously on where the tumor is. I discuss the specific risks of a given tumor in detail with every patient before surgery. In broad terms:

• New or worsened neurological deficit — weakness, numbness, speech or vision problems, depending on location; often temporary from swelling, occasionally permanent. Mapping and monitoring exist to minimize this risk.
• Bleeding — a blood clot in the surgical bed requiring a return to the operating room occurs in roughly 1–2% of craniotomies.
• Infection — of the wound, bone flap, or (rarely) the brain and its coverings; occurs in around 1–3% of cases and may require antibiotics or, occasionally, temporary removal of the bone flap.
• Seizures — may occur after surgery even in patients who never had one before; anti-seizure medication is typically used around the time of surgery.
• Cerebrospinal fluid leak — more common with skull base and posterior fossa approaches; usually managed with a lumbar drain or a minor revision.
• Blood clots in the legs or lungs — brain tumor patients are at elevated risk; early walking and compression devices are used routinely.
• Anesthetic and medical complications — heart, lung, and stroke risks are individualized based on a patient's overall health and are part of the pre-operative evaluation.

Outlook

Prognosis for a brain tumor is entirely dependent on the type, and it's the question I'm asked most. A few honest anchors: most grade 1 meningiomas and vestibular schwannomas are cured or controlled indefinitely. Patients with IDH-mutant low-grade gliomas often live a decade or more, and that number is improving with targeted therapy. Glioblastoma remains the hardest diagnosis in neurosurgery, with median survival in the range of 15–18 months with standard treatment, though a meaningful minority of patients live considerably longer, particularly those with favorable molecular markers and complete resections. Outcomes for brain metastases now depend more on the underlying cancer and its available therapies than on the brain disease itself. Whatever the diagnosis, the plan is built around two goals held together: the longest possible life and the best possible function.

A Note to Patients

If you've just been told there is a mass on your scan, the first thing to know is that the report is a starting point, not a verdict. The words on it don't yet tell you what the tumor is, whether it's benign, or what — if anything — needs to be done. That conversation happens after we've looked at the images together, sometimes after additional imaging, and occasionally only after tissue has been examined. Bring someone with you to that first visit, bring your questions written down, and know that for many of the people who sit in that chair, the answer turns out to be considerably better than the fear that walked in with them. For those whose diagnosis is more serious, you will not be navigating it alone: you will have a team, a plan, and a surgeon who will tell you the truth and stay with you through it.