Epidemiology

Brain tumors represent a significant health challenge affecting people across all age groups worldwide. According to recent data, approximately 321,476 new cases of brain and other central nervous system tumors were diagnosed globally in 2022, with an estimated 248,305 deaths occurring that same year^[3]. In the United States alone, an estimated 24,820 new cases are expected to be diagnosed in 2025, with approximately 18,330 deaths anticipated from these tumors^[13].

The combined incidence rate of brain and other central nervous system (CNS) tumors—which includes both brain and spinal cord tumors—stands at about 6.2 cases per 100,000 people per year in the United States, based on data from 2017 to 2021. The mortality rate during this period was 4.4 deaths per 100,000 people annually^[13]. These numbers reveal that brain tumors, while not among the most common cancers, carry a substantial burden due to their location and potential impact on essential body functions.

The distribution of brain tumors shows interesting patterns across different populations. In general, the incidence of primary CNS tumors is higher among individuals of White ethnicity compared to those of Black ethnicity. Additionally, mortality rates tend to be higher in men than in women^[13]. There are more than 100 distinct types of primary brain tumors documented by researchers, each presenting its own spectrum of characteristics, treatment approaches, and outcomes^[3].

Age plays an important role in who develops brain tumors. These growths are more commonly diagnosed in two specific groups: children and older adults. Among children, brain tumors represent a particularly significant concern as they are one of the more common forms of childhood cancer. In adults, the risk increases with advancing age^[6]. When examining the types of brain tumors most frequently diagnosed, meningiomas—tumors that develop in the membranes surrounding the brain—are the most common primary brain tumors, accounting for 27% of all cases. These are followed by anaplastic astrocytomas and glioblastomas, which together make up 38% of primary brain tumors^[13].

Only about one-third of all brain tumors are cancerous. The remaining two-thirds are classified as benign or noncancerous. However, this distinction doesn’t mean benign tumors are harmless. Whether cancerous or not, brain tumors can significantly impact brain function and overall health if they grow large enough to press on surrounding nerves, blood vessels, and tissue^[2].

Causes

The exact cause of most brain tumors remains unknown to medical science. Unlike some cancers where clear triggers have been identified, brain tumors often develop without any obvious environmental or lifestyle factors that researchers can point to. This uncertainty can be frustrating for patients and families seeking to understand why this condition developed^[1].

Brain tumors can begin in two different ways. Primary brain tumors start in the brain itself, developing from the various types of cells that make up brain tissue or the structures immediately surrounding it. These include the nerves, the pituitary gland (which regulates hormones), the pineal gland (which produces melatonin), and the meninges (the protective membranes covering the brain’s surface)^[1]. Primary tumors are named according to the specific type of brain tissue where they originate, and there are many different varieties^[2].

The second way brain tumors develop is through spread from other parts of the body. These are called secondary brain tumors or metastatic brain tumors. In these cases, cancer cells break away from a tumor located elsewhere—such as the lungs, breast, or skin—and travel through the bloodstream to reach the brain. In adults, most brain tumors are actually secondary tumors that have spread from other organs. Metastatic brain tumors are more common than primary ones and occur more frequently in adults than in children^[5][6].

When cells in the brain undergo changes in their genetic material, something goes wrong with the genes that normally manage cell growth. These genetic changes, called mutations, allow cells to grow and divide out of control, forming a solid mass. The cells seem to be unchecked by the mechanisms that would normally keep them under control^[5][7].

Risk Factors

While the specific cause of brain tumors often cannot be determined, certain factors have been identified that may increase a person’s likelihood of developing these growths. It’s important to understand that having a risk factor doesn’t mean someone will definitely develop a brain tumor—it simply means their chances may be somewhat higher than average^[6].

One of the few definitive environmental risk factors identified is exposure to radiation directed at the brain or head area. People who have previously received radiation therapy to these regions show an increased risk of developing brain tumors later in life^[6][13]. Some research has also suggested that exposure to vinyl chloride, a chemical used in certain industrial processes, may be a risk factor for developing gliomas—a category of tumors that develop from glial cells in the brain^[13].

Certain inherited genetic conditions significantly increase the risk of brain tumors. About one in twenty brain tumors may be linked to these hereditary syndromes. The conditions include neurofibromatosis type 1 (NF1) and type 2 (NF2), Li-Fraumeni syndrome, von Hippel-Lindau disease, tuberous sclerosis, Turcot syndrome, and nevoid basal cell carcinoma syndrome. Each of these conditions involves abnormalities in specific genes or chromosomes that can predispose individuals to developing tumors in the brain and other parts of the body^[6][13].

Family history also plays a role, though most brain tumors occur in people without any known family connection. Having close relatives who have been diagnosed with brain tumors may slightly increase an individual’s risk^[6]. Age is another important factor. As mentioned earlier, brain tumors are more likely to develop in two distinct age groups: children and older adults^[6].

Gender differences exist as well. Men have a slightly higher overall risk of developing brain tumors compared to women. However, certain specific types of tumors, such as meningiomas, are actually more common in women^[8]. People with compromised immune systems face elevated risks for specific types of brain tumors. For instance, individuals infected with Epstein-Barr virus, transplant recipients who take immunosuppressive medications, and patients with AIDS all have a substantially increased risk of developing primary CNS lymphoma—a type of brain tumor that arises from lymphatic tissue^[13].

It’s worth emphasizing that most people who develop brain tumors have no identifiable risk factors at all. The condition can affect anyone, regardless of their background or lifestyle^[6].

Symptoms

The symptoms that brain tumors produce depend heavily on where the tumor is located in the brain, how large it has become, and how fast it’s growing. Some brain tumors are discovered when they’re still very small because they immediately cause noticeable symptoms. Others can grow quite large before they’re detected because they develop in areas of the brain that are less active or don’t immediately produce obvious signs^[1].

When a tumor grows inside the skull, it creates pressure on the brain tissue around it and changes how that tissue functions. This pressure and interference with normal brain operations lead to the various symptoms that patients experience. The brain controls virtually everything the body does—from complex functions like language and thought to basic survival functions like breathing and heartbeat. When a tumor disrupts any part of this control center, problems can arise^[1][6].

Headaches are among the most common symptoms reported by people with brain tumors. These headaches may feel different from typical tension headaches and often occur in conjunction with other symptoms. Patients may also experience nausea and problems with balance, which occur because the tumor is affecting the brain’s ability to coordinate movement and maintain equilibrium^[1].

Seizures represent another frequent symptom. These occur when abnormal electrical activity spreads through the brain, often triggered by the tumor’s presence. Some people experience their first seizure ever when they have a brain tumor^[13]. Visual changes can occur if the tumor affects the parts of the brain responsible for processing what we see or if it presses on the optic nerves. Patients might notice blurred vision, double vision, or loss of peripheral vision^[13].

The location of a tumor determines which specific functions will be affected. For example, tumors in areas controlling speech may cause difficulty communicating. Patients might struggle to find the right words, understand what others are saying, or form coherent sentences. Tumors affecting motor areas can lead to weakness on one side of the body or problems with coordination. Those impacting sensory regions might cause numbness or unusual sensations^[20].

Cognitive changes are common and can be particularly distressing. People may notice problems with memory, difficulty concentrating, confusion, or changes in their ability to think clearly. These symptoms occur because the tumor is interfering with the brain regions responsible for these mental processes^[20]. Some patients experience personality changes or alterations in their emotional responses. They might become more irritable, withdrawn, or behave in ways that are unusual for them.

Fatigue is an extremely common and often debilitating symptom for people living with brain tumors. Unlike ordinary tiredness that improves with rest, this type of exhaustion can be persistent and relentless, impacting every aspect of daily life. It can result from the tumor itself, from treatments, or from the body’s overall response to the disease^[17].

Some tumors produce specific symptoms related to their location. For instance, tumors near the pituitary gland may disrupt hormone production, leading to symptoms related to hormonal imbalances. Tumors affecting the cerebellum—the part of the brain that coordinates movement—might cause problems with walking and fine motor control^[11].

Prevention

Unlike some other diseases where clear preventive measures exist, there are no proven strategies to prevent brain tumors from developing. This reality stems from the fact that most brain tumors occur without any identifiable cause or preventable risk factor^[6]. The limited understanding of what triggers these tumors means that specific lifestyle changes, dietary modifications, or supplements cannot be recommended with confidence to reduce risk.

However, there are some general approaches that may support overall brain health, though it’s important to emphasize that these have not been proven to prevent brain tumors specifically. Maintaining overall health through regular physical activity, a balanced diet, adequate sleep, and stress management supports the body’s general functioning and may contribute to better outcomes if health problems do arise^[24].

For individuals with known genetic risk factors—such as those with inherited syndromes like neurofibromatosis or Li-Fraumeni syndrome—genetic counseling and regular medical monitoring may be valuable. While these measures won’t prevent tumors from forming, they can help detect any growths early when they may be more manageable^[6].

Avoiding unnecessary radiation exposure to the head is one of the few concrete recommendations that can be made. Since radiation therapy to the brain or head area is a known risk factor, medical radiation should only be used when clearly necessary and beneficial. This doesn’t mean avoiding important medical treatments, but rather ensuring that radiation-based tests and therapies are used appropriately and judiciously^[13].

There is no evidence that cell phone use, power lines, artificial sweeteners, or other commonly suspected environmental factors cause brain tumors. These concerns have been extensively studied, and no reliable link has been established. People should not feel that they caused their brain tumor through everyday activities or choices^[24].

Pathophysiology

Understanding what happens in the body when a brain tumor develops helps explain why these growths cause the symptoms they do. The pathophysiology—or the changes in normal bodily functions—involves multiple interconnected processes that affect how the brain works^[1].

At the cellular level, brain tumors form when something goes wrong with the genes controlling cell growth. Normally, cells have built-in mechanisms that regulate when they divide, how many times they divide, and when they should stop growing or die. When mutations occur in these controlling genes, cells can begin to divide uncontrollably. They form masses of abnormal cells that continue to grow, seemingly unchecked by the body’s usual regulatory systems^[7].

Different types of brain tumors arise from different cell types. Glial tumors, which make up a large proportion of brain tumors, develop from glial cells. These are the supportive cells in the brain that surround and assist nerve cells. There are several types of glial cells, and each can give rise to different tumor types. For example, astrocytomas develop from star-shaped glial cells called astrocytes. Ependymomas arise from ependymal cells that line the fluid-filled spaces in the brain. Oligodendrogliomas come from cells that produce the insulating coating around nerve fibers^[2][11].

Non-glial tumors develop from other structures in or around the brain. Meningiomas grow from the meninges, the membrane layers that protect the brain and spinal cord. Schwannomas arise from Schwann cells, which provide electrical insulation for nerves. Pituitary adenomas develop in the pituitary gland itself. Each tumor type has its own growth pattern and characteristics^[5][11].

The distinction between benign and malignant tumors is important but somewhat different in the brain than in other parts of the body. Benign tumors grow slowly and don’t invade surrounding tissue aggressively. They tend to have clear boundaries and, if completely removed, usually don’t grow back. However, even benign brain tumors can be serious because they occupy space inside the rigid skull. As they grow, they press on surrounding brain tissue, potentially causing significant damage^[2][7].

Malignant brain tumors grow more rapidly and invade nearby healthy tissue. They don’t have clear boundaries, making them difficult to remove completely with surgery. These cancerous tumors can spread within the brain and spinal cord, though they rarely metastasize to other parts of the body—a behavior that distinguishes them from most other cancers^[1][7].

As a brain tumor grows, it creates several problems. First, it takes up space in the confined area of the skull, increasing pressure on the brain. This increased intracranial pressure can cause headaches, nausea, and vomiting. Second, the tumor presses on and damages the brain tissue around it, interfering with whatever functions that brain region controls. If it’s in an area controlling movement, weakness results. If it’s in a region processing speech, communication problems arise^[1][6].

Some tumors can block the flow of cerebrospinal fluid (CSF), the protective liquid that cushions the brain and spinal cord. This blockage leads to a buildup of fluid called hydrocephalus, which further increases pressure inside the skull and can cause additional symptoms^[7]. Tumors can also irritate brain tissue, causing abnormal electrical activity that manifests as seizures. Blood vessels feeding the tumor may be fragile and prone to bleeding. Additionally, some tumors produce or interfere with hormones if they’re located near glands, leading to hormonal imbalances and their associated symptoms^[11].

The rate at which different tumors grow varies tremendously. Some types are slow-growing and may be present for years before causing noticeable symptoms. Others are aggressive and can cause significant problems in a matter of weeks or months. This growth rate, combined with the tumor’s location and size, determines the severity of symptoms and the urgency of treatment^[8].