Natural History of Brain Tumor
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A brain tumor is a mass or growth of abnormal cells in the brain. Brain tumors can be either benign (non-cancerous) or malignant (cancerous) and can originate from different types of cells in the brain. Other brain tumors are known as metastatic tumors, which means they have spread to the brain from another part of the body, such as the lung or breast.
After the tumor is formed, it grows and may begin to press on or invade nearby tissues and structures. During this growth stage, the brain tumor can begin to cause symptoms such as headaches, seizures, weakness, and changes in cognitive function (memory, language, and learning). As the tumor continues to grow, if it is aggressive, it may become more invasive and spread to other parts of the brain or even rarely to other organs in the body. The brain tumor can also cause increased pressure inside the skull, which can lead to additional symptoms such as vomiting, vision changes, and altered consciousness.
The specific timeline and characteristics of each stage of the natural progression of a brain tumor vary depending on the type of tumor and other factors. Understanding the causes and symptoms helps to diagnosis brain tumors and is important for developing effective treatment plans and improving patient outcomes.
Causes and Risk Factors for Brain Tumors
The exact causes of brain tumors are not well understood, but researchers have identified some factors that may increase the risk of developing a brain tumor. Here are some known and suspected risk factors for brain tumors:
- Age: Brain tumors can occur at any age, but the risk tends to increase as people get older.
- Genetics: In some cases, brain tumors may be caused by inherited genetic mutations that increase the risk of tumor development. For example, neurofibromatosis type 1 and type 2 are inherited conditions that increase the risk of developing tumors in the nervous system, including the brain.
- Radiation exposure: Exposure to high doses of radiation, such as radiation therapy for other types of cancer, may increase the risk of developing a brain tumor. Similarly, working in jobs with an exposure to radiation, such as radiology technicians, surgeons, radioactivity researchers, and radioactive material miners, can make you more prone to developing cancers.
- Chemical exposure: Exposure to certain chemicals, such as pesticides, solvents, or plastics, may increase the risk of developing a brain tumor. Farmers have been seen to have more than a 3-fold increase in developing brain tumors because of exposure to pesticides.
- Immune system disorders: People with certain immune system disorders, such as HIV/AIDS, may have an increased risk of developing brain tumors.
- Family history: In some cases, brain tumors may run in families, although this is relatively uncommon. Some inherited conditions, such as Li-Fraumeni syndrome and Turcot syndrome, are associated with an increased risk of developing various types of cancer, including brain tumors.
Most people with risk factors for brain tumors never develop them, and many people with brain tumors have no known risk factors. Often the cause of a brain tumor is not clear, and it is likely due to a complex interaction of genetic and environmental factors.
Types of Brain Tumors
Metastases are the most common type of brain tumor in adults, accounting for more than half of all brain tumors. Brain metastases occur when cancer spreads from its primary location, which may be anywhere in the body, to the brain. Therefore, brain metastases are referred to as secondary tumors, and they most commonly spread from melanoma, lung, breast, colorectal, or renal cancer.
Meningiomas are the most common type of primary brain tumors occurring in adults, especially those older than 40. They originate in the meninges, which is the covering around the brain. Most meningiomas are slow-growing, benign tumors.
Pituitary and craniopharyngeal duct tumors also are common benign brain tumors in adults, accounting for 18% of brain tumors in adults over 40. In adults under 40, they are the most common brain tumor, making up 37% of all brain tumors.
The most common primary malignant brain tumor is glioblastoma. Glioblastomas originate in the brain and are characterized by the rapid growth of abnormal glial cells. They are aggressive tumors that tend to invade the surrounding brain tissue.
Among children, the most common brain tumor is a pilocytic astrocytoma (a low-grade, or slow-growing, tumor), and the most common malignant brain tumor is a medulloblastoma. Childhood brain tumors are usually caused by inherited genetic mutations. An exception to this is a tumor known as a craniopharyngioma, which does not have any known genetic risk factors.
Brain Tumor Locations
The location of brain tumors determines the symptoms you experience. Location also plays an important role in deciding the best treatment strategies. The most common locations of brain tumors differ between adults and children: In adults, brain tumors are commonly found above the tentorium (supratentorial), whereas in children they are typically found below the tentorium (infratentorial). The tentorium is a tough sheet of tissue that separates the cerebrum (known as the “forebrain” because it is the frontmost part of the brain) from the cerebellum (known as the “hindbrain” because it is located at the back of the brain).
The most common location of brain tumors in adults 40 or older are the meninges (39%), followed by pituitary and craniopharyngeal duct (18%) and the frontal lobe (8%). Among adults between 18 and 40, the most common brain tumor location is the pituitary and craniopharyngeal duct (37%), followed by the meninges (16%) and the frontal lobe (10%).
In children younger than 14, cerebellar tumors are the most common, making up 17% of all childhood brain tumors. This is followed by tumors of the brainstem (12%). In children over 14, tumors in the pituitary and craniopharyngeal duct are most common, accounting for more than 35% of brain tumors.
Symptoms of Brain Tumor
With brain tumors, the nature of symptoms varies with the type of tumor and its location in the brain. Tumor symptoms may occur suddenly or develop gradually over time. Commonly, the initial symptoms of brain tumors can be vague. Unlike specific symptoms that can be easily attributed to particular parts of the brain, vague symptoms are difficult to attribute to brain tumors. Early detection of brain tumors depends on picking up early symptoms, which is not easy when the symptom may be just a headache. Common symptoms associated with brain tumors include:
- Headaches: Those associated with a brain tumor can be constant and felt on both sides of the head. They usually occur early in the morning and may be accompanied by nausea or vomiting.
- Seizures: May be an early symptom of brain tumors, particularly if they occur in someone who has not had seizures before.
- Cognitive changes: Can include difficulty with memory, concentration, and other mental tasks.
- Vision changes: May cause blurriness, double vision, or loss of peripheral vision.
- Speech difficulties: Can cause problems like slurred speech or difficulty finding the right words.
- Weakness or paralysis: Weakness or paralysis may occur on one side of the body or in one limb.
- Balance problems: May cause problems with balance and coordination, increasing the risk of falls.
- Numbness or tingling: Usually experienced in the arms or legs.
Lower grade tumors grow slowly, allowing the brain to accommodate and adjust. This causes symptoms to develop gradually. This is in stark contrast with higher grade tumors, which grow fast and can produce symptoms that come on suddenly.
Depending on the location of the brain tumor, specific symptoms can occur. Frontal lobe tumors can cause speech disturbances and gradually developing personality changes. Temporal lobe tumors can cause seizures and memory problems. Tumors in the occipital lobe can cause visual disturbances. Cerebellar tumors can cause incoordination and issues with balance.
If your symptoms raise a concern, your primary care physician may order a computed tomography (CT) or magnetic resonance imaging (MRI) scan to rule out a brain tumor. If a tumor is detected, the next step involves a consultation with a neurosurgeon. Although symptoms do not always mean a brain tumor is present, consult a doctor if you are experiencing symptoms because early diagnosis and treatment lead to the best patient outcomes.
- A brain tumor is a mass or growth of abnormal cells in the brain.
- The common risk factors for brain tumors include age, environmental exposure, genetic syndromes, family history, and certain immune system disorders.
- The most common brain tumor in adults is metastasis from cancers in other parts of the body, and the most common brain tumor in children is pilocytic astrocytoma.
- Location of brain tumors can determine the symptoms you experience and plays an important role in deciding the best treatment strategies.
- The common symptoms of a brain tumor include headache, seizures, cognitive or vision changes, speech difficulty, weakness or paralysis, balance problems, and numbness or tingling.