What is a Brain Tumor?
In its simplest definition, a brain tumor is the proliferation of abnormal cells in the brain. Cells are the basic structural and functional units in a human. In healthy individuals, new cells form only to replace old or damaged cells. However, when cells grow when they are not needed, they create a mass in the brain. Such a mass is called a tumor.
Tumors in the brain may create pressure on the brain or spread to other parts of the brain. They can block the flow of the cerebrospinal fluid in the central nervous system or can completely block the flow and cause an increased intracranial pressure. Brain tumors are classified in two categories as primary brain tumors and secondary (metastatic) brain tumors.
What Does a Primary Brain Tumor Mean?
A brain tumor forms in consequence of an abnormal growth of the brain tissue. If the tumor has originated in the brain, it is called a primary brain tumor. Primary brain tumors are classified as benign or malignant.
Benign Brain Tumors
Benign brain tumors are not cancerous. They grow slowly, mostly have distinct borders, and rarely spread. However, benign tumors can be dangerous, as well. They can compress or damage some parts of the brain, which have critical functions. Sometimes benign brain tumors can be life threatening when they are located in hard-to-reach areas or areas where a surgical operation carries a high risk of complication. They also cause serious loss of function in the areas where they cause damage. Benign brain tumors are usually surgically removed. They are less likely to recur. Very rarely, benign brain tumors turn into malignant brain tumors.
Malignant Brain Tumors
Malignant brain tumors are cancerous. In other words, the tumor tissue contains cancer cells. They typically grow rapidly. They spread to surrounding healthy brain tissues. Such tumors pose a serious mortality risk. They very rarely spread to the spinal cord.
What are the Most Common Types of Primary Brain Tumors?
There are more than 120 types of primary brain tumors. They are named for the cells where they have originated from. Glioma is the most common type of primary brain tumor. It has subtypes called ependymomas, oligodendrogliomas, and brain stem gliomas. Other common types of brain tumor other than gliomas arising from glial cells are meningiomas, pituitary neoplasms, medulloblastomas, acoustic neurinomas, germ cell tumors, pineal region tumors, and craniopharyngiomas.
What is a Metastatic Brain Tumor?
Metastatic brain tumors are also called secondary brain tumors. A tumor in any part of the body can spread (metastasizes) to the brain or any other organ suitable for metastasis. Secondary, i.e. metastatic brain tumors are four times more common than primary brain tumors.
What are the Most Common Types of Secondary (Metastatic) Brain Tumors?
The most common types of cancer that can spread to the brain are:
- Breast cancer
- Colon cancer
- Kidney cancer
- Lung cancer
- Skin cancer (melanoma)
Metastatic brain tumors spread through the bloodstream. They are always malignant tumors. As a result of the spread of the tumor from the primary cancerous tissue through the bloodstream, metastasis is seen in the cerebral hemispheres, or in the cerebellum. Cancer can also spread to the spine. Tumors that spread to the spine are called metastatic spinal tumors. Metastatic brain tumors grow rapidly and damage the nearby brain tissue. In some patients, a metastatic focus can be found in several areas of the brain. Some metastatic brain tumors can spread to the brain years after the detection of a primary tumor in another organ. However, most of brain metastases are found to be located in the brain tissue before the detection of a primary tumor. In some patients, no primary tumor located in another organ can be found, even though a metastasis has been detected in the brain.
The ways of treatment for metastatic brain or spinal tumors include:
What are the Causes of Metastatic Brain Tumors?
Metastatic brain tumors are caused by the spread of cancer cells in any part of the body to the brain through the bloodstream. One-third of patients with another type of cancer have also one or more metastatic brain tumors. The risk of metastatic brain tumors increases between 45 and 65 years of age, and peaks after 65 years of age.
Why do Brain Tumors in Children Differ from Brain Tumors in Adults?
In children, brain tumors develop in different groups of cells and in different parts of the brain. Tumors in children can usually be detected earlier than tumors in adults because the signs and symptoms are more obvious in children, who are also closely and carefully followed up by their parents. The signs and symptoms can be related to memory, learning, hearing, sight, smell or emotion.
- Brain tumors show different symptoms than the same type of tumors in adults.
- Brain tumors may require different treatment procedures.
- Less advanced malignant tumors less commonly change to more advanced tumors.
- Brain tumors allow for a better chance of surviving.
Brain tumors are the second most common type of cancer in children. Brain tumors account for 21% of childhood cancers. Although brain tumors can be seen in children of all ages, children under the age of 7 are at a higher risk. Tumors in the spinal cord can also be encountered in childhood. However, their incidence rate is lower than that of brain tumors.
What are the Most Common Types of Brain Tumor in Childhood?
The most common type of tumor is glioma. They are classified under different names, depending on the cells, from which they originated. For example; Brainstem gliomas originate from primitive neuroectodermal tumors. When these tumors occur in the cerebellum, they are called medulloblastoma that rapidly grow and block the drainage of cerebral spinal fluid, causing increased intracranial pressure. Medulloblastoma can spread to other parts of the brain and spinal cord.
What are the Causes of a Brain Tumor?
There are many ongoing studies on the causes of brain tumor. For now, there is almost no blamable cause for it. However, it is known that some factors play a role in patients with brain tumor more commonly. These factors can be listed as male sex, white race, and ages over 65. Exposure to radiation and radiation therapy are known to increase the risk of brain tumor. Some brain tumors show familial transmission. In addition, certain raw materials used in the plastic and textile sectors are identified as risk factors.
What are the Symptoms of Brain Tumors?
Different parts of the brain control different functions. Therefore, signs and symptoms vary depending on the location of tumors. The size, location and growing speed of a tumor are the most important factors for the emergence of signs and symptoms. The common signs and symptoms (one or more of these may exist together) include:
- Seizures or convulsions
- Difficulty and/or slowdown in thinking, speaking, or finding words
- Changes in personality or behaviors
- Weakness in one part or one side of the body
- Loss of balance, dizziness, dullness
- Hearing loss
- Vision disorders
- Confusion and disorientation
- Memory loss
- How is a Brain Tumor Diagnosed?
- The methods commonly used for diagnosing are:
- Story – As a patient, you are asked to explain the details of your complaints and findings and to specify their development process.
- Neurological examination
- Radiological examination
How is a Neurological Examination performed?
When you see the neurosurgeon for examination, he/she first ask you and/or your relatives about your complaint(s). Afterwards, duration of these complaints, their continuity and other details are questioned. Then, a detailed physical examination is performed. In neurological examination, sight, hearing, strength, sensation, balance, coordination, reflexes, thinking skill, memory and recall functions are evaluated. If a radiological examination is considered to be necessary as a result of this evaluation, the examinations and their reasons will be explained to you.
What are the Radiological Examination Techniques?
An angiogram is a kind of examination method involving X-ray imaging. This examination shows the arteries and veins in the brain. You are injected with a contrast agent and then the vascularization in the brain is displayed. By this way, abnormalities (aneurysm—bubble in the brain, arteriovenous malformation—abnormal tangle of blood vessels etc.) in the vascularization structure are identified.
Computed Brain Tomography
In computed brain tomography, examination is performed with the help of X-ray. In the examination, 3D images of the brain are obtained by applying X-ray from different angles. These images are converted into images on a computer by means of a special software program, and then abnormalities or tumors are detected in the brain. Computed brain tomography is very useful in the diagnosis of brain tumors adjacent to bone tissues or brain tumors that have caused damage in the bone tissue. This diagnostic tool can also be used to identify tissue damages, bleeding, and bone-tissue calcifications. Computed brain tomography is used as a first-choice diagnostic method in daily clinical use but mostly in emergencies.
Magnetic Resonance Imaging (MRI)
It is one of the best diagnostic methods for imaging brain tissue. This diagnostic method involves the use of magnetic waves and radio waves instead of X-ray. It is a diagnostic method that displays brain tissue much better than computed brain tomography. In recent years, it has become one of the indispensable diagnostic tools of neurosurgeons. With magnetic resonance imaging, it is possible to take lateral vertical, anterior vertical and lateral cross-sectional images of the brain tissue, and display the relationship between the tumoral formation and surrounding tissues. Some cases may require additional imaging procedures performed by giving contrast agents to patients.
Magnetic Resonance Spectroscopy (MRS)
This diagnostic method is a part of the magnetic resonance imaging method. It has many aspects similar to that of magnetic resonance imaging. Biochemical changes in a determined region of the brain can be detected by means of a special software program. With magnetic resonance imaging, it is possible to obtain supportive information for the diagnosis of infections, stroke, Alzheimer’s Disease, multiple sclerosis, post-radiotherapy scars and tumor.
Diffusion Tensor Imaging (DTI)
In this imaging method, water flow in the brain’s white matter tracts is measured. During the procedure, the brain’s current structural status is identified. It is possible to make comparisons between this image and the new ones in later periods. This imaging technique is important because it shows the relationship between the tumor and white matter, and contributes to the surgeon’s ability to prevent these tracks from being damaged during surgery.
Functional Magnetic Resonance Imaging (FMRI)
Functional magnetic resonance imaging is used to identify areas of the brain that have specific functions. For example, imaging of the speech center and certain regions that enable motor activities in our bodies. The functioning of this technique is similar to that of standard magnetic resonance imaging. However, it provides a more advanced level of knowledge by making it possible to measure the amount of oxygen in the blood vessels and ensure slight changes in them. These changes in the amount of oxygen indicate the functional regions of the organ. For example, if the relationship between the speech center and a tumor close to it should be identified in detail, the patient reads a paper on his/her hand during the imaging; and at the same time, the speech center is determined by using special software programs. The relationship of the tumor with this region is identified. The neurosurgeon will also have the opportunity to plan the surgical intervention in this area in more detail.
Positron Emission Tomography (PET)
This examination method is used to identify changes (e.g. growth) in cells. Patients are injected with a very low dose of radioactive glucose. Depending on its stage, the tumor absorbs a little bit more radioactive glucose compared to the surrounding normal tissues, and then the tumor tissue is detected by means of radionuclear imaging software programs. Positron emission tomography gives a rough idea about the severity of the tumor’s growth.
Biopsy (Tissue Sample Analysis)
Biopsy is a diagnostic method that enables neurosurgeons to obtain very important information as a result of the evaluation of a tumor tissue samples taken by pathologists during surgery. If the tissue sample has been taken during surgery, it is called an ‘open biopsy’. Stereotactic brain biopsy is an alternative diagnostic biopsy method for cases where the tumor is in a very critical part of the brain, where surgical removal of the tumor poses a high risk of serious damage, or where the patient has health problems that prevent the completion the operation. In this method, a special head frame is attached to the patient’s head. Then, the location of the tumor is determined with 3D images and a biopsy is performed.
The pathologist evaluates the tissue sample taken by biopsy and then makes a diagnosis accordingly. After this process, the neurosurgeon can talk more clearly about the course of the disease, and can plan additional treatments or a second surgery (if necessary). For this reason, pathologic diagnosis is of vital importance for both the patient and the neurosurgeon.
Cerebrospinal Fluid (CSF) Analysis
Under local anesthesia, a needle is inserted through the lumbar region to take cerebrospinal fluid. Biochemical and pathological analyses are then performed on the fluid. After resting for 1 to 3 hours, the patient is discharged from the hospital.
Other Tests Used for the Diagnosis of Brain Tumor
Some types of blood and urine tests are required in the diagnosis of some types of brain tumors (such as pituitary tumors). With these tests, the levels of hormones and metabolites of the patient are analyzed, and the obtained results are evaluated with the results of tests performed with other radiological diagnostic methods.