Brain tumor: Understanding the brain, Symptoms, Types, Grades, Causes and Risk factors and Diagnosis


A primary brain tumor is a tumor which begins in the brain tissue. If a cancerous tumor starts elsewhere in the body and spread to the brain and grow there, then these are called secondary or metastatic brain tumors.

August 14, 2018

The brain composed of nerve cells and supportive tissues like glial cells and meninges which control your activity like breathing (brain stem), activity like moving muscles to walk (cerebellum) and your senses like sight and our memory, emotions, thinking and personality (cerebrum).
Primary brain tumors can be either malignant that contain cancer cells or benign which do not contain cancer cells. A primary brain tumor is a tumor which begins in the brain tissue. If a cancerous tumor starts elsewhere in the body and spread to the brain and grow there, then these are called secondary or metastatic brain tumors. Brain tumors can occur at any age. The exact cause of brain tumor is unknown. Risk factors include exposure to ionizing radiation and family history of brain tumors.
The signs and symptoms of brain tumors depend on their size, type, and location. The most common symptoms include headaches, numbness or tingling in the arms or legs, seizures, memory problems, mood and personality changes, balance and walking problems, nausea and vomiting, or changes in speech, vision, or hearing.
Brain tumors can be classified by grade from grade I to grade IV. The grade is determined by the way the cells look under a microscope. The higher the grade number, the more abnormal the cells appear, and the more aggressively the tumor usually behaves.
The most common types of primary brain tumors among adults are astrocytoma, meningiom which is a tumor that arises from the membranes surrounding the brain and spinal cord and oligodendroglioma. The most common type of primary brain tumors in children are medulloblastoma, grade I or II astrocytoma, glioma or ependymoma, and brain stem glioma. Diagnosis can be made by a neurologic exam by a neurologist or neurosurgeon, which include CT scan or magnetic resonance imaging (MRI), and other tests like an angiogram, spinal tap and biopsy. Your diagnosis helps predict the treatment.
Treatment options may include surgery, radiation therapy, or chemotherapy or a combination of treatments based on the type, location, and size of the tumor, your health, and age. Supportive care is important before, during and after treatment to minimize symptoms and to improve your quality of life. Some patients can qualify for clinical trials also.

Understanding the brain:

The brain is a soft, spongy mass of tissue and is protected by:

  • The bones of the skull
  • Three thin layers of tissue called as meninges
  • Watery fluid called as cerebrospinal fluid that flows through spaces between the meninges and through spaces (ventricles) within the brain.

It control your activity like breathing (brain stem), activity like moving muscles to walk and talk (cerebellum) and your senses like sight, hearing, touch, taste, and smell and our memory, emotions, thinking and personality (cerebrum). Messages and signals are carried by a network of nerves , back and forth between the brain and the rest of the body. Some nerves carry signal directly from the brain to the eyes, ears, and other parts of the head, where as other nerves run through the spinal cord to connect the brain with the other parts of the body.
Glial cells surround nerve cells and hold them in place within the brain and spinal cord. The three major parts of the brain control different activities. These include:

Cerebrum:

The cerebrum uses information from our senses to tell us what is going on around us and tells our body how to respond. It controls reading, thinking, learning, speech, and emotions. The cerebrum is divided into the left and right cerebral hemispheres. The right hemisphere controls the muscles on the left side of the body, where as the left hemisphere controls the muscles on the right side of the body.

Cerebellum:

The cerebellum controls balance for walking and standing, and other complex actions.

Brain stem:

The brain stem connects the brain with the spinal cord. It controls breathing, body temperature, blood pressure, and other basic body functions.

Symptoms of Brain Tumor:

The symptoms of a brain tumor depend on tumor size, type, and location. Symptoms may be caused when a tumor presses on a nerve or harms a part of the brain. Also, they may be caused when a tumor blocks the fluid that flows through and around the brain, or when the brain swells because of the buildup of fluid.
Symptoms of benign brain tumors often are not specific. The most common symptoms include:

  • headaches
  • numbness in extremities
  • changes in mental ability, such as concentration, memory, speech
  • seizures, muscle jerking
  • change in sense of smell
  • nausea/vomiting
  • vision problems
  • hearing problems
  • balance problems
  • facial paralysis

All of these symptoms can occur in many other diseases also.

Types of Brain Tumor:

Brain tumor can be either primary or secondary. A primary brain tumor is a tumor which begins in the brain tissue. If a cancerous tumor starts elsewhere in the body and spread to the brain and grow there, then these are called secondary or metastatic brain tumors.
Usually when the normal cells grow old or get damaged, they die, and new cells are formed that take their place. When this process goes wrong and new cells form when the body does not need them, while old or damaged cells do not die as they should, extra cells are buildup to form a mass of tissue called a growth or tumor.
Primary brain tumors can be benign or malignant:

Benign brain tumors:

These tumors
  • do not contain cancer cells
  • can be removed, and they seldom grow back.
  • have an obvious border or edge and cells from benign tumors rarely invade tissues around them. They do not spread to other parts of the body. However, benign tumors can press on sensitive areas of the brain and cause serious health problems.
  • are sometimes life threatening like other benign tumors.
  • may become malignant.

Malignant brain tumors:

These are also called as brain cancer that contain cancer cells. These tumors

  • are generally more serious and often are a threat to life.
  • are likely to grow rapidly and crowd or invade the nearby healthy brain tissue.
  • may spread to other parts of the brain or to the spinal cord when the cancer cells break away from the malignant brain tumors. They rarely spread to other parts of the body.

Types of primary brain tumors:

There are many types of primary brain tumors which are named according to the type of cells or the part of the brain in which they begin. The primary brain tumors that begin in glial cells is called as a glioma.
The most common types that are found in adults include:

Astrocytoma:

The tumor arises from star-shaped glial cells called astrocytes. It can be any grade. An astrocytoma most often arises in the cerebrum in adults.
Grade I or II astrocytoma may be called a low grade glioma.
Grade III astrocytoma is called as a high grade or an anaplastic astrocytoma.
Grade IV astrocytoma is called aa a glioblastoma or malignant astrocytic glioma.

Meningioma:

The tumor arises in the meninges. It can be grade I, II, or III. Usually it is benign or grade I and grows slowly.

Oligodendroglioma:

The tumor arises from cells that make the fatty substance that covers and protects nerves. It usually occurs in the cerebrum. It is most common in middle aged adults and can be grade II or III.
The most common types that are found among children include:

Medulloblastoma:

The tumor usually arises in the cerebellum. It is sometimes called a primitive neuroectodermal tumor and is grade IV.

Grade I or II astrocytoma:

This lowgrade tumor can occurs anywhere in the brain in children. The most common astrocytoma among children is juvenile pilocytic astrocytoma which is of grade I.

Ependymoma:

The tumor arises from cells that line the ventricles or the central canal of the spinal cord. It is most commonly found in children and young adults. It can be grade I, II, or III.

Brain stem glioma:

The tumor occurs in the lowest part of the brain. It can be either a lowgrade or highgrade tumor. The most common type is diffuse intrinsic pontine glioma.

Grades of Brain Tumor:

The grade of a tumor refers to the way the cells look under a microscope. The tumors are classified as:

  • Grade I: The tissue is benign. The cells look nearly like normal brain cells, and they grow slowly.
  • Grade II: The tissue is malignant. The cells look like less normal cells than do the cells in a Grade I tumor.
  • Grade III: The malignant tissue has cells that look very different from normal cells. The abnormal cells are actively growing (anaplastic).
  • Grade IV: The malignant tissue has cells that look most abnormal and tend to grow quickly.

Cells from low grade tumors that is grades I and II look more normal and generally grow more slowly than cells from high grade tumors which are grades III and IV.
A low grade tumor may become a high grade tumor over time. However, the change to a high grade tumor happens more often among adults than children.

Causes and Risk factors for Brain tumors:

The exact causes of brain tumor is unknown. People with certain risk factors are more likely to develop a brain tumor than others. A risk factor is something that may increase the chance of getting a disease. Risk factors for brain tumor include:

Ionizing radiation:

Ionizing radiation from high dose x-rays such as radiation therapy from a large machine aimed at the head and other sources can cause cell damage that leads to a tumor. People exposed to ionizing radiation may have an increased risk of a brain tumor, such as meningioma or glioma.

Family history:

It is rare for brain tumors to run in a family. There is not so much risk to develop brain tumor if your parents or siblings have it. There is a possibility of developing brain tumor by using cell phones, having had a head injury, or having been exposed to certain chemicals at work or to magnetic fields. However there is no studies which has shown consistent links between these possible risk factors and brain tumors. 

Diagnosis of Brain Tumor:

A physical examination is done and you will be asked about your personal and family health history by your doctor. One or more of the following tests will be done if you have symptoms that suggest a brain tumor:

Neurologic examination:

Your vision, hearing, alertness, muscle strength, coordination, and reflexes will be checked by your doctor. Also your eyes will be examined to look for swelling caused by a tumor pressing on the nerve that connects the eye and the brain.

MRI:

MRI stands for magnetic resonance imaging is a technique where the MRI scanner uses magnetic and radio waves to create pictures of tissues, organs and other structures within the body, which can then be viewed on a computer. MRI scanning is painless and there is no exposure to X-rays or any other damaging forms of radiation. Sometimes a special dye or contrast material is injected into a blood vessel in your arm or hand to help show differences in the tissues of the brain. The pictures can show abnormal areas, such as a tumor. The images help the specialist determine how advanced the cancer is, and where it has spread to in the body. This types of scans also help the doctor decide on the most appropriate treatment.

CT scan:

CT scans are special X-ray tests that produce cross-sectional images of your organs, bones, and other tissues using X-rays and a computer. It shows more detail images than a regular X-ray. The higher-resolution images produced in CT scan help assist the doctor in making a diagnosis of small nodules or tumors, which is not possible with a plain film X-ray. You may receive contrast material by injection into a blood vessel in your arm or hand. The contrast material makes abnormal areas easier to see.

Angiogram:

A dye is injected into the bloodstream that makes blood vessels in the brain show up on an x-ray. If a tumor is present, the x-ray may show the tumor or blood vessels that are feeding into the tumor.

Spinal tap:

A sample of cerebrospinal fluid, the fluid that fills the spaces in and around the brain and spinal cord will be removed by your doctor using local anesthesia. The doctor uses a long, thin needle to remove fluid from the lower part of the spinal column.
This sample is then sent to the laboratory to checks the fluid for cancer cells or other signs of problems. A spinal tap takes about 30 minutes. You must lie flat for several hours after the procedure to avoid getting a headache.

Biopsy:

The removal of sample of tissue to look for tumor cells is called a biopsy. A pathologist looks at the cells under a microscope to check for abnormal cells. A biopsy can show cancer, tissue changes that may lead to cancer, and other conditions. A biopsy is the only sure way to diagnose a brain tumor, the grade, and plan treatment. Surgeons can obtain tissue samples in two ways to look for tumor cells:

Biopsy at the same time as treatment:

The surgeon takes a tissue sample when you have surgery to remove part or all of the tumor.

Stereotactic biopsy:

For stereotactic biopsy, you may get local or general anesthesia and wear a rigid head frame. A small incision will be made by the surgeon in the scalp and a small hole will be drilled into the skull. Imaging technique such as CT or MRI is used to guide the needle through the small hole to the location of the tumor. A sample of tissue will be then removed by the surgeon with the help of the needle. A needle biopsy may be used when a tumor is deep inside the brain or in a part of the brain that can not be operated on.
However, the surgeon may not be able to remove tissue from the tumor without harming normal brain tissue if the tumor is in the brain stem or certain other areas. In this case, MRI, CT, or other imaging tests are used by the doctor to learn as much as possible about the brain tumor.