General Info about Brain Tumor
The brain is one of the largest and complex organs in the human body and weighs about 1.3 Kgs. Neurons and glial cells are the basic units that make up the brain. There are about 40 billion nerve cells, known as neurons, in the brain.
The brain controls our body, receives, analyzes, and stores information. It produces electrical signals, which, together with chemical reactions, helps in the communication of the different parts of the body. The brain has three main parts: the cerebrum, the cerebellum, and the brain stem (medulla).
Blood vessels (arteries, capillaries, and veins) supply the brain with oxygen and nourishment and remove waste products. The cranium (the top of the skull) surrounds and protects the brain. Cerebrospinal fluid (CSF) is a clear, watery liquid surrounding the brain and cushioning it from jolts.
The neurons in the brain divide rapidly till about 7 years of age. Further development is by the existing cells making increasingly elaborate connections with each other. When this control is lost in a single cell, then it starts dividing in an uncontrolled manner.
As the cell makes more and more copies of itself, it grows to form a tumor. Not all brain tumors are cancerous. Brain cancer can arise from any of the cells, which make up the brain. Brain tumors are among the most challenging medical conditions due to their critically delicate location and impairment of important functions.
Primary brain tumors account for about 2.4% of all tumor diagnoses.
In the US, primary brain tumors are the leading cause of cancer-related deaths in patients younger than 35 years. In the case of secondary tumors, the incidence increases with age. This accounts for almost 20% of total cancer deaths each year. Primary brain tumors account for about 20% of the cancers in children.
The brain is made up of many different types of cells. Brain cancers occur when one type of cell transforms from its normal characteristics and grows and multiplies in an abnormal way. Based upon the malignancy, brain tumors can be generally of two types:
- Benign tumors (Non-cancerous)
- Malignant tumors (Cancerous)
It is reported that almost 70% of all adult brain tumors are benign. However, this is inverse in children. Brain tumors are the 2nd most commonly diagnosed cancer (after blood cancer) in children.
Depending on the site of origin, brain tumors may be either primary or secondary.
Brain tumors that result from this transformation and abnormal growth of brain cells are called primary brain tumors because they originate in the brain. Usually, they are named after the part of the brain or the type of brain cell from which they arise. Many of them are benign and can be successfully removed.
Generally, the benign tumors are treated only when the patient’s symptoms are progressive, or the location tumor is in an eloquent area. Malignant primary brain tumors are aggressive in nature with rapid growth. They cause problems by spreading into the normal brain tissue, thereby increasing the pressure and causing damage to the surrounding areas of the brain.
These tumors rarely spread outside the brain to other parts of the body. The malignant tumors demand proactive treatment as delayed intervention can be life-threatening. The most common primary brain tumors are gliomas. They begin in glial cells. There are many types of gliomas:
Astrocytoma: The tumor arises from star-shaped glial cells called astrocytes. In adults, astrocytomas most often arise in the cerebrum. In children, they occur in the brain stem, the cerebrum, and the cerebellum.
Brain stem glioma: The tumor occurs in the lowest part of the brain. Brain stem gliomas most often are diagnosed in young children and middle-aged adults.
Ependymoma: The tumor arises from cells that line the ventricles or the central canal of the spinal cord. They are most commonly found in children and young adults.
Oligodendroglioma: This rare tumor arises from cells that make the fatty substance that covers and protects the nerves. These tumors usually occur in the cerebrum. They grow slowly and usually do not spread into surrounding brain tissue. They are most common in middle-aged adults.
Other primary tumors that do not begin in the glial cells are
Medulloblastomaor primitive neuroectodermal tumor: This tumor usually arises in the cerebellum. Rarely do these tumors spread outside the brain. It is the most common brain tumor in children.
Meningioma: This tumor arises in the meninges and grows slowly. Meningiomas are benign and do not spread from their original site. Malignant meningiomas are very rare.
Schwannoma: This tumor arises from the Schwann cells. These cells line the nerve that controls balance and hearing. This nerve is in the inner ear. The tumor is also called an acoustic neuroma. It occurs most often in adults. They are more common in people who have a genetic disease called neurofibromatosis type 2.
Craniopharyngioma: The tumor grows at the base of the brain, near the pituitary gland. This type of tumor most often occurs in children.
Hemangioblastoma: This is a rare type of tumor that develops from cells that line the blood vessels. They are benign and grow slowly.
Pituitary tumors: These types of tumors develop in the pituitary gland. They are benign and are called pituitary adenomas.
Germ cell tumor of the brain: The tumor arises from a germ cell. Most germ cell tumors that arise in the brain occur in people younger than 30 years. The most common type of germ cell tumor of the brain is a germinoma.
Pineal region tumor: This rare brain tumor arises in or near the pineal gland. The pineal gland is located between the cerebrum and the cerebellum. The most common tumors are germinomas, teratomas, pineocytomas, and pineoblastomas.
Secondary brain tumors or metastatic tumors occur when cancer cells from other parts of the body, such as the lung, breast, skin, kidney, colon, spread to the brain. These tumor cells reach the brain via the bloodstream. Secondary tumors in the brain are far more common than primary brain tumors. About 25% of tumors elsewhere in the body metastasize to the brain.
Childhood brain tumor:
Brain tumors are the most common solid tumors that occur in children. Children of any age may be affected. Boys are affected more often than girls. Two types of brain cancers that are more common in children than in adults are medulloblastoma and ependymoma. Treatment and chance of recovery depend on the type of tumor, its location within the brain, the extent to which it has spread, and the child's age and general health.
The exact cause of most brain tumors is unknown. A small number of brain tumors occur in people who have known genetic conditions, such as neurofibromatosis, tuberous sclerosis, Li Fraumeni syndrome, or von Hippel Lindau syndrome.
Other factors that have been suggested as possible causes of brain tumors include certain types of viruses like HIV.
Research has shown that people with certain risk factors are more likely than others to develop a brain tumor. The following risk factors are associated with an increased chance of developing a primary brain tumor:
- Sex: In general, brain tumors are more common in males than females. However, meningiomas are more common in females.
- Race: Brain tumors occur more often among white people than among people of other races.
- Age: Most types of brain tumors are detected in people who are 70 years old or older. However, brain tumors are the second most common cancer in children. Brain tumors are more common in children younger than 8 years old than in older children.
- Family history: People with family members who have gliomas may be more likely to develop this disease. Other hereditary disorders also increase the risk of brain tumors.
- Exposure and occupational history:Being exposed to radiation or certain chemicals at work:
- Radiation: Workers in the nuclear industry have an increased risk of developing a brain tumor due to excessive exposure to radiation therapy. Cellular radiations also increase the risk of brain tumors.
- Formaldehyde: Pathologists and embalmers who work with formaldehyde have an increased risk of developing brain cancer.
- Vinyl chloride: Workers who make plastics may be exposed to chlorinated hydrocarbons like vinyl chloride and benzene. This chemical may increase the risk of brain tumors.
- Acrylonitrile: People who make textiles and plastics may be exposed to acrylonitrile. This exposure may increase the risk of brain cancer.
- Chemicals: Exposure to fertilizers, and pesticides through food products raise the risk of brain cancer.
Brain tumors can damage vital neurological pathways, invade and compress brain tissue. Symptoms usually develop over time and their characteristics depend on the location and size of the tumor. Not all brain tumors cause symptoms, and tumors of the pituitary gland are found mainly after death. Symptoms may be caused when a tumor presses on a nerve or damages a certain area of the brain. They also may be caused when the brain swells or fluid builds up within the skull. The most common symptoms of brain tumors (primary tumors) are:
- Progressive and relapsing headache (usually worse at night or in the early morning; frequently reported symptom)
Nausea, vomiting- Especially early in the morning (commonly seen in middle-aged or older people)
- Weakness in limbs and fatigue
- Difficulty in walking
- Seizures and convulsions (muscle jerking or twisting)
- Altered mental status - Changes in concentration, memory, attention, sleep or alertness
- Abnormalities in vision or other sensory problems like hearing deterioration
- Difficulty with speech or in expressing oneself
- Gradual changes in the intellectual or emotional capacity
- Changes in behavior or personality
- Sudden onset of fever, especially after chemotherapy (usually worse in the morning)
- Problems balancing
- Numbness or tingling in the arms or legs
Symptoms of brain tumors must be noted at the earliest and expert consultation should be sought without delay by the patients. The first step in diagnosing brain cancer involves evaluating symptoms and taking a medical history. If there is any indication that there may be a brain tumor, various tests are done to confirm the diagnosis.
- The diagnosis is done by either a neurologist (a specialist in brain and nerve disorders) or an oncologist (a doctor who specializes in cancer treatment) who both check for physical signs
- Nervous system examination: The doctors examine the nerves and the brain regions that control the eyes and face, check for equal strength &sensation on both sides of the body, coordination & balance, and memory &judgment.
- Mental exercises, such as simple arithmetic and simple questions.
- An eye examination using an ophthalmoscope (an instrument that shines a light at the back of the eye). This test is done to see if the optic disc at the back of the eye is swollen. A swollen optic disc is known as papilloedema and is a sign of raised intracranial pressure due to the growing brain tumor.
- Hearing tests.
- Facial muscle tests - smiling, grimacing.
- Tongue movement is also tested.
- Checking the strength of your arms and legs, knee jerks, and other reflexes.
- The doctor will test one's ability to feel sensations like pinpricks on areas of skin, to tell the difference between hot and cold and possibly to recognize the feeling and shape of familiar objects like coins.
- The gait of the patient is noted.
- Routine laboratory tests may be performed such as analysis of blood, electrolytes, liver function tests, and a blood coagulation Blood or urine tests may be done to detect drug use.
- CT scan: An X-ray machine linked to a computer takes a series of detailed pictures of the head. The patient may receive an injection of a special dye so the brain shows up clearly in the pictures. The pictures can show tumors in the brain.
- Magnetic Resonance Imaging (MRI): A powerful magnet linked to a computer makes detailed pictures of areas inside the body. These pictures are viewed on a monitor and can also be printed. Sometimes a special dye is injected to help show differences in the tissues of the brain. The pictures can show a tumor or other problem in the brain.
- Positron emission tomography (PET scan): It helps the physician evaluate brain function and cell growth by producing images of physical and chemical changes in the brain. PET can precisely locate a tumor and detect metastatic and recurrent brain cancer at earlier stages than MRI or CT scan. This technique also can be used to evaluate the tumor's response to chemotherapy and radiation treatment.
- Angiogram: Dye injected into the bloodstream flows into the blood vessels in the brain to make them show up on an x-ray. If a tumor is present, the doctor may be able to see it on the x-ray.
- Skull x-ray: Some types of brain tumors cause calcium deposits in the brain or changes in the bones of the skull. With an x-ray, the doctor can check for these changes.
- Spinal tap: The doctor may remove a sample of cerebrospinal fluid with local anesthesia. The doctor uses a long, thin needle to remove fluid from the spinal column. A laboratory test checks the fluid for cancer cells or other signs of problems.
- Myelogram: This is an x-ray of the spine. A spinal tap is performed to inject a special dye into the cerebrospinal fluid. The patient is tilted to allow the dye to mix with the fluid. This test helps the doctor detect a tumor in the spinal cord.
- Biopsy: The removal of tissue to look for tumor cells is called a biopsyy. A pathologist looks at the cells under a microscope to check for abnormal cells. A biopsy is the only sure way to diagnose a brain tumor. The three ways of obtaining the tissue samples are:
- Needle biopsy: The surgeon makes a small incision in the scalp and drills a small hole into the skull . This is called a burr hole. The doctor passes a needle through the burr hole and removes a sample of tissue from the brain tumor.
- Stereotactic biopsy: An imaging device, such as CT or MRI, guides the needle through the burr hole to the location of the tumor. The surgeon withdraws a sample of tissue with the needle.
- Biopsy during the treatment: The surgeon takes a tissue sample when the patient has surgery to remove the tumor.
- Other refined advancements in the brain imaging techniques for brain tumors includeMRS and Functional MRI.
- Magnetic resonance spectroscopy (MRS): It is a non-invasive analytical technique, also known as nuclear magnetic resonance (NMR) spectroscopy. It is generally used to study the metabolic changes in the brain to diagnose various neurological disorders including brain tumors.
- Functional MRI: Functional magnetic resonance imaging or fMRI is used to measure brain activities by detecting changes in the cerebral blood flow. The blood flow to certain regions increases when there is a neuronal activation. The concept is utilized to diagnose brain tumors.
Treatment for brain cancer depends on the age of the patient, the stage of the disease, the type and location of the tumor, and whether the cancer is a primary tumor or brain metastases. The treatment plan is developed by the multidisciplinary team consisting of neurosurgeons, neurooncologists, medical oncologists, radiation oncologists and the patient. It primarily involves three pillars of combination - neurosurgery, radiation therapy, and chemotherapy.
Some tumors require several different surgical procedures, and some can be treated with radiation alone. However, advancements in neurosurgery with the advent of microscopes and navigation-guided neurosurgery result in more efficient removal of brain tumors.
Surgery: Surgery is the treatment of choice for accessible and localized primary brain tumors, when the patient is in good health. The goal of surgery is to remove as much of the tumor as possible without damaging nearby normal brain tissue.
Craniotomy: It is to remove as much of the tumor as possible. The procedure is performed under general anesthesia and involves opening the skull (cranium).
Laser microsurgery: MRI is used to pinpoint the location of the tumor and a laser is used to destroy the tumor. This procedure may be used after a craniotomy to remove the remaining tumor tissue.
Brain-mapping: It is performed under local anesthesia and sedation. Electrodes stimulate nerves in the brain and measure responses. The surgeon removes as much of the tumor as possible without damaging vital areas of the brain, such as those that control motor function and speech.
Radiation therapy: Radiation is used when the entire primary tumor cannot be surgically removed. Moreover, it is an essential cornerstone of brain tumor treatment. Radiation therapists use several different approaches to treat primary brain tumors like external-beam radiation, brachytherapy, and stereotactic radiosurgery, 3-dimensional conformal radiation therapy, and proton beam radiation therapy. With this critical location of brain tumors, radiation therapy delivers more precise, accurate, and effective treatment.
Radiosurgery: Radiosurgery techniques like gamma knife/cyberknife/linac X-knife impart very high tumoricidal doses of radiation beams that can be accurately, precisely, and efficiently focused on tumors.
Chemotherapy: Chemotherapy is generally not a very effective treatment for most malignant primary brain tumors or metastatic tumors. The problem with chemotherapy is that it works by interrupting mitosis, the process of cell division. Many brain tumors grow slowly by nature, so slowing their growth by chemotherapy doesn't do much good. Chemotherapy is also used as a radio-sensitizing agent with radiation to control a recurrent tumor and to treat patients who can no longer tolerate radiation therapy. It is beneficial in specific brain tumors like optic glioma, lymphoma, or progressive malignant tumors.
Immunotherapy: Various techniques that attempt to boost a person's immune system so that it more effectively fights the tumor cells are used as supportive therapy.
Gene therapy: Inserting genes into a person's tumor cells or immune system to change the way the tumor cells operate.
Steroid therapy: Steroids are drugs that are used to reduce the swelling that often surrounds brain tumors. Although steroids do not treat the tumor itself, they are very useful in improving symptoms and making you feel better. They may be used before or after surgery, or during or after radiotherapy.
Anticonvulsant medicines: Anticonvulsants are drugs to prevent epileptic fits. These medicines are prescribed for people who have brain tumors and also after brain surgery. Some commonly used types are phenytoin and carbamazepine.
Several advancements in the treatment modalities of brain tumors contribute to a paradigm shift in the diagnosis. It is thereby crucial to diagnose brain cancer at an early stage to achieve better management.
Treatment may damage healthy cells and tissues, unwanted side effects are common. These side effects depend on many factors, including the location of the tumor and the type and extent of the treatment. Side effects may not be the same for each person, and they may even change from one treatment session to the next. Some of the common side effects are:
- Tiredness or weakness
- Edema due to the accumulation of cerebrospinal fluid in the brain.
- Vomiting and nausea
- Hair loss occurs after the treatment
- Some people develop a skin reaction; similar to sunburn sometimes the treated area becomes red and sore or itchy.
Anemiaand breathlessness are common symptoms of chemotherapy.
- Brain surgery damages normal tissues and the patient may have problem thinking, and speaking normally.
- Brain tumors and their treatment have a drastic effect on how a person functions. Rehabilitation is an important part of recovery.
- Occupational rehabilitation involves restoring normal daily functioning, from working with one's hands to driving.
- Physical therapy involves improving motor functions.
- Speech and language therapy may be important for restoring the ability to speak clearly.
- Cognitive therapy may be important for helping one deal with short-term memory loss. There are specialists available to help with vision, balance, or facial paralysis. Sometimes patients need vocational therapy to help them return to the working world.
- Rehabilitation for children would involve a combination of the above-mentioned therapies.
Survival rates in primary brain tumors depend on the type of tumor, age, functional status of the patient, and the extent of surgical tumor removal.
Patients with benign gliomas may survive for many years while survival in most cases of the last stage of glioblastoma is limited to a few months after diagnosis. In the case of single metastatic tumors, the prognosis is determined by the primary tumor, and it is generally poor.
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