The body is made up of a wide variety of cells with separate functions. The vast majority of these cells grow and die throughout our lives. The ones that die are replaced by new ones by the division of other cells. In this way, it is ensured that the body remains healthy and performs its duties correctly. The division of cells while they are being renewed has been subject to very strict rules as a result of millions of years of evolution, and most of the time it runs smoothly throughout a person’s life. However, as a result of diseases, hereditary factors and the factors that the body is exposed to from the environment, the proper functioning of the cells is impaired, and the cells lose their growth control and begin to divide very often, rapidly and in more numbers than they should. These defective cells form misoperational cell communities called tumors. The same is true for other cells of the brain and nervous system. Brain tumors are diagnosed in approximately 16,000 people each year.
Tumors are divided into two main groups as benign (benign) and malignant (malignant). Benign tumors are the group that do not contain cancer cells. They can usually be removed, do not recur and do not spread to the surrounding normal working tissues and disrupt their functions. Benign brain tumors have good margins and can be surgically removed. However, by compressing other normal tissues in the brain, they can prevent their normal functioning.
Malignant brain tumors contain cancer cells. They threaten life. They grow rapidly and spread to surrounding normal tissues, preventing them from functioning. They usually survive by taking root, just like trees, and stealing the substances necessary for their nutrition from healthy brain tissue.
The central nervous system, especially the brain, is very sensitive to pressure changes since it is in a tightly guarded closed box (skull). For this reason, although some benign tumors do not contain cancer cells, they can cause life-threatening conditions by pressing on important structures.
Tumors originating from brain tissue are called primary brain tumors. Secondary brain tumor occurs when a non-cerebral cancer spreads to the brain. Brain tumors are named according to the type of tissue from which they originate. The most common primary brain tumor is gliomas. These originate from the brain’s extraneural support cells.
A very short information about common brain tumors is given below.
– Astrocytomas: They arise from small, star-shaped cells called astrocytes. They can be seen in the brain, cerebellum, spinal cord. While they are usually located in the cerebral hemispheres in adults, they are more common in the brainstem in children. According to the staging system, stage 1 tumor is called pilocytic astrocytoma, stage 2 tumor is called diffuse astrocytoma, stage 3 tumor is called anaplastic astrocytoma, and stage 4 tumor is called glioblastoma multiforme. Stage 1 and stage 2 tumors are called low grade, while others are called high grade tumors.
– Ependymomas: They usually develop from the cells lining the walls of the cavities of the brain called ventricles. They can also be seen in the spinal cord. Although they can occur at any age, they are usually seen in childhood and young adulthood. They constitute 2-9% of primary brain tumors. They can spread in the cerebrospinal fluid. It is accepted that ependymomas with clinical manifestations at a young age show a worse prognosis.
– Oligodendrogliomas: They originate from cells that produce the fat layer called myelin, which is responsible for protecting the extensions of nerve cells. They grow slowly and do not spread to surrounding tissues. They are rare tumors that are more common in middle age. They constitute 4-5% of primary brain tumors. An important feature of these tumors is that they show varying degrees of calcification morphologically and radiologically.
– Medulloblastomas: Recent studies have shown that these tumors originate from primitive (developing) nerve cells that should not remain in the body after birth. For this reason, medulloblastomas are also called Primitive Neuro-Ectodermal (PNET). They mostly develop in the cerebellum. They are usually childhood tumors and are more common in males. They constitute 4-10% of primary brain tumors. They constitute 15-20% of brain tumors seen under the age of 20.
– Menengiomas: They develop from the brain membranes called meninges. Since they are slow-growing tumors that do not usually spread to the surrounding tissues, the brain tissue can adapt to the presence of these tumors and remain undetected until they reach large sizes. They are usually seen in women aged 30-50 years. More than 95% are benign. They constitute 15% of brain tumors.
– Craniopharyngiomas: They develop in the area where the pituitary gland is located. They are usually benign, but sometimes they are called malignant because they cause much damage to the surrounding tissues. They are more common in children and teenagers.
– Pineal region tumors: They are seen in the localization of the pineal gland. It is a small organ located deep in the middle of the brain. There are two types, slow growing and fast growing. They constitute 3-8% of brain tumors in childhood and less than 1% in adults. Approximately 80% of tumors in this region are malignant.
– Brain stem tumors: These are common tumors that are more common in children. Its incidence in children is 10-20%. The average age of onset is 3-9. Among the brain stem tumors, gliomas form a distinctive group and are divided into 4 groups. Diffuse, cervicomedullary, focal, dorsal exophytic tumors. All diffuse tumors are malignant.
– Corner Tumors: The junction of the cerebellum and brain stem is called the corner. Although various tumor types can be seen in this region, the first tumor type that comes to mind when talking about corner tumor is schwannomas, the sheath tumor of the eighth cranial nerve, the vestibular nerve responsible for hearing and balance. They are benign, slow growing tumors. They cause hearing and balance problems by pressing on the hearing and balance nerve. If the tumor grows larger, it may cause facial numbness by pressing on the nerve that receives facial sensation. Tumors that grow larger can cause facial paralysis and even pressure on the brain stem, causing life-threatening conditions. These tumors, which are usually seen unilaterally, can be seen bilaterally with a hereditary disease called neurofibromatosis type 2. They constitute 8% of unilateral brain tumors. This tumor is seen in one of 100,000 people every year. Early diagnosis plays a key role so that it can be treated without serious problems. In 70% of patients, the first complaint is hearing loss. Dizziness, headache, tinnitus are also common complaints. Facial paralysis, double vision, difficulty swallowing, facial pain or numbness are other complaints in patients with larger tumors. Special tests are performed to determine the degree of hearing loss. In cases where the diagnosis is suspected, MRI is performed to clarify the diagnosis.
– Metastatic Tumors: Metastasis is the spread of a cancer. If a cancer in another part of the body spreads and reaches the brain, it is called a secondary brain tumor. Cancer that has spread to the brain is the same as the original cancer and is named the same way. For example, if lung cancer spreads to the brain, it is called metastatic lung cancer. Because the cells of the metastatic tumor in the brain are similar to lung cells, not brain cells. Treatment in secondary brain tumors depends on the place of onset of the cancer, the extent of its spread, the patient’s age, current state of health, and response to the treatment applied for the first disease.
Treatment of Brain Tumors
There are many factors that affect the choice of treatment. These are the type, location, size and condition of the patient. Options for children and adults are different. A unique treatment plan is chosen for each patient.
Brain tumors can be treated with surgery, radiation, and medication. Many methods can be used together according to the needs of the patient. The treatment of the patient is usually carried out by a team. This team includes a neurosurgeon, medical oncologist and radiation oncologist. In addition to these, a physical therapist and speech therapist can also join the team.
Surgery is the first line of treatment for many brain tumors. If possible, the surgeon removes the entire tumor. However, if the entire tumor cannot be removed without damaging the surrounding healthy tissue, the doctor will remove as much of the tumor as possible. Since partial removal will reduce intracranial pressure, it helps to reduce the patient’s complaints and to reduce the tumor tissue to be targeted with radiation or drugs.
In some cases, the tumor cannot be removed. In such cases, the surgeon only performs a biopsy and removes a small portion of the tumor. The removed part is sent to pathology and the exact type is learned by examining it under the microscope. This is an important source of information in shaping treatment. Biopsy can be performed with open surgery or with a needle using special systems in patients whose general condition does not allow it. The doctor takes MR and/or CT images by attaching a special frame to the patient’s head. In this way, the exact location of the tumor tissue in the skull is determined by its coordinates. With this information, a small hole is made in the skull, and the biopsy needle is aimed directly at the tumor and a biopsy is taken. This technique is called stereotaxy.
Radiation therapy (radiotherapy) can be administered in a variety of ways. In the method in which radiation is given to the whole head through a large machine, patients are irradiated 5 days a week for a few weeks. The duration of treatment is determined by the type and size of the tumor. The purpose of doing the treatment piecemeal in this way is to reduce the damage to normal tissues. Radiation can also be applied by surgically placing special substances directly into the tumor. Depending on the radioactive properties of the substance, either a short-term application is made or the substance is left in the brain permanently.
Stereotactic radiosurgery is another treatment option. The treatment is done in a single session. In many respects, high-dose radiation is directed only at the tumor tissue. This way, normal brain tissue is not damaged. This method is called GAMMA KNIFE RADIO SURGERY. It provides a more effective, more accurate treatment method in a shorter time. In this method, tumor sizes should be smaller than three centimeters.
Chemotherapy is the use of drugs to kill cancer cells. It can be administered with a single drug or a combination of many drugs at various doses. The treatment can be done orally or intravenously, or it can be administered directly into the cerebrospinal fluid in the spine.
Patients treated with one of these forms of treatment, the duration of which is determined by the doctors, and more frequently at first; then they come to the controls that are opened. During the controls, changes in the tumor are followed with CT or MR images, and a full examination of the patients is performed. If necessary, drug treatments are arranged.
References
1- Gazi Unv. Faculty of Medicine Gamma Knife Unit Web Page
2- Turkish Neurosurgery Society Publications Basic Neurosurgery Book
