Brief overview
- Causes: The cause of primary brain tumors is usually unclear. Secondary brain tumors (brain metastases) are usually caused by other cancers. In some cases, the trigger is a hereditary disease such as neurofibromatosis or tuberous sclerosis.
- Diagnosis and examination: The doctor carries out physical examinations and takes a detailed medical history. Other diagnostic procedures include computed tomography (CT), magnetic resonance imaging (MRI), electroencephalography (EEG), tissue examination (biopsy) and a cerebrospinal fluid and blood test.
- Treatment: Surgery, radiotherapy and/or chemotherapy, accompanying psychotherapy
- Course and prognosis: The prognosis depends heavily on the severity of the tumor and the patient’s state of health. The more severe the tumor and the later treatment begins, the worse the prognosis.
What is a brain tumor?
Compared to other cancers, brain tumors are the second most common type of tumor in children. According to the Children’s Cancer Registry, one in 1,400 children under the age of 18 is affected, which is around a quarter of all tumors in children. Both malignant and benign forms occur, although benign tumors are less well recorded. Overall, boys are affected 20 percent more frequently than girls.
However, not all brain tumors are the same. First of all, a distinction is made between primary and secondary brain tumors. Primary brain tumors include both benign (benign) and malignant (malignant) forms (“brain cancer”), while secondary brain tumors are always malignant.
Primary brain tumors
A brain tumor that develops directly from cells of the brain substance or the meninges is called primary. Doctors also refer to such tumors as brain tumors.
Primary brain tumors often include those that originate from a cranial nerve. The cranial nerves originate directly from the brain and are therefore partly located in the skull. However, they do not belong to the central nervous system (CNS: brain and spinal cord), but to the peripheral nervous system (PNS). If a tumor in the head originates from a cranial nerve, it is therefore strictly speaking a neoplasm of the peripheral nervous system.
Primary brain tumors are further subdivided according to various criteria. The World Health Organization (WHO) classifies the individual tumors according to the tissue from which they originate and the extent to which the brain tumor is malignant or benign. This distinction influences both the treatment and the prognosis of a brain tumor.
Interestingly, only a small proportion of brain tumors originate from nerve cells (neurons). More than every second primary brain tumor develops from the supporting tissue of the brain and thus belongs to the group of gliomas. The following table provides an overview of the most important primary brain tumors:
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Gliomas originate from the supporting cells of the CNS. These include, for example, astrocytoma, oligodendroglioma and glioblastoma. |
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This brain tumor forms from cells that line the inner ventricles of the brain. |
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Medulloblastoma forms in the cerebellum. It is the most important brain tumor in children. |
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Neurinoma |
This tumor originates from cranial nerves. It is also known as a schwannoma. |
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This brain tumor develops from the meninges. |
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CNS lymphoma |
CNS lymphoma develops from a cell group of white blood cells. |
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Germ cell tumors |
Germ cell tumors include germinoma and chorionic carcinoma. |
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Brain tumor of the sella region |
In every age group, some brain tumors occur more frequently than others. Among the primary brain tumors, gliomas, meningiomas and pituitary tumors are the most common in adults. If a brain tumor occurs in children, it is usually a medulloblastoma or a glioma.
A neuroblastoma is a so-called embryonal brain tumor that mainly occurs in small children and infants. Neuroblastoma develops from certain nerve cells of the autonomic (vegetative) nervous system, which can be found in numerous places in the body, for example next to the spine and in the adrenal gland.
Secondary brain tumors
In addition to primary brain tumors, secondary brain tumors are just as common. They develop when cells from other organ tumors (e.g. lung cancer, skin cancer, breast cancer) reach the brain and form a secondary tumor. These are therefore brain metastases. Some experts do not even consider these to be “real” brain tumors.
With brain metastases, a distinction is made between metastases in the brain tissue (parenchymal metastases) and those in the meninges (meningeosis carcinomatosa).
Signs of a brain tumor
You can read everything you need to know about possible signs of a brain tumor in the article Brain tumor – symptoms.
What causes brain tumors?
In contrast, there are brain tumors that are genetic and hereditary. They occur in certain hereditary diseases such as neurofibromatosis, tuberous sclerosis, von Hippel-Lindau syndrome or Li-Fraumeni syndrome. However, these diseases are extremely rare. Only a small proportion of brain tumors can be attributed to one of these diseases.
CNS lymphomas develop more frequently in patients with a severely weakened immune system, for example due to HIV or when the immune system is suppressed by special medication (immunosuppressants). Such treatment is usually used to prevent rejection reactions after an organ transplant.
Otherwise, the only known risk factor for a brain tumor to date is radiation to the nervous system. Doctors use it, for example, for life-threatening diseases such as acute leukemia. Overall, only very few people develop a brain tumor after brain irradiation. Ordinary X-ray examinations do not usually cause a brain tumor.
Secondary brain tumors, i.e. brain metastases, usually form when there is cancer elsewhere in the body. If there are risk factors for a certain type of cancer, the risk of brain metastases often increases. However, not every malignant tumor spreads to the brain.
How is a brain tumor diagnosed and examined?
The right person to contact if you have a brain tumor is a specialist in neurology (neurologist). As part of the diagnosis, he will take a precise medical history. He will ask about your exact complaints, any previous illnesses and medical treatments. Possible questions include, for example
- Do you suffer from new types of headaches (especially at night and in the morning)?
- Do the headaches increase when lying down?
- Do conventional headache remedies help you?
- Do you suffer from nausea and vomiting (especially in the morning)?
- Do you have visual disturbances?
- Have you had a seizure? Has one side of your body twitched involuntarily?
- Have you had or do you have problems moving or coordinating any part of your body?
- Have you had or do you have problems speaking?
- Do you notice any limitations when you try to concentrate, memorize or understand something?
- Have new hormonal disorders occurred?
- Do your relatives or friends think that your personality has changed?
This is often followed by further examinations such as computed tomography (CT), magnetic resonance imaging (MRI), electroencephalography (EEG) and a cerebrospinal fluid examination. If these examinations indicate a brain tumor, the doctor will then take a tissue sample (biopsy) in order to classify the previous results more precisely.
A blood test often also provides information on whether a brain tumor is present or not. In the blood values, the doctor looks for so-called tumor markers – substances that the tumor cells secrete. Genetic changes (genetic abnormalities) can also be detected in this way.
If your neurologist suspects that brain metastases are causing your symptoms, the underlying cancer must be diagnosed. Depending on the suspicion, your doctor may refer you to another specialist (such as a gynecologist or gastroenterologist).
CT and MRI
During a CT scan, the patient lies on their back on a table that moves into an examination tube. The brain is x-rayed. The brain structures and, in particular, hemorrhages and calcifications in them can then be recognized on the computer in individual cross-sectional images.
In recent years, an MRI scan has become increasingly common when a brain tumor is suspected. This examination is also carried out in an examination tube. It takes longer than a CT scan, but does not use X-rays. Instead, the images of the body are created by magnetic fields and electromagnetic waves flowing through it. The image is often even more detailed than with CT. As with CT, the person undergoing the MRI must remain very still and should not move if possible.
Sometimes it is necessary and helpful to carry out both procedures one after the other. Both examinations are not painful. However, some patients find the tube and the high noise level unpleasant.
Measurement of electrical brain waves (EEG)
A brain tumor often changes the electrical currents in the brain. An electroencephalogram (EEG), which records these currents, provides revealing information. To do this, the doctor attaches small metal electrodes to the scalp, which are connected to a special measuring device with cables. The brain waves are recorded, for example, at rest, during sleep or under light stimuli.
Examination of cerebrospinal fluid (cerebrospinal fluid puncture)
In order to rule out an altered cerebrospinal fluid pressure (CSF pressure) or meningitis, the doctor sometimes performs a cerebrospinal fluid puncture in the lumbar region (lumbar puncture). Cells altered by a brain tumor can also be detected in the cerebrospinal fluid.
The patient is usually given a sedative or light sleeping pill before this examination. Children are usually given a general anesthetic. The doctor then disinfects the lumbar region on the back and covers the area with sterile drapes.
To ensure that the patient does not feel any pain during the puncture, the doctor first numbs the area with an anaesthetic, which he injects under the skin. The doctor then guides a hollow needle into a cerebrospinal fluid reservoir in the spinal canal. In this way, he determines the cerebrospinal fluid pressure and takes some cerebrospinal fluid for a laboratory examination.
The risk of injury to the spinal cord is very low during this examination because the puncture site is below the end of the spinal cord. Although most people find the examination unpleasant, it is tolerable, especially as the cerebrospinal fluid puncture usually only takes a few minutes.
Taking a tissue sample
In open surgery, the patient is given a general anesthetic. The top of the skull is opened in a certain area so that the tumor structures can be reached by the surgeon. The doctor usually chooses this procedure if he wants to completely remove the brain tumor in the same operation. The entire tumor tissue is then examined under a microscope. Further treatment often depends on the results.
Stereotactic surgery, on the other hand, is almost always performed under local anesthesia so that the patient does not feel any pain. The patient’s head is immobilized while the sample is taken. The doctor uses an imaging procedure to determine exactly where the tumor is located in the head. He then drills a small hole in the skull at a suitable location (trepanation), through which he inserts the surgical tools. As a rule, the movement of the biopsy forceps is computer-controlled and therefore very precise, making it possible to take a targeted sample.
How is a brain tumor treated?
Every brain tumor requires individual treatment. In principle, it is possible to operate on a brain tumor, give it radiotherapy or chemotherapy. These three options are adapted to the respective tumor and differ in the way they are carried out or combined.
Surgery
Brain tumor surgery often pursues various goals. One goal is usually to either remove the brain tumor completely or at least reduce its size. This can alleviate symptoms and improve the prognosis. Even a reduction in tumor size creates better conditions for subsequent treatments (radiotherapy, chemotherapy).
Surgery for brain tumor patients is sometimes also aimed at compensating for a tumor-related drainage disorder of the cerebrospinal fluid. This is because if the cerebrospinal fluid does not drain away unimpeded, the pressure in the brain increases, resulting in serious symptoms. During an operation, the doctor implants a shunt, for example, which drains the cerebrospinal fluid into the abdominal cavity.
The doctor usually performs open surgery under general anesthesia: The head is immobilized. Once the skin has been cut, the surgeon opens the skull bone and the underlying hard meninges. The brain tumor is operated on using a special microscope. Before the operation, some patients are given a fluorescent agent that absorbs the cells of the brain tumor. During the operation, the tumor then glows under a special light. This makes it easier to distinguish it from the surrounding healthy tissue.
After the operation, the doctor stops the bleeding and closes the wound, which usually only leaves a scar. The patient initially remains in a monitoring ward until their condition is stable. The doctor usually arranges for another CT or MRI scan to check the results of the operation. In addition, patients are usually given a cortisone preparation for a few days after the operation. This is to prevent the brain from swelling.
Radiation
Some brain tumors can only be treated with radiotherapy. For others, this is only one of several treatment measures.
Radiation is intended to destroy the brain tumor cells while sparing neighboring healthy cells as much as possible. In general, it is not possible to target only the brain tumor. However, thanks to good technical possibilities, the area to be irradiated can be calculated very well with prior imaging. Irradiation is carried out in several individual sessions, as this improves the result.
Individual face masks are made so that the tumor area does not have to be determined anew for each session. This allows the patient’s head to be placed in exactly the same position for each radiotherapy session.
Chemotherapy
Special cancer drugs (chemotherapeutic agents) are used to kill brain tumor cells or stop them from multiplying. If chemotherapy is carried out before surgery (to shrink the tumor), this is referred to as neoadjuvant chemotherapy. If, on the other hand, it follows the surgical removal of the brain tumor (to kill any remaining tumor cells), experts refer to it as adjuvant.
Different drugs are suitable for different types of brain tumors. Some brain tumors do not respond to chemotherapy at all and therefore require a different form of therapy.
Unlike other types of cancer, in the case of brain tumors the chemotherapeutic drugs first have to cross the blood-brain barrier to reach their target. In some cases, the doctor injects the chemotherapeutic agents directly into the spinal canal. They then enter the brain with the cerebrospinal fluid.
As with radiotherapy, chemotherapeutic agents also affect healthy cells. This sometimes results in certain side effects, such as a disruption of blood formation. The doctor will discuss the typical side effects of the medication used before treatment.
Supportive therapy
Psycho-oncological care is also usually part of supportive therapy: it is intended to help patients and their relatives cope with the serious illness.
What are the chances of survival with brain tumors?
Every brain tumor has a different prognosis. The course of the disease and the chances of recovery depend very much on the structure of the tumor tissue, how quickly it grows, how aggressive it is and where exactly in the brain it is located.
As a guide for doctors and patients, the WHO has developed a severity classification for tumors. There are a total of four degrees of severity, which are defined based on the tissue character (malignancy criteria), among other things. These describe a tumor in terms of its superficial cell changes, its growth and size as well as the extent of tissue damage (necrosis) caused by the tumor.
The classification also takes into account various genetic characteristics that cause corresponding changes in the way the tumor cells function. Other aspects that are taken into account in the classification are the location of the tumor, the patient’s age and the patient’s general state of health.
- WHO grade 1: Benign brain tumor with slow growth and very good prognosis
- WHO grade 3: Malignant brain tumor, increasingly uncontrollable and high recurrence rate
- WHO grade 4: Very malignant brain tumor with rapid growth and poor prognosis
This classification is not only used to assess the individual chances of recovery. It also determines which treatment method offers the best prognosis. For example, a first-degree brain tumor can usually be cured by surgery.
A second-grade brain tumor recurs more frequently after an operation, so-called recurrences develop. With WHO grade 3 or 4, the chances of recovery through surgery alone are usually poor, so doctors always recommend radiotherapy and/or chemotherapy after surgery.
In 2016, the survival rate for brain tumors in Germany was around 21% for men and 24% for women five years after treatment.
