Brain tumours

The body is composed of many different types of cells, each with its own function. Most of the cells grow old and die over lifetime. Dead cells are replaced by the division of other cells. Thus, the body is kept healthy and is ensured to perform its tasks properly.  The divisions of cells while renewing themselves are bound by very strict rules as a result of millions of years of evolution and often it functions smoothly throughout a person's life.  However, the proper functioning of cells is broken down and the cells begin to divide more often and quickly than normal by losing their growth control as a result of diseases, genetic factors and environmental factors that the body is exposed to.  These damaged cells form malfunctioning cell populations called tumours.  This condition is same for other cells of the brain and nervous system. Approximately 16,000 people are diagnosed with brain tumours every year.

Tumours are divided into two main categories as benign and malignant.  Benign tumours are the group that do not contain cancer cells.  Usually they can be removed and do not recur and do not spread to surrounding normally-functioning tissues and do not disrupt their functions.  Benign brain tumours have well demarcated borders and can be surgically removed.  However, they may compress on other normal tissues in the brain and prevent them from functioning normally.

Malignant brain tumours contain cancer cells.  They thread life.  They rapidly grow and spread to surrounding tissues and prevent them from functioning normally.  Usually, they survive by stealing the substances they need from the healthy brain tissue for rooting and feeding just like trees.

The central nervous system is very sensitive to pressure changes, especially since the brain is in a closed box (skull) that is very strictly protected.  Therefore, some benign tumours, although they do not contain cancer cells, they may be life-threatening by compressing on important structures.

Tumours originating from brain tissue are called primary brain tumours.  Secondary brain tumours are caused by the spread of other cancers to the brain.  Brain tumours are named according to the type of tissue they are originating from. The most common primary brain tumour is the gliomas.  These tumours are caused by the supporting cells of the nervous system.

Very short information on common brain tumours is given below.

Astrocytomas: They originate from a particular kind of glial cells, star-shaped brain cells called astrocytes. They can be seen in the brain, cerebellum, spinal cord. In adults, they are generally localized in the brain hemispheres, whereas in children they are commonly seen in the brain stem.  According to the grading system, grade 1 tumour is called pilocytic astrocytoma, grade 2 tumour is called diffuse astrocytoma, grade 3 tumour is called anaplastic astrocytoma and grade 4 tumour is called glioblastome multiforme. Grade 1 and 2 tumours are called low-grade, others are called high-grade tumours.

Ependymomas : They usually originate in the cells that line the wall of the brain called ventricles.  They can also be seen in the spinal cord.  Although they may occur in all age groups, they are usually seen in childhood and young adulthood.  They account for 2-9% of primary brain tumours.  They may spread into the cerebrospinal fluid.  It is considered that ependymomas revealing clinical signs at a young age show poor prognosis.

Oligodendrogliomas: They originate from the cells that produce a fatty layer called myelin, which is responsible for protecting the extensions of the nerve cells.  They grow slowly and do not spread to the surrounding tissues.  They are rare tumours that are more common at middle ages.  They account for 4-5% of primary brain tumours.  An important characteristic of these tumours is that they morphologically and radiologically show various degrees of calcification.

Medulloblastomas: Recent studies have shown that these tumours originate from primitive (developing) nerve cells that should not be left in the body after birth.  Therefore, medullablastomas are also called Primitive Neuroectodermal (PNET).  They usually develop in the cerebellum.  They are usually childhood tumours and are more common in men.  They account for 4-10% of primary brain tumours. And they account for 20% of brain tumours seen below the age of 20.

Meningiomas: They originate from the cerebral cortex (membrane) called meninx.  Since they are slowly growing tumours, which usually do not spread to the surrounding tissues, brain tissue can adapt to the presence of these tumours and they may remain without being noticed until they reach large sizes.  They are usually seen in women aged 30-50 years. More than 95% of them are benign. They account for of brain tumours.

Craniopharyngiomas: They originate in the region where the pituitary gland is localized.  They are usually benign, but they are sometimes called malignant since they damage the surrounding tissues. They are more common in children and young people.

Pineal region tumours: They are seen in the region where the pineal gland is localized.  Pineal gland is a small organ with deep localization in the center of the brain.  These tumours have two types that are slowly and rapidly growing.  They account for 3-8% of brain tumours seen in childhood and account for less than 1% in adulthood.  Approximately 80% of this region's tumours have malignant characteristic.

Brain stem tumours: They are common tumours mostly seen in children.  The rate of incidence in children is approximately 20%.  The median age of incidence is 3-9.  Gliomas form a specific group among the brain stem tumours and are divided into 4 groups  that are diffuse, cervicomedullary, focal, dorsal exophytic tumours. All of the diffuse tumours are malignant.

Angle tumours : The junction of cerebellum and brain stem is called angle.  Although various types of tumours can be seen in this region, the first tumour type of angle tumours reminds schwannomas, which is the tumour of eighth cranial nerve, vestibular nerve sheath that is responsible for hearing and balance. They are benign, slowly growing tumours.  They cause hearing and balance problems by compressing vestibulocochlear (hearing and balance) nerve.  If the tumour grows larger, it may cause numbness in the face by compressing the trigeminal nerve that is responsible for sensation in the face.  Larger tumours may cause facial paralysis and even life-threatening conditions by compressing on the brain stem.  These tumours, usually seen unilaterally, can be seen bilaterally with a genetic disease called neurofibromatosis type 2.  Unilateral type accounts for 8% of brain tumours.  Every year this tumour is seen in one in 100,000 people.  Early diagnosis plays a key role to able to treat it before causing serious problems. The first complaint in 70% of the patients is hearing loss.  Dizziness, headache, tinnitus are the complaints also seen in this disease.  Other complaints that may be seen in patients with larger tumours are facial paralysis, diplopia (double vision), dysphagia (difficulty swallowing), pain or numbness the face.  Specific tests are performed to determine the level of hearing loss.  If the diagnosis is suspected, MRI is performed to confirm the diagnosis.

Metastatic tumours: Metastasis is the spread of a cancer. If a cancer in other organ of the body spreads to the brain, it is called secondary brain tumour.  The cancer spread to the brain is the same as the original cancer and is called accordingly.  For example, when lung cancer spreads to the brain, it is called metastatic lung cancer.  Because the cells of metastatic tumour in the brain are similar to lung cells, not brain cells.  Treatment in secondary brain tumours depends on the origin of cancer, the extent of spread, the age and current health condition of patient, and the response of the previous treatment for the primary disease.

Treatment of Brain tumours

There are many factors that influence treatment preference.  These are the type, localization, size of the tumour and the condition of patient.  The options in children and adults are different from each other.  A specific treatment is planned for each patient.

Brain tumours can be treated by surgery, chemotherapy, radiation.  Many techniques can be used together according to the needs of a patient.  The treatment of the patient is usually carried out by a team.  This team includes a brain surgeon, a medical oncologist, and a radiation oncologist.  In addition, a physical therapist and speech therapist may also join the team.

Surgery is the first treatment option in many brain tumours.  If possible, the surgeon removes the entire tumour.  However, if the tumour cannot be removed completely without damaging the surrounding intact tissue, the surgeon removes as much of the tumour as possible.  Partial tumour removal helps reduce the complaints of the patient since it will reduce the intracranial pressure and reduce the size of the tumour tissue to be targeted with radiation or chemotherapy.

In some cases, the tumour cannot be removed.  In such cases, the surgeon only performs a biopsy and a small part of the tumour is removed.  The removed part is sent to pathology laboratory and the exact type is revealed by examining under the microscope.  This is an important source of information for planning the treatment.  Biopsy can be performed by open surgery or by a needle using special systems in patients whose general conditions are not appropriate.  The doctor puts a special frame on the head of the patient to obtain MRI and/or CT images.  Thus, the exact localization coordinates of the tumour tissue is obtained.  According to this information, a small hole is drilled on the head and the biopsy needle is targeted directly to the tumour and the biopsy specimen is collected.  This technique is called stereotaxy.

Radiation therapy (radiotherapy) can be administered in various forms.  In the method in which the radiation is delivered to the whole head through a large machine, the patients are irradiated for 5 days a week for a few weeks.  The duration of the treatment depends on the type and size of the tumour.  The purpose of administering the treatment in this way is to reduce the damage of the normal tissues.  Radiation can also be administered by direct placement of the special substance into the tumour surgically.  Depending on the radioactive characteristics of the substance placed, either a short-term administration is carried out or the substance is left permanently in the brain.

Stereotactic radiosurgery is the other treatment option.  The treatment is carried out in one session.  In many respects, high dose radiation is only directed to the tumour tissue.  Thus, normal brain tissue is not damaged.  This technique is called GAMMA KNIFE RADIOSURGERY.  It ensures a more effective, more accurate treatment technique in a shorter time.  The tumour size should be less than three centimeters to carry out this technique.

Chemotherapy is the use of drugs to kill the cancer cells.  It can be administered by a single drug or by the combination of multiple drugs at various doses.  The treatment may be administered orally or intravenously, or may be administered directly into the cerebrospinal fluid in the spinal column.

Patients treated with one of these treatment types visit for follow-up examination, the period of which is determined by doctors; at first follow-ups are more frequent then the periods are extended.  Changes of the tumour are monitored with CT or MR images during the follow-ups and a complete examination of the patients is performed.  Medical treatments are arranged if necessary.

Sources

1- Gazi University  Faculty of Medicine Gamma Knife Unit Web Page

2 Turkish Neurosurgical Society Publications, Basic Neurosurgery Book

Glial Brain tumour Pre-op MRI

Glial Brain tumour Post-op MRI