Family doctor

Brain tumours are among the most common childhood malignancies and they vary widely in their type, location, and growth rate.

 Epidemiology

Brain tumours are the most common solid tumours in children and account for 20% of all childhood malignancies, second only to leukemia. However, in the general population, brain tumours are still quite rare. The incidence of new pediatric brain tumours is approximately 3 per 100,000 children per year.

 Symptoms

Brain tumours can cause a myriad of symptoms. This can sometime lead to some difficulty in establishing the diagnosis. The symptoms caused by any brain tumour depend on its location, its rate of growth, and the age of the child.

Tumours in any location can cause increased pressure within the skull causing the child to experience headaches, nausea, vomiting, and double vision. In very young infants, the increased pressure may cause excessive, rapid head growth. Tumours located in the back of the brain (posterior fossa) can also cause unsteadiness and difficulties with speech and swallowing. Tumours located in the top part of the brain (supratentorial) can cause seizures (involuntary convulsions with or without loss of consciousness) or weakness of the arms or legs. Tumours located near the base of the brain (suprasellar) can cause visual problems as well as hormonal imbalances that can lead to several conditions including growth disorders.

Diagnosis

When a child develops symptoms that are suggestive of a brain tumour, the mainstay of establishing the diagnosis is through imaging of the brain. This is done by either a computed tomographic scan (CT scan) or magnetic resonance imaging (MRI). While these types of images will demonstrate whether an abnormal mass is present in the brain, in only a few cases will this be enough to establish what type of a mass it is. Aside from brain tumour, abnormal masses in the brain could be caused by infection, bleeding, or a long-standing congenital abnormality. In most cases, some form of surgery is required in order to remove a sample of tissue. By analyzing the tissue, one can know for sure whether the mass is a tumour and, more importantly, exactly what type of tumour it is.

 Treatment

The treatment of brain tumours varies greatly and is dictated by several factors including the size and location of the tumour, the age of the child, and the expected growth rate of the tumour. The main general modalities of treatment are surgery, radiation therapy, and chemotherapy.

 1-Surgery

Surgery for brain tumours can be performed for different purposes, depending on the type, size and location of the tumour. The possible goals of surgery may be one of or any combination of the following:

1. To remove as much of the tumour as is safely possible. One of the great difficulties in removing brain tumours, as opposed to tumours in other locations in the body, is that extreme care must to be taken to try to prevent harm to the very delicate brain tissue. For most childhood tumours, the prognosis is generally better if the tumour can be either totally or near-totally removed. Therefore, surgery remains the mainstay of therapy for the majority of childhood tumours.

2. To remove enough of the tumour to improve the patient's symptoms. For example, if a large tumour is causing increased pressure in the skull, or weakness of the arms or legs, or seizures, then surgery on the tumour may help relieve these symptoms.

3. To provide a tissue sample of the tumour. This tissue sample is analyzed by pathologists and this will tell the surgeon what type of tumour it is and, possibly, how aggressively it might be expected to behave. This will also help decide what type of treatment is needed.

 2-Radiation Therapy

Radiation therapy involves passing high energy radiation through the body. Radiation slows rapidly growing tissue, like tumours. Radiation therapy is often used in conjunction with surgical therapy. The dose and timing of the radiation regimen depends on the type of tumour. In some cases, radiation might only be applied to the local area of the tumour, whereas in other cases, an additional radiation dose might be given to the entire brain and spinal cord to try to prevent the tumour from seeding via the spinal fluid. Because of the fear that radiation therapy may adversely effect the very young, developing brain, it is usually not performed in infants and very young children. Potential side-effects of radiation therapy include hair loss, nausea, vomiting, fatigue, and local skin irritation.

 3-Chemotherapy

Chemotherapy involves giving very strong medications (directly into the bloodstream or occasionally as pills) that preferentially destroy tumour cells. There are numerous drugs that may be used for various types of brain tumours. Although some chemotherapy drugs can improve the survival of children with certain brain tumours, the drugs themselves can have substantial side-effects, including severe nausea, hair loss, and risk of infection.

 Experimental Therapies

There are some other forms of therapy that are currently being studied but have not been established as conclusively showing benefit, e.g., gene therapy. These types of therapies are usually only offered in the context of a clinical trial at large hospitals. As well, new types of radiation or chemotherapy are also being studied and may also be offered in the context of a clinical trial.

 Types of Brain Tumours

There are several different types of brain tumours that can affect children. Only some of the more common ones will be discussed here. It is important to note that for most childhood tumours, the optimal therapy and the prognosis depend greatly on the particular features of the individual case. The following provides only a simplified overview. The actual factors that go into the decision-making process for any single child is very complex and must be decided by the child's physicians and surgeons. As well, therapy for individual tumours can change rapidly and many new treatment regimens are being studied every day at most large children's hospitals.

 Astrocytoma

Astrocytomas are tumours that can either be low-grade or high-grade. The low-grade variety is commonly found in the back of the brain (posterior fossa) and these account for approximately 10% of all childhood brain tumours. They may, however, also be located in the top of the brain (supratentorial). Surgical removal of these tumours, especially in the posterior fossa, carries an excellent prognosis for complete cure. If full removal is not possible, children may simply be watched with regular brain imaging or receive radiation or chemotherapy. The overall prognosis for these tumours is very good.

Another distinct location for the low-grade astrocytoma is in the optic tract or hypothalamus, located near the front of the brain behind the eyes. These tumours account for 3-6% of tumours in children and are sometimes associate with neurofibromatosis type 1. Although these tumours are low-grade, their behaviour varies from very slow-growing to fast-growing. For very small tumours with brain images that clearly reveal the diagnosis, treatment usually consists of just watching with repeated brain imaging. Surgery is sometimes performed either to establish the diagnosis and/or to remove as much of a larger tumour as possible. This is followed in very young children by chemotherapy and in older children by some combination of chemotherapy and radiation therapy.

High-grade astrocytomas are most commonly located in the top of the brain (supratentorial). Treatment usually consists of a combination of surgery, chemotherapy, and radiation. These are quite aggressive tumours and the prognosis is much worse than for the low-grade variety.

 Ependymoma

Ependymomas most commonly occur in the back of the brain (posterior fossa) and account for 10-15% of childhood brain tumours. Therapy consists of surgery, attempting to remove as much of the tumour as is safely possible, and radiation therapy. Chemotherapy has so far shown little benefit for these tumours, but can be helpful in very young children for whom radiation therapy is being avoided.

 Medulloblastoma

Medulloblastoma is another common tumour of the back of the brain (posterior fossa), accounting for 15-20% of all childhood brain tumours. Treatment initially consists of surgical removal. This is usually followed by radiation therapy, which frequently involves radiation to the entire brain and spinal cord to prevent the spread of the tumour to another location. Depending on the extent of the tumour, chemotherapy may also be considered.

 Brainstem Glioma

The brainstem is the central area of the brain, where all the nerve fibers that travel between the brain and body meet. Tumours that arise in this delicate location are usually gliomas that can either be high-grade or low-grade and together these account for 10-20% of all childhood brain tumours.

High-grade brainstem gliomas are very difficult to treat. They may be diagnosed based on brain imaging alone. Surgical removal is extremely difficult and so therapy is usually confined to radiation and, sometimes, chemotherapy. Low-grade brainstem gliomas are quite different and sometimes need no urgent therapy. They can sometimes simply be watched with repeated brain imaging. It is not uncommon for these to remain unchanged for many years.

Tumours in the brainstem are particularly prone, due to their location, to obstruct the flow of the brain's natural fluid. This causes a build-up of fluid in the brain (hydrocephalus) and increased pressure in the skull. The treatment for this can involve either placement of a silastic tube (shunt) to drain the fluid into the abdomen or the creation of a separate hole in the brain to divert the tumour obstruction (endoscopic third ventriculostomy). Hydrocephalus and its treatment is dealt with in more detail in a separate article on this website.

 Craniopharyngioma

Craniopharyngiomas account for about 6-9% of childhood brain tumours. These tumours are located near the optic nerves and the pituitary gland, so they frequently cause visual problems and hormonal imbalances. The standard therapy for these tumours is surgery, attempting to remove as much of the tumour as is safely possible. Total removal of the tumour is very difficult and, because of its location, visual disturbances and hormonal imbalances are not uncommon after surgery. Radiation therapy is occasionally used if substantial tumour remains after surgery or if the tumour shows re-growth.