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Surgery for childhood brain and spinal cord cancer
Surgery is the primary treatment for childhood brain and spinal cord cancer. Surgery is used to:
- remove a sample of the tumour (biopsy) to find out the type of tumour and plan treatment
- remove as much of the tumour as possible (resection) while sparing neurologic function
- Many studies show that removing as much of the tumour as possible tends to slow the progression of the cancer and leads to longer periods of survival.
- debulk the tumour to reduce its size and relieve symptoms
- place a shunt inside one of the ventricles to allow the flow of cerebrospinal fluid (CSF)
- place an Ommaya reservoir in the brain to help deliver chemotherapy drugs directly into the CSF or tumour
Advances in technology have made it possible for doctors to do a biopsy in almost any area of the brain. For certain types of tumours, new technologies also allow surgeons to remove more of the tumour with fewer side effects. Surgical tools and techniques have become more intricate and allow surgeons to operate in tiny areas of the brain without disturbing the surrounding areas.
Even with improvements in tools and techniques, there are some tumours that can't be removed by surgery (unresectable). These could include tumours:
- in the "eloquent" areas of the brain that control speech, vision and movement
- Tumours can't be removed from these areas because the surgery would cause significant long-term effects.
- that have spread to other areas of the brain or spinal cord
- in the brain stem
- in the pineal or thalamic areas deep in the centre of the brain
Trying to remove these tumours may be too dangerous or would not improve the prognosis.
Brain tumours can often cause swelling of the surrounding normal tissue. This is called tumour associated edema or peritumoral edema.
- The swelling is due to a buildup of fluid in the tissue around the tumour.
- Swelling can increase intracranial pressure or worsen neurological symptoms, such as headache, nausea, vomiting and weakness.
- Doctors will often give corticosteroids before surgery to reduce the swelling, relieve symptoms and improve neurologic function. The 2 corticosteroids that are commonly used are dexamethasone (Decadron) and prednisone.
Brain tumours can also cause abnormal electrical signals within the brain, which can lead to seizures.
- Seizures are a common symptom of a brain tumour and are often the first sign that there is something wrong.
- Doctors may give anti-convulsants or anti-epileptic medications before surgery to control seizure activity. They may continue to give these drugs after surgery until the brain heals and the seizures stop.
Hydrocephalus can also occur in children with brain tumours. Hydrocephalus is a buildup of CSF in the brain. It occurs when the tumour blocks the flow of CSF through its normal channels and pathways around the brain and spinal cord. This blockage causes the CSF to build up in the ventricles which leads to an increase in intracranial pressure.
- Infants with hydrocephalus will have a bulging fontanelle (soft spot on the top of the head), an increase in head size or rate of head growth, vomiting, lethargy, seizures and high-pitched crying.
- Older children could have headaches, vomiting, irritability and seizures.
- Doctors may place a shunt (a tiny, soft piece of flexible tubing) into the ventricle before surgery to debulk or remove the tumour in order to drain the buildup of fluid, reduce the pressure in the brain and relieve the symptoms.
The type of surgery done depends mainly on the size and location of the cancer and other factors, such as the type of tumour and whether or not it is causing any symptoms. Side effects of surgery depend on the type of surgical procedure.
The surgeon will remove a sample of the tumour to find out what type of tumour it is. There are 2 types of surgical biopsy for brain tumours.
Stereotactic brain tumour needle biopsy
This is the most common type of biopsy.
- First, either a special stereotactic frame is placed on the child's head or MRI-compatible markers are placed on the child’s scalp. The frame or markers provide reference points that help the surgeon aim directly at the tumour.
- With the frame or markers in place, a CT or MRI scan is done to determine the exact part of the brain where the biopsy needs to be taken from. The surgeon uses this information to plan the biopsy.
- The child is then taken to the operating room for the biopsy.
- The surgeon makes a small cut in the scalp and then drills a small hole in the skull.
- Using the stereotactic plan, the surgeon inserts a biopsy needle into the brain tumour.
- A small piece of the tumour is removed and sent to the pathologist for examination.
Open brain tumour biopsy
An open biopsy is done when the tumour is near the surface of the brain.
- A small piece of the skull directly over the tumour is removed.
- The surgeon then takes a sample of the tumour.
- The small piece of skull is replaced and the incision is stitched together.
The goal of a tumour resection is to remove as much of the tumour as possible without affecting brain functions. This is more involved than a biopsy and will take longer.
- During the operation, an incision is made in the scalp. A piece of the skull is removed to expose the area where the brain tumour is growing. This piece of skull is often called the bone flap.
- An incision is then made in the dura mater and it is pulled apart slightly to allow the surgeon to identify and reach the tumour.
- The surgeon removes as much of the tumour as possible, usually starting in the centre of the tumour and working towards the outer edges.
- A special ultrasound machine is sometimes used to break up the tumour and make it easier to remove. The surgeon may also use a special operating microscope that helps to identify the edges of the tumour.
- Once the surgeon has removed as much of the tumour as possible, the dura mater is sewn together.
- The surgeon will decide whether or not to replace the bone flap. If the bone flap is replaced, the surgery is called a craniotomy. If it is not replaced, the surgery is called a craniectomy.
- The scalp is then sewn or stapled together.
A shunt may be needed if the brain tumour is blocking the flow of cerebrospinal fluid (CSF) and causing extra fluid to build up in the brain (hydrocephalus). A shunt is a narrow, soft, flexible piece of tubing. During surgery, the shunt is inserted through a small hole in the skull into one of the ventricles in the brain. The shunt has a valve system that regulates the pressure of the CSF and prevents fluid from flowing back into the ventricles. Many shunts have reservoirs that may be used to remove CSF samples.
A shunt may be temporary or permanent.
- Temporary shunts are usually external and are called an external ventricular drain (EVD). This means the tube is placed inside the ventricle and then connected to a container outside the body where the amount and pressure of the CSF can be monitored. At some point, the surgeon will clamp the shunt to see if the body can circulate and reabsorb the CSF on its own.
- There are 2 kinds of permanent shunts.
- A ventriculo-peritoneal (VP) shunt runs from the ventricle out to the scalp. From there, it runs under the skin, down the neck to the abdominal cavity (not the stomach). The CSF that drains into the abdominal cavity is reabsorbed into the blood stream. This is the most common type of shunt.
- A ventriculo-atrial (VA) shunt is similar to a VP shunt except that it enters a large vein in the neck and drains the CSF into one of the chambers in the heart. In the heart, the CSF enters the bloodstream and is filtered through the liver and kidneys along with other body fluids. This type of shunt is uncommon.
In some cases, a shunt isn’t used. Instead a surgeon makes a small hole, usually in the third ventricle, that allows the CSF to bypass the blockage and continue to circulate around the brain and spinal cord. This is called an endoscopic third ventriculostomy (ETV).
An Ommaya reservoir is a small dome shaped device that is placed under the scalp during surgery. A tiny tube connects the reservoir to the ventricles or to a tumour cyst. The reservoir may be used to get samples of CSF or to inject drugs, such as chemotherapy, which then circulate in the CSF throughout the brain and spinal cord. The reservoir may also be used to inject chemotherapy drugs directly into the tumour.
Stereotactic radiosurgery is not a surgical procedure. Instead, it is a form of radiation therapy that delivers a large dose of radiation precisely to the tumour while sparing healthy brain tissue.
Find out more about radiation therapy for childhood brain and spinal cord cancer.
The following types of surgery may be needed, depending on the type of treatments given.
Surgery to insert a central venous catheter
If a child is going to receive chemotherapy, the surgeon may insert a central venous catheter (CVC). A CVC may remain in place throughout treatment, or it may be removed once the most intensive part of treatment is done and maintenance therapy has started. The CVC can be used to withdraw blood and give intravenous fluids and medications. There are 2 types of CVCs:
- An external catheter (also called a Broviac, Hickman or central line) is a long, flexible tube that has one end inserted into one of the large blood vessels leading to the heart and the other end closed off outside the skin of the chest.
- A subcutaneous port (also called a Port-a-Cath) is a small metal chamber with a silicone rubber top that sits just under the skin of the chest. A small tube runs from the metal chamber into one of the large blood vessels leading to the heart. Whenever the port is used, a needle is inserted through the skin and into the silicone rubber part of the port.
Surgery to protect the ovaries
If a girl needs to have radiation given to her spine, surgery may be done to move her ovaries out of the radiation field, to protect their reproductive function. Another surgery is done after treatment to place the ovaries back to their normal position. This surgery is called an oophoropexy.
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