A brain tumour is an abnormal growth of brain tissue within our skull cavity. It can arise from the inner portion of skull bone, the membranes covering the brain and from the various types of cells making up the brain. A brain tumour is usually discovered after performing a computed tomography (CT) or magnetic resonance imaging (MRI) scan. There are various symptoms that one may experience that prompts your doctor to request for such an investigation. Examples of such symptoms are:
The MRI or CT scan that is performed can give a provisional diagnosis as to what the brain lesion may be but it may not be confirmed that it is a tumour. The other possible different diagnosis include an infection (brain abcess) or abnormalities from blood vessels.
If the lesion is likely to be a tumour, it could either be a benign or malignant growth. In the brain however, because of the constrains of the skull cavity; a growth within the confined space has the propensity to compress adjacent tissues and cause potential damage and may even eventually be a danger to life.
After a brain lesion is discovered, majority of the patients will require surgery in order to confirm the diagnosis and plan for appropriate subsequent treatment. In certain circumstances, a small lesion that is discovered may not cause any neurological symptoms or do not have obvious features on the CT or MRI scan suggesting infiltration to surrounding brain tissue. Such patients may be monitored closely with follow-up repeat scans at regular intervals and surgery planned if the lesion progresses.
Once a brain lesion is discovered, most patients are usually started on medications to prevent fits caused by the lesion causing irritation to the surrounding brain tissue. Patients may also be started on steroid medications to reduce the swelling of surrounding brain tissue caused by the tumour. The reduction in swelling will also help improve the neurological symptoms of head, nausea, vomiting or limb weakness.
Surgery for brain tumours requires a procedure called a craniotomy.
Brain lesions which are benign and located near the surface of the brain can usually be completely removed with minimal disturbance or injury to the adjacent brain tissues. Brain lesions that are infiltrative in nature do not have a well defined margin, hence it may not be possible to completely remove all of the tumour. In addition, there are also certain crucial areas of the brain responsible for vital neurological functions and it is not possible to remove tumours involving these areas without causing serious neurological consequences. In such cases, a stereotactic biopsy may be performed instead to obtain cells for further testing.
Stereotactic Biopsy
This is a procedure by which we can obtain a sample of cells originating from a brain lesion in order to confirm the diagnosis and guide treatment.
The procedure is usually performed under general anaesthesia or may be done under mild sedation. A small incision is made on the overlying scalp at the relevant location and an area of skull is exposed. A bone drill is used to create a 5 cent coin diameter size hole and the membrane covering the brain is cut open. With the guidance from sophisticated computer technology, we can accurately target the lesion in question with special instruments and obtain a sample of cells. As with most neurosurgical operations, this procedure carries a risk of bleeding, injury to brain structures, infection and fits.
It is important to note that there is a 5% chance of failure of this procedure in that we may not be able to obtain significant or positive results to guide further management. The sample of cells obtained in such a biopsy may also not reflect the nature of the remaining cells around the lesion and hence may lead to a false sense of security if it is negative. In such cases of a non-diagnostic result, the recommendation would be to perform an open biopsy in which a craniotomy procedure will have to be performed.
After surgery is performed, the cells are sent for analysis and this takes about 5 to 7 days. Once the results are known, the decision can be made if further therapy such as radiotherapy or chemotherapy is necessary. If this is required, one will be referred to the neuro-oncologist to decide on chemotherapy and to the therapeutic radiologists for a decision on starting radiotherapy.
Recovery may at times be limited by the extent of damage caused by the tumour and by the brain’s ability to recover. Therapists are available to commence physiotherapy, occupational therapy and speech therapy in the wards. If there is persistent disability, the patient may be transferred to the Department of Rehabilitation Medicine or to a nursing care facility for a further period of rehabilitation to maximise the recovery process. To fully benefit from rehabilitation, the patient and family should maintain a positive attitude, set realistic goals and work steadily to accomplish each goal.
The World Health Organisation has very complicated classification systems for the multitude of different possible brain tumours that occur in the brain.
The common brain tumours encountered include:
Meningioma
This is a tumour arising from cells originating from the membrane covering the brain surface called meninges. Meningiomas account for 15% of intracranial tumours. They commonly occur in the fourth through sixth decades of life. Meningiomas are more common in females; they are rare in children (only 1.5% of all meningiomas occur in childhood). Ninety percent of meningiomas are intracranial. The meninges surround the brain completely hence such tumours can occur at many various locations around the brain and compress on brain structures producing the associated symptoms. The clinical symptoms and signs of meningiomas are related to those of an intracranial mass lesion or seizure. The tumour has a predilection for certain regions and produces symptoms and signs specific to the tumour's location. The clinical course of a meningioma characteristically spans a period of years. The tumours which are located along the midline of the brain or along the base of the brain are often associated with important blood vessels and nerves, hence making surgery more difficult and challenging. In such cases the risk of postoperative neurological deficits will be increased.
They are usually benign tumours which do not infiltrate into surrounding brain substance hence most tumours do not require further treatment after complete surgical removal. If there are areas of tumour which cannot be removed because of close proximity to important blood vessels or nerves, then post-operative radiotherapy or radiosurgery may need to be performed. In a small proportion of them, the cells are more aggressive and can turn into a malignant form of tumour or have the propensity to recur with a higher percentage even after complete removal. Patients with these more aggressive tumours will need to be treated with radiotherapy after surgery.
The following are the various types of meningioma based on the location where they occur:
Convexity Meningioma
More than 70% on convexity meningiomas are in the frontal region. If located in this region they may remain asumptomatic while growing to a large size. Epilepsy and focal neurologic signs are common. These meningiomas have the best potential for total removal.
Parasagittal Meningioma
These meningiomas arise in association with the superior sagittal sinus and are located in the midline. They often cause focal epilepsy and later paralysis, especially of the lower extremities.
Falcine Meningiomas
Tumours arising from the falx are located in the midline and often extend to both sides of the brain. These tumours are difficult to remove totally and often recur after surgery.
Olfactory Groove
Olfactory groove meningiomas arise from the cribriform plate. They grow bilaterally and become large without causing significant neurologic deficits or evidence of increased intracranial pressure. Loss of smell can often be the only symptom. Changes in mental status are seldom striking until the tumour has reached a large size. Once the tumour becomes large it impinges on the optic nerves and chiasm resulting in visual loss.
Tuberculum Sellae Meningioma
These meningiomas arise from the planum sphenoidale, tuberculum sellae or the diaphragm sellae. They cause early and characteristic visual failure. Typically, loss of visual acuity and field is progressive and asymmetric, although it can be sudden.
Sphenoid Ridge Meningioma
Meningiomas of the sphenoid ridge are traditionally divided into three types: outer, middle, and medial. The outer sphenoid ridge meningiomas are usually accompanied by epilepsy, focal weakness, and trouble with language function when present on the left side. The tumours of the inner sphenoid ridge usually compress the optic nerve and present with early unilateral visual loss. They also may involve the cavernous sinus to cause double vision and numbness of the face.
Posterior Fossa Meningioma
These constitute about 10% of all meningiomas. The neurologic findings in these tumours can be a combination of posterior fossa and supratentorial symptoms. These can be headache, language disturbance, visual changes, nausea/vomiting, and balance difficulties. These tumours can also cause extensive cranial nerve findings, including facial weakness, hearing loss, swallowing difficulty, and facial numbness. Some of these symptoms may mimic the usual symptoms seen with acoustic neuromas. Finally, some of these tumours may cause weakness and spasticity.
Metastatic Tumour
These are tumours that spread to the central nervous system (brain and spinal cord) from other organs in the body. Cerebral metastases are the most common brain tumour seen clinically. These tumours usually spread to the brain via the blood stream where they reach the brain to divide and produce a metastatic tumour. Head and neck tumours may reach the brain by direct spread from surrounding areas. The common tumours that spread to the brain include cancers involving the lung, breast, kidneys, intestines and skin.
CT or MRI scans are used to identify the tumours within the brain and often multiple tumours are found 35-50% of the time. When metastatic disease is suspected based on imaging or on surgical tissue, it is necessary to search for the primary location where the tumour arose from. Investigations will include a chest x-ray as well as CT scans of the chest, abdomen and pelvis.
Initial treatment will involved the use of anticonvulsants to prevent seizures and steroids to decrease the amount of swelling. The subsequent treatment will depend on the stage of the illness, patient factors, location and number of tumours within the brain. Treatment will usually involve radiotherapy with or without prior surgery and the oncologist will then further decide if chemotherapy is necessary. Stereotactic biopsy may be considered for certain lesions to establish the diagnosis.
Glioma
The brain is made up of neurons (nerve cells) and tissues that support the neurons (glial cells). A glioma is a tumour in the brain that arises from these supporting cells of the brain neurons. The common cells causing such tumours are called astrocytes. They develop into tumours called astrocytomas. These tumours are classified into 4 grades. Grade 1 and 2 tumours are considered low grade while grade 3 and 4 tumours are high grade. The highest grade tumour (grade 4) is also called a glioblastoma. This grading system tells us how malignant and aggressive the tumour is and how fast it may grow. The grading of such tumours are decided by the pathologist (a doctor who looks at the cell sample obtained at surgery) when they are analysed under microscope. Low grade tumours have a better outcome after treatment and patients have a longer survival rate when compared to patients with high grade tumours.
Surgery is usually the mainstay of treatment for gliomas. After surgery, other therapies such as radiotherapy or chemotherapy may be necessary. The other form of treatment which is suitable for some tumours is the use of radiosurgery.
The following three factors generally affect the prognosis of a patient with brain tumour. They are 1) age, 2) histological features seen on pathological examination of the tissue, and 3) performance status (degree of neurologic or functional impairment). In general, younger age carries a better prognosis.
Astrocytomas
An astrocytoma is a type of glial tumour. Glial cells, which are "supportive" cells that help brain cells (neurons) function, are the most common cellular component of the brain. The most common type of glial cell is an astrocyte. Glial cells have a greater potential for abnormal growth and are the chief source of central nervous system tumours.
Glioblastoma
Glioblastomas are the most common primary central nervous system neoplasm, representing 15% to 20% of these tumours. Approximately half of all astrocytomas are glioblastomas. The diagnosis of high-grade glioma is made by biopsy. If a tumour is suspected based on MRI (or CT) imaging, definitive diagnosis can only be made by direct examination of a tissue specimen. In general, the larger amount of tissue that is examined reduces the chances of making an incorrect diagnosis due to "sampling error." Therefore, needle biopsies are typically limited to cases in which a direct open surgical procedure is not advisable due to surgical risk.
Surgery
If the tumour is surgically accessible, an attempt to remove the tumour mass visible on the MRI scan is made. Although doing so is not curative, several clinical studies suggest that the degree of removal of tumour can affect the duration of survival. In some cases, tumour may be located very close to adjacent important brain centers responsible for control of movement or speech. Our neurosurgeons have the skill to combine advanced diagnostic imaging techniques pre-operatively plus intra-operative mapping techniques to ensure maximal safe removal of the brain tumour.
A powerful 3-T MRI scanner that is capable of non-invasively speech and motor areas of the brain. This information can be transferred to the intra-operative neuronavigational system used by the surgeon to determine the exact corresponding location on the patient's brain while performing the surgery.
Once the diagnosis is confirmed, higher grade astrocytomas usually undergo radiation therapy. Radiation can be administered to the whole brain or it can be relatively focused to a region of the brain.
Radiotherapy
The purpose of radiotherapy is to kill a percentage of tumour cells and slow down the rate of growth of the tumour. This treatment is performed and planned by specialist doctors called therapeutic radiologists.
Low grade tumours that are treated with radiotherapy after surgery may help with a cure but as for high grade tumours, the role of radiotherapy is to control the growth of tumour and help prolong survival. Radiotherapy is given in small daily doses over a period of 4 to 6 weeks. Each session lasts only about 15 minutes and it is a painless procedure like taking an x-ray. The common side effects of radiation therapy include hair loss, dizziness, generalised weakness and drowsiness. Serious side effects are rare. An MRI is usually obtained about 2 to 4 weeks after the end of radiation therapy in order to judge the effect of treatment.
Chemotherapy
Chemotherapy is a specialised treatment involving administration of very strong medical agents that are able to destroy and kill some tumour cells. This treatment is decided by the oncologists (cancer specialist). Treatment is usually given depending on the grade of the tumour. The treatment may be given simultaneously together with radiotherapy or at a later date if the tumour recurs and has failed treatment with radiotherapy. The treatment is given at specific intervals over a period of time. There are often many potential side effects depending on the types of agents given and these will be discussed with you by the oncologists before treatment commences.
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