What Are Meningiomas?
Meningiomas are “brain tumours” although they do not grow from brain tissue. They arise from the meninges - the thin tissue covering the brain and spinal cord. They usually grow inward causing pressure on the brain or spinal cord, although occasionally they also grow outward and cause the skull to thicken.
They are usually benign i.e., non-cancerous, and slowly growing, and often grow to a large size before showing symptoms.
They are the most common tumour in Singapore, and occur most often in people between 40-60 years of age. Benign meningiomas occur in both men and women.
The first symptoms are usually due to increased intracranial pressure caused by the growing tumour. Seizures and headaches are common symptoms. Other symptoms depend on the size and location of the tumour.
Like other brain tumours, the cause of meningiomas is unknown. In some cases, an abnormal chromosome #22 has been found, but what causes this chromosome abnormality is uncertain.
The diagnosis may be suspected from symptoms and the neurological examination, but CT and/or MRI scans are required to determine the location, size and probable type of tumour.
Surgery is the primary treatment for meningiomas in the brain or spinal cord. Surgery often involves removal of the tumour, part of the meninges and abnormal bone. Some tumours can only be partially removed because of their location or adherence to vital brain structures. Partial removal will relieve symptoms, and because tumour growth is slow, it could be many years before further treatment, if any, is necessary.
Several surgical “tools” are available to help the neurosurgeon during surgery. High-powered operation microscopes allow the surgeon to see the tumour and vital structures clearly. Ultrasonic aspirators may be used to break up and suck out the tumour. In some cases where the tumour has a rich blood supply, cerebral angiography (X-ray of the blood vessels of the brain) may be required to allow embolization (blockage) of the tumour blood supply.
Surgical removal of benign meningiomas usually provides a cure. The length of recovery after surgery varies according with the age and general health of the patient, the location and size of the meningioma. Steroids are often given to reduce brain swelling around the tumour before and after the operation. Anti-convulsants may be used to control seizures before surgery or prevent their occurrence after surgery. Weakness, co-ordination or speech problems may occur after surgery. Physical, occupational and speech therapy may help reduce these impairments which are often temporary in duration.
In the elderly, small meningiomas may be monitored frequently and brain scans done during the period of observation to see whether the tumour is enlarging in size. Surgery can be avoided if the tumour does not increase in size. New symptoms or signs must be reported to the attending doctor so that he can reassess the situation.
Radiation treatment may be used for meningiomas that cannot be operated on for medical reasons, when total removal was not possible or for small recurrences. Radiosurgery is carried out using the Novalis Shaped-Beam machine located at the NNI-Khoo Teck Puat Radiosurgery Suite at Singapore General Hospital (SGH) Level B1, Block 2. This delivers narrow beams of strong radiation aimed precisely at the tumour from many different directions. Normal brain tissue therefore receives only a fraction of the total radiation dose received by the tumour. Exact knowledge of the tumour location is necessary, and this is achieved by securing the head firmly but painless in a custom-made mask system and doing a computed tomography (CT) scan of the head with the mask system in place. For treatment planning, a magnetic resonance imaging (MRI) scan of the head is also required.
Recurrence can however occur when the entire tumour or its meningeal origin cannot be removed by surgery or killed by other treatment, or when it is of a malignant nature. The recurrence rate is also higher when the tumour has a typical features. It is therefore important that the patient comes for regular follow-up and CT or MRI Scans that may be ordered by the neurosurgeon from time to time. Treatment for a recurrent meningioma may be a second surgery or radiosurgery. For recurrent malignant meningioma, second surgery, radiation therapy or chemotherapy may be used.
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