Neurosurgeon

Gliomas

Gliomas are the most common brain and spinal cord tumour, making up about half of all brain tumours. The cause is unknown and only rare cases are inherited. A glioma is a tumour of glial cells. Glial cells are the cells which form the "glue" of the brain... i.e. they help hold the nerve cells together. There are three types of glial cell and therefore three types of glioma:

2. The oligodendrocyte makes myelin, an insulating sheath around nerve cells. Loss or damage to myelin slows down nerve conduction (myelin is damaged in multiple sclerosis, which has nothing to do with brain tumours). A tumour is called an oligodendroglioma and makes up about 5% of gliomas. We are increasingly finding that there are mixed tumours containing both astrocytoma and oligodendroglioma, so the proportion of gliomas which are oligodendrogliomas is actually higher than 5%. These mixed tumours respond better to chemotherapy than pure astrocytomas.

3. The ependymocyte is the cell which lines the ventricles, or cavities within the brain and spinal cord. A tumour is called an ependymoma, which make up about 5% of gliomas. These tumours are more common in children.

Pathologists classify gliomas into four types (some parts of the world only talk about three types). These types are called grades. Grade 1 is the slowest growing. Grade 4 is the fastest growing and is also known as a glioblastoma or glioblastoma multiforme.

Grade 1 - these usually occur in children and can be cured with surgery. The most common example is the juvenile pilocytic astroctyoma, which often occurs in the cerebellum.

Grade 2 or low grade astroctyoma usually occurs in adults, as with grades 3 and 4. It is also called simply astrocytoma or diffuse astroctyoma.

Grade 3 - anaplastic astrocytoma is also called malignant astroctyoma.

Grade 4 - glioblastoma multiforme contains dead tissue within it.

Glioma cells are quite different to a lot of other tumours outside the brain. Firstly and primarily, these tumours spread locally. I use the analogy of "black sand in white sand". Secondly, they rarely spread to other parts of the body... e.g. lungs, bones. Sometimes they may spread within the spinal fluid spaces. There are no clear boundaries, which is why they tend to regrow after removal. In fact, it is unusual to be able to cure these with surgery because of the tendency for the tumour cells to extend well beyond where they can be seen on x-rays or at surgery. This is why gliomas tend to regrow at the site of the original problem.

Because there is usually no cure for gliomas, there are many treatments to be found. Only surgery, radiotherapy and chemotherapy have been proven to help. There are many experimental therapies available. It is reasonable to pursue these when they are being done in a controlled trial situation... i.e. are being scientifically studied. These include gene therapy, dendritic cell therapy, immunotherapy, photodynamic therapy, and others. There are many completely unsubstantiated therapies and I urge you to be careful pursuing these. Too often I have seen patients and their families misled and financially disadvantaged.

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Meningioma

Meningioma is a tumour of the coverings of the brain and spinal cord. These coverings are called the meninges. Meningitis is an infection of the meninges. Meningioma is a tumour of the meninges. They tend to grow on the surface of the brain, which can be at the base of the skull, and compress the brain or spinal cord. Surgery is the primary treatment and many meningiomas can either be cured or controlled for the life of the patient. Most meningiomas are benign but a few are more aggressive and tend to recur, and are called "atypical" and are rarely malignant (also called anaplastic). These aggressive meningiomas may require standard radiotherapy. Sometimes a very localized form of radiotherapy - called stereotactic radiosurgery - can be used for small tumours (less than 3cm).

Pituitary tumour

Pituitary tumours, or pituitary adenomas, are almost all benign tumours of the anterior (front) part of the pituitary gland which produces several important hormones (chemical messengers) that control other glands in the body... e.g. thyroid, adrenal, testes and ovaries.

The anterior pituitary gland produces the following hormones:

• FSH - or follicle stimulating hormone - stimulates the ovaries to produce eggs but is also important in the male for fertility.

• LH - or luteinizing hormone - stimulates the ovaries to produce progesterone to help prepare the uterus for reception of a fertilized egg.

• ACTH - or adrenocorticotrophic hormone - stimulates the adrenal gland to produce cortisol and aldosterone, two very important hormones.

• TSH - or thyroid stimulating hormone - stimulates the thyroid gland.

• GH - or growth hormone - stimulates the liver to produce ILF-1, which stimulates many cells in the body to grow.

• Prolactin is necessary for milk production.

The posterior pituitary gland produces two hormones:

• Antidiuretic hormone - this hormone prevents the kidneys from losing many litres of water per day.

• Oxytocin - is important for the release of milk when a baby suckles the breast.

The posterior pituitary gland rarely forms tumours so this discussion will be on anterior pituitary tumours.

Broadly speaking, there are two sizes of pituitary tumours - macroadenomas (large tumours over 1cc) or microadenomas. 1cc is the important size criterion because the bony space (pituitary fossa) in which the gland sits is 1cc. Therefore, a macroadenoma is a tumour which enlarges and/or spills out of the pituitary fossa. A pituitary tumour can either be functioning or non-functioning. If functioning, it produces an excess of one type of hormone (rarely two). The most common type of functioning tumour is a prolactinoma, one which produces excess prolactin. This usually presents in young women as absent periods (amenorrhoea) and/or infertility.

The following tumours produce characteristic problems:

• Prolactin: prolactinoma - amenorrhoea or infertility in women and impotence in men.

• Growth hormone - excess causes acromegaly where soft tissues enlarge... e.g. nose, tongue, fingers, heart and other conditions develop such as hypertension and diabetes mellitus. In children, excess GH produces gigantism.

• ACTH - excess causes Cushing's disease where patients develop obesity, hypertension, diabetes mellitus, easy bruising, depression and other psychiatric problems, osteoporosis and other problems.

• TSH - tumours are rare and are a rare cause of a hyperactive thyroid gland.

Tumours may be both macroadenomas and functioning. The problem with macroadenomas is that once they become large enough, they may press on adjacent nerves. The major nerves next to the pituitary gland are the optic (eye or vision) nerves which sit above the gland. Visual loss is the most common presentation of a non-functioning macroadenoma. If left untreated it can produce blindness. Less often, macroadenomas can enlarge sideways to compress the nerves which move the eyes (cranial nerves 3, 4 and 6) and the nerves which supply feeling to the face (nerve 5). Rarely, a pituitary tumour can enlarge dramatically and suddenly, producing sudden blindness, abnormal eye movements or facial numbness, a condition called pituitary apoplexy (pituitary stroke) which requires urgent treatment. The other problem with a macroadenoma is that it can compress the normal pituitary gland to produce a lack of production of the normal hormones, which will then need replacement.

Treatment of pituitary tumours requires the help of an endocrinologist, or hormone specialist. Sometimes pituitary tumours can be treated with drugs, particularly prolactinomas which usually don't require surgery, particularly if they are microadenomas. Some tumours are only partly responsive to drugs and also require surgery and/or radiotherapy, particularly GH and ACTH producing tumours.

If surgery is needed there are two approaches used:

Pituitary surgery is usually performed through the nose (transsphenoidal surgery) using a microscope and/or endoscope and is only rarely done using a craniotomy. Post-operatively there is not much pain because the cuts have been made deep in the nose. The main discomfort relates to nasal packing for 24 hours post-operatively. Sometimes some fat is removed from the abdomen to seal the back of the nose from possible spinal fluid leak. Occasionally a spinal drain (a fine tube in the low back) is needed to drain spinal fluid for a few days in order to avoid a spinal fluid leak through the nose.

• Craniotomy - means performing a skull opening through the forehead or temple. This is rarely required and is used when tumours are quite large and extend sideways.

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Acoustic neuroma

This is a tumour of the 8th cranial nerve. There are 12 pairs of cranial nerves. For example, the 2nd nerves are the optic nerves which supply vision. The 8th nerve provides hearing (acoustic nerve) and balance (vestibular nerve). In fact, about 90% of acoustic neuromas arise from the balance part of the 8th nerve and really should be called vestibular tumours.

Not only this, but they are not even neuromas (nerve tumours) but are actually tumours of the lining sheath of the nerves. The linings of nerves outside the brain are made by Schwann cells and tumours of these cells are thus called schwannomas. Therefore, these tumours should really be called vestibular schwannomas.

These tumours tend to cause gradually increasing deafness rather than any balance problems, surprisingly. Once large, they compress the brain stem, the stalk that the brain sits on. Surgery has been the mainstay of treatment and is usually curative. More recently, stereotactic radiosurgery has been used for small (less than 3cm) tumours. This is being increasingly used but tumours tend to shrink rather than go away and lifelong 1-2 yearly scanning is required. Nonetheless, radiosurgery appears to be a valid treatment option.

There are three types of surgery for acoustic neuromas:

1. Posterior fossa approach means approaching from the back of the skull. This is done when hearing is trying to be preserved.

2. Translabyrinthine approach is the fancy term for going through the inner ear and cutting behind the ear, which necessarily sacrifices the hearing apparatus. This approach is done by an ENT (ear, nose and throat specialist), often in conjunction with a neurosurgeon. The great advantage of this approach is that much pressure is placed on the brain stem compared to a posterior fossa approach. This approach probably also protects the facial (7th) cranial nerve better than a posterior fossa approach.

3. For quite small tumours the middle fossa approach, done above the ear, is good but is rarely done. Hearing is usually intact preoperatively and can be preserved.

In the bad old days the major concern with this type of surgery was killing the patient. These days the main concern is preservation of normal facial movements, controlled by the facial nerve. The facial nerve is intimately related to the 8th nerve, traveling for a few centimetres directly beside each other.

To help protect the facial nerve, its function is continuously examined throughout surgery by using electrical monitoring. If the facial nerve is damaged with surgery, it usually improves. If facial movements remain poor, there are various operations that can be done to improve function but usually the face does not return to normal.

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