Brain tumours are usually classified as primary or secondary
tumours. Primary tumours arise from the brain or its covering(dura
mater), and secondary tumours have migrated(metastasized) to the
brain from sites such as lung or breast cancers.
Primary or secondary tumours occur with roughly the same
frequency. As our population continues to age, however, the relative
proportion of metastatic tumours will increase. The latter are all
cancers, whereas approximately half of primary tumours are benign. It
is to date an unexplained peculiarity that it is exceptionally rare
for a primary, malignant tumour to metastasize outside the brain and
spinal cord. A variety of studies over the past few decades have
suggested that there has been a slight rise in the incidence of new
primary brain tumours, resulting in concern in some quarters.
However, the most likely explanation for this phenomenon is merely
the advent of CT and MR scanning over this period. They have allowed
earlier detection of smaller tumours than was previously possible.
The cause of most primary tumours is unfortunately unknown at
present, although immunossuppressant drugs and radiation to the head
are responsible in some cases. Much speculation exists regarding a
possible carcinogenic(cancer-causing) role for mobile(cell) phones.
However, there is presently no conclusive scientific evidence
substantiating this. In such a situation, it would be wise to
moderate use of mobiles(particularly when driving!) until more
definitive data are available. Children, with thinner skulls, may be
theoretically more vulnerable to harmful effects of cell phones.
Symptoms Caused by Brain Tumours
Brain tumours may give rise to a large number of different
symptoms,depending on their exact position in the brain and how
quickly they are growing.These may include
1-Headaches; these will be present in over half of patients
and will usually have been present for some time.They may be worse in
the morning and possibly associated with vomiting.It is important
however to realise that most headaches are in fact not caused by
brain tumours.It is important to discuss any persistent headaches
with your doctor to clarify if there may be any concerning
2-Seizures;a brain tumour may cause a variety of different
seizures.Any new or unexplained seizures should be carefully assessed
3-Mental Changes; these may include certain forms of
depression,confusion,memory loss and personality changes.
A detailed neurological examination will provide further useful
information and prompt the need for further testing.
Diagnosis of brain tumours requires imaging studies. CAT scans are
often initially used, but today more and more tumours are detected
with MRI. MR(Magnetic Resonance) images offer exquisite detail of
brain anatomy and pathology and assist the surgeon in planning safer
surgical corridors. Brain images are often suspicious of certain
tumour types, but in the majority of cases it is necessary to obtain
a sample to confirm the exact diagnosis.
Different types of Brain Tumours
The most common primary brain tumour is called an astrocytoma, as
it is derived from star-shaped cells called astrocytes. They are the
most numerous cells in the brain, and provide structural and
nutritional support to the nerve cells(neurons). Neurons are the
'hardware' of the brain that allow thought processes to occur.
Astrocytomas are graded from 1-4, grade 1 being benign and and grade
4 highly malignant. Grade 4 is commonly termed "glioblastoma
multiforme". Astrocytomas are also called gliomas, as the word glial
is derived from the Greek for glue, explaining the role of astrocytes
as "brain glue". Unfortunately, the majority of astrocytomas are
malignant(grades 3 and 4). A rarer form of glioma, oligodendroglioma,
is derived from oligodendrocytes. These cells produce a fatty sheath
that insulates the processes going to and from the neurons, much as
an electrical wire is covered in a plastic coat.
Gliomas present in a variety of ways. Patients may develop severe
headaches, often worse in the morning and accompanied by vomiting.
Seizures can occur, and weakness may affect one side of the body.
Personality changes are common.
Meningiomas are tumours derived from the membrane covering the
brain, the dura mater(latin for "tough mother"). The vast majority
are benign. They are often decorated with special proteins(receptors)
that recognize oestrogen and progesterone. Women that have
meningiomas are twice as likely to have breast cancers. Meningiomas
have similar symptoms to gliomas.Pituitary tumors are also commonly
occurring, benign tumours. They arise from the pituitary gland at the
base of the brain, and frequently release hormones. These hormones
may affect bodily function considerably, depending on which ones are
manufactured. Excessive growth hormone, for example, can cause people
to become giants(you may be familiar with the James Bond character
"Jaws" who had this condition). These tumours can also press on optic
nerves, resulting in blindness. The next most common tumour type is
the acoustic neuroma, which is also called a vestibular schwannoma or
neurilemmoma. These benign tumours press on the acoustic ( eighth
cranial) nerve, resulting in deafness, ringing in the ears(tinnitus)
and balance difficulty. They may occur on one or both sides of the
Patients with a brain tumour will require referral to a brain
surgeon, and the majority will undergo an operation to either biopsy
or excise the tumour. Tumours that are benign and not located in
"eloquent" brain regions(eg speech cortex) can be resected, often
resulting in a cure. This is particularly true for meningiomas,
pituitary adenomas and acoustic tumours.
Malignant brain tumours usually require radiation and/or
chemotherapy to supplement surgery. This will help control the tumour
for short periods of time. There are a great number of
trials(studies) on brain tumour patients at the moment, where
experimental agents such as viruses are used to attack tumour
Dr Deon Louw
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