Family doctor

Overview

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 features.

2-Seizures;a brain tumour may cause a variety of different seizures.Any new or unexplained seizures should be carefully assessed and investigated.

3-Mental Changes; these may include certain forms of depression,confusion,memory loss and personality changes.

Further investigations

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 head.

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 cells.