Neurosurgical Research Foundation

WHAT IS NEUROSURGERY?

What does a Neurosurgeon do?

The difference between a neurologist and a neurosurgeon.

A neurosurgeon deals with neurological problems that require or may require surgery whereas neurologists manage neurological disorders that can be treated medically. There is often overlap (eg) epilepsy is usually treated with drugs by neurologists but sometimes may be treated with an operation by a neurosurgeon) but only neurosurgeons perform operations.

In simple terms, neurosurgery can be defined as surgery of the nervous system but this does not adequately describe the breadth of modern neurosurgical practice.

Neurosurgeons are involved directly in patient care and neurosurgical research is driven by practical problems and aimed at improving the outcome of neurosurgical patients through advances in diagnosis, investigation and treatment.

Below is a brief outline of the range of conditions that are managed by neurosurgeons today and emphasise those areas where research is helping to provide answers to important questions.

Trauma (Janes Photo)

Head injury form motor vehicle accidents is an enormous problem in our community.

In all areas of medicine prevention is the best treatment and the main cause of head injury in our community is still road crashes. The road accident mortality figures have shown a continual decline over the past 10-20 years and the total numbers of injuries from motor vehicle accidents has also been declining recently. We saw a significant reduction in admissions of patients with severe head injury to our neurosurgical unit at the Royal Adelaide Hospital in the early nineties from approximately 120 patients a year down to only 45 in 1992. The numbers have crept back up but still run at about 60 a year, or half the number 10 years ago.

Some of the possible reasons for this reduction include the introduction of legal blood alcohol limits for drivers in all states of Australia between 1964 and 1974: the introduction of compulsory helmets for motorcyclists in 1974, the introduction of seatbelts in1972-1974 and the compulsory wearing of helmets for pedal cyclists in 1990. The more recent introduction of air bags into our vehicles may also be having an effect. The policing methods have also changed recently with the use of random breath testing and red light and speed cameras. In 1984 51% of fatalities were over the legal blood alcohol limit and this fell to 28.9% in 1991.

Many of these changes have been campaigned for by the neurosurgical community and we continue to promote road safety as the best way to reduce the effects of severe head injury.

As far as treatment of head injury is concerned, surgery has improved to the point where new techniques are unlikely to make any significant impact on the outcome from head injury. The trends for research recently have been centring on the cellular response to injury. Contrary to earlier beliefs, it now seems that not all of the damage is done at the time of the impact and by instituting suitable treatment at an early stage it may be possible to reduce the total amount of permanent damage to the brain. This work is still in its infancy but show great promise for the use of protective drugs early after head injury to minimise permanent brain injury.

Tumours

Malignant glioma is the most common primary brain tumour. It affects young adults in the prime of their life and we see about 50 cases a year in South Australia .

Early results of glioma surgery were poor, and in the early 1900’s even the best surgeon had an operative mortality of 30%. The average survival was a matter of weeks to a few months. Modern anaesthetic and operative techniques have reduced the operative mortality but the overall prognosis has changed very little over the past few decades. The average life expectancy is till under a year.

One of the problems one faces when dealing with gliomas is determining the extent of the tumour. When CT was first introduced it was felt that this would define the limits of the tumour and allow curative surgery. This was not the case however and similar results have been found with MRI. We have studied the correlation between MRI and neuropathology in gliomas and found considerable diversity within a particular tumour with regard to its appearance on MRI. In some areas the abnormal area on MRI defines the tumour very well but in other areas of the same brain the tumour spread is grossly underestimated by the MRI and tumour can even spread to the opposite hemisphere and remain undetected. This has significance in both surgical and non-surgical treatment of gliomas. Even if one removes all of the abnormal brain as defined by MRI there will still be tumour left behind. Not only that but standard radiotherapy fields which include a 1-2 cm margin around the radiologically abnormal area will also miss active tumour. A glioma that is too small to detect on CT (less than 5mm) can grow to a mass of several centimetres diameter within four weeks, explaining why surgical removal of large amounts of tumour makes little or no difference to the prognosis.

It is generally accepted that the successful treatment for glioma will relay on differentiating tumour cells from normal cells using some cellular characteristic rather than an anatomical one. The treatment should be able to reach all cells of the brain but only kill those that carry the abnormality that defines them as malignant. Malignant glioma cells contain many abnormalities in their genetic make-up, including extra or deficient chromosomes, additional, altered or deficient genes and altered proteins consequent upon this. Some of these abnormalities have been shown to be fairly specific for gliomas and others are found in a wide variety of tumours. Research is in progress all over the world to determine which markers best define the tumour cells and how they can be targeted and selectively killed.

Other Tumours (USE photos Missy / tonia / christopher)

Malignant tumours that have spread from cancer in other parts of the body are easier to distinguish from the normal brain. Newer methods of radiotherapy (radiosurgery), using very accurate targeting of high doses of radiation are being used with considerable success for those tumours that are not removable surgically.

Benign tumours do not spread to other parts of the body like malignant tumours and usually grow much more slowly. Benign brain tumours can still cause significant morbidity and mortality however, because there is only a finite amount of space in the skull and as they enlarge they cause pressure on the brain. Some benign tumours are being treated with radiosurgery, particularly acoustic neuromas, which grow on the nerves to the ear and cause deafness.

Another common benign brain tumour is the meningioma. These are more common in females and have been shown to contain various hormone receptors, raising the possibility treating them with tablets to block these hormones, as is done with breast cancer. Indeed, epidemiological research has demonstrated an association between breast cancer and meningioma.

The treatment of pituitary tumours has also changed over recent years due to advances in neurosurgical research. Most pituitary operations are performed through the nose rather that through the skull and endoscopy is increasingly being use. The most common type of pituitary tumour is now often treated with tablets instead of surgery.

Brain Haemorrhage / Strokes / Aneurysms. (Use Tina and Zia Photos)

Most strokes are managed by neurologists but neurosurgeons are involved with subarachnoid haemorrhage and intracerebral haemorrhages. This is an area with many unanswered questions but also excellent examples of the benefits of clinical research. The most common cause of subarachnoid haemorrhage is an aneurysm. Clipping an aneurysm is a technically difficult operation that has been dramatically improved by advances in neuroanaesthesia, neuroimaging and the use of the operating microscope.

Many aneurysms are now being treated without surgery by placing coils into them through a catheter inserted through an artery in the leg. This is changing the whole concept of management of a patient with subarachnoid haemorrhage.

Another benefit of epidemiological research is the vast amount of information that is available regarding the natural history of these aneurysms. This is vital in deciding which aneurysms to clip and when to do so. Modern imaging is now detecting aneurysms before they have ruptured and this leads to the difficult decision about undertaking a potentially high-risk operation or living with the risk of rupture of the aneurysm. It is impossible to compare the choice unless information is available on the risks and benefits of them. Some patients who have a subarachnoid haemorrhage may die or have a stroke because the arteries go into spasm. This has been known about for a long time but the causes and treatment are still being defined. Large international trials of drugs aimed at reducing this complication are under-way, costing many millions of dollars. We have been involved in some of these are currently part of a trial of these drugs in subarachnoid haemorrhage due to trauma.

Spinal problems

Most neurosurgeons spend about half of their time dealing with spinal problems. These range from disc prolapses causing sciatica and arm pain to tumours causing paralysis. More workers compensation money is spent on back injuries than anything else yet we still do not know what causes the pain in many cases. A multitude of treatment options is available, both surgical and non-operative, but very often there is little evidence to support their use. Clinical research is required to validate treatment methods and basic research to define the underlying mechanisms.

We have an interest in the long-term effects of spinal cord injury and in particular a condition called syringomyelia. This is the development of a cyst in the cord some years after an injury. It can cause further damage to an already injured spinal cord and our research has discovered some of the basic mechanisms of formation of these cysts. We have also produced these cysts in the rat, which allows us to study their development and possibly find ways of preventing their formation.

Congenital abnormalities / Spina Bifida / Hydrocephalus

(Use Photos Sammy and Twins)

Paediatric neurosurgeons deal with a wide variety of congenital abnormalities such as hydrocephalus (water on the brain), craniofacial abnormalities and spina bifida. Fortunately spina bifida has become a rarity because of the results or research into the use of folate and antenatal screening. Hydrocephalus remains a common problem and is an excellent example of the benefits of practical research. The treatment most commonly used today, a shunt containing a valve to regulate the amount of spinal fluid draining away, was developed by John Holter, a technician in a machine shop, when he had a child with hydrocephalus in 1955.

Neuroimaging, neurosurgical instruments, microscopes, frameless stereotaxy etc.

It is now possible for us to see inside the brain using a magnetic field which sounds like something from Star Trek but is being used as part of our everyday management of neurosurgical patients. MRI is a prime example of the value of clinical research. The principles of MRI were known in 1945 and won the Nobel Prize for Bloch and Purcell, but the clinical use of MRI only began in the 1980’s. This required the input of physics, computer technology and radiology, as well as neurology/neurosurgery. Neurosurgeons have taken this even further to develop frameless stereotaxy which allow us to see exactly where we are in the brain or spine on a computer screen, similar to the latest computer navigation systems installed in cars.

OTHER NEUROSURGICAL CONDITIONS:

Peripheral nerve disorders

Neurosurgeons see many patients who have problems with the nerves in their arm or less commonly their leg. This is usually due to simple pressure which can be readily relieved, the most common being carpal tunnel syndrome in the hand. Less commonly we treat tumours on the nerves and sometimes nerve injuries that require grafting. Many neurosurgeons are involved in research into nerve grafting and nerve growth and this research is closely linked with similar work in the spinal cord injury field.

Infections

Abscesses in the brain from ear infections used to be quite common but decreased markedly with the introduction of antibiotics. We are now seeing an increase in infection in the central nervous system related to immune deficiency, either from AIDS or as a consequence of the treatment of some malignancies. CNS infection is also a major problem in our indigenous population where a resurgence in tuberculosis is causing major concerns.

Functional neurosurgery

Functional neurosurgery allows the placement of needles and electrodes at precise locations in the brain to produce lesions that can alleviate tremors and other movement disorders and in some cases can benefit psychiatric conditions and chronic pain disorders. Surgery can also help epilepsy by dividing connections in the brain or removing areas that initiate seizures.