'The success rate of surgery is high'

Dr. William Harkness is Professor of Neurosurgery at National Hospital, London, and Senior Consultant Neurosurgeon at the Hospital for Sick Children, Great Ormond, London. His research interests includes the application of image-guided neurosurger y and the development of surgery for epilepsy in adults and children. He spoke to Asha Krishnakumar on the various forms of epilepsy treatment, the effects of surgery and state-of-the-art research on surgical treatment. Excerpts from the interview :

What are the various forms of treatment of epilepsy?

Medication is still the most important form of treatment. There are a number of medications appropriate for different types of epilepsy. At least 80 per cent of the patients can get very good control of epilepsy with the medical treatment. For the remain ing, surgical intervention is advised at an early stage. It is recommended only after medical treatment is tried.

For what kinds of epilepsy is surgery suitable?

For most part, surgery is for epilepsy of focal onset. It is important to understand the pathology of epilepsy. When epilepsy involves the whole brain, it is unlikely that an operation to remove parts of the brain is going to be effective in controlling the disorder. However, if it is caused at a specific area of the brain, then the chances of surgery being effective are very good.

Would removing the affected part of the brain not have side-effects?

For patients who have had epilepsy for several years, the functions of the affected part of the brain could have moved to some other part or parts. Hence, they may not notice any change, post-surgery. The decision on surgery depends on what part of the b rain has to be removed and how much of it has to be removed as also on the outcome of patient counselling.

What is the most common form of surgery?

The most common form is surgery done on the temporal lobe (this constitutes about 70 per cent of the surgical procedures in adults and 30 per cent in children). This is done for the type of epilepsy called complex partial seizure, arising from this part of the brain. This is characterised by patients losing the ability for interaction with their environment and tending to become unresponsive to people. They may also perform abnormal repetitive movements such as chewing and fiddling with their hands. Thi s may lead to convulsions. This type of epilepsy can be very disturbing because usually there are no apparent signs of a seizure. As seizure for most is only convulsion, shaking all over.

A number of pathologies can cause this type of seizure. If it pertains to the temporal lobe, surgery can be attempted. There is a 75 per cent chance that the attacks would stop completely and a 10 to 15 per cent chance that the seizures would be reduced considerably. Surgery is advised for those on multiple drug treatment as there is a very good chance of controlling seizures.

Is there any difference in the surgical procedures for adults and children?

In children, epilepsy is mainly caused by congenital abnormalities in the brain and is also severe as it manifests itself early in life. When children are brought for surgery, they are usually severely affected. Investigations reveal that most children s uffer from developmental abnormalities of the brain or brain injuries during, before or after birth, resulting in severe epilepsy. So, the pathology is different. In children often we tend to use larger procedures to get the disorder under control. Most children who are operated upon have severe and diffused abnormality on the whole of one side of the brain. We generally try to disconnect that side of the brain effectively so that it is functionally isolated.

What effect would this have on these children?

These children very often suffer from hemiplagia, in which that side of the brain is weak. In children, in contrast to adults, if the operation is done early in life, the functions of the affected side, even if it is the dominant side, would be taken ove r by the other side of the brain. The brain of children has greater plasticity to be able to adapt.

What is the success rate of surgery?

A pathology called hipppocampal sclerosis, which causes considerable damage to one area of the brain, carries a very good surgical prognosis. In bigger operations, the seizure-free rate depends very much on the pathology. For example, the prognosis is di fferent if there is an abnormality in the architecture of the brain compared to the condition acquired later on in life. The success rate is high for the latter, in which 80 per cent of the patients become seizure-free after a surgery compared to 50 per cent if there is a congenital abnormality in the architecture of the brain.

For what age is surgery advisable?

Surgery is done on three-months-old babies to above-60 adults. I have even operated upon babies just a few weeks old.