A pioneering drug trial to treat patients with severe epilepsy is under way at St Vincent's Hospital in Melbourne and holds hope for other brain diseases.

A world-first trial to administer drugs directly to the brain of epilepsy patients through a pump drilled into the skull has begun in Australia.

This direct form of administration means the patient's whole body isn't flooded with the anti-seizure drugs, normally taken orally as a tablet, and will hopefully mean fewer side-effects.

The trial is being driven by Professor Mark Cook, the director of neurology at St Vincent's Hospital in Melbourne.

He says this is a "first in man study" that holds huge potential for treating other brain diseases such as Parkinson's disease.

"It won't affect just people with epilepsy potentially, but there are lots of brain diseases that might be better treated by delivering drugs directly to brain," Prof Cook told AAP.

However, the trial is only in its infancy and is very much pioneering work, so there is still a lot researchers don't know, cautioned Prof Cook.

"We don't really understand how the brain will react to these drugs and how it metabolises them, and how long they last," he said.

Epilepsy is a disruption of the normal electrochemical activity of the brain that results in seizures.

The problem at the moment is that the oral forms of medications, which can cause side-effects such as weight gain and bone-thinning, must be absorbed into the bloodstream to reach the brain.

"Only a very tiny amount gets to the brain and the whole body gets soaked in the drug in the meantime. The advantage of being able to deliver a drug in this way is that we can put the drug directly to where it is needed and we can use very small quantities," Prof Cook said.

The first patient to be implanted with the drug pump is 27-year-old Natalie Kellalea from the Victorian town of Numurkah.

Unable to be effectively treated, Ms Kellalea had become so disabled by her severe seizures that she had been in hospital for a couple of months just prior to the trial commencing.

"She's going very well so far but its obviously early days," Prof Cook said.

The plan is to implant the pump in a further eight patients before the researchers reassess and look at how to extend the trial.

If all goes well, patients would no longer need to take numerous medications every day because the pump would only need to be topped up every few months.

More importantly, the pump technology offers the possibility that more effective drugs currently unable to be absorbed by the body could be used in the future.

"We are starting off with drugs that we know and once we finish studying those drugs and have seen how effective they are, we can look at using other newer drugs which at the moment can't be given any other way."

The longer-term hope, said Prof Cook, was that lots more effective drugs can be given to patients with other severe neurological conditions.