A new drug could aid stroke rehabilitation
Strokes occur when a part of the brain stops receiving oxygen, due to either a clot or a damaged blood vessel, which causes that area to effectively die. They are one of the leading causes of death in the UK, but even if someone survives a stroke the effects can be severe, they can cause problems in speech, movement and memory, depending on where the ‘hole’ in the brain is. Recovery is a slow process, but now a paper is out in Science that has announced promising results of a drug designed to increase the speed of recovery and this has been tested in both mice and primates. Georgia Mills spoke to Professor Nick Ward, at the National Hospital for Neurology and Neurosurgery and UCL, who was not involved in the study, about why getting better from stroke is so difficult.
Nick - In terms of recovery, the ‘hole’ itself in the brain doesn’t fill in. People don’t recover by generating lots of new brain cells, they recover because the brain has the capacity for what we call ‘plasticity’ so, in other words, reorganising to improve function and that can lead to improvement in the ability of the person to do things that they weren't able to do before.
Georgia - Right, so it’s kind of flexibility?
Nick - Yeah. What we call plasticity, so a change in the structure of the brain that leads to an improvement in function over a period of time.
Georgia - Tell me about this new paper then; what have they done?
Nick - We just mentioned the fact that plasticity is an important idea when we come to think about recovery from stroke. Most of recovery is going to take place because of some kind of behavioural intervention so, in other words, if you have a problem with moving you need to practice the moving, usually with the help of a physiotherapist or an occupational therapist. If you have a problem with communicating you’ll work with a speech language therapist. You usually require hundreds or thousands of hours in order to try and recover.
Now, in heath services around the world, we’re struggling to deliver that kind of dose of therapy and so the idea behind the science of recovery is that it might be possible to somehow improve the potential for plasticity in the brain so that the same amount of therapy is going to have a bigger effect. In this paper they’ve looked at a drug which is changing the potential for plasticity and it does that by increasing ampa receptors. Ampa receptors are important for regulating what we call ‘inhibition’ or ‘excitation’ in the brain. If there was a little bit less inhibition and a bit more excitation, the brain will be more plastic, so for the same amount of training you should have a bigger effect. They use this drug in animal models of stroke to see what the effect was on a rehabilitation training regime.
Georgia - What did they find?
Nick - They were able to speed up the rate of recovery in animals who were treated with the drug. What they did, which is relatively unusual, was that they moved the experiment into primates. Three monkeys didn’t receive the drug and three did, and they found that the improvements in performance on an arm reaching task improved in the treated group. Most of the work that gets done in this field is done in the rodent model, and what they argued was if we’re going to translate it into something that works in humans, then we need a model that’s a bit closer to humans.
In terms of the general approach, in other words using drugs or some kind of intervention that increases the potential for plasticity, I think that it’s important to say that this idea has been around for a long time, you really need to couple training with the drug. The drug by itself, which might change brain state, is not the thing that leads to recovery, it’s training itself, so it might maximise the effects of training.
Georgia - As someone who’s a specialist in this field and a looking at this paper, how hopeful or you or how much significance would you attribute to it?
Nick - I’ve always been hopeful that we’ll be able to take one of the many drugs that have been studied in this field and understand how to use them. But one would temper that enthusiasm with the fact that we haven’t really been able to deliver enough, or a high enough dose of rehabilitation to patients and this applies not just to the UK, but this goes throughout the world generally. The training that you require in order to get better, the rehabilitation training, is really insufficient - we're delivery tiny tiny doses. The worry that we have is that even if you come along with a drug like this, if you maximise the effects of not very much, you still have not very much. So what we really have to fix first is systems that are going to deliver big enough doses of therapy that are going to make a difference to patients.