Not so long ago, stroke patients were told by doctors that their brains wouldn’t recover. Now, it’s a very different picture, says Niamh Kennedy, lecturer in psychology at Ulster University.
“Now we know this isn’t true, and that the brain is constantly changing,” she says.
Kennedy’s research focuses on neuroplasticity, which is the concept that the brain can rewire itself. This has gone from an abstract concept to there being an explosion of research, she says.
“Neuroplasticity was first talked about over 100 years ago, but it wasn’t until the last 20 years that researchers have begun thinking about how to utilise this extraordinary phenomenon.”
Neuroplasticity is all about connections. Neurons are connected to each other by synapses, and a good connection between them allows pathways to form that can affect a person’s movement, speech, memory and learning, Kennedy says.
The amount of neurotrophins, proteins that induce the survival, development and function of neurons, spike after a stroke, sending a cascading chemical reaction in the brain that promotes reorganisation, Kennedy says. In other words, the brain becomes primed for recovery.
“We know from animal research that, in an ideal world, when someone has had a stroke and has stabilised, we’d be boot-camping these people, we’d be sending them for rehab 9-5 for 12 weeks,” she says.
“Now, after you have a brain injury, we know that the brain is trying to do what it can for itself. Neuroplasticity starts to peak after a brain injury, which means in the first few days and weeks after a stroke is the optimum time to use increased levels of neuroplasticity to start rehab and start recovery.
“Only 20 years ago, when someone had a stroke they were seen as being sick, and basically went to bed for three weeks until they were better, then doctors started to think about whether to give the patient rehab.”
The brain starts by absorbing as much of the swelling and blood as it can after an injury, then starts the process of releases more neurotransmitters and neurotrophins to begin to reorganise.
“They say that the formation of new synapses increases up to eight times its usual rate after a stroke, flooding the brain with mechanisms and chemical messengers that help the brain be as efficient as possible,” Kennedy says.
We all depend on neuroplasticity in our daily lives to learn new things, but it’s particularly important after a brain injury or stroke. For decades, rehab has been using interventions that centre around neuroplasticity to reorganise the brain after damage and help patients regain functions they lost.
Kennedy uses non-invasive brain Transcranial Magnetic Stimulation (TMS), a very weak magnet that can be placed on a person’s head to measure the amount of neuroplasticity by looking at changes and activity in the brain.
This, she says, allows researchers to look at the living brain in more detail. Using TMS, Kennedy can look at a patient’s cortical activity, send it off to a physiotherapist and measure it again to see how the brain changes as the patient recovers function.
It’s arguably much less restrictive than MRIs, which are expensive and not routinely available, Kennedy says. Although TMS is specialist equipment, one costs around £10,000 to £15,000, compared to one or two million pounds for an MRI.
TMS can also be done in conjunction with other standard clinical measures, such as walking speed. It is also used in treatment for patients with depression who aren’t responsive to drugs.
Kennedy is working on research looking at patients’ arm function after a stroke, measuring neuroplasticity before and after physiotherapy to see brain changes and cortical pathway changes because of the intervention.
This will help researchers to see more holistically how someone recovers from a stroke, instead of just relying on behavioural measures, such as completing tasks, she says, where progress can sometimes come down to using other muscles to compensate.
Non-invasive brain stimulation is mainly a research tool, but it has the potential to be incorporated more widely into stroke units, Kennedy says, to investigate patients’ brain connectivity and plasticity or potentially predict recovery following a stroke.
“For people with the worst outcomes, however, you might invest money differently. Instead of putting them through SAS-style physiotherapy to get them walking if it’s unlikely they’ll walk again, let’s concentrate on making sure their mobility skills, such as the use of their arms, is prioritised,” Kennedy says.
However, she warns, there is potential for misuse.
“You don’t want something that determines a patient isn’t worth doing rehab on. The severity of someone’s stroke is still the best predictor.”
TMS is currently being trialled in some university hospitals in Australia and New Zealand, Kennedy says, to see if it can be used after a stroke to predict recovery, as TMS can show if the pathways between the brain and muscles are intact. Where they are, this could indicate a better recovery than if someone is given brain stimulation and their muscles don’t respond.
“This is important because stroke survivors are now in hospital for a lot less time, so there’s no time to try something and it not work well for a patient. Any additional information you can get to try and personalise someone’s rehab is seen as really positive,” Kennedy says.
Like all new technologies, TMS will take time, she says. Once it’s been trialled, it might be incorporated into clinical practice via university hospitals, and then physios may start using it more often.
It’s key that neuroplasticity is at the centre of stroke rehab, Kennedy argues, because the brain needs a lot of repetition to strengthen its pathways.
“That’s why rehab is such hard work. Our brains are sponges, we need to keep repeating things to get them into our heads.”
“You also need an enriched, stimulating environment with social interaction, of which there isn’t much in hospital. I worry about how, with Covid-19, people are having fewer visitors and less interaction, and their brains aren’t getting as much stimulation or interest,” Kennedy says.
Kennedy is also concerned that the Covid-19 pandemic will slow recovery as diagnoses as delayed.
“There’s evidence coming out that fewer people turned up at A&E with suspected strokes during lockdown, even though we know the rate is reasonably stable.
“This means people won’t have begun treatment or rehab and recovery promptly, therefore there’s a missed opportunity to stop the stroke becoming so bad, a missed opportunity for the golden time. The sooner we can start therapies and treatment, often the better.”
Kennedy says it’s an exciting time to be in stroke research, and a promising time for stroke survivors.
“Stroke research, although it’s always crying out for more rehab, is also trying to improve efficiency of rehab and interventions. I’m interested in how, the more we understand how the brain works and how it changes after brain damage, for example after a stroke, it allows us to have a better understanding of how it fixes itself and how we can promote that, and see how interventions can improve recovery as much as possible.
“It’s exciting, all the different things we’re beginning to learn about the brain and how some of this research is being translated into clinical practice with new technologies, from brain stimulation to virtual reality.
“There’s a slow path to adoption in the UK system, however, especially as the NHS needs loads of evidence.”
And, Kennedy adds, there’s much more research to be done.
“Researchers feel that brain stimulation is a promising technique, but people seem to respond differently to it. We need to understand why this is, then apply it in the best way for stroke survivors.”
Neuroplasticity isn’t a panacea, Kennedy concedes, but emerging technology that allows the patient to use it to their full advantage is very promising.
“If neuroplasticity was perfect, everyone would make a full recovery from a stroke. It gives stroke survivors a bit of hope that they can salvage things back.”
