Applying an electric current to the brain can help recovery from stroke, Oxford University researchers have found. A team from Oxford’s Nuffield department of clinical neurosciences, led by Professor Heidi Johansen-Berg and Dr Charlotte Stagg, studied the use of transcranial direct current stimulation (tDCS) to support rehabilitation training. The technique involves placing electrodes on the scalp to pass a constant low current through a particular area of the brain.
In this case, the team used a variant called ipsilesional anodal tDCS, where a positive (anodal) current is applied on the side of the brain where damage has occurred. Anodal stimulation has previously been shown to increase the learning of motor skills in healthy people. The hope was that this effect could also be demonstrated in stroke patients, using tDCS to reinforce training that helps patients relearn how to use their body.
Johansen-Berg said: “For stroke patients, longer and more intensive training leads to greater recovery. However, cost and staff availability limit what can be provided. That means that there is increasing interest in therapies that can be used to boost the effects of training.”
The study included twenty-four volunteers who had had a stroke affecting their hand and arm function, split into two groups. Both groups were given nine days of motor training. One group had tDCS during the training sessions, while the other group acted as a control: they were fitted with electrodes but did not receive tDCS.
Before, and at various times up to three months after the training, the volunteers’ motor skills were assessed using established clinical measures to see how much they had improved.
Johansen-Berg said: ‘The assessments before the training were used to establish a baseline score for motor skills. Further assessments could then be used to determine what improvement there was above that baseline.
‘Three months after training, the group that had received tDCS had improved more on our clinical measures than those in the control group. This showed that the patients who had received tDCS were better able to use their hands and arms for movements such as lifting, reaching and grasping objects.’
‘If we take at face value what the results are telling us, it is that the stimulation doesn’t completely change the way that the brain can produce a movement, in that it doesn’t make you stronger, but it makes the brain better at being able to carry out a particular task like lifting up an object,’ said Johansen-Berg.
‘It is an exciting message because there is so much frustration about people not reaching their true recovery potential,’ said Professor Heidi Johansen-Berg, an author of the study from the University of Oxford, highlighting the fact that the cost of programmes and limited availability of therapists often restricts the amount of rehabilitation offered to patients.
MRI scanning also showed that those who had had tDCS had more activity in the relevant brain areas for motor skills than the control group.
The research also found that patients who underwent the brain stimulation had larger increases in activity in regions of the brain associated with movement than those who had been given the placebo treatment – an effect that was seen from fMRI scans taken immediately after the nine-day programme and one month later.
‘What is particularly important about [the study] is that it does relate the functional improvements with the neuroimaging changes – and that is very encouraging,’ said Burridge.
But Burridge also cautions that the results should not be taken as a sign that brain stimulation will benefit all stroke patients. ‘One has to remember that this is one quite small study,” she said. “The overall view at the moment of when we put all the data [from many studies] together is that there is no clear benefit.’
The research team conclude that there is positive evidence for the use of tDCS to aid stroke recovery but caution that the technique must be proved to have long term benefits not only in clinical measurements but also in the ability to carry out tasks important to daily life. Larger studies, they say, will be needed before this approach could enter routine clinical care.
Anodal transcranial direct current stimulation (tDCS) can boost the effects of motor training and facilitate plasticity in the healthy human brain. Motor rehabilitation depends on learning and plasticity, and motor learning can occur after stroke. We tested whether brain stimulation using anodal tDCS added to motor training could improve rehabilitation outcomes in patients after stroke. We performed a randomized, controlled trial in 24 patients at least 6 months after a first unilateral stroke not directly involving the primary motor cortex. Patients received either anodal tDCS (n = 11) or sham treatment (n = 13) paired with daily motor training for 9 days. We observed improvements that persisted for at least 3 months post-intervention after anodal tDCS compared to sham treatment on the Action Research Arm Test (ARAT) and Wolf Motor Function Test (WMFT) but not on the Upper Extremity Fugl-Meyer (UEFM) score. Functional magnetic resonance imaging (MRI) showed increased activity during movement of the affected hand in the ipsilesional motor and premotor cortex in the anodal tDCS group compared to the sham treatment group. Structural MRI revealed intervention-related increases in gray matter volume in cortical areas, including ipsilesional motor and premotor cortex after anodal tDCS but not sham treatment. The addition of ipsilesional anodal tDCS to a 9-day motor training program improved long-term clinical outcomes relative to sham treatment in patients after stroke.