A study by Campus Bio-Medico neurologists published in Nature Reviews Neurology lays the foundations for the development of more effective transcranial brain stimulation techniques for the recovery of stroke patients

Using 'one size fits all' in post-stroke recovery therapy often leads to poor outcomes. To avoid this, a differentiation of interventions must be implemented based on the extent of brain damage. The news comes from work by researchers atUniversità Campus Bio-Medico di Roma, recently published on Nature Reviews Neurology. “The indications of this study - emphasizes the Dr. Giovanni Di Pino, researcher in Neurology and Bioingengineering of the Bio-Medico Campus and first signature of the study – pave the way for increasingly personalized and, therefore, more effective stroke recovery therapies even years after the event".

"To make a parallel - explains the Prof. Vincenzo Di Lazzaro, Director of the Chair of Neurology on the Bio-Medico Campus and senior author of the research – it is as if, while crossing a road, we see a speeding car approaching. The choice of quickening our pace to the other side or turning back depends on how far we have already traveled from the pavement. In this way, a more targeted use of electrical impulses and magnetic fields will make it possible to interface with the brain by 'rebooting' and 'reprogramming' it, a bit like computers".

The human brain works by transforming electrical impulses into chemical signals (release of neurotransmitters) and vice versa. Through this apparently simple mechanism, billions of nerve cells communicate at all times and allow us to think, speak and move. When a cerebral stroke occurs, these mechanisms can be damaged in a more or less serious way, with consequent damage to normal brain functions. In recent years, neurosciences have opened the door to a new therapeutic approach to promote recovery after a stroke, which could complement rehabilitation. It is an 'electromagnetic' strategy capable of modulating the transmission of brain electrical signals and enhancing communication between different brain areas and between these and the muscles. But this innovative approach, based on the use of electric and magnetic fields, has so far made it possible to obtain very limited results. From the analysis carried out by the researchers of the Campus Bio-Medico it emerges that the two main 'schools of thought' on the treatment with non-invasive cerebral neuromodulation techniques in stroke are not to be opposed, but must be adapted according to the extent of the damage suffered from the brain. The first model is that of the so-called 'competition between hemispheres', according to which, in a brain affected by a stroke, the healthy part should be inhibited to prevent its hyperactivity from slowing down the recovery of the damaged hemisphere. On the contrary, the other approach sees in the stimulation of the hemisphere not affected by the stroke an element of strength to favor the best recovery of the patient's motor functions, exploiting its 'replacement' activity. Researchers at the Campus Bio-Medico indicate that there is no single route that is generically valid for all patients. The choice of treatment, rather, depends on how severe the brain damage is. According to scholars, in fact, if it is small, the goal is to return to having a brain that works as it did before the stroke. Consequently, the most appropriate approach is to inhibit the hyperactivity of the healthy hemisphere. If, on the other hand, the brain damage is very extensive, the winning recovery strategy is the one that strengthens the cerebral hemisphere not affected by the stroke to replace the damaged one.

This research is linked to a second study, also carried out by the neurologists of the Bio-Medico Campus and published in the journal Brain Stimulation. Researchers have found that certain genetic characteristics influence how a stroke victim's brain reorganizes after the event. The study focused on the effects of variants of an singol gene, which encodes a protein of the neurotrophin family, called Brain Derived Neurotrophic Factor (BDNF). This protein promotes the survival of neurons and influences brain plasticity phenomena.

"We discovered – he clarifies Di Lazzaro - that in order to be able to define post-stroke therapeutic and rehabilitative programs, the genetic characteristics of the individual also represent a relevant element to be taken into consideration. In fact, this gene influences the way in which the two cerebral hemispheres react to a stroke: in subjects with the most widespread form of the gene, the unaffected cerebral hemisphere takes over, becoming hyperexcitable to external stimuli. In people with a variant of the gene, called a polymorphism, the imbalance between the activity of the two hemispheres that occurs after a stroke is nine times less. The hyperexcitability of the hemisphere not affected by the stroke plays a significant role in the recovery processes, as it can favor it, especially when the damage caused by the stroke is very extensive, but it can also interfere with it in the case of smaller lesions”. The results of these two studies will pave the way for much more promising post-stroke therapeutic approaches, potentially effective even years after the event.