Dystonia “is an illness that causes the muscles to be permanently contracted involuntarily. The patients find it difficult to move and use their limbs, and the illness can lead to serious disabilities, for instance not being able to use an arm”, stated João Paulo Cunha, researcher at INESC TEC’s Centre for Biomedical Engineering Research.

This study resulted from a project that brings together INESC TEC and the University of Munich, in Germany.

"The Portuguese researchers" involved in this initiative "obtained this result by studying a part of the brain called called GPi (Globus Pallidus Internus), located in the centre of the brain and composed of structures with primary functions", according to a press release from INESC TEC.

In 2016, the researchers developed “neurocomputing methods to study the density of connectivity of the fibres that leave the GPi to other areas of the brain in healthy people with no indication of pathology”. They discovered “that this nucleus at the base of the brain seems to have at least three substructures with different connectivities, and one of them was clearly connected by the Thalamus to the sensorimotor cortex.” 

The GPi is one of the targets of the Deep Brain Stimulation (DBS) technique, where electrodes are put inside the patient’s head. This sort of brain pacemaker helps improve symptoms, “always depending on the target, that is, Parkinson’s disease, dystonia, or others”, the researcher explained.

With this study, it was possible to understand that “the DBS electrodes implanted in that substructure produce best clinical results as opposed to electrodes implanted in other substructures”, making these results “useful for planning and executing neurosurgical procedures”, stated João Paulo Cunha, who also teaches at the Faculty of Engineering of the University of Porto (FEUP).

Another advantage of this method is the ability “to personalise the pattern of connectivity in each surgical candidate, adapting the neurosurgical target to the connectivity profile of each specific patient. This means that the precision of the procedure can be improved.”, he added.

To reach these conclusions, the team of researchers from Portugal and Germany used a technique called Diffusion Tensor Imaging, which is a magnetic resonance technique that helps understand the connectivity density between brain structures, thus making it possible to map the fibres that connect the different structures in the brain.

The results have just been published in one of the most prestigious journals in the field of Neuroscience, Neuroimage.

In 2014, the team of researchers from INESC TEC and the University of Munich had already demonstrated, also on NeuroImage, that the location of deep brain stimulation electrodes, used in patients with dystonia, produced more significant effects when positioned in certain areas.

“We found that the connectivity projections of the fibres from the DBS electrodes in the GPi, for different cortical and subcortical structures, seemed to be associated with the positive or negative result of those neurosurgeries.”, he added.

This study “made it possible to understand that the GPi could have different preferential connections to other parts of the brain, which consequently would stimulate those brain structures. The results would be better if those structures were connected to motor regions, and worse if they were connected to regions with non-motor functions.” This was the motivation behind this study.

TVI 24, 24 January 2016