Impact of rTMS on BCI Control in Upper Limb Motor Rehabilitation of Patients With Chronic Stroke

Cerebrovascular accidents (strokes) are a major public health issue. Stroke is the 3rd leading cause of death and the leading cause of disability and loss of autonomy. In France, there are currently 130,000 new cases per year, and the aging of the population will lead to an increase in this number over the next few years. Among post-stroke impairments, motor deficit of the upper limb is the most common disability, affecting 73-88% of first-time stroke patients and 55-75% of chronic patients. Associated deficits can complicate rehabilitation management and affect recovery. The clinical profile of patients with motor deficits is therefore varied and complex, requiring an individualized approach. At present, only physiotherapy is recommended, with modest results.

Repeated transcranial magnetic stimulation is a therapy that can improve motor recovery, but currently has a low level of evidence according to the HAS (French Hight Health Authority), notably because of variability in efficacy due to heterogeneity in the clinical profile of patients. Nevertheless, it is still recommended for the recovery of cognitive functions, but also for resistant depression, and could be used to stimulate motor imagery (MI). MI training also has the advantage of stimulating the motor network. Difficult to achieve for a number of patients, the use of rTMS could facilitate this cognitive task and, in particular, provide better access to brain-computer interfaces (BCI). Indeed, among the innovative rehabilitation therapies, BCIs have emerged as the most promising. By translating brain activity during a cognitive task into a command such as electrical muscle stimulation, BCIs would restore the damaged motor network and induce motor recovery. The main obstacle to their widespread use in clinical practice is their lack of reliability, as almost 30% of patients are unable to control them correctly, either because of difficulty in performing the MI task, or because of difficulty in identifying a universal brain signature.

The BCINET project aims to improve the reliability of BCIs in two ways: by improving detection of the motor imagination task using new brain signatures, and through cognitive facilitation using rTMS.

1. - Using the dynamic communication of different brain areas during the MI task (or functional connectivity), we can identify patient-specific signatures. Studies of functional connectivity in healthy subjects performing an MI task without associated BCI have shown the interest of certain measures such as node degree or clustering coefficient. To find out whether functional connectivity parameters can be used in BCI algorithms, we will evaluate their effectiveness on an initial group of 5 patients to define their performance in discriminating the MI task and to determine their evolution over time in the absence of brain stimulation in stroke patients. Their initial study will also enable us to identify their evolution when TMS stimulation is applied.
2. - Cerebral magnetic stimulation could facilitate the MI task and enable better BCI rehabilitation for a number of patients. Two studies using either an inhibitory or excitatory stimulation protocol showed an improvement in spectral power signal and better discrimination of the MI task. However, the results were acquired using a single pre- and post-therapy measurement, and did not take into account behavioral variability in the use of BCIs or variability in TMS response according to patient profile. Therefore, in order to identify whether rTMS would improve BCI control, we would perform 9 Single-Case Experimental Design (SCED) studies in multiple baselines on a group of 5 patients according to 3 clinical profiles and 3 rTMS stimulation strategies. SCEDs are suitable experimental models for heterogeneous populations, particularly when the intervention presents some inter-individual variability in efficacy. They have the advantage of being able to demonstrate, on an individual scale, the effectiveness of the intervention on a small group of patients. Replication of the SCED allows us to increase the external validity of the intervention on sub-groups of patients (clinical severity, presence of associated hemineglect) and to study modifications in the interventional strategy (stimulation frequency, stimulation site).