Effects of priming therapies on motor dysfunctions and cortical excitability in stroke patients: systematic review

Introduction: Approximately 90% of stroke patients are left with some type of functional limitation. A number of auxiliary techniques have emerged in the rehabilitation field, such as priming, which is an unconscious process associated with learning, in which the previous exposure to a stimulus alters the response to a subsequent stimulus. When used in conjunction with another therapeutic intervention, priming may result in a change in behaviour that appears to coincide with changes in neural networks. Objectives: To review and analyse randomised controlled trials (RCT) that evaluate the effects of priming on motor limitations and cortical excitability in stroke patients. Material and Methods: A bibliographic search was made in 3 databases (Pubmed, PEDro and CENTRAL), using the research methodology - Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Studies conducted in patients who suffered a stroke, whose intervention explicitly used priming therapy, were included. Results: Fourteen studies were included. Four used transcranial magnetic stimulation, 3 used transcranial direct current stimulation, 2 used imagery and action observation, and 5 used movement-based priming. Due to the clinical and methodological heterogeneity of the studies, meta-analysis was not possible. Of the included studies, 10 showed that priming associated with rehabilitation had significant improvements and 4 showed that there were no significant improvements between groups. Conclusions: Priming therapies, when used in conjunction with another therapeutic intervention, seem to enhance the rehabilitation of motor functions after a stroke. In the future, experimental studies with larger samples should be conducted and the way each priming technique is applied should be standardised.