The use of immersive virtual reality in neurorehabilitation and its impact in neuroplasticity

This thesis aim to test the effectiveness of an immersive virtual reality set-up by using an embodied virtual body in neurorehabilitation, specifically for motor and chronic pain disorders. More specifically, my first study entitled: Motor-cognitive training through Immersive Virtual Reality during the immobilization period in distal radius fracture patients, aims to investigate whether an upper limb immersive virtual reality (IVR) training program, may improve the motor and functional ability of a fractured arm in 54 distal radius fracture (DRF) patients during the immobilization period. With this intention, we compared 6 weeks of our IVR training group (n=20), with 6 weeks of a non-IVR training group (n=20), and with another conventional rehabilitation group (n=14), during the immobilization period. We observed that through our training program patients in the IVR training group reached a better motor-functional ability of the fractured arm after cast removal, compared to the patients in the control groups: non-immersive virtual reality group and conventional rehabilitation group. Finally, patients in the IVR training group presented better results in the follow-up (6 weeks later) compared to the control groups, especially in the wrist range of motion. Secondly, we wanted to investigate the effects of the upper limb IVR training program in chronic stroke patients without arm mobility with a case study: Using immersive virtual reality to rehabilitate the paretic upper limb in chronic stroke patients. In that case study, we tested the IVR program in three chronic stroke patients. To this aim all three chronic stroke patients, underwent two IVR training periods during 5 weeks every day, with a 3 weeks period of pause between the two training periods. After the first training period we found improvements in motor recovery of the paretic arm, as well as in the cognitive capability and quality of life of all three chronic stroke patients. Further, we observe that the motor-cognitive improvements obtained after the first IVR training period remained over time, during the period of pause. However, the second IVR training period was not effective to further enhance motor and cognitive improvements. Further, a pre-post brain imaging analysis by using resting state and diffusor tension imaging (DTI) techniques, allowed us to identify the underpinning neuroplastic changes following the first IVR training, that were mainly found at the cerebellum from a functional connectivity point of view, and in the primary motor cortex from an structural point of view, in all three chronic stroke patients. Finally, the last study of this thesis entitled: Immersive virtual reality reliefs pain in patients with complex regional pain syndrome type I but not with peripheral nerve injury, aimed to investigate whether varying properties of a virtual arm co-located with the real arm modulated pain ratings in patients with chronic arm/hand pain due to complex regional pain syndrome (CRPS) type I (without nerve injury) or peripheral nerve injury (PNI). CRPS (n=9) and PNI (n=10) patients were immersed in VR and the virtual arm was shown at four transparency levels (transparency test) and three sizes (size test). We evaluated pain ratings throughout the conditions and assessed the virtual experience, finding that patients with chronic pain can achieve levels of ownership and agency over a virtual arm similar to healthy participants. All seven conditions globally decreased pain ratings to half. Increasing transparency decreased pain in CRPS but did the opposite in PNI, while increasing size slightly increased pain ratings only in CRPS. In overall my doctoral thesis pave the way to the use of embodiment through an IVR set-up in neurorehabilitation following the principles of body illusions for rehabilitation.La presente tesis pretende hacer una breve revisión de las diferentes técnicas de integración multisensorial en rehabilitación utilizando principalmente el feedback visual y que han llevado a la implementación de la realidad virtual como herramienta terapéutica. Actualmente, la realidad virtual está adquiriendo un papel importante en el campo de la rehabilitación, y en específico en el campo de la neurorehabilitación para el tratamiento de alteraciones motoras, cognitivas y síndromes dolorosos. Sin embargo, todavía es una incógnita cuál es la manera más efectiva de aplicarla y que pacientes se pueden beneficiar en mayor grado de ella. Por esta razón, en esta tesis doctoral se presentan tres diferentes estudios en los cuales se aplica el uso de un sistema de realidad virtual immersiva, generando la ilusión de posesión de un cuerpo virtual. Específicamente, el primer estudio está realizado con pacientes ortopédicos. El segundo estudio es un caso estudio realizado con tres pacientes neurológicos, y el tercer estudio está realizado con un grupo de pacientes que sufren dolor crónico neuropático. En los tres estudios, se demuestra que el hecho de generar la ilusión de posesión de un cuerpo virtual mediante el uso de un sistema de realidad virtual immersiva, permite mejorar déficits motores, cognitivos y dolorosos en diferentes patologías. Esta tesis doctoral abre el camino a la introducción de nuevas técnicas de tratamiento en el campo de la neurorehablitación mediante el uso de técnicas de integración multisensorial, como los sistemas de realidad virtual immersiva