Combined Effects of Transcutaneous Vagus Nerve Stimulation and Modified Constraint Induced Movement Therapy on Upper Extremity Function, Cognition and Quality of Life in Individual With Chronic Stroke

Stroke is the third leading cause of death and the leading cause of adult disability. Patients with stroke suffer from neuromuscular disabilities, including impairments in motor control. Stroke survivors with hemiplegia exhibit more upper-limb (UL) than lower-limb (LL) disability. Dysfunction from upper extremity hemi paresis impairs performance of many daily activities such as dressing, bathing, self-care and writing, thus reducing functional independence. Only 5% of adults regain full arm function after stroke, and 20% regain no functional use. Restoration of full function to the stroke affected upper extremity is a major problem in rehabilitation. Hence alternative strategies are needed to reduce the long-term disabilities and functional impairment resulting from upper extremity hemi paresis.

The severity of the neurological deficits and early patterns of improvement are the two best predictors of recovery from impairments. Patients are generally thought to experience less UL motor recovery than LL motor recovery; however, this clinical belief is typically based on disability assessments rather than tests of specific motor deficits of UL and LL. Since UL function needs finer motor control than LL function, this might explain the common scenario of less variation between impairment and disability. There are several promising treatment options available for upper-limb stroke rehabilitation, such as cross education, constraint-induced movement therapy, virtual reality therapy, functional electrical stimulation, robotic therapy, anodal transcranial direct current stimulation, and motor imagery.

Unfortunately, VNS necessitates a costly, invasive surgical procedure. In the last years, transcutaneous VNS (ta-VNS) has been proposed as a noninvasive and patient friendly method to stimulate the vagus nerve, through the skin, by delivering weak electric current to the sensory afferent fibers of the auricular, thick-myelinated, branch of the vagus nerve in the outer ear. Such stimulation activates the auricular branch of the vagus nerve and, via this pathway, the nuclei of the nerve located in the brainstem, enhancing brain GABA and Noradrenaline levels, which plays a pivotal role in brain plasticity. These connections regulate the release of neuromodulators, including acetylcholine, norepinephrine, serotonin, and brain-derived neurotrophic factors, which promote cortical plasticity.

The rationale for this study lies in its potential to uncover synergistic benefits from combining these two therapies, ultimately aiming to enhance functional recovery and cognitive engagement among chronic stroke survivors, thereby improving their daily lives and reintegration into society. The exploration of effective rehabilitation strategies is crucial, as traditional therapies frequently provide limited benefits for chronic stroke patients, particularly concerning upper extremity function. This research investigates the combined effects of ta-VNS and Modified CIMT on these patients, aiming to enhance motor recovery and cognitive engagement. The findings may inform future therapeutic approaches and offer hope for improved independence and well-being among individuals affected by chronic stroke.