Transcutaneous Auricular Vagus Nerve Stimulation in Patients with Stroke

Stroke is a neurological condition caused by vascular problems such as cerebral infarction and/or intracerebral or subarachnoid hemorrhage(1). In 2019, more than 12 million strokes occurred worldwide, making it one of the leading causes of morbidity. Motor impairment is considered one of the main problems resulting from this condition(2). Recovery of motor function occurs spontaneously during the first months after stroke(3) as a result of brain plasticity processes in the sensory and motor systems(4). It is estimated that 50 to 75% of patients with stroke persist with significant motor sequelae limiting daily activities(5). Recently, Vagus Nerve Stimulation (VNS) has been proposed as an intervention that could have beneficial effects in the recovery of motor function in these patients, since it contributes to the generation of adaptive neuroplasticity and the activation of neuromodulators that reduce brain inflammation(6). VNS has mainly been administered by using implanted electrodes, but more recently, a non-invasive technique, known as transcutaneous VNS (cervical or auricular) has been proposed. VNS has traditionally required the implantation of an electrical pulse generator at the left subclavicular level, which is connected to electrodes in the left cervical branch of the vagus nerve(7). Its insertion is performed by a surgical procedure, which presents a higher risk of adverse events(8), the most frequent being dysphonia during stimulation, due to its proximity to the laryngeal nerve(9). On the other hand, transcutaneous VNS works through the placement of non-invasive electrodes on the neck or auricle for stimulation of the cervical or auricular branch of the vagus nerve respectively(7). Transcutaneous VNS has a lower risk of adverse events, is reversible and easy to implement(7). In addition, experimental evidence suggests that the effects of transcutaneous VNS on brain function are comparable to those obtained with VNS(8). This study will evaluate the effects of transcutaneous vagus nerve stimulation (tVNS) in combination with physical rehabilitation on upper limb motor function of patients with stroke. Thirty patients with ischemic stroke will be included in the study. Subjects will be randomized to tVNS + physical rehabilitation or sham stimulation + physical rehabilitation. Therapy sessions will be performed 3 times a week for six consecutive weeks. Efficacy will be evaluated by assessing the change in motor function of the upper limb, the next day and 30 days after the end of the intervention. The motor function of the upper limb will be assessed by means of the Fugl-Meyer scale score.