Optometry clinical training and practice at the public health facilities in South Africa: a documentation review.

Stroke is a leading cause of long-term disability worldwide and represents a major public health burden, particularly in aging societies. Advances in acute stroke management have substantially reduced mortality. However, a large proportion of stroke survivors continue to experience persistent neurological impairments. Among these, motor deficits—especially of the upper limbs—are the most common and disabling, severely limiting patients’ independence in activities of daily living and overall quality of life. Motor recovery after stroke is often incomplete, with more than half of survivors failing to regain adequate upper limb function, even after receiving routine rehabilitation. This limited recovery not only restricts functional independence but also imposes substantial socioeconomic and caregiving burdens on patients, families, and healthcare systems. The primary goal of post-stroke rehabilitation is to facilitate adaptive neuroplasticity that supports functional reorganization and behavioral recovery. However, spontaneous post-stroke plasticity is frequently insufficient or maladaptive, particularly during the subacute and chronic stages of recovery. Without appropriate modulation, these maladaptive processes may reinforce abnormal movement patterns and compensatory strategies, exacerbate interhemispheric imbalance, and ultimately lead to long-term disability. Therefore, there is a critical need for adjunctive therapeutic strategies that can enhance the effectiveness of routine rehabilitation by promoting more favorable neurophysiological responses. To enhance neurorehabilitation outcomes, adjunctive neuromodulatory interventions such as vagus nerve stimulation (VNS) have gained attention. VNS has received approval from the U.S. Food and Drug Administration (FDA) for clinical use in epilepsy and treatment-resistant depression. Recent studies have further demonstrated its potential to enhance motor function recovery in patients with stroke. While traditional VNS requires surgical implantation, limiting accessibility and posing surgical risks, left-sided transcutaneous auricular stimulation (taNS) has emerged as a non-invasive alternative that targets the auricular branch of the vagus nerve. Currently, there is ongoing controversy regarding the terminology of transcutaneous auricular vagus nerve stimulation and transcutaneous auricular nerve stimulation, because the innervation of the ear is highly complex and not exclusively mediated by the vagus nerve. In addition, due to the complexity of the anatomical structure, many of the therapeutic mechanisms of taNS remain unclear, and whether its effects are truly mediated through vagal pathways is still speculative. Therefore, whether the mechanisms of transcutaneous auricular stimulation described in this paper are consistent with the effects of direct vagus nerve stimulation requires further investigation. Systematic reviews and meta-analyses have shown that taNS paired with physical rehabilitation can significantly improve upper limb motor function after stroke. In 2021, Dawson et al. conducted a series of randomized, double-blind clinical trials showing that implanted VNS combined with motor training significantly improved upper limb motor function in patients with ischemic stroke compared with sham VNS combined with motor training. Since then, increasing attention has been directed toward the application of non-invasive taNS for the recovery of post-stroke motor dysfunction. Bashar et al. subsequently reported in a clinical trial that closed-loop motor-activated auricular vagus nerve stimulation (MAAVNS) significantly improved upper limb Fugl–Meyer motor scores and enhanced quality of life in stroke patients. However, the overall evidence remains heterogeneous across studies. While some randomized controlled trials have demonstrated significant improvements in motor outcomes, others have reported modest or inconsistent effects, particularly at long-term follow-up or under varying stimulation protocols. For example, a systematic review by Li et al. reported that although short-term motor improvements were observed, the overall effect size was limited and not consistently sustained over time. Similarly, another study by Li et al. highlighted that differences in stimulation timing, patient characteristics, and rehabilitation paradigms may contribute to variability in clinical outcomes. Moreover, previous studies suggest that bilateral transcutaneous auricular nerve stimulation (BtaNS) activation may provide greater sensory afferent input to brainstem pathways, thereby potentiating the therapeutic effects of VNS. Compared with unilateral stimulation, bilateral auricular stimulation appears to produce more pronounced neuromodulatory benefits. However, the optimal laterality of taNS remains a subject of ongoing debate.