ESTIM-UL: FES for Upper Limb Recovery After Stroke

Overview

Stroke is a leading cause of long-term disability, frequently resulting in impaired upper limb motor function and spasticity. Although Botulinum Toxin Type A (BoNT-A) is effective in reducing focal spasticity, functional recovery of the upper limb often remains limited without intensive, task-specific rehabilitation. Functional Electrical Stimulation (FES), when synchronized with voluntary movement during Task-Oriented Training, may enhance motor recovery by facilitating muscle activation and neuroplasticity. This randomized controlled trial aims to evaluate whether FES combined with Task-Oriented Training is superior to conventional Task-Oriented Training alone in improving upper limb function in post-stroke patients treated with BoNT-A.

Stroke remains one of the leading causes of long-term disability worldwide. Among its most disabling and persistent sequelae is impairment of upper limb motor function, affecting approximately 50-80% of stroke survivors in the acute phase and persisting in a substantial proportion of patients over time. Incomplete recovery of manual dexterity and fine motor control significantly limits independence in activities of daily living and negatively impacts quality of life. A major factor limiting upper limb recovery after stroke is the development of spasticity, a sensorimotor disorder resulting from upper motor neuron lesions. Upper limb spasticity typically evolves toward pathological flexor synergies which, if left untreated, lead to increased muscle tone, altered muscle-tendon properties, soft tissue shortening, and fixed joint deformities. These changes interfere with voluntary motor control, functional use of the limb, hygiene, and caregiving. Current international guidelines identify focal injection of Botulinum Toxin Type A (BoNT-A) as the first-line treatment for focal upper limb spasticity. By blocking presynaptic acetylcholine release at the neuromuscular junction, BoNT-A induces a temporary chemical denervation that effectively reduces muscle overactivity. However, clinical experience and scientific evidence consistently demonstrate a frequent dissociation between technical success, defined as reduction in spasticity scores, and functional success, defined as improved active use of the upper limb. Reduction of muscle tone alone, although necessary, is not sufficient to restore voluntary motor control in a damaged central nervous system unless it is integrated into an intensive neuromotor rehabilitation program. This observation has led to the concept of a "therapeutic window," in which BoNT-A reduces peripheral biomechanical resistance, creating favorable conditions that must be exploited through targeted adjunctive rehabilitation therapies. Among these, Task-Oriented Training (TOT), based on repetitive and intensive practice of meaningful functional tasks, represents one of the most effective approaches to promote post-stroke neuroplasticity. Nevertheless, in patients with moderate to severe paresis, insufficient voluntary muscle activation often limits the effective execution of task-oriented exercises. In this context, Functional Electrical Stimulation (FES) emerges as a key rehabilitative technology. Beyond inducing muscle contraction through peripheral nerve stimulation, FES acts as a powerful modulator of cortical plasticity. When synchronized with the patient's voluntary movement attempts, FES provides enhanced somatosensory feedback to the sensorimotor cortex. The coupling of motor intention, assisted execution, and afferent feedback reinforces synaptic connections according to Hebbian learning principles. Despite a strong neurophysiological rationale, there remains a lack of rigorous randomized controlled trials quantifying the specific added value of FES when combined with task- oriented rehabilitation in patients treated with BoNT-A. The present study is based on the hypothesis that applying FES to wrist and finger extensor muscles during Task-Oriented Training, in post-stroke patients previously treated with BoNT-A to inhibit spastic flexor muscles, produces a synergistic effect superior to conventional task-oriented rehabilitation alone. By simultaneously reducing spasticity-related resistance and enhancing muscle recruitment and cortical plasticity, this multimodal approach is expected to result in greater improvements in manual dexterity and overall upper limb function.