Home-Based Digital Rehabilitation Program Optimized With Transcutaneous Spinal Cord Stimulation for Upper Limb Functional Enhancement in Tetraplegia (HOPE): A Safety, Efficacy, and Feasibility Study

Spinal Cord Injury (SCI), resulting from trauma or other causes, is a debilitating condition characterized by damage to the spinal cord. It leads to profound and often irreversible impairments in motor, sensory, and autonomic function, resulting in substantial limitations in activities of daily living (ADLs) and ambulation. These impairments significantly impair quality of life (QoL) and often result in long-term healthcare dependence. Globally, SCI affects approximately 20.6 million individuals, with an estimated 0.9 million new cases reported annually. In Singapore, the prevalence of SCI increased from 5 to 6 per 100,000 in 1990 to an estimated 13 to 15 per 100,000 in 2019. The economic burden is substantial, with annual direct costs related to SCI exceeding US$45 billion in the United States alone.

Among SCI types, incomplete tetraplegia is the most prevalent, accounting for 47.1% of all cases. This is reflected in local data; a study reported 44 new surgically treated SCI cases admitted to Singapore General Hospital (SGH) and Changi General Hospital (CGH) between January 2020 to December 2021, of which 39 were cervical SCI. Another local epidemiology study found that 75% of 55 traumatic SCI cases were tetraplegic.

For individuals with tetraplegia, upper limb function is often severely compromised, significantly limiting independence in daily tasks and impacting overall QoL. Restoration of hand and arm function is regarded as the top rehabilitation priority, considered six times more important than restoring walking ability in this group of population. A survey done by Snoek et al, 77% of 565 individuals with tetraplegia identified improvement in hand function as a key factor in improving their QoL.

Spinal cord stimulation (SCS) has emerged as a promising neuromodulation technique for improving neurological function after SCI. SCS delivers electrical impulses to activate afferent fibers, enhancing interneuronal connections between sensory afferents and motor neurons, enhancing motor neuron excitability, and promoting communication between spinal network. Transcutaneous spinal cord stimulation (tSCS), a non-invasive form of SCS, has gained significant attention, with numerous studies examining its effectiveness in improving motor function following SCI. tSCS typically involves the application of active electrodes over the cervical spinal region (C3/4 and C6/7) and return electrodes over the anterior superior iliac spine (ASIS), and it is combined with in-clinic rehabilitation or home-based exercise to enhance its therapeutic effect. Recent clinical trials have demonstrated that tSCS significantly improves upper limb function in individuals with chronic tetraplegia. For instance, the Up-LIFT trial enrolled 60 participants with nonprogressive incomplete cervical SCI. After 12-20 sessions of tSCS therapy, 72% of participants demonstrated improvements greater than the minimally important difference for both strength and functional domains. Notably, the tSCS demonstrated a favorable safety profile, even for home use.

To address these gaps, a commercially available neuromuscular electrical stimulation (NMES) devices, such as HSA-approved NeuroTrac® MultiTENS, offer a potential alternative. These devices can deliver similar stimulation parameters at a fraction of the cost. Despite differences in stimulation parameters such as pulse width and carrier frequency, the NeuroTrac® MultiTENS has demonstrated a profile that appears safe and effective in managing SCI-related complications .

This prospective, open-label study investigates a home-based rehabilitation program by repurposing a commercially available, HSA-approved neuromuscular electrical stimulation (NMES) device to deliver tSCS. The intervention integrates daily tSCS with a structured, mobile application-guided upper limb exercise program delivered through an AI-enabled digital platform that provides instructional content, real-time movement feedback, and adherence monitoring. Caregivers assist participants with device setup and therapy execution following standardized training.

The study employs a single-case experimental design with multiple baselines across participants. A total of 9 to 30 individuals with chronic, non-progressive cervical SCI (AIS B, C, or D) and impaired upper limb function will be enrolled and randomized into three groups. Each group will begin the intervention after a different baseline duration, allowing participants to serve as their own controls. All participants will complete a total study duration of 22 weeks, with the intervention lasting between 6 and 18 weeks depending on group assignment.

The primary outcome is upper limb function, assessed using the Graded Redefined Assessment of Strength, Sensibility and Prehension (GRASSP), measured every two weeks throughout the study. Secondary outcomes include upper extremity motor strength, quality of life, and goal attainment. Feasibility outcomes include adherence to the home-based program and participant and caregiver acceptability. Safety outcomes include monitoring and documentation of all adverse events related to tSCS and home-based therapy.

The results of this study will provide early evidence on the safety, feasibility, and potential efficacy of a scalable, home-based neuromodulation rehabilitation model using commercially available technology for individuals with tetraplegia.