Brain-Controlled Stimulation of the Cervical Spinal Cord to Restore Upper Limb Motor Functions in People With Tetraplegia

Every day, we engage in simple activities - standing up, grabbing a coffee in town, driving - without realizing we are exposed to the risk of spinal cord injury (SCI). A simple event, such as a fall, can drastically alter any individual's life, resulting in a loss of mobility and other debilitating symptoms. Depending on the lesion severity, partial recovery is possible but, after entering the chronic phase, the prospectives of recovering lost functions slowly disappears. In cases of a high cervical SCI (above C4 spinal level), the independence of the individual is greatly compromised. On top of nursing needs, patients typically rely on human assistance for most daily tasks - transferring from bed to wheelchair, turning on their computers, phones, preparing food and even feeding themselves. In summary this population often requires 24/7 care. In most countries, insurances cannot cover the expense of a long-term home care for the patients, and in the absence of family support, returning home can become impossible. SCI disrupts the communication between the brain and the spinal cord below the lesion, yet, the sub lesional structures remain intact, more or less patiently waiting to receive new commands from the cortex. To bypass the lesion, we envisioned a neuroprosthetic system, artificially relaying the commands originating from the brain to the spinal cord. Epidural electrical stimulation (EES) offers a promising platform to restore motor functions due to its stability, and rapid setup for daily-use. If EES has shown success in restoring lower limb motor functions after a lower spinal cord injury in the past 5-10 years, and translating this approach to arm and hand control poses greater complexity due to the fine motor synergies required to execute a wide variety of tasks. In parallel, brain-computer interfaces (BCIs) â interpretating brain signals through sensors measuring neural activity- developed exponentially in the past 30 years. Yet, only recently has the concept of using neural signals to directly modulate spinal stimulation became feasible. In this thesis, we designed and established a framework and clinical trial to investigate the concept of a brain to cervical spinal cord interface to restore upper limb mobility after a chronic SCI. We deployed such a system in two participants suffering from high cervical injuries. Through this first-in-human clinical trial, we established a methodological framework encompassing neural decoding, control strategies, and configuration of cervical EES parameters. We showed that once configured, voluntary motor functions such as self-feeding could be restored and that the extended use of this system could lead to neuro-rehabilitation effects. The results presented in this manuscript, pave the way towards a system that would restore upper limb motor functions and promote recovery after a high cervical spinal injury. Moreover, they provide key insights into the next steps required to scale and democratize