New method for neuromodulation against pain using minimally invasive electrodes outside the epidural space

Chronic pain is cumbersome, difficult to treat and a growing and costly problem in modern medical care. Spinal cord stimulation (SCS) has proven to be an effective technique for pain mitigation in many cases. Despite being generally safe, the procedure carries increased risks for patients on anti-coagulant medication due to the catheter placement in the epidural space inside the spinal canal. Since these medical conditions are mainly prevalent in the elderly, among which chronic pain is also particularly common and problematic, a large group of patients are nowadays potentially excluded from the benefits of the spinal cord stimulation. Furthermore, the occurrence of SCS catheter dislocation adds to these challenges. In this paper, we present a novel multi-electrode implant platform (SNAP, safe neuromodulation against pain) that does not need entry into the vulnerable epidural space. This technique aims to extend pain mitigation benefits to patients currently ineligible for traditional spinal cord implants. Moreover, the implant is rigidly locked onto the vertebral bone, has the potential to reduce the risk of migration. As a first step, the feasibility of stimulating the spinal cord electrically using only the SNAP electrodes located outside the epidural space, has been tested using finite element method (FEM) computer simulations, assessing the implant's ability to selectively stimulate the dorsal column fibers without the undesired stimulation of the muscles in the back. Furthermore, in-vitro experiments have been performed to test the feasibility of the wireless energy transfer method. The FEM simulations conducted in this paper show that a low-frequency current of 6.30 mA and 1.26 mA from the primary and the secondary SNAP electrodes, respectively, gives rise to a selective stimulation of the dorsal column fibers. The in-vitro experiments confirm the feasibility of sufficient wireless energy transfer. We presented a first proof of concept for a new method of safe neuromodulation against pain, focussing on the electric aspects of the method. Our preliminary results suggest that this new approach may potentially overcome some limitations associated with standard SCS.