First Objective Evidence Characterizing Differences in Cervical and Thoracic Spinal Cord Neurophysiology Using ECAP-Controlled Closed-Loop Technology.

Introduction: Spinal cord stimulation (SCS) is a widely accepted therapy in patients with chronic intractable neuropathic pain in the trunk and limbs. However, open-loop (OL) SCS systems, which rely on fixed stimulation parameters and subjective feedback, face limitations in delivering consistent neural activation and durable pain relief. Anatomical and physiological characteristics of the cervical spinal cord, such as decreased cerebrospinal fluid thickness and increased mobility, exacerbate these challenges. Limited evidence exists on differences in cervical and thoracic neurophysiology, and the corresponding impact on neural activation in SCS. This post hoc analysis characterizes neurophysiological differences between the cervical and thoracic regions using evoked compound action potential (ECAP)-controlled closed-loop (CL) technology to assess implications for SCS dosing and therapy optimization.

Methods: Global study and real-world chronic pain patients implanted with ECAP-controlled CL-SCS systems were included. To identify differences between cervical (n = 187) and thoracic (n = 1899) neurophysiology, the relationship between stimulation current and neural activation was analyzed. Additionally, neural activation stability was evaluated in both in-clinic and out-of-clinic settings.

Results: The cervical spinal cord demonstrated significantly lower ECAP thresholds (p < 0.001) and > 100% higher spinal cord sensitivity compared to the thoracic region (p < 0.001). Cervical therapeutic dosing range was ≥ 48% narrower (p < 0.001), increasing the risk of overstimulation with OL-SCS. CL-SCS significantly improved dose accuracy in both regions (p < 0.001) during postural changes simulating activities of daily living. These findings highlight the superior precision and consistency in neural dosing with ECAP-controlled CL systems.

Conclusions: This is the first study to objectively characterize differences in cervical and thoracic spinal neurophysiology using SCS. ECAP-controlled CL-SCS maintains consistent neural activation in both cervical and thoracic regions. Given the heightened sensitivity and narrow dosing range in the cervical region, ECAP-controlled CL-SCS may enhance therapeutic outcomes through more precise and consistent neural dosing compared to OL systems.