Authors: David Darrow, MD; David Darrow, MD; David Balser, MD; Ann Parr, MD, PhD; Uzma Samadani, MD, PhD; Aaron Phillips; Andrei Krassioukov, MD, PhD; Andy Lamperski, PhD; Theoden Netoff, PhD (Minneapolis, MN)
Spinal cord stimulation has now been shown to restore some volitional movement and autonomic function in patients with motor-complete spinal cord injury, but little has been done to evaluate the millions of possible frequency, pulse width, and amplitude parameter settings. The E-STAND trial was designed to efficiently and systematically evaluate the parameter space for optimal restoration of volitional movement and autonomic function through novel, remotely-collected quantitative and qualitative assessments.
Seven patients have been enrolled in the E-STAND trial and undergone implantation of SCS to restore volitional movement after motor-complete SCI. Ages range from 28 to 60 and time since injury ranges from 2 years to 15 years. Remotely-collected daily survey and daily task data was modeled monthly using a probit response function over frequency and pulse width. Bayesian optimization was performed to find the most important settings each month.
All patients had restoration of some volitional movement. Probit response surfaces demonstrate that some variability exists across the most optimal settings for restoration of volitional movement with peaks ranging from 24 Hz to 40 Hz while pulse width preference ranges from 350 to 450 us. When compared to the evaluated parameter space, there is significant overall preference for frequencies between 30 and 40 Hz (p <-1e10) compared with higher settings. Colinear results were found for optimal settings for restoration of posture but not restoration of autonomic function.
Using a novel probit response surface and Bayesian optimization for setting selection, the optimal ranges for SCS parameters is actually quite narrow (30Hz, 350 to 450 us), though individual preferences vary slightly. This significant finding will enable further research into the effect of SCS on restoration of volitional movement and aid computational modeling efforts to optimize electrode configuration.