MR-based measurement of spinal cord motion during flexion of the spine: implications for intradural spinal cord stimulator systems

Abstract

This study develops a means of delivering electrical stimuli directly to the pial surface of the spinal cord for treatment of intractable pain. This intradural implant must remain in direct contact with the cord as it moves within the spinal canal. Therefore, magnetic resonance imaging was used to measure the movement of the spinal cord between neutral and flexed-back positions in a series of volunteers (n = 16). Following flexion of the back, the mean change in the pedicle-to-spinal cord dorsal root entry zone distance at the T10-11 level was (8.5 ± 6.0) mm, i.e. a 71% variation in the range of rostral-caudal movement of the spinal cord across all patients. There will be a large spectrum of spinal cord strains associated with this observed range of rostral-caudal motions, thus calling for suitable axial compliance within the electrode bearing portion of the intradural implant.

• Dorsal root entry zone
• intradural implants
• neuromodulation
• spinal cord
• spinal cord stimulator

Acknowledgements

The first two authors have made equal contributions to this work and are therefore designated as co-first authors. We thank Hiroyuki Oya, MD, Hiroto Kawasaki, MD, W. R. Smoker, MD, and H. Chen for several useful discussions and technical assistance. We also thank R. Shurig and colleagues of Evergreen Medical Technologies LLC for skillful fabrication of the prototype HSCMS devices and for the illustration used in Figure 1. AMS subject classification: 92C10; 92C.