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We have developed a spinal cord surrogate for use in testing a pial-surface spinal cord stimulator. Our surrogate is of a commercially available silicone mix, has an oval cross-sectional area that matches that of actual human spinal cord at the lower thoracic level, and has measured values of durometer A = (10.96 ± 1.68), durometer O = (14.76 ± 1.48), and durometer OO = (50.24 ± 2.65). These correspond to model-inferred elastic moduli of 0.41 to 0.44 MPa, which match well with the existing low-strain rate measurements of ex vivo human spinal cord. Upcoming applications for this surrogate in developmental studies of the new stimulator system are discussed. [ABSTRACT FROM AUTHOR]

We introduce an intradural approach to spinal cord stimulation for the relief of intractable pain, and describe the biophysical rationale that underlies its design and performance requirements. The proposed device relies on wireless, inductive coupling between a pial surface implant and its epidural controller, and we present the results of benchtop experiments that demonstrate the ability to transmit and receive a frequency-modulated 1.6 MHz carrier signal between micro-coil antennae scaled to the ≈ 1 cm dimensions of the implant, at power levels of about 5 mW. Plans for materials selection, microfabrication, and other aspects of future development are presented and discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We have designed, built and tested a novel spinal cord surrogate that mimics the low-amplitude cardiac-driven pulsations of the human spinal cord, for use in developing intradural implants to be used in a novel form of neuromodulation for the treatment of intractable pain and motor system dysfunction. The silicone surrogate has an oval cross section, 10 mm major axis × 6 mm minor axis, and incorporates a 3 mm diameter × 3 cm long angioplasty balloon that serves as the pulsation actuator. When pneumatically driven at 1 Hz and 1.5 atmospheres (≈≈ 1140 mm Hg), the surrogate's diametric pulsation is ≈≈ 100 μm, which corresponds well to in vivo observations. The applications for this surrogate are presented and discussed. [ABSTRACT FROM AUTHOR]