Distribution of Applied Electrical Current in the Spinal Cord and Its Effects on Evoked Potentials
Date of Award
Dissertation - Restricted
Doctor of Philosophy (PhD)
These studies were undertaken to measure the current distribution from four spinal cord implant systems used clinically and to evaluate the underlying physiological phenomena and their clinical relevance. The electrode configurations used in the current density studies were: a. 5-etectrode system: 5 in line platinum-iridium discs, 2 mm diameter, spaced 4 mm apart at their center with adjacent discs of alternate polarity. b. 4-electrode system: 4 platinum oval electrodes, 1.5 x 3 mm, with rectangular spacing 4 mm wide x 8 mm long, adjacent ovals of the same polarity. c. 3-electrode system: 3 platinum squares, 4 x 4 mm spa~ed in line 9 mm apart alternate polarity. d. Anterior-posterior (A-P) system: 2 sets, each consisting of 3 platinum discs 2 mm diameter spaced in line 4 mm apart at center. Current is passed from one set on anterior cord to the other posterior set. Current density was measured in fresh human cadaver spinal cord, in vivo stumptail macaque monkey cords and in saline models using a parallel plate (.03 x .03 cm) loaded probe technique. The electrical field distribution was also plotted on teledeltos paper for each system...