Characterization of longitudinal field gradients from electrical stimulation in the normal and injured rodent spinal cord

R. John Hurlbert, Charles H. Tator

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

THE PURPOSE OF this experiment was to characterize the longitudinal field gradients from exogenously applied electrical stimulation in the normal and injured rodent spinal cord. In addition, we compared the field gradients arising from stimulation with two different types of stimulating electrodes. Twenty normal rats underwent the surgical implantation of either extradural disc (n = 10) or cuff (n = 10) electrodes in the lower cervical and upper thoracic spinal cord. Sine waves of 1.5 to 50 μA and 0.5 to 50 Hz were used for stimulation. Field gradients were measured differentially from two extracellular glass microelectrodes, positioned stereotactically in the spinal cord at different locations between the stimulating electrodes. The effect of acute spinal cord injury on local field strength was studied in five animals from each group. The field gradients from stimulation with disc electrodes were greatest in close proximity to the discs and decreased markedly toward the point equidistant between the electrodes. In contrast, the gradients produced by cuff electrodes were much more evenly distributed along the spinal cord, increasing only slightly in proximity to the electrodes. These fields were also more evenly distributed throughout the spinal cord in cross-section but were generally weaker than those arising from disc electrodes. Acute spinal cord injury significantly increased the field gradients arising from both disc and cuff electrodes. However, the observed gradients remained substantially lower than those reported to enhance neurite growth in vitro. We conclude that the position and design of stimulating electrodes has a profound effect on longitudinal field gradients within the mammalian spinal cord, as does the presence of an acute spinal cord injury.

Original languageEnglish (US)
Pages (from-to)471-483
Number of pages13
JournalNeurosurgery
Volume34
Issue number3
DOIs
StatePublished - Mar 1994
Externally publishedYes

Keywords

  • Electrical stimulation
  • Extracellular field gradients
  • Field contours
  • Field mapping
  • Rat
  • Spinal cord injury

ASJC Scopus subject areas

  • Surgery
  • Clinical Neurology

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