Chronic regenerative changes in the spinal cord after cord compression injury in rats.

Long-term regenerative changes and pathological effects after acute compression injury of the spinal cord were studied in rats. Twenty adult female Wistar rats underwent cord injury by the extradural clip compression technique at T6-7. Following injury, extradural electrodes attached to receiver-stimulators that were implanted subcutaneously were placed proximal and distal to the injury site. The animals were maintained in cages with electromagnetic fields created by encircling antennae. The control animals were in a field adjusted to a frequency below the sensitive frequency range of the receiver-stimulators so that they received no spinal cord stimulation. After 15-20 weeks of continuous spinal cord stimulation, histological sections of the cords were assessed and scored blindly for pathological changes including magnitude and extent of cord injury, and cystic cavitation, and for regenerative changes including proliferation of axons, Schwann cells and ependymal cells, and formation of myelin. In all 20 animals, there was a complete absence of normal cord tissue at the injury site, and cystic cavitation was frequently present at the injury site and beyond. Extensive regenerative changes were seen in all animals including regeneration of axons, Schwann cells and ependymal cells, and formation of myelin. Statistical analysis did not show a significant difference between treatment and control groups.