Spinal Cord NeoplasmsSpinal Cord CompressionSpinal NeoplasmsSpinal CordSpinal Cord InjuriesSpinal Cord DiseasesSpinal Cord IschemiaInjections, SpinalParaplegiaSpinal Nerve RootsSpinal NervesMotor NeuronsSpinal Cord RegenerationSpinal CanalCervical VertebraeAnesthesia, SpinalQuadriplegiaThoracic VertebraeSpinal DiseasesUmbilical CordPosterior Horn CellsLaminectomyRats, Sprague-Dawley