Magnesium in a Polyethylene Glycol Formulation Provides Neuroprotection After Unilateral Cervical Spinal Cord Injury

Abstract

Study Design. Experimental animal study. Objective. To investigate the neuroprotective efficacy of this magnesium in polyethylene glycol (PEG) formulation in a contusive model of cervical spinal cord injury (SCI). Summary of Background Data. Intravenously administered magnesium has been extensively investigated as a neuroprotective agent in animal models of SCI, stroke, and traumatic brain injuries, and has been evaluated in large scale clinical trials for the latter 2 indications. We have developed a novel formulation of magnesium chloride (MgCl(2)) within PEG, and have previously demonstrated the neuroprotective benefit of this formulation in animal models of thoracic SCI. Methods. Twenty-two Sprague Dawley rats underwent a unilateral cervical hemicontusion at C4-C5 and were randomized 2 hours later to either the MgCl(2) in PEG formulation, or normal saline. Each treatment was administered in 5 intravenous infusions spaced 6 hours apart. Behavioral recovery was assessed over 6 weeks, after which the cord was analyzed to measure the extent of gray matter and white matter sparing through the injury site. Results. In the horizontal ladder test, the percentage of forelimb errors made by the animals treated with MgCl(2) in PEG formulation was significantly lower than the saline-treated controls. Histologic analysis also revealed a significantly higher cumulative white matter sparing through the injury site in the MgCl(2) in PEG group. Conclusion. MgCl(2) in a PEG formulation reduced secondary damage and improved behavioral recovery when administered 2 hours after a unilateral cervical hemicontusion injury. These findings are consistent with the neurologic benefit observed when administering this magnesium formulation in contusive and compressive models of thoracic SCI. Demonstrating the robustness of this neuroprotective effect in multiple injury models (and in the cervical injury model in particular) is important when considering the applicability of such a therapy for human SCIs.