Metabolic Changes in the Spinal Cord After Brachial Plexus Root Re-implantation

Objective. To investigate metabolic changes within the spinal cord using proton magnetic resonance spectroscopy ((1)H-MRS) and determine their relationship with clinical function in patients with complete brachial plexus avulsion who underwent reimplantation of the ventral roots. Methods. Single-voxel (1)H-MRS of the cord between C1 and C3 was performed in 10 patients with normal spinal cord on MRI, who underwent reimplantation of C5 to T1 ventral roots on average 5.5 years earlier, and 19 healthy controls. The ratios of the concentrations of the following main metabolites, with respect to total creatine levels, were obtained: total N-acetyl-aspartate, choline-containing compounds, creatine and phosphocreatine (Cr), and myo-inositol (m-Ins). Patient disability was assessed using upper limb scales. Differences in metabolite concentration ratios and their correlations with disability were investigated. Results. Patients showed increased m-Ins/Cr ratio compared with controls, which was associated with the level of function of the affected arm and time from injury. Conclusions. The finding of increased m-Ins/Cr in patients suggests that reactive gliosis, perhaps in response to the degeneration of avulsed fibers, may occur in the spinal cord above the site of injury and be relevant to motor dysfunction. However, this pathological process appears to diminish with time. These insights underline the need to integrate metabolic imaging with structural and functional magnetic resonance imaging to obtain a complete view of spinal cord plasticity. Last, this study provides the first steps toward identifying markers to serve as outcome measures for trials comparing strategies of plexus repair following avulsion injury.