Brain free magnesium concentration is predictive of motor outcome following traumatic axonal brain injury in rats.

A number of studies have supported a role for brain free magnesium as an important secondary injury factor in the development of neurologic deficits following traumatic brain injury. Despite this, few studies have characterised free magnesium changes in diffuse models of brain injury relevant to clinical trauma, and none have critically examined the association between brain free magnesium concentration and degree of neurologic deficit following graded trauma. In the present study, a combination of nuclear magnetic resonance spectroscopy and rotarod motor function tests were used to characterise the relationship between brain free magnesium concentration and neurologic motor function following graded traumatic axonal brain injury in rats. Induction of moderate or severe impact-acceleration induced traumatic brain injury resulted in a profound decline (p < 0.01) in brain free magnesium concentration that persisted for a minimum of 4 days post-trauma in both injury groups. Posttraumatic rotarod deficits assessed on a daily basis after injury were linearly correlated with brain free magnesium concentration measured in the same animals immediately after the motor tests were performed (r = 0.87; p < 0.001). These results suggest that brain free magnesium declines following graded diffuse axonal brain injury and that the concentration of the ion after trauma may be a prognostic indicator of motor outcome following.