Repeated 31P-Magnetic Resonance Spectroscopy in Severe Traumatic Brain Injury: Insights into Cerebral Energy Status and Altered Metabolism

Phosphorous magnetic resonance spectroscopy (31P-MRS) is suited to noninvasively investigate energy metabolism and to detect molecules containing phosphorus in the human brain. The aim of this longitudinal study was to perform 31P-MRS at two different time points (within 72 h and between day 10-14) after severe traumatic brain injury (sTBI) to reveal alterations in cerebral energy metabolism. Twenty-six ventilated patients with sTBI, aged between 20 and 75 years, with a median initial Glasgow Coma Scale score of 5 were analyzed prospectively. The 31P-MRS data of the structurally more affected side were compared with data from contralateral normal appearing areas and with data of age- and gender-matched healthy controls. There were no significant intraindividual differences between the lesioned and the less affected side at either of the time points. In the acute phase, phosphocreatine/adenosine triphosphate (PCr/ATP) and phosphocreatine/inorganic phosphate (PCr/Pi) were significantly elevated whereas phosphomonoesters/phosphodiesters (PME/PDE) and Pi/ATP were significantly decreased in contrast to healthy controls. In the subacute phase, these differences gradually dissipated, remaining lower Pi/ATP ratio, and only partly altered levels of PCr/Pi and PME/PDE. Our data affirm that cerebral metabolism is globally altered after sTBI, demonstrating the diffuse impairment of brain bioenergetics at multiple levels, with resultant developments in terms of time.