Metabolite concentrations and relaxation in perinatal cerebral hypoxic-ischemic injury

Regional cerebral metabolite concentrations, principally of choline-containing compounds (Cho), total creatine (Cr), N-acetylaspartate (Naa), and lactate (Lac), can be quantified by in vivo proton magnetic resonance spectroscopy. In order to estimate a metabolite concentration, it is often necessary to measure the transverse relaxation time (T-2). Metabolite T(2)s depend on cytosolic viscosity: as [adenosine triphosphate] falls leading to Na+/K+ pump failure, cytosolic water increases and T(2)s lengthen. In central grey-matter in human infants, Naa may be almost exclusively neuronal: Naa T-2 may index neuronal edema and energy generation. In this preliminary report, metabolite concentrations and T(2)s have been measured in central grey matter in human infants suspected of perinatal hypoxic-ischemic cerebral injury. In infants who developed serious cerebral injury or died, [Cho] and [Naa] were low (the latter suggesting neuronal loss), [Lac] and all metabolite T(2)s were increased: the Naa T-2 increase possibly reflected neuronal edema following failure of energy generation in a fraction of remaining neurons.