14 Magnetic Resonance Spectroscopy

Traumatic brain injury continues to be the major cause of death in individuals under 44 years of age (Chapter 1). In addition to the high degree of mortality, the morbidity associated with survivors of severe head injury imposes significant social and financial costs upon the community. Despite being such a major public health issue, the mechanisms that result in the irreversible tissue damage after brain trauma are still unclear. It has become increasingly accepted that irreversible tissue damage after brain trauma occurs through both primary and secondary means. Primary events are generally considered to be the mechanical changes to nervous tissue that occur at the time of insult, while secondary events are the physiological and biochemical changes that occur over time after the initiating insult (Chapter 4). The fact that the secondary events occur over hours to days after the trauma encourages attempts to prevent, or at least attenuate, the secondary injury cascade. Nonetheless, before preventative therapies can be introduced, there is a clear need to identify the factors involved in the secondary injury process, and a need to be able to identify whether a selected ‘antifactor’ is indeed having the desired effect on brain metabolism. While a number of techniques can be used in experimental studies to investigate metabolic events associated with trauma and pharmacological intervention, these are primarily invasive techniques that cannot be translated to a clinical setting. However, the recent application of non-invasive magnetic resonance spectroscopy (MRS) to experimental trauma studies has now resulted in MRS techniques being applied to metabolic studies of clinical head injury. The purpose of this chapter is to provide an overview of magnetic resonance spectroscopy and its utility in non-invasive metabolic studies. Recent clinical applications of MRS in head injury and how they correlate with previous experimental studies will be summarized, and newer magnetic resonance imaging (MRI) techniques for studies of brain metabolism and function will be briefly discussed.