Neurophysiological recording is the major neuromonitoring technique employed in ICU. In addition, continuous recording of intracranial pressure has proved to provide infomation useful for critical care of the patient with severe brain damage. It is, however, difficult to assess neurochemical and/or metabolic environments of the brain with these conventional neuromoni- toring techniques. Information regarding these changes, if available on a real-time basis, is undoubtedly useful for patient care. Many important developments in bedside techniques to monitor these changes have been achieved...