The subspecialty of critical care neurology continues to develop at a remarkable pace Respite significant regulatory and social barriers. It is quite remarkable that despite the absence of either unitary or coordinated organizational sponsorship that the area of acute care of brain injuries continues to grow rapidly and in more than one direction. This section illustrates the contributions from neurosurgery, neuroradiology, neurology, and intensive care medicine to intensive care aspects of patient care. Perhaps it is because the growth of this area has so many origins that outpatient based physicians often ask, what is neurocritical care? While the answer has no consensus there are clear definitions as to the scope of what should be the purview of neurocritical care. Three important aspects of the word critical are time, physiology, and outcome.