Monitoring of patients with critical neurologic illness has expanded significantly over the past several decades. Prior to the advent and application of technologies such as continuous EEG (electroencephalogram), intracranial pressure monitoring, brain tissue oxygenation and multimodal monitoring, the care of these critically ill patients relied on frequent clinical examinations to detect subtle changes that may signal an acute neurologic deterioration. This type of monitoring was limited by the availability of highly trained clinicians and nursing staff. The severity of the patient's illness can also obscure clinical changes, and then the interventions taken in order to treat the illness, such as induced coma for status epilepticus or intracranial hypertension, could further mask the clinical signs that would be necessary for detection of an acute change.