Disorders of consciousness (DoC) are neurologic conditions characterized by severe alteration in level of consciousness. Categories of DoC may include coma, unresponsive wakefulness syndrome/vegetative state, minimally conscious state (MCS
can be further categorized into MCS+ and MCS- based on the presence or absence of language-related behaviors), emergence from MCS, confusional state or delirium, and cognitive motor dissociation (CMD). CMD is a recently defined condition in which the patient fails to demonstrate observable behavioral responses on bedside assessment but demonstrates covert cognitive processing on functional imaging or EEG studies. Accurate differential diagnosis in DoC is aided by adherence to basic principles of assessment, including use of standardized assessment scales. Clinicians should serially administer standardized assessment tools to ensure valid interpretation of results and optimize diagnostic accuracy. Among standardized scales, the Coma Recovery Scale-Revised is most widely used and has the strongest psychometric validity in assessing DoC. The Neurocritical Care Society's Curing Coma Campaign has proposed a slate of DoC common data elements that is expected to improve the consistency and precision of DoC research.