Since the foundational descriptions of the comatose [1], vegetative [2], and minimally conscious [3] states in the late twentieth and early twenty-first centuries, there has been rapid progress in elucidating the pathophysiologic mechanisms [4], clinical phenotypes [5], and recovery trajectories [6, 7] of patients with disorders of consciousness (DoC). Diagnostic classification systems have evolved from a behavior-centric paradigm to a multimodal paradigm that considers covert forms of cognition [8] detected by advanced neurotechnologies, such as task-based functional magnetic resonance imaging [9,10,11,12] and electroencephalography [7, 13,14,15]. Accordingly, clinical guidelines [16, 17] and expert consensus recommendations [18] now endorse the use of advanced neurotechnologies to evaluate patients with DoC. In this rapidly evolving landscape, investigational insights have often outpaced the diagnostic nomenclature, leading to variability in how patients are classified in research studies and in clinical settings [19, 20].

To bring clarity to the dynamic field of DoC research and to facilitate the international collaboration that is essential for further progress, the Neurocritical Care Society launched the Curing Coma Campaign in 2019 [21, 22], bringing together the worldwide community of DoC clinicians and researchers in common cause. The Campaign’s overarching goal is to address the “grand challenge” of improving the management and outcomes of patients with DoC. To achieve this goal, the Campaign is pursuing a broad range of initiatives [23], which include identification of current gaps in knowledge [24,25,26], establishing infrastructure for multicenter prospective studies [27], and developing a standardized framework and shared nomenclature for conducting future research studies. Central to this latter effort is the development of common data elements (CDEs), the building blocks for data harmonization, data sharing, and multisite collaboration. Inspired by similar initiatives led by the National Institutes of Health (NIH) that provide CDEs for a range of neurological diseases (https://www.commondataelements.ninds.nih.gov/), and with guidance provided by the NIH National Institute of Neurological Disorders and Stroke, the Curing Coma Campaign’s DoC CDE initiative aimed to bring together the international community to create a common language for future research.

The DoC CDE initiative was thus launched in 2020 and included ten working groups in the domains of behavioral phenotyping [28]; hospital course, confounders, and medications [29]; neuroimaging [30]; electrophysiology [31]; biospecimens and biomarkers [32]; physiology and big data [33]; therapeutic interventions [34]; goals of care and family/surrogate decision-making [35]; pediatrics [36]; and outcomes and end points. These working groups met regularly via teleconference for 2 years to develop CDEs specific to patients with DoC. Each working group leveraged existing NIH CDEs developed for other conditions (e.g., traumatic brain injury, ischemic stroke, and aneurysmal subarachnoid hemorrhage) whenever possible to ensure that the DoC CDEs were consistent with established standards. Wherever existing NIH CDEs did not sufficiently address data elements relevant to DoC research, the working groups proposed new CDEs based on consensus opinion.

All CDEs were then classified as “disease core,” “basic,” “supplemental,” or “exploratory,” consistent with the classification system used in prior NIH CDE initiatives [37,38,39]. We assigned the disease core designation to CDEs that are required for all DoC studies, the basic designation to CDEs that are strongly recommended for all DoC studies, the supplemental designation to CDEs that are recommended for specific DoC studies (i.e., depending on the context and goals of the study), and the exploratory designation to CDEs that can be considered for use in DoC studies but require further validation. Finally, we included a designation of “key design element” for methodological parameters relevant to the acquisition, processing, or analysis of data.

The result of this international, multiyear effort was a set of case reports forms, containing all DoC CDEs and key design elements, which we released in preliminary form on www.zenodo.org (version 0.0) in October 2022 for a 2-month public feedback period, which was advertised at the 2022 Neurocritical Care Society annual meeting and via social media (i.e., Twitter). Public feedback was then incorporated into the final case report forms, which were released as version 1.0 at https://zenodo.org/records/8172359. We encourage ongoing feedback, which can be submitted via email to cde.curingcoma@gmail.com. All suggestions will be evaluated by the relevant working groups, and changes to the case report forms will be posted on the zenodo website with new version numbers. This adaptive approach is crucial to allow integration of emerging evidence, given ongoing rapid developments in the field.

Looking to the future, we encourage the international community of DoC investigators to use these CDEs, which are freely available and downloadable in domain-specific case report forms. By harmonizing our classification systems and nomenclature, we will ensure that researchers worldwide are speaking the same language as we continue to advance knowledge in our field. The dissemination of DoC CDEs is thus a foundation on which the overarching goal of the Curing Coma Campaign—to improve management and outcomes for patients with DoC—can be realized.