by Daniel Kondziella
The level of consciousness in patients with severe brain injury can be difficult to assess. The problem is that clinical evaluation often is unreliable – consciousness may wax and wane, requiring sufficient arousal which is often not achieved; and even when it is, patients may still be awake and aware but unable to show it due to motor paralysis or language deficits. This is true for the acute setting in intensive care and with chronic brain injury, e.g. in neurorehabilitation or nursing homes. The question is: How many unresponsive patients with acute brain injury have preserved consciousness or may have the potential for it? The answer is important for prognosis, treatment and resource allocation.
The new EAN guideline on the diagnosis of coma and other disorders of consciousness presents the state-of-the-art evidence for identifying signs of overt or covert consciousness in patients with acute and chronic brain injury, highlighting clinical, neuroimaging and EEG measures. Sixteen EAN members with a prominent track record in consciousness research reviewed the scientiﬁc evidence, extracting salient information following prespecified methods and calculating hazard ratios, and based recommendations on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system.
Importantly, the guideline was accomplished while having the needs of the general neurological practitioner is mind. Hence, a focus is on low-cost and easy-to-implement bedside measures with immediate clinical impact. These include the importance of probing for voluntary eye movements using a mirror; relying on repeated rather than isolated clinical assessments (preferentially using the Coma Recovery Scale-Revised); favoring the Full Outline of UnResponsiveness score over the Glasgow Coma Scale in the intensive care setting; and visual analysis of standard EEG, including searching for rapid eye movement sleep and slow-wave sleep patterns. In addition, the reader is provided with thorough evaluation of neuroimaging markers, including connectivity measures revealed by functional MRI and brain metabolism assessed with positron emission tomography, again highlighting potentials and pitfalls from a clinical perspective. One of its take-home messages is that the state of consciousness in a patient with severe brain injury should be diagnosed according to the highest level revealed by any of these three approaches (clinical, imaging or EEG); for instance, a clinically unresponsive patient who is able to follow commands in an active fMRI paradigm should be regarded as being conscious and in a state of cognitive motor dissociation.
Although many challenges remain regarding diagnostic definitions and the sensitivity and specificity of various consciousness measures, the data synthesized in this guideline have paved the way for a much greater understanding of coma and disorders of consciousness. This has translated into an entirely different mindset in those who care for these patients – from therapeutic nihilism towards a brighter future with clinical trials aiming to actually improve the lives of people belonging to one of the most vulnerable patient groups there are.
Background and purpose
Patients with acquired brain injury and acute or prolonged disorders of consciousness (DoC) are challenging. Evidence to support diagnostic decisions on coma and other DoC is limited but accumulating. This guideline provides the state‐of‐the‐art evidence regarding the diagnosis of DoC, summarizing data from bedside examination techniques, functional neuroimaging and electroencephalography (EEG).
Sixteen members of the European Academy of Neurology (EAN) Scientific Panel on Coma and Chronic Disorders of Consciousness, representing 10 European countries, reviewed the scientific evidence for the evaluation of coma and other DoC using standard bibliographic measures. Recommendations followed the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. The guideline was endorsed by the EAN.
Besides a comprehensive neurological examination, the following suggestions are made: probe for voluntary eye movements using a mirror; repeat clinical assessments in the subacute and chronic setting, using the Coma Recovery Scale – Revised; use the Full Outline of Unresponsiveness score instead of the Glasgow Coma Scale in the acute setting; obtain clinical standard EEG; search for sleep patterns on EEG, particularly rapid eye movement sleep and slow‐wave sleep; and, whenever feasible, consider positron emission tomography, resting state functional magnetic resonance imaging (fMRI), active fMRI or EEG paradigms and quantitative analysis of high‐density EEG to complement behavioral assessment in patients without command following at the bedside.
Standardized clinical evaluation, EEG‐based techniques and functional neuroimaging should be integrated for multimodal evaluation of patients with DoC. The state of consciousness should be classified according to the highest level revealed by any of these three approaches.