Diagnosis of coma and other disorders of consciousness

Key points

• The European Academy of Neurology (EAN) guideline, developed with GRADE by 16 panel members from 10 European countries, covers bedside examination, functional neuroimaging and EEG-based techniques.
• The eyes of patients without spontaneous eye opening should be opened passively to look for voluntary eye movements, and a mirror should always be used to test visual pursuit.
• The Coma Recovery Scale - Revised (CRS-R) is recommended to classify the level of consciousness, and classification should never rest on a single assessment.
• In the intensive care unit (ICU), the Full Outline of Unresponsiveness (FOUR) score is recommended instead of the Glasgow Coma Scale.
• A patient should be diagnosed with the highest level of consciousness revealed by any of the three approaches: clinical, EEG or neuroimaging.

Overview

This guideline summarises the evidence for diagnosing coma, the vegetative state/unresponsive wakefulness syndrome (VS/UWS) and the minimally conscious state (MCS) after acquired brain injury. The authors note that as many as 40% of non-communicating patients may be wrongly classified as VS/UWS, and that roughly 15% of behaviourally VS/UWS patients can follow commands during EEG- or fMRI-based paradigms.

Definitions

Coma is profound unawareness from which the patient cannot be aroused, with closed eyes and no normal sleep-wake cycle. VS/UWS denotes wakefulness without clinical signs of awareness. Patients in MCS show inconsistent but reproducible non-reflex behaviours and are subdivided into MCS plus and MCS minus. Patients who follow commands only during fMRI or EEG paradigms are considered to be in cognitive motor dissociation.

Bedside examination

Strong recommendations include passive eye opening, probing both vertical and horizontal eye movements (very low evidence), using a mirror for visual pursuit (low evidence), the CRS-R (moderate evidence), repeated assessments (low evidence) and the FOUR score in the ICU (moderate evidence). In prolonged disorders of consciousness, five assessments over several days (for example within 10 days) appear appropriate; in one study, misdiagnosis was 36% with a single assessment versus 5% with five. Weak recommendations support documenting spontaneous motor behaviour and considering the Nociception Coma Scale - Revised for signs of discomfort, and advise against the CAM-ICU in these patients.

EEG and functional neuroimaging

Clinical standard EEG is recommended (low evidence, strong recommendation); non-convulsive status epilepticus must be ruled out, and a flatline EEG of sufficient technical standard in an unsedated patient is incompatible with preserved consciousness. As weak recommendations within multimodal assessment, the panel suggests sleep EEG, quantitative high-density EEG, TMS-EEG, cognitive evoked potentials, resting state FDG-PET, adding a resting state fMRI sequence when structural MRI is indicated, and active fMRI paradigms in patients without bedside command following. Passive fMRI paradigms are suggested only within research protocols.

Frequently asked questions

Why use a mirror at the bedside?

In the pooled studies, a mirror detected visual pursuit more often than other stimuli, and it is a convenient bedside tool; if it evokes no response, pictures of familiar faces or personal objects may be tried.

Does a negative active fMRI or EEG paradigm exclude consciousness?

No. These paradigms have high specificity but very low sensitivity, so absence of command following is not proof of absence of consciousness.

Source

Kondziella D, Bender A, Diserens K, van Erp W, Estraneo A, Formisano R, et al. European Academy of Neurology guideline on the diagnosis of coma and other disorders of consciousness. Eur J Neurol 2020;27(5):741-756. doi:10.1111/ene.14151. Endorsed by the European Academy of Neurology. This summary was prepared by Medpresso from the original publication and is not a substitute for the full text or for medical advice.