Neurobehavioural evaluation of disorders of consciousness

Abstract

Although diagnostic guidelines for disorders of consciousness (DOC) have been consensually defined and are broadly used worldwide, a very high rate of diagnostic error remains among patients with DOC. Such failure to discern accurately between the different states of altered consciousness may influence tremendously the accuracy of prognosis, the decision-making process and medical care management or withdrawal. As there is no direct way to detect consciousness, one needs to infer its presence from behavioural observations and clinical examination at the bedside. Guidelines informing how one should approach clinical assessment of DOC have not yet reached the gold standard of diagnostic methodology. In the context of increasing demand for acute neurorehabilitation in Switzerland, there is a crucial need to improve the accuracy of initial diagnosis and prognosis, which profoundly impact treatment decisions in the short and long term. Validated neurobehavioural scales commonly used in our acute care setting are reviewed and their limitations considered. We assume that underlying deficits such as a severely damaged motor system compromise the detection of consciousness in the acute stage. Bearing out this claim, the results from our longitudinal pilot study demonstrate that the additional use of a new set of clinical items specifically oriented towards the observation of subtle aspects of motor behaviour in the acute phase helps to identify better the signs of consciousness with a strong predictive rate. According to our findings, many patients are potentially misdiagnosed with severe impairment of consciousness when rated with existing scales, whereas their condition prevents them from succeeding in the production of an adequate motor or verbal response. Such complex and alarming situations call for future profound modifications in DOC assessment. We posit that the development of a coordinated multimodal approach combining information from different sources will help in reaching an objective appreciation of DOC, overcome the current behavioural-based misdiagnosis issue and, most importantly, improve the care of DOC patients in the acute phase.