GREY MATTERS Ethical considerations in functional magnetic resonance imaging research in acutely comatose patients

Estimating the likelihood of recovery of cognitive function in the acutely comatose patient is one of the most difficult challenges facing neurologists and critical care physicians. Coma, defined as a state of unarousable unconsciousness, is most commonly caused by traumatic brain injury and anoxia following cardiopulmonary arrest. Patient outcome after severe brain injury is highly variable (Young and Schiff, 2014). Some patients regain high levels of functioning, whereas up to half have serious cognitive deficits and dependency. Acutely comatose patients are incapable of making decisions regarding their medical care, and thus their welfare is in the hands of both the health care team and their families. Accurate prognostic information critically informs treatment recommendations by the heath care team and decisions made on the patient’s behalf by the family. Prognosis in the acutely comatose patient is assessed using clinical examination, structural neuroimaging, biomarkers and electrophysiological testing (Young and Schiff, 2014). The dynamic nature of brain injury and the potential for confounding factors, such as medication and metabolic disturbance, must be taken into account during patient assessment. Indeed, these features highlight the importance of repeated examination and integration of findings from diverse diagnostic modalities. Recent reviews have summarized current prognostic markers in the assessment of comatose survivors of cardiac arrest (Sandroni et al., 2013a, b) (Table 1) and traumatic brain injury (Table 2) (Stevens and Sutter, 2013). Despite these indicators, a subset of patients retains an indeterminate prognosis and novel prognostic indicators—particularly those that predict neurological recovery—would be valuable. Prognostic uncertainty in the acutely comatose patient is associated with considerable practice variation in the withdrawal of life-sustaining therapy. Turgeon et al. (2011) studied 720 patients with severe traumatic brain injury in six Canadian level-one trauma centres. The mortality rate in this group of patients was 32% and in the majority of cases (70%) death was preceded by the withdrawal of lifesustaining therapy. Many decisions to withdraw lifesustaining therapy were made within 3 days of injury and, doi:10.1093/brain/awv272 BRAIN 2015: Page 1 of 8 | 1