Clinical and public translation of neuroimaging research in disorders of consciousness challenges current diagnostic and public understanding paradigms

Dynamics of intracellular neonatal Fc receptor-ligand interactions in primary macrophages using biophysical fluorescence techniques

The neonatal Fc receptor (FcRn) is responsible for the recycling of endocytosed albumin and IgG, and contributes to their long plasma half-life. We recently identified an FcRn-dependent recycling pathway from macropinosomes in macrophages; however, little is known about the dynamics of intracellular FcRn–ligand interactions to promote recycling. Here we demonstrate a multiplexed biophysical fluorescent microscopy approach to resolve the spatiotemporal dynamics of albumin–FcRn interactions in living bone marrow–derived macrophages (BMDMs). We used the phasor approach to fluorescence lifetime imaging microscopy (FLIM) of Förster resonance energy transfer (FRET) to detect the interaction of a FcRn–mCherry fusion protein with endocytosed Alexa Fluor 488–labeled human serum albumin (HSA–AF488) in BMDMs, and raster image correlation spectroscopy (RICS) analysis of single fluorescent-labeled albumin molecules to monitor the diffusion kinetics of internalized albumin. Our data identified a major fraction of immobile HSA–AF488 molecules in endosomal structures of human FcRn-positive mouse macrophages and an increase in FLIM-FRET following endocytosis, including detection of FRET in tubular-like structures. A nonbinding mutant of albumin showed minimum FLIM-FRET and high mobility. These data reveal the kinetics of FcRn–ligand binding within endosomal structures for recruitment into transport carriers for recycling. These approaches have wide applicability for analyses of intracellular ligand–receptor interactions.

Canadian perspectives on the clinical actionability of neuroimaging in disorders of consciousness

BACKGROUND

Acquired brain injury is a critical public health and socioeconomic problem in Canada, leaving many patients in vegetative, minimally conscious, or locked-in states, unresponsive and unable to communicate. Recent advances in neuroimaging research have demonstrated residual consciousness in a few exemplary patients with acquired brain injury, suggesting potential misdiagnosis and changes in prognosis. Such progress, in parallel with research using multimodal brain imaging technologies in recent years, has promising implications for clinical translation, notwithstanding the many challenges that impact health care and policy development. This study explored the perspectives of Canadian professionals with expertise either in neuroimaging research, disorders of consciousness, or both, on the potential clinical applications and implications of imaging technology.

METHODS

Twenty-two professionals from designated communities of neuroimaging researchers, ethicists, lawyers, and practitioners participated in semistructured interviews. Data were analyzed for emergent themes.

RESULTS

The five most dominant themes were: (1) validation and calibration of the methods; (2) informed consent; (3) burdens on the health care system; (4) implications for the Canadian health care system; and (5) possibilities for improved prognosis.

CONCLUSIONS

Movement of neuroimaging from research into clinical care for acquired brain injury will require careful consideration of legal and ethical issues alongside research reliability, responsible distribution of health care resources, and the interaction of technological capabilities with patient outcome.

Observations on the Ethical and Social Aspects of Disorders of Consciousness

The care of chronically unconscious patients raises vexing medical, ethical, and social questions concerning diagnosis, prognosis, communication with family members, and decision making, including the withdrawal of life support. We provide updates on major controversies surrounding disorders of consciousness. Issues such as withdrawal of artificial nutrition and hydration – which had been considered “settled” by many in the medical, legal and ethical communities – have resurfaced under the pressure of social groups and religious authorities. Some assumptions about the level of awareness and the prognosis of vegetative state and minimal conscious patients are questioned by advances in clinical care because of insights produced by neuroscience research techniques, particularly functional neuroimaging. Both the clinical and neuroscience dimensions of disorders of consciousness raise complex issues such as resource allocation and high levels of diagnostic inaccuracies (at least, for the vegetative state). We conclude by highlighting areas needing further research and collaboration.

Ethical Issues in Neuroprognostication after Severe Pediatric Brain Injury

Neurologic outcome prediction, or neuroprognostication, after severe brain injury in children is a challenging task and has many ethical dimensions. Neurologists and intensivists are frequently asked by families to predict functional recovery after brain injury to help guide medical decision making despite limited outcome data. Using two clinical cases of children with severe brain injury from different mechanisms: hypoxic-ischemic injury secondary to cardiac arrest and traumatic brain injury, this article first addresses the importance of making a correct diagnosis in a child with a disorder of consciousness and then discusses some of the clinical challenges with deducing an accurate and timely outcome prediction. We further explore the ethical obligations of physicians when supporting parental decision making. We highlight the need to focus on how to elicit family values for a brain injured child, how to manage prognostic uncertainty, and how to effectively communicate with families in these challenging situations. We offer guidance for physicians when they have diverging views from families on aggressiveness of care or feel pressured to prognosticate with in a "window of opportunity" for limiting or withdrawing life sustaining therapies. We conclude with a discussion of the potential influence of emerging technologies, specifically advanced functional neuroimaging, on neurologic outcome prediction after severe brain injury.

Longitudinal changes in functioning and disability in patients with disorders of consciousness: the importance of environmental factors

Disorders of consciousness are neurological conditions associated with low levels of functioning which pose a serious challenge to public health systems. The current study aimed to examine longitudinal changes in functioning in patients with disorders of consciousness and to identify associated biopsychosocial factors using the International Classification of Functioning, Disability, and Health. An Italian sample of 248 patients was assessed longitudinally. Differences in relative variability (an index of change that controls for baseline levels) between acute and chronic patients and predictors of relative variability in "Activities & Participation" were examined. Results showed that there were subgroups of patients whose functioning improved over time. The number of problems in "Activities & Participation" decreased in acute patients over time, whereas in chronic patients, an increase was found. The significant difference in relative variability for the environmental factor "support and relationships" reflects the increase in facilitators in acute patients, whereas the number of facilitators in chronic patients remained unchanged over time. Age at event, time from event, and relative variability in "Environmental Factors" were significant predictors of relative variability in "Activities & Participation". It is of clinical relevance that patients with disorders of consciousness are kept in a supportive and facilitative environment, in order to prevent a decline in their functioning. Moreover, caregivers should receive tailored support in order to enhance and facilitate appropriate care of patients with disorders of consciousness.

Disorders of consciousness: responding to requests for novel diagnostic and therapeutic interventions

Severe brain injury can leave patients with chronic disorders of consciousness. Because of impaired responsiveness, many of these patients have traditionally been regarded as unaware. However, findings from recent clinical studies herald a potential paradigm shift: functional imaging and neurophysiological studies have identified ways to assess awareness and have revealed astounding cases of awareness despite clinical unresponsiveness. Hence, diagnostic classifications have been rewritten, prognostic knowledge is improving, and therapeutic studies have regained momentum, showing for the first time some therapeutic effects on responsiveness. Clinicians must increasingly respond to requests by patients' families and surrogate decision makers to use novel techniques for diagnosis, prognosis, and treatment, and in doing so several ethical and social issues need to be considered. Such requests provide an opportunity for clinicians to learn about patients' values and preferences and to maintain clinical acumen for changes in patient status with the patients' best interests in mind.