Pain assessment and management in disorders of consciousness. Curr Opin Neurol 20: 620-626

Coma Science Group, University of Liege, Liege, Belgium.
Current Opinion in Neurology (Impact Factor: 5.31). 01/2008; 20(6):620-6. DOI: 10.1097/WCO.0b013e3282f169d9
Source: PubMed


Pain and suffering controversies in persons with disorders of consciousness continue to be debated by the scientific, legal and medical ethics communities. This review examines the current knowledge base for guiding decisions regarding assessment and management of pain in persons with disorders of consciousness.
Studies have shown that brain processing linked to pain in persons in a vegetative state is incomplete and is processed only at a primary and not higher secondary level. Therefore, such painful stimuli would not reach the threshold for conscious experience. In contrast, persons in a minimally conscious state have been shown to have brain activation patterns to pain similar to controls. Therefore, these patients may have sufficient cortical integration and access to afferent information to allow for nociceptive stimuli to be consciously processed. Data to date do not allow for differentiation of the degree of any conscious pain experience or determination of whether individuals with disorders of consciousness are able to suffer.
Pain and suffering should be considered in all persons with disorders of consciousness and adequately treated. Behavioural assessment scales developed for patients unable to speak could be used to assess pain. Future studies should focus on methodologies for specific pain measures relevant to this unique and challenging patient population.

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Available from: Caroline Schnakers
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    • "They may grimace, cry, smile, move their eyes, head, and limbs, but they have no unambiguously detectable responsiveness to contingent events or stimuli. However, reactions to pain are easily obtained (Schnakers C and Zasler N D, 2007) and eye movements are regarded as indicative of responsiveness (Leigh RJ et al., 1984), 1984) (Balazs S et al., 2006). "
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    ABSTRACT: The functional assessment and prediction of outcome of subjects with severe disorder of consciousness such as those in the vegetative (VS) or minimally conscious (MCS) states requests that the residual brain function of these subjects be characterized. Ad hoc scales to assessment residual cognitive processes or responses to nociception (Coma Recovery Scale-R, Wessex Head Injury Matrix, Nociception Come Scale) and fMRI/PET scan protocols have been implemented. fMRI studies have identified cortical areas activated by external input also in subjects otherwise unambiguously diagnosed as being in a VS. However, activated primary cortices do not appear functionally connected to higher order (associative) cortices and evidence of the corticocortical interplay deemed crucial for conscious perception, emotional response and cognitive processes to occur is lacking. In this respect, MCS subjects show a partially restored and functionally connected activity in these cortical areas, but the estimated diagnostic error between the VS and MCS remains high (up to 25-45%). The CNS and autonomic nervous systems are thought to interact in physiological conditions and a model (the Central Autonomic Network; CAN) has been developed to describe the bidirectional functional connection between the heart and brain. This relationship becomes crucial in the severe disorder of consciousness. Measures of heart rate variability (HRV) are thought to reflect the relationship between brain function and the CAN and advanced artificial intelligence procedures (e.g. Data Mining and Machine Learning) have documented the HRV suitability in detecting the autonomic system functional status and residual responsiveness in the severe disorder of consciousness.
    Full-text · Chapter · Jan 2012
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    • "Furthermore, according to the Multi-Society Task Force on PVS (1994b), neither behavioral nociceptive responses, such as flexor or extensor spasms and withdrawal of extremities following painful stimulation (e.g., pinprick), nor grimacing and crying behavior necessarily imply the perception of pain. Therefore, the subjective and private nature of the experience of pain as well as our incomplete understanding of its neural substrate have long invited discussion (Klein 1997, Schnakers & Zasler 2007) and development of novel clinical tools (Schnakers et al. 2010). Laureys et al. (2002a) "
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    ABSTRACT: Awake but not aware: This puzzling dissociation of the two central elements of consciousness defines the vegetative state. Traditionally, this condition has been believed to imply a brain with preserved hypothalamic and brainstem autonomic functions but with no capacity for cortical cognitive processes. As is discussed in this review, over a 20-year span neuroimaging techniques have clearly demonstrated that this characterization of patients in a vegetative state is incorrect. Contrary to the initial belief, the "vegetative" brain can retain several high-level aspects of cognitive functions, across sensory modalities, including language processing and learning dynamics. Nonetheless, the residual cognitive functions observed in vegetative patients might reflect intact but functionally disconnected cortical modules that do not give rise to the subjective feeling of phenomenological awareness.
    Full-text · Article · Apr 2011 · Annual Review of Clinical Psychology
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    • "- Indication for sedation/analgesia: A crucial challenge is determining which non-communicating brain-injured patients need palliative sedation. Classical clinical criteria for possible pain consist of high blood pressure, tachycardia, tachypnea, wincing, and motor reactions to noxious stimuli [9]. An EEG or functional MRI response to noxious stimuli suggests pain, but the usefulness of these methods for identifying patients who require sedation/analgesia has not been assessed. "
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    ABSTRACT: To fulfill their crucial duty of relieving suffering in their patients, physicians may have to administer palliative sedation when they implement treatment-limitation decisions such as the withdrawal of life-supporting interventions in patients with poor prognosis chronic severe brain injury. The issue of palliative sedation deserves particular attention in adults with serious brain injuries and in neonates with severe and irreversible brain lesions, who are unable to express pain or to state their wishes. In France, treatment limitation decisions for these patients are left to the physicians. Treatment-limitation decisions are made collegially, based on the presence of irreversible brain lesions responsible for chronic severe disorders of consciousness. Before these decisions are implemented, they are communicated to the relatives. Because the presence and severity of pain cannot be assessed in these patients, palliative analgesia and/or sedation should be administered. However, palliative sedation is a complex strategy that requires safeguards to prevent a drift toward hastening death or performing covert euthanasia. In addition to the law on patients' rights at the end of life passed in France on April 22, 2005, a recent revision of Article 37 of the French code of medical ethics both acknowledges that treatment-limitation decisions and palliative sedation may be required in patients with severe brain injuries and provides legal and ethical safeguards against a shift towards euthanasia. This legislation may hold value as a model for other countries where euthanasia is illegal and for countries such as Belgium and Netherlands where euthanasia is legal but not allowed in patients incapable of asking for euthanasia but in whom a treatment limitation decision has been made.
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