Brain function in coma, vegetative state, and related disorders

Brain function in coma, vegetative state, and related disorders Laureys Owen Schiff

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Brain function in coma, vegetative state, and related disorders 2004 The Lancet. Neurology 10.1016/s1474-4422(04)00852-x Laureys2004-brain-function-in-coma-vegetative-state-and Laureys2004-brain-function-in-coma-vegetative-state-and.txt, the project's staged copy 2160040c1024c1a1315096dd652d60df8e7780dd not-redistributable neuroscience

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0 spans located by searching the stored text for the quote's exact words, allowing any whitespace between them mechanism Quotation withheld because this record is not cleared for redistribution. disorders of consciousness after severe brain damage Quotation withheld because this record is not cleared for redistribution. review review Quotation withheld because this record is not cleared for redistribution. mechanisms progressive Wallerian and transsynaptic neuronal degeneration drives the further fall of brain metabolism as a vegetative state becomes permanent Quotation withheld because this record is not cleared for redistribution. mechanisms sparing of brainstem structures (pedunculopontine reticular formation, hypothalamus, basal forebrain) preserves arousal and autonomic function while the cortex is impaired, producing wakeful unawareness Quotation withheld because this record is not cleared for redistribution. mechanisms functional disconnection of primary sensory cortex from multimodal and limbic areas stops residual cortical processing from reaching the integrative stage held to be necessary for awareness Quotation withheld because this record is not cleared for redistribution. The imaging methods reviewed are hard to apply and interpret in this patient population. what this limits: this patient population specifically: USE OF THESE TECHNIQUES IN SEVERELY BRAIN-DAMAGED PERSONS IS METHODOLOGICALLY COMPLEX AND REQUIRES CAREFUL QUANTITATIVE ANALYSIS AND INTERPRETATION Quotation withheld because this record is not cleared for redistribution. PET metabolic measures cannot yet be linked to patient outcome. what this limits: any prognostic use of PET metabolism: AT PRESENT, THERE IS NO ESTABLISHED CORRELATION BETWEEN CEREBRAL METABOLIC RATES OF GLUCOSE OR OXYGEN AS MEASURED BY PET AND PATIENT OUTCOME Quotation withheld because this record is not cleared for redistribution. The minimally conscious state has almost no imaging evidence base yet. what this limits: any claim about the minimally conscious state: BECAUSE CRITERIA FOR THE MCS HAVE ONLY RECENTLY BEEN INTRODUCED, THERE ARE VERY FEW FUNCTIONAL IMAGING STUDIES OF PATIENTS IN THIS CONDITION Quotation withheld because this record is not cleared for redistribution. The central construct has no objective measure; its estimation is stated to require interpretation of clinical signs. what this limits: any consciousness determination in these patients as an objective measurement: the review states it cannot be measured by any machine and requires interpretation of clinical signs Quotation withheld because this record is not cleared for redistribution. The criteria for brain death are stated to differ between countries, some requiring brainstem death only and others whole-brain death. what this limits: a brain-death determination as a jurisdiction-independent fact: the review states the diagnostic criteria differ from country to country Quotation withheld because this record is not cleared for redistribution. Diagnosis rests on inference from responses observed at the moment of examination, and misdiagnosis of these states is stated to be frequent. what this limits: a recorded diagnosis of VS, MCS or locked-in syndrome as settled: the review states misdiagnosis is frequent and assessment infers from responses at the time of examination Quotation withheld because this record is not cleared for redistribution. The three sources of uncertainty are stated together in one sentence and compound each other: motor responses may be limited or inconsistent, consciousness is not all-or-none, and the assessment is an inference from responses observed at the moment of examination. Quotation withheld because this record is not cleared for redistribution. studies whose clinical detail was too thin to guarantee the accuracy of the diagnosis were excluded from the review eliminates: that the review's conclusions rest on cases whose diagnostic category - coma, vegetative state, minimally conscious - cannot be trusted · outcome (stated by the tagger, no quotation): held Quotation withheld because this record is not cleared for redistribution. brain death brain death Quotation withheld because this record is not cleared for redistribution. minimally conscious state minimally conscious state Quotation withheld because this record is not cleared for redistribution. consciousness consciousness Quotation withheld because this record is not cleared for redistribution. consciousness - defined here for assessability rather than for correctness: as it can be assessed at the patient's bedside Quotation withheld because this record is not cleared for redistribution. consciousness - explicitly not an all-or-none phenomenon, which is why bedside assessment is difficult Quotation withheld because this record is not cleared for redistribution. emergence from the minimally conscious state - defined by a capability: functional interactive communication or functional use of objects Quotation withheld because this record is not cleared for redistribution. brain death - a category whose criteria are jurisdictional: brainstem death in some countries, whole-brain death in others, with the concept itself 'largely accepted' either way Quotation withheld because this record is not cleared for redistribution. qualifies → the irreversible-neuronal-loss reading (ref. 64) differs in: WHETHER THE SAME METABOLIC IMPAIRMENT IS DAMAGE OR DYSFUNCTION - and the review states the disagreement rather than settling it: 'It is still controversial whether the observed metabolic impairment in this large cortical network reflects an IRREVERSIBLE STRUCTURAL NEURONAL LOSS, OR FUNCTIONAL AND POTENTIALLY REVERSIBLE DAMAGE.' The evidence offered against the first reading is a rare case class, not a test: 'However, in the rare cases where VS patients recover awareness ... PET SHOWS A FUNCTIONAL RECOVERY of metabolism in these same cortical regions' Quotation withheld because this record is not cleared for redistribution. builds-on → Andrews et al. 1996, Childs et al. 1993 and five others (refs. 1-7) differs in: WHAT THE MISDIAGNOSIS RATE IS EVIDENCE OF. The review cites seven misdiagnosis studies not as a finding about clinicians but as evidence that THE CATEGORY IS HARD TO APPLY AT THE BEDSIDE, and gives two reasons in the same passage: 'motor responses may be very limited or inconsistent', and 'consciousness is not an all-or-none phenomenon and its clinical assessment relies on inferences made from observed responses to external stimuli at the time of the examination' Quotation withheld because this record is not cleared for redistribution. The metabolic hallmark of the vegetative state is impaired metabolism in the polymodal associative cortices - bilateral prefrontal regions, Broca's area, parieto-temporal and posterior parietal areas, and precuneus. Quotation withheld because this record is not cleared for redistribution. Intense noxious stimulation reached midbrain, contralateral thalamus and primary somatosensory cortex in every one of 15 vegetative patients, so primary sensory cortex remains reachable even when cortical evoked potentials are absent. Quotation withheld because this record is not cleared for redistribution. The same noxious stimulation failed to activate secondary somatosensory, insular, posterior parietal and anterior cingulate cortices in any vegetative patient, although all of these were activated in every control subject. Quotation withheld because this record is not cleared for redistribution. The precuneus and adjacent posterior cingulate cortex seem to be the regions that differentiate minimally conscious from vegetative patients. Quotation withheld because this record is not cleared for redistribution. PET showed significantly higher brain metabolic levels in locked-in than in vegetative patients. Quotation withheld because this record is not cleared for redistribution. The lumped constant used to compute glucose metabolism from FDG-PET is not stable in damaged brains: it falls globally after traumatic brain injury and rises regionally in severe cerebral ischaemia, so absolute metabolic rates in these patients are unreliable. Quotation withheld because this record is not cleared for redistribution. Despite the promise of functional neuroimaging, clinical examination and the nosological categories it establishes remain the standard for diagnosis and prognosis in these patients. Quotation withheld because this record is not cleared for redistribution. consciousness consciousness Quotation withheld because this record is not cleared for redistribution. coma coma Quotation withheld because this record is not cleared for redistribution. persistent vegetative state persistent vegetative state Quotation withheld because this record is not cleared for redistribution. minimally conscious state minimally conscious state Quotation withheld because this record is not cleared for redistribution. locked-in syndrome locked-in syndrome Quotation withheld because this record is not cleared for redistribution. hollow skull phenomenon hollow skull phenomenon Quotation withheld because this record is not cleared for redistribution. 40-50% — overall cortical metabolism of vegetative patients as a proportion of normal values Quotation withheld because this record is not cleared for redistribution. 30-40% — brain metabolism in permanent vegetative state (12 months after trauma, 3 months after non-traumatic damage) as a proportion of normal values Quotation withheld because this record is not cleared for redistribution. 28% — lowest reported brain metabolism, measured under propofol anaesthesia, as a proportion of normal values Quotation withheld because this record is not cleared for redistribution. 40% — cortical cerebral metabolism during deep sleep (stages III-IV) as a proportion of normal values Quotation withheld because this record is not cleared for redistribution. 75% — cerebral metabolic rate for glucose, as a proportion of normal, in patients who recover from postanoxic coma Quotation withheld because this record is not cleared for redistribution. 15 — number of vegetative patients in whom noxious electrical stimulation activated midbrain, thalamus and primary somatosensory cortex Quotation withheld because this record is not cleared for redistribution.

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