Rev Neuroscience
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We have reviewed the literature on transcranial magnetic stimulation studies in patients with brain death, coma, vegetative, minimally conscious, and locked-in states. Transcranial magnetic stimulation permits non-invasive study of brain excitability and may extend our understanding of the underlying mechanisms of these disorders. However, use of this technique in severe brain damage remains methodologically ill-defined and must be further validated prior to clinical application in these challenging patients.
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There exists much controversy in providing an effective definition of human death, largely due to the lack of a rigorous separation and ordered formulation of three distinct elements: a universally accepted definition of death, the medical criterion (anatomical substrata) for determining that death has occurred, and the tests to prove that the criterion has been satisfied. The papers herein review medical standards, philosophical arguments, neurophysiological knowledge, behavioural and cognitive theory and the legal ramifications of the brain-oriented standards of death (whole brain, brainstem and higher brain). The papers examine the notion of connectivities and networks of conscious experience in order to formulate an effective definition of death, based on the basic physiopathological mechanisms of consciousness. ⋯ The thread of the arguments is the basis for a standard of human death that includes consciousness as the most important function of the body, because it provides the capacity for integrating the functions of the body. The notion of consciousness as the ultimate integrative function is more consistent with the biologically-based systems than the more philosophically-based notions of personhood. Both sides of the argument are presented herein.
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The clinical criteria for brain death consist of the demonstration of the absence of any clinical sign of encephalic activity. Confirmatory testing is usually not required for the diagnosis of brain death, except in some special situations that Spanish law details. In these situations demonstrating cerebral circulatory arrest (CCA) by cerebral flow studies is necessary to support the diagnosis of brain death. ⋯ TCD is a useful method for detecting CCA and therefore can be used to confirm brain death in a clinically brain-dead patient. The presence of reverberating flow, systolic spikes or absence of flow in the basilar and both middle cerebral arteries observed in two examinations is highly specific for the prediction of CCA and brain death in all patients.
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To determine the safety and effectiveness of mild induced hypothermia in children after traumatic or posthypoxic brain injury. Thirteen patients after traumatic or poshypoxic brain injury were involved in the study. Mean age was 11.1 +/- 5.7 years. Median GCS 6 (3-8), PIM2 20.3 +/- 28.2%. ⋯ Mild induced hypothermia can be safely used in pediatric patients after severe traumatic or posthypoxic brain injury. This method may be of benefit while improving outcomes in children.
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The early recognition of comatose patients with a hopeless prognosis--regardless of how aggressively they are managed--is of utmost importance. Median somatosensory evoked potentials (SSEP) supplement and enhance neurological examination findings in anoxic-ischemic coma and are useful as an early guide in predicting outcome. The key finding is that bilateral absence of cortical evoked potentials reliably predicts unfavorable outcome in comatose patients after cardiac arrest. ⋯ The remaining 27 patients with normal or delayed central conduction times had an uncertain prognosis because some died without awakening or entered a persistent vegetative state. The majority of patients with normal central conduction times had a good outcome, whereas a delay in central conduction times increased the likelihood of neurological deficit or death. Greater use of SSEP in anoxic-ischemic coma would identify those patients unlikely to recover and would avoid costly medical care that is to no avail.