Seminars in neurology
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Clinical guidelines for the determination of brain death in children were first published in 1987. These guidelines were revised in 2011 under the auspices of the Society of Critical Care Medicine, the American Academy of Pediatrics, and the Child Neurology Society, and provide the minimum standards that must be satisfied before brain death can be declared in infants and children. After achieving physiologic stability and exclusion of confounders, two examinations including apnea testing separated by an observation period (24 hours for term newborns up to 30 days of age, and 12 hours for infants and children from 31 days up to 18 years) are required to establish brain death. ⋯ Ancillary studies (electroencephalogram and radionuclide cerebral blood flow) are not required to establish brain death and are not a substitute for the neurologic examination. The committee concluded that ancillary studies may be used (1) when components of the examination or apnea testing cannot be completed, (2) if uncertainty about components of the neurologic examination exists, (3) if a medication effect may be present, or (4) to reduce the interexamination observation period. When ancillary studies are used, a second clinical examination and apnea test should still be performed and components that can be completed must remain consistent with brain death.
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Despite well-described international variabilities in brain death practices, de facto there already exists a minimum international clinical standard for the diagnosis of brain death. This remains rooted in the Harvard criteria and based on the characteristics of a permanently nonfunctioning brain. Medicine is evolving toward a single unified determination of death based on the cessation of brain function subsequent to catastrophic brain injury or circulatory arrest. ⋯ The cessation of clinical functions of the brain that will not resume is determined by the absence of capacity for consciousness, centrally mediated motor responses, brainstem reflexes, and capacity to breathe. A known proximate cause and the absence of confounding or reversible conditions must be confirmed. Regional medical, legal, cultural, religious, or socioeconomic factors may require testing beyond this minimal clinical standard.
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Seminars in neurology · Feb 2015
ReviewChronic traumatic encephalopathy: a neurodegenerative consequence of repetitive traumatic brain injury.
Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease that develops as a result of repetitive mild traumatic brain injury. Chronic traumatic encephalopathy is characterized by a unique pattern of accumulation of hyperphosphorylated tau in neurons and astrocytes. The tau abnormalities begin focally and perivascularly at the depths of the cerebral sulci, spread to the superficial layers of the adjacent cortex, and eventually become widespread throughout the medial temporal lobes, diencephalon, and brainstem. ⋯ To date, CTE can only be diagnosed by postmortem neuropathological examination, although there are many ongoing research studies examining imaging techniques and biomarkers that might prove to have diagnostic utility. Currently, the incidence and prevalence of CTE are unknown, although great strides are being made to better understand the clinical symptoms and signs of CTE. Further research is critically needed to better identify the genetic and environmental risk factors for CTE as well as potential rehabilitation and therapeutic strategies.
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Despite decades of basic and clinical research, treatments to improve outcomes after traumatic brain injury (TBI) are limited. However, based on the recent recognition of the prevalence of mild TBI, and its potential link to neurodegenerative disease, many new and exciting secondary injury mechanisms have been identified and several new therapies are being evaluated targeting both classic and novel paradigms. This includes a robust increase in both preclinical and clinical investigations. ⋯ They address putative new therapies for TBI across both the spectrum of injury severity and the continuum of care, from the field to rehabilitation. They discussTBI therapy using 11 categories, namely, (1) excitotoxicity and neuronal death, (2) brain edema, (3) mitochondria and oxidative stress, (4) axonal injury, (5) inflammation, (6) ischemia and cerebral blood flow dysregulation, (7) cognitive enhancement, (8) augmentation of endogenous neuroprotection, (9) cellular therapies, (10) combination therapy, and (11) TBI resuscitation. The current golden age of TBI research represents a special opportunity for the development of breakthroughs in the field.
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Seminars in neurology · Feb 2015
ReviewNeuropathology of traumatic brain injury: comparison of penetrating, nonpenetrating direct impact and explosive blast etiologies.
The neuropathology of traumatic brain injury (TBI) from various causes in humans is not as yet fully understood. The authors review and compare the known neuropathology in humans with severe, moderate, and mild TBI (mTBI) from nonpenetrating closed head injury (CHI) from blunt impacts and explosive blasts, as well as penetrating head injury (PHI). Penetrating head injury and CHI that are moderate to severe are more likely than mTBI to cause gross disruption of the cerebral vasculature. ⋯ Neuronal injury is more prevalent in PHI and moderate to severe CHI than mTBI. Astrocyte and microglial activation and proliferation are found in all forms of animal TBI models and in severe to moderate TBI in humans. Their activation in mTBI in the human brain has not yet been studied.