Seminars in neurology
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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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The United Kingdom (UK) has incorporated a brainstem formulation into its brain death criteria since the first guidelines were published in 1976. A clinical diagnosis incorporating three sequential but interdependent steps is sufficient for the determination of brain death in the UK. There must be no doubt that the patient's comatose condition is due to irreversible brain damage of known etiology, and potentially reversible causes of coma and apnea, such as drug effects, metabolic or endocrine disturbances, or hypothermia, must be excluded. ⋯ Confirmatory tests are not required in the UK, but may be useful to reduce any element of uncertainty or minimize the period of observation prior to the diagnosis of brainstem death if the preconditions for clinical testing are not met, or if a comprehensive neurologic examination is not possible. Brainstem death must be diagnosed by two doctors who must be present at each of the two sets of clinical tests that are required to determine death. Although death is not confirmed until the second test has been completed, the legal time of death is when the first test confirms the absence of brainstem reflexes.
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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
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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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.