Adequate Intake The recommended average daily intake level for a nutrient, based on observed or experimentally determined approximations or estimates of intake by a group of apparently healthy people, that is assumed to be adequate. Used when there is no Recommended Dietary Allowance available.
Amygdala Almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. The amygdala is involved in learning and memory, especially fear-related, and is central to the development of expression of conditioned fear reactions.
Angiogenesis The process involving the growth of new blood vessels from preexisting vessels. (This term incorporates both vasculogenesis, or spontaneous blood-vessel formation; and intussusception, formation of new blood vessels by splitting off existing ones.)
Anoxia A total decrease in level of oxygen reaching tissues of the body; an extreme form of hypoxia that can result in permanent damage.
Apoptotis Also known as programmed cell death. Describes the biochemical events leading to characteristic morphological cell changes (blebbing, loss of cell membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal deoxynribonucleic acid fragmentation) and death.
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D Glossary Adequate Intake The recommended average daily intake level for a nutrient, based on observed or experimentally determined approximations or estimates of intake by a group of apparently healthy people, that is assumed to be adequate. Used when there is no Recommended Dietary Allowance available. Amygdala Almond-shaped groups of nuclei located deep within the medial tem- poral lobes of the brain in complex vertebrates, including humans. The amygdala is involved in learning and memory, especially fear-related, and is central to the development of expression of conditioned fear reactions. Angiogenesis The process involving the growth of new blood vessels from preexist- ing vessels. (This term incorporates both vasculogenesis, or spontane- ous blood-vessel formation; and intussusception, formation of new blood vessels by splitting off existing ones.) Anoxia A total decrease in level of oxygen reaching tissues of the body; an extreme form of hypoxia that can result in permanent damage. Apoptotis Also known as programmed cell death. Describes the biochemical events leading to characteristic morphological cell changes (blebbing, loss of cell membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal deoxynribonucleic acid fragmentation) and death. 413
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414 NUTRITION AND TRAUMATIC BRAIN INJURY Astrocytes A subtype of glial cells that supply glucose needed for nerve activity, maintain the blood-brain barrier, maintain extracellular ion balance, and play a principal role in the repair and scarring process of the brain and spinal cord following traumatic injuries. Astrocytosis An abnormal increase in the number of astrocytes due to the destruc- tion of nearby neurons, typically because of hypoglycemia or oxygen deprivation (hypoxia). Astrocytosis represents a reparative process; in some cases, it may be diffuse in a large region. Autocoid An organic substance, such as a hormone, produced in one part of an organism and transported by the blood or lymph to another part of the organism where it exerts a physiologic effect on that part. Axonal The ability of the adult brain to form new connections in areas dener- sprouting vated by a lesion. Barthel Index First published in the 1965 Maryland State Medical Journal, this mea- surement of 10 activities of daily living and mobility is used to assess physical disability. Blood-brain A separation of circulating blood and the brain extracellular fluid barrier in the central nervous system, with especially tight junctions around capillaries that prevent diffusion of bacteria and large, hydrophilic molecules into the cerebrospinal fluid. Brain The functional part of the brain (i.e., neurons and glial cells). parenchyma Bregma The anatomical point on the skull where the frontal and parietal bones meet, i.e., at the intersection of the coronal and the sagittal sutures. Caudate nucleus The caudate nuclei are located near the center of the brain, one within each hemisphere, sitting astride the thalamus. They are involved in learning and memory (feedback processing). Cerebral edema Excess accumulation of water in intracellular/extracellular spaces of the brain. Cerebral Any pathophysiological state in which there is insufficient blood ischemia flow to the brain to meet metabolic demand, which leads to depleted oxygen supply and thus the death of brain tissue. Ischemic stroke is caused by the formation of a clot that blocks blood flow through an artery to the brain. Cerebrospinal A tear between the dura and arachnoid membrane, resulting in leakage fluid fistula of CSF into subdural space.
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415 APPENDIX D Chronic A progressive neurodegenerative disease believed to be caused by traumatic repeated trauma to the brain, including mild concussions and subcon- encephalopathy cussive blows. Its symptoms occur years or decades following head trauma and continue to worsen, and are distinct from the acute or postacute effects of a head injury. The early symptoms may include memory and cognitive difficulties, depression, impulse control prob- lems, and behavior changes. Movement abnormalities are more com- mon later; in many cases, full-blown dementia occurs. Coma A state in which a patient is totally unconscious, unresponsive, un- aware, and unarousable. Compressive Cranial nerve injuries that may be caused by fractures, especially at the cranial bottom of the skull. Damage to the facial nerve, the most commonly neuropathy damaged, results in paralysis of facial muscles. Computerized A noninvasive test combining a series of X-ray views taken from many tomography different angles to produce cross-sectional images of bones and soft (CT) tissues. In the head, CT scans can show bone fractures, hemorrhage, hematomas, contusion, and swelling. Contusion Focal injuries with an area of cerebral bruising, particularly involving gray matter, in which blood leaks into extravascular space resulting in cell death and loss of tissue. Bleeding from damaged blood vessels is usually the most obvious feature on macroscopic or microscopic examination. Diffuse axonal An injury defined by diffuse damage to axons in the cerebral subcorti- injury (DAI) cal parasagittal white matter, corpus callosum, brain stem, and cerebel- lum. The loss of connections among neurons leads to breakdown of communication. Diffuse A brain injury due to hypoxia, meningitis, or damage to blood vessels; traumatic brain can include DAI, ischemic brain injury, vascular injury, or swelling and injury resulting intracranial pressure. Such injuries, which may result from acceleration/deceleration injuries, are often microscopic, multifocal, and difficult to detect. Disability Rating A functional assessment developed specifically for patients with mod- Scale erate to severe traumatic brain injury (TBI). Edema Abnormal accumulation of fluid beneath the skin or in one or more cavities of the body. Edema Intracellular water accumulation in neurons, astrocytes, and microglia (cytotoxic) irrespective of the integrity of the vascular endothelial wall. It is due to the increased cell permeability for ions, ionic pump failure, and cel- lular reabsorption of osmotically active solutes.
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416 NUTRITION AND TRAUMATIC BRAIN INJURY Edema Caused by mechanical or autodigestive disruption or functional (vasogenic) breakdown of the endothelial cell layer of brain vessels that are a key element of the BBB. This allows for the uncontrolled transfer of ions and proteins from the intravascular to the extravascular brain com- partments, leading to water accumulation. Estimated The average daily nutrient intake level estimated to meet the require- Average ment of half of the healthy individuals in a particular life stage and Requirement gender group. Excitotoxicity Excessive stimulation of glutamate receptors by neurotransmitters resulting in damage to the nerve cells. Excitotoxins like N-methyl- D-aspartate and kainic acid that bind to these receptors, as well as pathologically high levels of glutamate, can cause excitotoxicity by allowing high levels of calcium ions to enter the cell. As a result, an enzymatic cascade, including phospholipases, endonucleases, and pro- teases, damages cell structures and can cause cell death. Feeney’s weight- One of several methods used to induce brain trauma (primary in- drop model jury is mostly focal) in rats and mice. The impact is delivered to the intact dura, causing cortical contusion and damage to the blood-brain barrier. Focal traumatic A focal traumatic injury results from direct mechanical forces and is brain injury usually associated with brain tissue damage visible to the naked eye. It typically has symptoms related to the damaged area of the brain; e.g., a stroke can produce focal damage associated with signs and symp- toms that correspond to the part of the brain that was damaged. Focal injuries include cerebral contusions; cerebral lacerations; and epidural, subdural, intracerebral, and intraventricular hemorrhage. Glasgow Coma A standardized test of level of consciousness and neurological function Scale that uses three measures: eye opening, best verbal response, and best motor response. Patient assessment by the criteria of the scale yields a score between 3 (indicating deep unconsciousness) and either 14 (origi- nal scale) or 15 (the more widely used revised scale). Glasgow A five-point score (dead, vegetative, severely disabled, moderately Outcome Scale disabled, good recovery) given to victims of TBI postinjury. It is a very general assessment of the overall functioning of head-injury patients. It is not used in the clinical management of patients, but in research to quantify the level of recovery patients have achieved. Hematoma Heavy bleeding into or around the brain usually caused by damage to a major blood vessel in the head. Hemorrhagic A stroke caused by the breakage or rupture of a blood vessel in the stroke brain. Hemorrhages can be caused by a number of disorders that af- fect the blood vessels, including long-standing high blood pressure and cerebral aneurysms (weak or thin spots in the vessel wall). There are two types of hemorrhagic stroke: intracerebral and subarachnoid. Hippocampus One of two structures in the adult brain where neurogenesis persists.
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417 APPENDIX D Hydrocephalus The accumulation of cerebrospinal fluid resulting from dilation of or posttraumatic ventricles and increase in intracranial fluid. ventricular enlargement Hyperemia or An excessive increase in blood flow to tissue(s) hyperfusion Hypothalamus The hypothalamus, an extremely complex region in the human brain, is responsible for certain metabolic processes and other activities of the autonomic nervous system, such as the control of body temperature, hunger, thirst, fatigue, sleep, and circadian cycles. The hypothalamus is located below the thalamus, just above the brain stem. It is the pri- mary link between endocrine and nervous systems; nerves in the hypo- thalamus control the pituitary gland by producing neurohormones that either stimulate or suppress hormone secretions. The hypothalamic- releasing hormones, for example, stimulate or inhibit the secretion of pituitary hormones. Hypoxia A deficiency of oxygen reaching the tissues of the body. Intracranial A result of swelling of the brain and accumulation of fluids due to pressure injury. Ischemia The blockage of arteries and cut-off of blood flow. Ischemia The damage to tissue caused when blood supply returns after a period reperfusion of ischemia. The absence of oxygen and nutrients from blood creates injury a condition in which the restoration of circulation results in inflamma- tion and oxidative damage through the induction of oxidative stress rather than restoration of normal function. Ischemic stroke Ischemia can be caused by embolic and thrombotic strokes. In an embolic stroke, a blood clot forms somewhere in the body (usually the heart), then travels through the bloodstream to the brain, where it eventually reaches a blood vessel too small to allow its passage, caus- ing a stroke. In thrombotic stroke, blood flow is impaired because of blockage to one or more arteries supplying blood to the brain. Isch- emic strokes can also occur as the result of an unhealthy blood vessel clogged with a buildup of fatty deposits and cholesterol. Ketogenic diet A diet formulated to mimic fasting, with limited glucose supply and high fat availability, that favors fatty acid oxidation, ketone body pro- duction, and utilization of ketone bodies by the brain as an alternative energy substrate. Locked-in A condition in which the patient is awake and aware but cannot move syndrome or communicate due to complete paralysis of the body. Luria Memory A test used to assess the memory of elderly patients diagnosed with Words test dementia by presenting word lists in given time periods.
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418 NUTRITION AND TRAUMATIC BRAIN INJURY Magnetic A medical imaging technique that uses the property of nuclear mag- resonance netic resonance to visualize areas inside the body but that, unlike CT imaging scans or traditional X-rays, uses no ionizing radiation. It provides more detail and contrast than a CT scan. Medial The anterior part of the frontal lobes of the brain, it has been impli- prefrontal cortex cated in planning complex cognitive behaviors, personality expression, decision making, and moderating correct social behavior. The most typical psychological term for functions carried out by the prefrontal cortex area is executive function. Biological models suggest that a fundamental mechanism underpinning posttraumatic stress disorder involves an exaggerated response of the amygdala, which results in impaired regulation by the medial prefrontal cortex. Modified Rankin First published in 1988, this measures activities of daily living to assess Scale physical disability in stroke patients and is now the most commonly used clinical outcome measure for stroke clinical trials. Morris water A test widely used in behavioral neuroscience to study the psychologi- maze cal processes and neural mechanisms of spatial learning and memory. Animals are placed in a large circular pool of water and required to escape onto a hidden platform whose location can normally be identi- fied only by using spatial memory. Necrosis The premature death of cells and living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. Cells that die due to necrosis do not usually send the same chemical signals to the immune system that cells undergoing apoptosis do. This prevents nearby phagocytes from locating and engulfing the dead cells, leading to a buildup of dead tissue and cell debris at or near the site of the cell death. Neuroglycopenia A shortage of glucose (glycopenia) in the brain, usually due to hypo- glycemia. Glycopenia affects the function of neurons, and alters brain function and behavior. Prolonged neuroglycopenia can result in perma- nent damage to the brain. Perfusion Process of nutritive delivery of arterial blood to a capillary bed in the biological tissue. Polytrauma Two or more injuries to physical regions or organ systems, one of which may be life-threatening, that result in physical, cognitive, psy- chological, or psychosocial impairments and functional disability. Postconcussive Symptoms of mild TBI that continue for longer than three months. syndrome These vary from person to person but include numerous cognitive, affective, or somatic symptoms such as headache, dizziness, balance problems, nausea, vision problems, increased sensitivity to noise and/ or light, and depression, among many others. Recommended The average daily dietary nutrient intake level that is sufficient to meet Dietary the nutrient requirements of nearly all (97–98 percent) healthy indi- Allowance viduals in a particular life stage and gender group.
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419 APPENDIX D Refractory Epilepsy that is resistant to treatment. epilepsy Rhinorrhea In the context of brain injury, cerebral spinal fluid leakage from the nose. Rotarod A performance test applied to animals that uses a rotating rod with performance test forced motor activity being applied. It measures parameters such as riding time (seconds) or endurance, balance, and coordination. Rotarod score Measures performance on a Rotarod treadmill in order to assess mo- tor coordination, and thus neurological performance, in mice and rats. Second impact A repeat concussion that occurs before the brain recovers from the syndrome first, usually within a short period of time (hours, days, or weeks), that results in brain swelling, permanent brain damage, and even death. Stupor A state of consciousness in which the patient is unresponsive but can be aroused by a strong stimulus. Subarachnoid Bleeding in the space beneath the arachnoid mater, a membrane that hemorrhage covers the brain. This area, called the subarachnoid space, normally contains cerebrospinal fluid. Such hemorrhage can lead to stroke, sei- zures, and other complications. Synapses The junction between the axon terminals of a neuron and the receiving cell that permits neurons to pass signals to individual target cells. Most neurons achieve their effect by releasing chemicals, the neurotransmit- ters, to a receiving cell. Syndrome of A common fluid and hormonal imbalance occurring as a result of inadequate disruption to the pituitary, thyroid, or other glands. secretion of antidiuretic hormone and hypothyroidism Tolerable Upper The highest average daily nutrient intake level that is likely to pose Intake Level no risk of adverse health effects to almost all individuals in the genera (UL) population. As intake increases above the UL, the potential risk of adverse effects may increase. Vasospasm A condition in which blood vessels spasm, leading to vasoconstriction, that can induce tissue ischemia and death (necrosis). Cerebral vaso- spasm may arise in the context of subarachnoid hemorrhage. Symp- tomatic vasospasm or delayed cerebral ischemia is a major contributor to postoperative stroke and death, especially after aneurysmal sub- arachnoid hemorrhage. Vasospasm typically appears four to ten days after subarachnoid hemorrhage.
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420 NUTRITION AND TRAUMATIC BRAIN INJURY Vegetative state The condition of patients who are unconscious and unaware of their surroundings but who may have a sleep-wake cycle, periods of alert- ness, and periodically open eyes, unlike coma patients, and may move and show reflexes. Many patients recover from this state within a few weeks, but some will remain in a persistent vegetative state. It can result in diffuse injury to the cerebral hemispheres without damage to the lower brain and brainstem. Ventriculostomy Procedure to drain cerebrospinal fluid from the brain to reduce intracranial pressure (mannitol and barbiturates are pharmaceutical alternatives).