Medical Terminology

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  • a

  • actigraphy
    Actigraphy is used to non-invasively measure body movement. An actigraph, which looks like an oversized watch, is typically worn on the nondominant wrist (that is, if you are right-handed, you would wear it on your left wrist). It contains an accelerometer and records movements, which are then downloaded from the device and analyzed offline. When combined with a sleep diary or sleep log, actigraphy can be used to measure sleep patterns and circadian rhythms.
  • agonist
    An agonist is a chemical that binds to and activates a receptor. The result is a biologic response — an action. (An antagonist is the opposite of an agonist.)
  • allele
    An allele is a variant form of a gene. Each gene resides at a specific locus (location on a chromosome) in two copies; one copy of the gene is inherited from each parent. The copies, however, are not necessarily identical. When the copies of a gene differ from each other, they are known as alleles. A given gene may have multiple different alleles, but only two alleles are present at the gene’s locus in any individual. (Read more HERE.)
  • allosteric modulator
    Allosteric modulators are substances that indirectly influence or modulate the effects of an agonist at a receptor. For example, with respect to the GABAA receptor, positive allosteric modulators increase the activity of the GABAA receptor protein in the central nervous system of mammals. (Examples of positive allosteric modulators include alcohol, benzodiazepines [such as Valium], benzodiazepine-receptor agonists [such as Ambien or Lunesta], anesthetic gases, and propofol.) In contrast, negative allosteric modulators inhibit or decrease the activity of the GABAA receptor protein. (Examples of negative allosteric modulators or inhibitors of GABAA activity are flumazenil, bicuculline, pentylenetetrazol, and gabazine.)
  • ANS
    The autonomic nervous system (ANS) controls several basic bodily functions, including heart rate, body temperature, breathing rate, digestion, skin sensation, bladder, sweat glands, and metabolism. The ANS regulates functions that are involuntary or that we usually cannot consciously influence. The ANS is made up of 3 parts: (1) sympathetic nervous system (responsible for the body's "fight or flight" response, by increasing the heart rate and releasing energy); (2) parasympathetic nervous system (responsible for controlling body processes during relaxation and other ordinary situations, including slowing down heart rate and reducing blood pressure); and (3) enteric nervous system (responsible for governing the function of the gastrointestinal system through a mesh-like system of neurons [also called nerve cells]).
  • antagonist
    An antagonist is a chemical that binds to and inactivates a receptor. The result is a blocking of a biologic response. (An antagonist is the opposite of an agonist.)
  • apathy
    Apathy refers to a lack of feeling, emotion, interest, or concern for self or others.
  • ARS
    Autonomic reflex screen (ARS) testing includes a variety of tests to measure how heart rate and blood pressure change in response to changes in position (e.g., tilt table testing) and breathing. The testing may also evaluate how the nerves that regulate sweat glands respond to stimulation.
  • autonomic nervous system
    The autonomic nervous system (ANS) controls several basic bodily functions, including heart rate, body temperature, breathing rate, digestion, skin sensation, bladder, sweat glands, and metabolism. The ANS regulates functions that are involuntary or that we usually cannot consciously influence. The ANS is made up of 3 parts: (1) sympathetic nervous system (responsible for the body's "fight or flight" response, by increasing the heart rate and releasing energy); (2) parasympathetic nervous system (responsible for controlling body processes during relaxation and other ordinary situations, including slowing down heart rate and reducing blood pressure); and (3) enteric nervous system (responsible for governing the function of the gastrointestinal system through a mesh-like system of neurons [also called nerve cells]).
  • autonomic reflex screen test
    Autonomic reflex screen (ARS) testing includes a variety of tests to measure how heart rate and blood pressure change in response to changes in position (e.g., tilt table testing) and breathing. The testing may also evaluate how the nerves that regulate sweat glands respond to stimulation.
  • b

  • BDI
    The Beck Depression Inventory (BDI) is a widely used 21-item questionnaire for measuring severity of depression.
  • Beck Depression Inventory
    The Beck Depression Inventory (BDI) is a widely used 21-item questionnaire for measuring severity of depression.
  • BeyondSleepy
    Our slogan “Let’s get #BeyondSleepy” is a metaphor intended to provoke a discussion or consideration of the many ways that idiopathic hypersomnia and related disorders affect people. We strive to “get beyond” all the life-altering symptoms, including “beyond sleepiness,” “get beyond” the stigma, “get beyond” the lack of understanding, “get beyond” misdiagnosis and length of time to a diagnosis, and “get beyond” off-label treatments.
  • biomarker
    A biomarker (which is a short for biological marker) is a substance that is found in blood, other body fluids, or tissues that indicates a normal or abnormal process, a condition or disease, or the effects of treatment.
  • c

  • carnitine

    Carnitine is a substance that our bodies make in our liver and kidneys. It is then stored in our skeletal muscles, heart, brain, and sperm. Carnitine helps to turn fat into energy. Our bodies usually make enough carnitine to satisfy all of our needs, but some people don't have enough carnitine because their bodies either can’t make enough or can’t transport the carnitine into tissues so it can be used.

  • cataplexy
    Cataplexy is a sudden and temporary episode of muscle weakness that is typically triggered by strong emotions (for example, laughing, crying, terror), during which the person remains fully conscious and aware.
  • CBT
    Cognitive behavioral therapy (CBT) is a form of therapy that is goal-oriented; it involves examining and changing your behavior and patterns of thoughts, with the guidance and coaching of a therapist specially trained in CBT. A number of clinical studies have shown CBT to be effective for many conditions, including depression and anxiety. Read more about Getting Support from a Mental Health Professional.
  • CCR1/CCR3
    The CCR1 and CCR3 (C-C chemokine receptor 1 and 3) genes are involved in regulating the body’s response to bacteria, viruses, and other substances that the body perceives to be harmful or not a part of itself (that is, “foreign”).
  • CDH
    The central disorders of hypersomnolence (CDH), as defined by the ICSD-3, include narcolepsy type 1, narcolepsy type 2, idiopathic hypersomnia, and Kleine-Levin syndrome. They also include hypersomnolence caused by a medical disorder, medication or substance, psychiatric disorder and insufficient sleep disorder.
  • central disorders of hypersomnolence
    The central disorders of hypersomnolence (CDH), as defined by the ICSD-3, include narcolepsy type 1, narcolepsy type 2, idiopathic hypersomnia, and Kleine-Levin syndrome. They also include hypersomnolence caused by a medical disorder, medication or substance, psychiatric disorder and insufficient sleep disorder.
  • cerebrospinal fluid
    Cerebrospinal fluid (CSF) is a clear, colorless liquid that bathes the brain and spinal cord. Its primary purpose is to protect the brain and spinal cord, acting as a barrier and shock absorber. This fluid also circulates nutrients and chemicals that are filtered from the blood and removes waste products, antibodies, chemicals, and disease-causing substances away from the brain and spinal-cord tissue into the bloodstream.
  • CGI
    There are two types of CGI (Clinical Global Impression) scales, which vary depending on the precise issue the professional or researcher is assessing. The first is the Clinical Global Impression-Severity (CGI-S) scale, which is a 7-point scale that healthcare professionals or researchers (clinicians) use to rate the patient’s severity of illness at the time of assessment, as compared with the clinician’s past experience with patients who have the same diagnosis. The second scale is the Clinical Global Impression-Improvement scale (CGI-I), which is a 7-point scale that requires the clinician to assess how much the patient's illness has improved or worsened relative to a baseline state at the beginning of an intervention. Responses include: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.
  • chemokine receptor 1 and 3
    The CCR1 and CCR3 (C-C chemokine receptor 1 and 3) genes are involved in regulating the body’s response to bacteria, viruses, and other substances that the body perceives to be harmful or not a part of itself (that is, “foreign”).
  • Clinical Global Impression scales
    There are two types of CGI (Clinical Global Impression) scales, which vary depending on the precise issue the professional or researcher is assessing. The first is the Clinical Global Impression-Severity (CGI-S) scale, which is a 7-point scale that healthcare professionals or researchers (clinicians) use to rate the patient’s severity of illness at the time of assessment, as compared with the clinician’s past experience with patients who have the same diagnosis. The second scale is the Clinical Global Impression-Improvement scale (CGI-I), which is a 7-point scale that requires the clinician to assess how much the patient's illness has improved or worsened relative to a baseline state at the beginning of an intervention. Responses include: 1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; or 7, very much worse.
  • cognitive behavioral therapy
    Cognitive behavioral therapy (CBT) is a form of therapy that is goal-oriented; it involves examining and changing your behavior and patterns of thoughts, with the guidance and coaching of a therapist specially trained in CBT. A number of clinical studies have shown CBT to be effective for many conditions, including depression and anxiety. Read more about Getting Support from a Mental Health Professional.
  • control subject
    In an experiment or clinical trial, control subjects make up a group of participants who have characteristics similar to those of the treatment group, but they do not receive the treatment being studied. In an observational study, the control subjects have similar characteristics as those participants being studied, except that they do not have the symptom, disease, syndrome, or disorder being studied.
  • crossover study
    In a crossover study, each participant receives both the placebo and the active drug for a defined period of time. The order in which people receive the different treatments is determined randomly, and the responses that participants have to each of the different treatments are compared. Crossover studies can be double-blind, single-blind, or unblinded.
  • CSF
    Cerebrospinal fluid (CSF) is a clear, colorless liquid that bathes the brain and spinal cord. Its primary purpose is to protect the brain and spinal cord, acting as a barrier and shock absorber. This fluid also circulates nutrients and chemicals that are filtered from the blood and removes waste products, antibodies, chemicals, and disease-causing substances away from the brain and spinal-cord tissue into the bloodstream.
  • d

  • derealization
    Derealization is the repeated sense of feeling as if you are observing yourself from outside your body or that things around you aren't real, or both.
  • differential diagnosis
    In medicine, the process of considering other diagnoses which have similar symptoms or signs.
  • double-blind
    A double-blind trial or study is one in which neither the people who are doing the experiment nor the people who are the subjects of the experiment know which of the groups being studied is receiving the substance under investigation (active group) or is receiving the placebo (control group).
  • dysautonomia
    Dysautonomia, or autonomic dysfunction, is a broad term that refers to any of a number of conditions that result from a problem or disturbance in the autonomic nervous system.
  • e

  • EDS
    Excessive daytime sleepiness (EDS) refers to persistent sleepiness that occurs despite adequate or even prolonged nighttime sleep.
  • EEG
    Electroencephalography (EEG) is the measurement and recording of the brain's electrical activity by a typically non-invasive monitoring method.
  • effector cell
    An effector cell is a muscle, gland or organ cell that is capable of responding to a stimulus.
  • electroencephalography
    Electroencephalography (EEG) is the measurement and recording of the brain's electrical activity by a typically non-invasive monitoring method.
  • EMA
    The European Medicines Agency (EMA), which began in 1995, is a decentralized agency of the European Union, located in London. The Agency is responsible for the scientific evaluation of medicines developed by pharmaceutical companies for use in the European Union. (It is similar to the Food & Drug Administration [FDA] in the United States.)
  • encoding
    With respect to genetics, encoding means that our genes provide the blueprint or code for arranging amino acids so that they make proteins in our bodies.
  • endogenous

    An endogenous substance originates from or is produced within an organism (such as the human body), tissue, or cell. (The opposite of endogenous is exogenous.)

  • Epworth Sleepiness Scale
    The Epworth Sleepiness Scale (ESS) is a set of questions that measures how likely you are to fall asleep in each of 8 situations. For example, you might respond to a question about dozing with an answer of 0 (would never doze), 1 (slight chance of dozing), 2 (moderate chance of dozing), or 3 (high chance of dozing). Your responses to all of the eight questions are combined for a final score, which can range between 0 and 24. Higher scores indicate higher levels of daytime sleepiness. Most doctors and scientists consider scores of 10 or higher to indicate abnormal sleepiness.
  • ESS
    The Epworth Sleepiness Scale (ESS) is a set of questions that measures how likely you are to fall asleep in each of 8 situations. For example, you might respond to a question about dozing with an answer of 0 (would never doze), 1 (slight chance of dozing), 2 (moderate chance of dozing), or 3 (high chance of dozing). Your responses to all of the eight questions are combined for a final score, which can range between 0 and 24. Higher scores indicate higher levels of daytime sleepiness. Most doctors and scientists consider scores of 10 or higher to indicate abnormal sleepiness.
  • etiology
    Etiology refers to the cause or basis of a disease or condition.
  • European Medicines Agency
    The European Medicines Agency (EMA), which began in 1995, is a decentralized agency of the European Union, located in London. The Agency is responsible for the scientific evaluation of medicines developed by pharmaceutical companies for use in the European Union. (It is similar to the Food & Drug Administration [FDA] in the United States.)
  • excessive daytime sleepiness
    Excessive daytime sleepiness (EDS) refers to persistent sleepiness that occurs despite adequate or even prolonged nighttime sleep.
  • exogenous

    An exogenous substance originates from or is produced outside an organism (such as the human body), tissue, or cell. (The opposite of exogenous is endogenous.)

  • f

  • FDA
    The United States Food and Drug Administration (FDA) is an agency within the U.S. Department of Health and Human Services. It is responsible for protecting the public health by ensuring the safety, effectiveness, quality, and security of human and veterinary drugs, vaccines, and other biologic products and medical devices. The FDA is also responsible for the safety and security of most of our nation’s food supply and of cosmetics.
  • flumazenil
    Flumazenil is a GABA receptor antagonist that is FDA-approved in the U.S. as an intravenous (IV) medication to reverse excessive or prolonged sedation suspected to be caused by benzodiazepines (e.g., Valium, Ambien, etc.). It is not FDA-approved for the treatment of IH or any other central disorder of hypersomnolence. However, as with any medication approved by the FDA, physicians can choose to prescribe flumazenil “off-label” for indications other than that for which it is approved. This includes the use of flumazenil for the treatment of IH and related sleep disorders. Because flumazenil is currently approved in liquid form for IV use, it must be formulated into a transdermal cream or lozenge (for topical or mucosal absorption, respectively) by a compounding pharmacy for use by people with IH.
  • Food and Drug Administration
    The United States Food and Drug Administration (FDA) is an agency within the U.S. Department of Health and Human Services. It is responsible for protecting the public health by ensuring the safety, effectiveness, quality, and security of human and veterinary drugs, vaccines, and other biologic products and medical devices. The FDA is also responsible for the safety and security of most of our nation’s food supply and of cosmetics.
  • FOSQ
    The Functional Outcomes of Sleep Questionnaire (FOSQ) was developed in 1997 as a means to measure the impact of excessive daytime sleepiness on a person’s daily ability to function. The 30 questions are divided into five subscales – activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcomes. A shorter version, FOSQ-10, is also available; this shorter version contains only 10 questions.
  • Functional Outcomes of Sleep Questionnaire
    The Functional Outcomes of Sleep Questionnaire (FOSQ) was developed in 1997 as a means to measure the impact of excessive daytime sleepiness on a person’s daily ability to function. The 30 questions are divided into five subscales – activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcomes. A shorter version, FOSQ-10, is also available; this shorter version contains only 10 questions.
  • g

  • GABA
    γ-Aminobutyric acid (Gamma-aminobutyric) or GABA is the main inhibitory neurotransmitter in the central nervous system (brain and spinal cord) of mammals. Its primary role is to reduce the excitability or dampen the actions of cells throughout the nervous system. In humans, GABA is also directly responsible for regulating muscle tone.
  • GABA-related hypersomnia
    GABA-related hypersomnia occurs in people who have one of the central disorders of hypersomnolence (idiopathic hypersomnia, Kleine-Levin syndrome, narcolepsy, or hypersomnia due to a medical or psychiatric disorder) and have the somnogen in their cerebrospinal fluid (CSF).
  • genome-wide association study
    A genome-wide association study (GWAS) is a study that looks at people’s complete genetic material in order to identify DNA markers. It then compares the markers from people with a disease or trait to the markers for people without the disease or trait.
  • genotype
    Your genotype is your complete heritable genetic identity; it is your unique genome that would be revealed by personal genome sequencing. However, the word genotype can also refer just to a particular gene or set of genes carried by an individual.” Read more HERE.
  • GWAS
    A genome-wide association study (GWAS) is a study that looks at people’s complete genetic material in order to identify DNA markers. It then compares the markers from people with a disease or trait to the markers for people without the disease or trait.
  • h

  • HF
    Hypersomnia Foundation
  • histamine
    Histamine is a substance produced in the body that acts as a neurotransmitter. It is an important part of the reticular activating system (the part of the brain that wakes people up). Histamine may serve as a biomarker for problems or dysfunction in the hypothalamus. It is also involved in a number of activities, including the body’s immune and inflammatory responses and regulating the function of the gut.
  • HLA DQB1*0602 positive
    The HLA, or human leukocyte antigen, system is the location of genes that encode for proteins on the surface of white blood cells that are responsible for regulating our immune systems, our ability to fight infection. Most people with Type 1 narcolepsy carry the HLA-DQB1*0602 gene.
  • HLA typing
    The human leukocyte antigen (HLA) system is the location of a set of genes that encode for specific proteins (also called antigens). These inherited proteins are located on the surface of the white blood cells and other tissues in your body and are responsible for regulating your immune system.
  • humoral

    A humoral substance is a body fluid, or related to a body fluid, especially with regard to immune responses involving antibodies in body fluids (as distinct from cells).

  • hypersexuality
    Hypersexuality is a clinical diagnosis used to describe increased or extremely frequent sexual urges or behavior.
  • hypersomnia
    Hypersomnia refers to the condition of sleeping excessive amounts. However, in current medical terminology, both “hypersomnia” and the related word “hypersomnolence” are used more broadly to indicate long sleep durations, excessive daytime sleepiness, or both. In some classification systems, “hypersomnia” is reserved to refer to a specific disease entity, such as idiopathic hypersomnia, while “hypersomnolence” refers to the symptoms of long sleep and/or excessive daytime sleepiness regardless of cause. For more details, see Classification of Hypersomnias.
  • hypersomnolence
    Hypersomnolence refers to the symptoms of long sleep and/or excessive daytime sleepiness. For more details, see Classification of Hypersomnias.
  • hypnagogic

    Hypnagogic is the transition from wakefulness to falling asleep.

  • hypnagogic hallucinations
    Hypnagogic or hypnopompic hallucinations are sensory experiences involving the apparent perception of something that is not present, that occur at the transition from wakefulness to sleep (hypnagogic) or from sleep to wakefulness (hypnopompic). These hallucinations are typically visual in nature, but can affect other forms of sensation, such as hearing or touch.
  • hypnopompic
    Hypnopompic refers to the transition from sleep to wakefulness.
  • hypocretin
    Hypocretin, also known as orexin, is a neurotransmitter that regulates alertness, mood, and appetite. Hypocretin/orexin was discovered almost at the same time by two different groups of researchers in the late 1990s. One of the groups, headed by Yanagasawa at University of Texas Southwestern in Dallas, was working on obesity and named the neurotransmitter orexin (orexis is Greek for appetite). The other group, based at Harvard named it hypocretin, because it is produced in thehypothalamus and somewhat resembles secretin, a hormone found in the gut. For now, the naming controversy continues—both camps are firmly entrenched in their terminology and neither will budge. Whatever its name, high levels of this neurotransmitter are associated with increased appetite, improved mood, and enhanced wakefulness. Low or nonexistent levels of hypocretin are found in the cerebrospinal fluid of people with Type 1 narcolepsy.
  • hypothalamus
    The hypothalamus is a very small part of the brain that has a number of very important functions: it controls the autonomic nervous system and processes and secretes neurohormones. These hormones regulate body temperature, hunger, thirst, sleep, fatigue, sex drive, mood, sleep, alertness, and circadian rhythms.
  • hypothesis
    In science, a hypothesis is an idea or explanation that researchers then test in an experiment.
  • i

  • idiopathic hypersomnia
    Idiopathic hypersomnia (IH) is a neurological disorder characterized by excessive daytime sleepiness (often with associated cognitive dysfunction), despite getting a full night’s sleep or longer. People with IH may also experience difficulty awakening, sleep drunkenness, automatic behaviors, and symptoms related to the autonomic nervous system, such as feeling lightheaded when standing up quickly. Read more About IH.
  • IH
    Idiopathic hypersomnia (IH) is a neurological disorder characterized by excessive daytime sleepiness (often with associated cognitive dysfunction), despite getting a full night’s sleep or longer. People with IH may also experience difficulty awakening, sleep drunkenness, automatic behaviors, and symptoms related to the autonomic nervous system, such as feeling lightheaded when standing up quickly. Read more About IH.
  • in vitro
    In vitro means that something — in this circumstance, an experiment — takes place outside the body in an artificial environment.
  • inhibitory
    Inhibitory neurotransmitters, such as GABA and serotonin, decrease the likelihood that a nerve cell will send its chemical message on to the next nerve cell.
  • k

  • Kleine-Levin syndrome
    Kleine-Levin syndrome (KLS) is a rare disorder in which affected people experience episodes at least once per year during which they sleep for at least 11 hours out of every day (but often for days at a time), eat excessively (megaphagia), have abnormal thinking and behavior, and are hypersexual. Between episodes, their alertness, behavior, and thinking are normal.
  • KLS
    Kleine-Levin syndrome (KLS) is a rare disorder in which affected people experience episodes at least once per year during which they sleep for at least 11 hours out of every day (but often for days at a time), eat excessively (megaphagia), have abnormal thinking and behavior, and are hypersexual. Between episodes, their alertness, behavior, and thinking are normal.
  • knockout mouse
    A knockout mouse is a mouse in which researchers have inactivated, or "knocked out," an existing gene in the animal by replacing the gene or disrupting it with a different piece of DNA.
  • l

  • LC-MS

    Liquid chromatography-mass spectrometry (LC-MS) is a chemical analysis technique used to separate, identify, measure, and analyze substances in a mixture. It combines the physical separation capabilities of liquid chromatography with the mass analysis capabilities of mass spectrometry. (While liquid chromatography separates the individual components of a mixture, mass spectrometry ionizes atoms or molecules to facilitate their separation and detection in accordance with their molecular masses and charges.) This tandem technique is used in a variety of fields, including biotechnology, pharmaceutical research and food processing, especially when the mixture is highly complex.

  • lead compound
    A lead compound is a peptide, small molecule, or other agent with pharmacological or biochemical properties, which may have therapeutic potential and value as a starting point for drug development.
  • liquid chromatography-mass spectrometry

    Liquid chromatography-mass spectrometry (LC-MS) is a chemical analysis technique used to separate, identify, measure, and analyze substances in a mixture. It combines the physical separation capabilities of liquid chromatography with the mass analysis capabilities of mass spectrometry. (While liquid chromatography separates the individual components of a mixture, mass spectrometry ionizes atoms or molecules to facilitate their separation and detection in accordance with their molecular masses and charges.) This tandem technique is used in a variety of fields, including biotechnology, pharmaceutical research and food processing, especially when the mixture is highly complex.

  • longitudinal
    In a longitudinal study, researchers observe the same subjects and repeatedly gather data, or information, over a period of time.
  • lumbar puncture
    A lumbar puncture is a medical procedure in which a needle is inserted through the skin of the lower back between two vertebrae, or bones of the spinal column, into the spinal canal. A sample of the cerebrospinal fluid is then removed and sent to a laboratory for testing.
  • m

  • MAB
    The Hypersomnia Foundation’s Medical Advisory Board. Read more HERE.
  • magnetic resonance imaging
    MRI (magnetic resonance imaging) uses strong magnets and radio waves housed inside a specialized machine or scanner to make detailed 3-D pictures or images of organs and tissues within the body.
  • Maintenance of Wakefulness Test
    The purpose of the Maintenance of Wakefulness Test (MWT) is to see if you are able to stay awake during the daytime. The MWT takes place in a darkened, quiet, comfortable room. A technician places sensors on your head, face, and neck that can measure sleep. You recline in bed and try to stay awake during each of four measurement periods. The four measurement periods start about 9 or 10 am and last 40 minutes each. If you fall asleep, you are allowed to sleep for 90 seconds and are then awakened and kept awake until the next measurement period. If you don’t fall asleep within 40 minutes, that measurement period is ended. The measurement periods typically take place every two hours. This test is similar to the Multiple Sleep Latency Test (MSLT), but the MWT measures your likelihood of falling asleep when you are trying to stay awake. This is a subtle but important difference. Most people without sleep problems are able to stay awake for at least the first 8 minutes of each measurement period.
  • megaphagia
    Megaphagia, also referred to as polyphagia or hyperphagia, is an excessive appetite or hunger and abnormally large intake of solid food.
  • messenger RNA
    After being produced during transcription, mRNA (messenger RNA) carries genetic information to the ribosome (the site in the cell where proteins are made).
  • metabolite
    A metabolite is any substance produced during digestion or other chemical processes that occur in the body. Metabolite may also refer to the product that remains after a drug is broken down by the body.
  • modafinil
    Modafinil is a wake-promoting drug that is approved by the U.S. Food and Drug Administration (FDA) to improve wakefulness in adult patients with excessive sleepiness associated with narcolepsy, obstructive sleep apnea, and shift work disorder. In English-speaking countries, it is sold under the brand names Alertec (Canada), Modavigil (Australia, New Zealand), and Provigil (Ireland, South Africa, United Kingdom, United States).
  • MRI
    MRI (magnetic resonance imaging) uses strong magnets and radio waves housed inside a specialized machine or scanner to make detailed 3-D pictures or images of organs and tissues within the body.
  • mRNA
    After being produced during transcription, mRNA (messenger RNA) carries genetic information to the ribosome (the site in the cell where proteins are made).
  • MSLT
    The Multiple Sleep Latency Test (MSLT) measures how quickly you fall asleep in a quiet environment during the day. The MSLT typically consists of five scheduled naps, each nap opportunity lasting 20 minutes, separated by two-hour breaks. During each of the nap opportunities, you lie in bed in a darkened quiet room and try to go to sleep. The time that it takes you to fall asleep is called the sleep latency. You will be allowed to sleep for a maximum of 15 minutes during each opportunity. (You will be awakened if you don’t wake up on your own). If you do not fall asleep within 20 minutes, the nap trial will end.
  • Multiple Sleep Latency Test
    The Multiple Sleep Latency Test (MSLT) measures how quickly you fall asleep in a quiet environment during the day. The MSLT typically consists of five scheduled naps, each nap opportunity lasting 20 minutes, separated by two-hour breaks. During each of the nap opportunities, you lie in bed in a darkened quiet room and try to go to sleep. The time that it takes you to fall asleep is called the sleep latency. You will be allowed to sleep for a maximum of 15 minutes during each opportunity. (You will be awakened if you don’t wake up on your own). If you do not fall asleep within 20 minutes, the nap trial will end.
  • MWT
    The purpose of the Maintenance of Wakefulness Test (MWT) is to see if you are able to stay awake during the daytime. The MWT takes place in a darkened, quiet, comfortable room. A technician places sensors on your head, face, and neck that can measure sleep. You recline in bed and try to stay awake during each of four measurement periods. The four measurement periods start about 9 or 10 am and last 40 minutes each. If you fall asleep, you are allowed to sleep for 90 seconds and are then awakened and kept awake until the next measurement period. If you don’t fall asleep within 40 minutes, that measurement period is ended. The measurement periods typically take place every two hours. This test is similar to the Multiple Sleep Latency Test (MSLT), but the MWT measures your likelihood of falling asleep when you are trying to stay awake. This is a subtle but important difference. Most people without sleep problems are able to stay awake for at least the first 8 minutes of each measurement period.
  • n

  • narcolepsy
    Narcolepsy is a chronic neurological disorder that affects the brain’s ability to control sleep and wakefulness. The most typical symptoms are excessive daytime sleepiness, cataplexy, sleep paralysis, and hallucinations. Additional symptoms of narcolepsy include fragmented sleep and insomnia, and automatic behaviors. Unlike persons with IH, persons with narcolepsy generally feel refreshed after taking a nap. There are two types of narcolepsy – Type 1 narcolepsy (in which a person either has low levels of a brain hormone [hypocretin] or has cataplexy), and Type 2 narcolepsy (in which a person does not have cataplexy or low hypocretin). Read more HERE.
  • neocortex
    If you look at a human or mammal’s brain from the top or the sides, what you see is the neocortex. In humans, this part of the brain, which is about 2-4 mm thick (a thickness somewhere between the size of the point of a crayon and the eraser end of a pencil), forms ridges or deep grooves called sulci. The neocortex in humans controls sensory perception, generation of motor commands, spatial reasoning, conscious thought, and language.
  • neuroendocrine
    Neuroendocrine means both neural and endocrine in structure and function. Neuroendocrine cells are like nerve cells (neurons), but they also make hormones like cells of the endocrine system (endocrine cells). Neuroendocrine cells receive neuronal input (neurotransmitters released by nerve cells) and, as a result of this input, release hormones into the bloodstream.
  • neuromodulator
    A neuromodulator is a chemical messenger released from a neuron in the central nervous system (the brain or spinal cord), or in the periphery, that affects not a single cell but groups of neurons or effector cells that have the appropriate receptors. Unlike a neurotransmitter, it may not be released at synaptic sites, it often acts through second messengers, and it can produce long-lasting effects. The release may be local, so that only nearby neurons or effectors are influenced, or it may be more widespread.
  • neuron
    A neuron is simply a nerve cell. Neurons are specialized cells in the nervous system that transmit information to other nerve cells, muscle, or gland cells.
  • neurotransmitter
    A neurotransmitter is a chemical “messenger” that allows nerve cells to “talk” with other nerve cells and with muscles, organs, or other tissue. This chemical is released from one nerve cell, or neuron, at a specialized location (synaptic site), or junction. It then spreads, or diffuses, across a narrow gap, or cleft, to affect one or sometimes two other neurons on the other side of the cleft (postsynaptic), a muscle cell, or another effector cell. A neurotransmitter influences a neuron in one of 3 ways: excitatory, inhibitory, or modulatory.
  • nucleotide
    A nucleotide is one of the structural components, or building blocks, of DNA and RNA. A nucleotide consists of one of four chemicals (adenine, thymine, guanine, or cytosine), plus a molecule of sugar and a molecule of phosphoric acid.
  • o

  • obstructive sleep apnea
    Obstructive sleep apnea (OSA) is a sleep disorder characterized by repetitive partial and/or complete collapses of the upper airway, associated with arousals/awakenings and/or decreases in oxygen levels in the blood. The episodes last more than 10 seconds, by definition, but can last up to 30-60 seconds. Untreated sleep apnea may cause daytime sleepiness and increased risk of cardiovascular events, such as high blood pressure, heart attack, and stroke.
  • OSA
    Obstructive sleep apnea (OSA) is a sleep disorder characterized by repetitive partial and/or complete collapses of the upper airway, associated with arousals/awakenings and/or decreases in oxygen levels in the blood. The episodes last more than 10 seconds, by definition, but can last up to 30-60 seconds. Untreated sleep apnea may cause daytime sleepiness and increased risk of cardiovascular events, such as high blood pressure, heart attack, and stroke.
  • oxidation

    Oxidation is the process by which oxygen combines with an element and changes the appearance of the element. A simple example of slow oxidation is when iron reacts with oxygen and changes the iron to rust. An example of quick oxidation is when fire burns a log.

  • p

  • PAAC
    The PAAC is the Hypersomnia Foundation's Patient Advisory and Advocacy Council (PAAC). This council consists of a group of patient and supporter volunteers who meet monthly by phone conference to offer feedback to HF and share the needs of the IH community. They play a very valuable role for HF and the hypersomnia community at large. Interested in joining the PAAC? It requires commitment to a monthly conference call, with possible email correspondence in-between. Members have IH or a related sleep disorder, or have a loved with one of these rare disorders. The group is small so that all members can join in the discussion, and members typically rotate after a period of time. If you are interested in volunteering, please send an email to info@hypersomniafoundation.org with the subject line “PAAC.”
  • periprocedural
    Periprocedural means occurring soon before, during, or soon after the performance of a medical procedure, like a surgery.
  • PET
    A positron emission tomography (PET) scan creates computerized images of chemical changes that take place in tissue. In this test, various radioactive materials (tracers) and substances are injected into patients’ veins. The patient is then scanned in a special machine or scanner. Radiologists can then identify activity in certain parts of the brain by measuring blood flow and oxygen and glucose metabolism in the tissues of the working brain.
  • phenotype
    A phenotype is a physical appearance or biochemical characteristic of an organism. Most phenotypes are influenced by both genotype and the environment. Read more HERE.
  • placebo
    A placebo is an inactive (or sham) substance that is designed to look like the substance or drug that is being studied. A placebo is used as a control in clinical trials and does not contain any active materials.
  • placebo-controlled trial
    placebo-controlled trial or study is one in which the effect of a drug is compared with the effect of a placebo. In placebo-controlled trials, participants receive either the drug being studied or a placebo. The results of the drug and placebo groups are then compared to see if the drug is more effective in treating the condition than is the placebo.
  • polysomnography
    Polysomnography, also called a sleep study, uses multiple electrodes and devices (multi-channel) to gather information about a patient during sleep. A standard in-laboratory study records brain waves, eye movements, oxygen levels in the blood, jaw movement, heart rate, breathing rate, airflow, respiratory effort, sound, and limb movements. Taken as a total picture, the results of these recordings allow a calculation of sleep stage and disorders of sleep. Limited-channel sleep studies can take place outside of the sleep laboratory.
  • positron emission tomography
    A positron emission tomography (PET) scan creates computerized images of chemical changes that take place in tissue. In this test, various radioactive materials (tracers) and substances are injected into patients’ veins. The patient is then scanned in a special machine or scanner. Radiologists can then identify activity in certain parts of the brain by measuring blood flow and oxygen and glucose metabolism in the tissues of the working brain.
  • postural orthostatic tachycardia syndrome
    Postural orthostatic tachycardia syndrome (POTS), also known as postural tachycardia syndrome, is a disorder of the autonomic nervous system characterized by an excessive increase in heart rate upon standing.
  • POTS
    Postural orthostatic tachycardia syndrome (POTS), also known as postural tachycardia syndrome, is a disorder of the autonomic nervous system characterized by an excessive increase in heart rate upon standing.
  • PSG
    Polysomnography, also called a sleep study, uses multiple electrodes and devices (multi-channel) to gather information about a patient during sleep. A standard in-laboratory study records brain waves, eye movements, oxygen levels in the blood, jaw movement, heart rate, breathing rate, airflow, respiratory effort, sound, and limb movements. Taken as a total picture, the results of these recordings allow a calculation of sleep stage and disorders of sleep. Limited-channel sleep studies can take place outside of the sleep laboratory.
  • psychomotor vigilance task
    The Psychomotor Vigilance Task (PVT) measures sustained attention. In this simple task, a light on a handheld device turns on randomly every few seconds, and the person presses a button in response to the light appearing.
  • r

  • randomized trial
    In a randomized controlled clinical trial, participants or subjects are randomly assigned (by chance) to one of two or more groups.
  • related sleep disorder
    In patients with certain other disorders, excessive daytime sleepiness and/or long sleep times are commonly present and can be very similar to that seen in idiopathic hypersomnia. These include narcolepsy types 1 and 2, Kleine-Levin syndrome, and hypersomnias associated with certain other disorders. Because current treatments for these disorders are very similar and current research indicates that there may also be significant overlap among them, it is important to address and research them together. For more details, please see About Related Sleep Disorders and Classification of Hypersomnias.
  • REM sleep
    Rapid Eye Movement (REM) sleep is one of the two basic states of sleep. REM sleep, also known as dream sleep, is characterized by rapid eye movements and more irregular breathing and heart rate compared to NREM sleep, the other basic state of sleep.
  • ribosome
    The site in the cell where proteins are made.
  • s

  • SAB
    The Hypersomnia Foundation’s Scientific Advisory Board. Read more HERE.
  • sensitivity
    The sensitivity of a diagnostic test indicates how often the test will be positive if a person truly has the disease (true positive rate). In other words, if the test is highly sensitive and the test result is negative, you can be nearly certain that the person doesn’t have the disease for which they’re being tested. A sensitive test helps rule out disease (when the result is negative). Read more HERE.
  • SF-36
    The SF-36 (or Short-Form Health Survey) is a questionnaire in which people answer 36 health-related and quality-of-life questions. The SF-36 is made up of eight scales that are summed to reach the total score. These scales include vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, mental health. The SF-36 does not include a scale to assess sleep.
  • single nucleotide polymorphism
    A SNP is a DNA variation in which one nucleotide (the building block of DNA) differs from what is generally observed in the population. SNPs happen normally throughout a person’s DNA—usually about once in every 300 nucleotides. These variations are typically found in the DNA between genes. They can act as markers, helping scientists locate genes that are associated with a specific disease. When SNPs appear within a gene or in a regulatory region near a gene, they may play a more direct role in disease by affecting the function of a gene.
  • single-photon emission computed tomography
    SPECT is similar to positron emission tomography (PET) in that it uses a radioactive substance (tracer) and a special camera to create 3-D pictures of an internal organ of the body. Like PET, SPECT is particularly useful for looking at blood flow to an organ, such as the heart or brain. The primary difference between the two tests is that the tracers used in SPECT last longer than those used in PET, allowing for a longer time to view the organ working.
  • sleep diary

    A sleep diary is a method of recording your sleep patterns, including the time you go to sleep and wake up, over an extended period of time.

  • sleep efficiency
    Sleep efficiency is the percentage of time spent asleep while in bed. It is calculated by dividing the amount of time spent asleep (in minutes) by the total amount of time in bed (in minutes). A normal sleep efficiency is considered to be 85% or higher.
  • sleep inertia
    Feelings of grogginess and sleepiness that occur upon awakening, which can result in impaired alertness and may interfere with the ability to perform mental or physical tasks.
  • sleep latency
    The sleep latency is the time it takes to fall asleep once a person attempts to go to sleep.
  • sleep log
    A sleep diary or sleep log is used to record a person’s waking and sleeping times over a period of time, typically at least two weeks.
  • sleep onset REM period
    Sleep onset REM periods (SOREMPs) are REM sleep periods within 15 minutes of sleep onset, considered to support the diagnosis of narcolepsy.
  • sleep paralysis

    Sleep paralysis is a phenomenon in which you are unable to move or speak during the transition from sleep to wake or from wake to sleep.

  • sleep stages
    Sleep is made up of four stages. These four stages can be subdivided into non-rapid-eye-movement (NREM, which typically makes up about 75% of your time asleep; Stages 1, 2, and 3) and rapid eye movement (REM, which makes up the other 25% of sleep). As you progress from wakefulness to deep sleep, you usually pass through progressively deeper stages, from stage 1 (the lightest) to stage 3 or slow wave sleep, (the deepest stage, in which critical substances such as growth hormone are released), and finally into REM sleep (during which the body doesn’t move and dreaming occurs). It is not uncommon for a person to move back and forth between stages 2 and 3 before moving into REM sleep. A typical sleep cycle lasts about 90 minutes, with more stage 3 sleep occurring earlier in the sleep period and more REM sleep later in the sleep period.
  • SNP
    A SNP is a DNA variation in which one nucleotide (the building block of DNA) differs from what is generally observed in the population. SNPs happen normally throughout a person’s DNA—usually about once in every 300 nucleotides. These variations are typically found in the DNA between genes. They can act as markers, helping scientists locate genes that are associated with a specific disease. When SNPs appear within a gene or in a regulatory region near a gene, they may play a more direct role in disease by affecting the function of a gene.
  • somnogen

    A somnogen is simply a substance that causes or induces sleepiness.

  • SOREMP
    Sleep onset REM periods (SOREMPs) are REM sleep periods within 15 minutes of sleep onset, considered to support the diagnosis of narcolepsy.
  • specificity
    The specificity of a diagnostic test indicates how often the test will be negative if a person does not have the disease (true negative rate). In other words, if the test result for a highly specific test is positive, you can be nearly certain that the person actually has the disease for which they’re being tested. A very specific test rules in disease with a high degree of confidence. Read more HERE.
  • SPECT
    SPECT is similar to positron emission tomography (PET) in that it uses a radioactive substance (tracer) and a special camera to create 3-D pictures of an internal organ of the body. Like PET, SPECT is particularly useful for looking at blood flow to an organ, such as the heart or brain. The primary difference between the two tests is that the tracers used in SPECT last longer than those used in PET, allowing for a longer time to view the organ working.
  • striatum
    The striatum (which looks as if it has grey and white stripes and thus the name striae or stripe) is a section of the brain that lies beneath the front part of the cortex. This area of the brain has a number of functions, including planning and executing movement and controlling the reward system.
  • susceptibility gene
    A susceptibility gene is a permanent change in a gene (mutation) that increases a person’s susceptibility to or likelihood of developing a certain disease or disorder. When such a mutation is passed from a biologic parent to a child, symptoms of the disease or disorder are more likely to happen, but it is not certain that the symptoms will occur.
  • t

  • T1N
    The International Classification of Sleep Disorders, third edition, divides narcolepsy into Type 1 and Type 2 (the previous edition included narcolepsy with and without cataplexy). The new criteria for T1N require a combination of hypersomnolence and either low hypocretin levels in the cerebrospinal fluid or cataplexy plus short average sleep latency (≤ 8 minutes) and 2 or more sleep-onset REM periods (SOREMPs) on the Multiple Sleep Latency Test (MSLT). A SOREMP (within 15 minutes) of sleep onset on polysomnography may replace one of the SOREMPs on the MSLT.
  • T2N
    The International Classification of Sleep Disorders, third edition, divides narcolepsy into Type 1 and Type 2 (the previous edition included narcolepsy with and without cataplexy). Type 2 narcolepsy refers to narcolepsy without cataplexy.
  • tilt table test
    A tilt table test is typically performed in individuals with significant fainting spells and/or dizziness of unknown cause. The test monitors an individual’s heart rate, blood pressure, and symptoms while lying flat on a table and then standing upright for a defined period of time. Diagnoses rendered after a tilt table test may include orthostatic hypotension, reflex syncope, and postural orthostatic tachycardia syndrome.
  • transcription
    Transcription is the process in which when RNA is made from DNA.
  • type 1 narcolepsy
    The International Classification of Sleep Disorders, third edition, divides narcolepsy into Type 1 and Type 2 (the previous edition included narcolepsy with and without cataplexy). The new criteria for T1N require a combination of hypersomnolence and either low hypocretin levels in the cerebrospinal fluid or cataplexy plus short average sleep latency (≤ 8 minutes) and 2 or more sleep-onset REM periods (SOREMPs) on the Multiple Sleep Latency Test (MSLT). A SOREMP (within 15 minutes) of sleep onset on polysomnography may replace one of the SOREMPs on the MSLT.
  • type 2 narcolepsy
    The International Classification of Sleep Disorders, third edition, divides narcolepsy into Type 1 and Type 2 (the previous edition included narcolepsy with and without cataplexy). Type 2 narcolepsy refers to narcolepsy without cataplexy.
  • v

  • vigilance
    Vigilance refers to the state of being alert and attentive.

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