Glossary

A glossary of common sleep-related terms.

Achondroplasia
Disease of cartilage and bone development which results in small stature(dwarf)
Adenoidectomy
Surgical removal of the adenoids.
Advanced sleep phase syndrome
Disorder of the sleep/wake timing. The person tends to go to sleep early in the evening eg 7am and wake up in the early hours of the morning. The patients complains of difficulty maintaining sleep (waking too early).
Apnoea
Stopping breathing completely.
Benzodiazepine
Medications widely used as sleeping tablets and anti-anxiety medication. Among the many benzodiazepine ValiumTM is widely known.
Brain stem
Part of the brain between the cerebral hemisphere (cortex) and the spinal cord. It is the most primitive of the brain present in all animals.
Cataplexy
Sudden onset of muscle weakness which can involve the entire body, like a jelly feeling or individual muscle. If it affects the knees the person can have a sensation of knee buckling or even fall on the ground without loss of consciousness.
Ciguatera
Medical condition contracted by eating fish from topical and sub-tropical areas, which contains cigua toxin.
Computerised tomography
Radiology technique helpful to visualise internal organs (eg. the brain).
Conversion syndrome
Another word for hysteria., where psychic symptoms are converted in body complaint. For example anxiety that presents as shortness of breath.
CT
Computerised tomography.
Delayed sleep phase syndrome
A sleep/wake function timing disorder characterised by inability to fall asleep until the early hours of the morning (past midnight) and tend to continue sleeping until late in the morning. Patient presents with difficulty initiating sleep and daytime tiredness.
Dopamine
A substance used by brain cells to communicate with each other(neurotransmitter).
Eckbom syndrome
This is another name for restless leg after the name of the researcher who initially described the symptoms.
EEG
Electroencephalogram.
Electroencephalogram
A technique for recording electrical brain activity.
Encephalitis
Inflammation of the central nervous system (the brain) usually due to viruses or bacteria.
Endorphin
Substance produced by the brain, which help reduce pain, ‘body-own pain killers’.
Endozepine
Substances produced by the nervous system, which promote sleep.
Entrainment
The coupling of two rhythms. For example body temperature with sleep and wake function.
Enuresis
Bed-wetting.
Epoch
Recording of sleep parameters (brain activity, eye movement, cardiograph, and muscle tone) in 20-30 seconds periods.
Fibromyalgia
Condition of chronic fatigue and diffuse aches and pains in the absence of inflammation in the muscle and joints.
Fibrositis
See fibromyalgia.
Flumazenil
Medication which counteracts the action of benzodiazepine.
Hallucinations
Perception of sensory experiences, seeing things, hearing things, feeling of abnormal body position, in the absence of a real stimulus.
Hypersomnia
Increased in sleepiness tendency.
Hypersomnolence
Another word for increased sleepiness tendency.
Hypnagogic hallucinations
Hallucinations, which occur at the beginning of, sleep (hypnagogic).
Hypnopompic hallucinations
Hallucinations, which occur at the end of, sleep (hypnopompic).
Hypopnoea
Reduction in breathing, contrary to apnoea which is stopping breathing completely.
Hypothalamus
Part of the brain located at the top of the brain stem which, among other things, is involved in regulation of hormone secretion.
Hypothyroidism
Condition characterised by reduction in the level of thyroid hormone.
Hysteria
A word used for conversion syndrome but currently not used in psychiatry.
Idiopathic
Medical word meaning ‘of unknown origin’, eg idiopathic hypersomnolence means increased sleepiness (hypersomnolence of unknown origin)
Kleine-Levin syndrome
A condition characterised by recurrent bouts of sleepiness lasting days to weeks and compulsive eating.
Limbic system
Part of the brain involved in the regulation of memory, concentration and emotion.
M.E.
See Myalgic encephalitis.
Magnetic resonance imaging
A radiological technique that uses magnetic field to visualise internal body parts. It allows visualisation of the brain in fine detail.
Melatonin
Hormone produced in the brain by the pineal gland. It helps to synchronise sleep/wake function with light and dark cycle.
MRI
See magnetic resonance imaging.
Myalgic encephalitis
Term used for people with chronic fatigue. It implies, but never demonstrated, diffuse aches (myalgic) due to inflammation of the brain (encephalomyelitis).
Narcolepsy
A condition characterised by increased tendency to fall asleep.
Neuro-asthenia
Name used for people with chronic fatigue. Literally it means weakness (asthenia) of the nervous system.
Neurone(s)
Cells in the nervous system are called neurones.
Neuropathy
Diseases of the peripheral nerves that can result in unpleasant sensation in the part of the body supplied by the nerve. It is very common in diabetes when it can cause numbness, tingling and pain particularly in the legs.
Non-REM
Non- rapid eye movement sleeps.
Non-REM narcolepsy
A condition characterised by the increased sleepiness tendency with no evidence of rapid eye movement related symptoms (cataplexy, hallucinations and sleep paralysis).
Nor-adrenaline
A substance which is used by brain cells to communicate with each other(neuro-transmitter). It increases alertness.
Occipital cortex
Part of the brain cortex underneath the back of the skull. It is responsible for vision.
Ondine curse
Particular form of central sleep apnoea (see text).
Periodic limb movement disorder
A sleep disorder characterised by recurrent fast jerks of the ankles, knees, hips or arms during sleep. It causes sleep fragmentation, daytime tiredness and unrefreshed sleep. It is one of the causes of insomnia.
Pickwickian syndrome
A condition characterised by obesity, apnoeas ,respiratory failure and daytime sleepiness. The name is derived from one of Charles Dicken’s character in Pickwick Papers.
PLMD
Periodic limb movement disorder.
Polysomnography
Recording of multiple (poly) parameters during sleep (somnography).
Psycho-asthenia
A name used for people with chronic fatigue. Literally it means weakness (asthenia) of the psyche.
REM
Rapid eye movement.
REM sleep behaviour disorder
A sleep disorder characterised by acting out dreams during sleep.
Restless leg
A condition characterised by sensation of cramps in the calves. It usually occurs at bedtime and causes the need to move the legs around to relieve the discomfort.
Reticular activating system
A group of neurones (cells of the nervous system) in the brain stem linked together like a net. They are active during wakefulness.
Retina
Light sensitive layer of cells in the back of the eye, where the light and outside world image are registered.
Sleep paralysis
Sensation of not being able to move (paralysis) usually when the person is waking up. It lasts from a few seconds to a few minutes. It is a frightening experience.
Snoring
The sound made by the air passing through the pharynx (the back of the throat) during sleep.
Synchroniser
An agent, such as melatonin or light, which determine the periodicity of a biological function. For example light and darkness cycle synchronises our sleep and wake function. Synchronisers are also known as zeitgeber (time givers) or entraining agents.
Tonsillectomy
Surgical removal of the tonsils.
Upper airway resistance Syndrome
A condition halfway between pure snoring (noisy making) and sleep apnoea. Breathing does not stop completely because the body makes an extra effort to drive the air through the narrow pharynx. This results in fragmentation of sleep.

Achondroplasia
Disease of cartilage and bone development which results in small stature(dwarf)
Adenoidectomy
Surgical removal of the adenoids.
Advanced sleep phase syndrome
Disorder of the sleep/wake timing. The person tends to go to sleep early in the evening eg 7am and wake up in the early hours of the morning. The patients complains of difficulty maintaining sleep (waking too early).
Apnoea
Stopping breathing completely.
Benzodiazepine
Medications widely used as sleeping tablets and anti-anxiety medication. Among the many benzodiazepine ValiumTM is widely known.
Brain stem
Part of the brain between the cerebral hemisphere (cortex) and the spinal cord. It is the most primitive of the brain present in all animals.
Cataplexy
Sudden onset of muscle weakness which can involve the entire body, like a jelly feeling or individual muscle. If it affects the knees the person can have a sensation of knee buckling or even fall on the ground without loss of consciousness.
Ciguatera
Medical condition contracted by eating fish from topical and sub-tropical areas, which contains cigua toxin.
Computerised tomography
Radiology technique helpful to visualise internal organs (eg. the brain).
Conversion syndrome
Another word for hysteria., where psychic symptoms are converted in body complaint. For example anxiety that presents as shortness of breath.
CT
Computerised tomography.
Delayed sleep phase syndrome
A sleep/wake function timing disorder characterised by inability to fall asleep until the early hours of the morning (past midnight) and tend to continue sleeping until late in the morning. Patient presents with difficulty initiating sleep and daytime tiredness.
Dopamine
A substance used by brain cells to communicate with each other(neurotransmitter).
Eckbom syndrome
This is another name for restless leg after the name of the researcher who initially described the symptoms.
EEG
Electroencephalogram.
Electroencephalogram
A technique for recording electrical brain activity.
Encephalitis
Inflammation of the central nervous system (the brain) usually due to viruses or bacteria.
Endorphin
Substance produced by the brain, which help reduce pain, ‘body-own pain killers’.
Endozepine
Substances produced by the nervous system, which promote sleep.
Entrainment
The coupling of two rhythms. For example body temperature with sleep and wake function.
Enuresis
Bed-wetting.
Epoch
Recording of sleep parameters (brain activity, eye movement, cardiograph, and muscle tone) in 20-30 seconds periods.
Fibromyalgia
Condition of chronic fatigue and diffuse aches and pains in the absence of inflammation in the muscle and joints.
Fibrositis
See fibromyalgia.
Flumazenil
Medication which counteracts the action of benzodiazepine.
Hallucinations
Perception of sensory experiences, seeing things, hearing things, feeling of abnormal body position, in the absence of a real stimulus.
Hypersomnia
Increased in sleepiness tendency.
Hypersomnolence
Another word for increased sleepiness tendency.
Hypnagogic hallucinations
Hallucinations, which occur at the beginning of, sleep (hypnagogic).
Hypnopompic hallucinations
Hallucinations, which occur at the end of, sleep (hypnopompic).
Hypopnoea
Reduction in breathing, contrary to apnoea which is stopping breathing completely.
Hypothalamus
Part of the brain located at the top of the brain stem which, among other things, is involved in regulation of hormone secretion.
Hypothyroidism
Condition characterised by reduction in the level of thyroid hormone.
Hysteria
A word used for conversion syndrome but currently not used in psychiatry.
Idiopathic
Medical word meaning ‘of unknown origin’, eg idiopathic hypersomnolence means increased sleepiness (hypersomnolence of unknown origin)
Kleine-Levin syndrome
A condition characterised by recurrent bouts of sleepiness lasting days to weeks and compulsive eating.
Limbic system
Part of the brain involved in the regulation of memory, concentration and emotion.
M.E.
See Myalgic encephalitis.
Magnetic resonance imaging
A radiological technique that uses magnetic field to visualise internal body parts. It allows visualisation of the brain in fine detail.
Melatonin
Hormone produced in the brain by the pineal gland. It helps to synchronise sleep/wake function with light and dark cycle.
MRI
See magnetic resonance imaging.
Myalgic encephalitis
Term used for people with chronic fatigue. It implies, but never demonstrated, diffuse aches (myalgic) due to inflammation of the brain (encephalomyelitis).
Narcolepsy
A condition characterised by increased tendency to fall asleep.
Neuro-asthenia
Name used for people with chronic fatigue. Literally it means weakness (asthenia) of the nervous system.
Neurone(s)
Cells in the nervous system are called neurones.
Neuropathy
Diseases of the peripheral nerves that can result in unpleasant sensation in the part of the body supplied by the nerve. It is very common in diabetes when it can cause numbness, tingling and pain particularly in the legs.
Non-REM
Non- rapid eye movement sleeps.
Non-REM narcolepsy
A condition characterised by the increased sleepiness tendency with no evidence of rapid eye movement related symptoms (cataplexy, hallucinations and sleep paralysis).
Nor-adrenaline
A substance which is used by brain cells to communicate with each other(neuro-transmitter). It increases alertness.
Occipital cortex
Part of the brain cortex underneath the back of the skull. It is responsible for vision.
Ondine curse
Particular form of central sleep apnoea (see text).
Periodic limb movement disorder
A sleep disorder characterised by recurrent fast jerks of the ankles, knees, hips or arms during sleep. It causes sleep fragmentation, daytime tiredness and unrefreshed sleep. It is one of the causes of insomnia.
Pickwickian syndrome
A condition characterised by obesity, apnoeas ,respiratory failure and daytime sleepiness. The name is derived from one of Charles Dicken’s character in Pickwick Papers.
PLMD
Periodic limb movement disorder.
Polysomnography
Recording of multiple (poly) parameters during sleep (somnography).
Psycho-asthenia
A name used for people with chronic fatigue. Literally it means weakness (asthenia) of the psyche.
REM
Rapid eye movement.
REM sleep behaviour disorder
A sleep disorder characterised by acting out dreams during sleep.
Restless leg
A condition characterised by sensation of cramps in the calves. It usually occurs at bedtime and causes the need to move the legs around to relieve the discomfort.
Reticular activating system
A group of neurones (cells of the nervous system) in the brain stem linked together like a net. They are active during wakefulness.
Retina
Light sensitive layer of cells in the back of the eye, where the light and outside world image are registered.
Sleep paralysis
Sensation of not being able to move (paralysis) usually when the person is waking up. It lasts from a few seconds to a few minutes. It is a frightening experience.
Snoring
The sound made by the air passing through the pharynx (the back of the throat) during sleep.
Synchroniser
An agent, such as melatonin or light, which determine the periodicity of a biological function. For example light and darkness cycle synchronises our sleep and wake function. Synchronisers are also known as zeitgeber (time givers) or entraining agents.
Tonsillectomy
Surgical removal of the tonsils.
Upper airway resistance Syndrome
A condition halfway between pure snoring (noisy making) and sleep apnoea. Breathing does not stop completely because the body makes an extra effort to drive the air through the narrow pharynx. This results in fragmentation of sleep.