Jargon Buster

All explanations / definitions are listed below in alphabetical order. Scroll down to find the one you are looking for.

Absence Seizure:
Also called Petit Mal ( “little illness” in French) absence seizures are a  type of epilepsy  characterised by brief “zoning out” episodes, a blank stare sometimes accompanied by an upward eye movement. It usually occurs in children between the ages of 4 and 15, and generally does not have long term consequences. During diagnosis an onset can be provoked by asking the patient to hyperventilate (breathing in and out as fast as possible). An EEG is also used for diagnosis as seizures produce characteristic wave patterns. Cataplexy has been misdiagnosed as absence seizures.

Excessive Daytime Sleepiness manifests itself as periodic, overwhelming, irresistible urges to sleep during the day, often in inappropriate places  and times, such as at work, in school, while driving etc. People have been known to fall asleep while swimming! These episodes of falling asleep can obviously be extremely dangerous for the person involved and sometimes for others, e.g. passengers in a vehicle like a  car or bus. These irresistible sleep periods can last for a number of seconds,  a number of minutes or up to an hour or more.

EDS is very often one of the first symptoms of narcolepsy to appear and is commonly initially ignored as being a real problem at all, even by the person affected. It is frequently misdiagnosed by medical professionals as being due to other factors which can also be associated with fatigue e.g depression, or even lifestyle.

(AB) Automatic Behaviour:
Automatic Behaviour is one of the classic symptoms of narcolepsy. Automatic behaviour is manifested by the person with narcolepsy continuing to perform an activity that they are engaged in but without any awareness or memory of actually carrying out that activity. An example might be when they are writing in a normal coherent way and then move into automatic behaviour and continue  to write in a totally non-coherent way, their perfectly normal writing style changing to an incomprehensible scrawl. Or the person may find themselves in a different room in their house without any recollection of how they got there. Automatic behaviour happens as the PWN is hovering between being awake and being asleep.

Cataplexy: 
Cataplexy is one of the classic symptoms of narcolepsy.

Cataplexy is considered an extremely specific marker for narcolepsy. There are no other known diseases of which  cataplexy is a symptom. 

Not all PWNs will have cataplexy. Estimates vary, as the statistics are difficult to pin down due to the poor diagnostic history of narcolepsy, but the current general consensus is that about 70% of people with narcolepsy will also have, or develop, cataplexy.

Narcolepsy with cataplexy is known as “Type 1 Narcolepsy”
Narcolepsy without cataplexy is known as “Type 2 Narcolepsy”

Cataplexy is where one’s muscles temporarily lose some or all of their strength, or their ability to function. The most severe form of cataplexy results in the person totally collapsing and being effectively temporarily paralysed for periods ranging from as short as a split second to. as long as several minutes. During this time the person remains  fully conscious but is unable to move or speak. The muscles which control vital bodily functions, heart beating, breathing and so on,  are not affected in any way. There is no residual damage caused to the muscles which are totally as before once the cataplectic episode is over.

Cataplexy often manifests itself in much less severe ways, such as a fleeting weakness or a momentary loss of grip, causing e.g. a cup to slip from one’s grasp - and consequently is very often misdiagnosed or undiagnosed and passed off as clumsiness. Cataplexy can vary in severity from total collapse to something  as simple as a slight lolling of the head, or the droop of an eyelid.

What causes cataplexy?
Cataplexy is usually triggered by instances of strong emotions, such as laughter, excitement, anger, fear and so on.  

But why?
The REM  periods of the normal sleep cycle are when we dream. To prevent us from physically acting out our dreams in our sleep by actually moving our arms and legs and our body in a way that mimics what we are doing in our dream, during REM periods the brain actually paralyses the body so that it cannot move during the dream. This temporary paralysis is totally normal and protects us from harming ourselves (or others) when we dream. In cataplexy, this paralysis, full or partial, occurs when the person is awake. It can last for as long as a split second to as long as several minutes. The consequences are often extremely distressing and can in some cases be life threatening, e.g. while driving.

 The frequency of cataplexy in PWNs can vary tremendously, occurring as few as one or two instances a year to multiple times per day.

(CNS) Central nervous system 
The brain and the spinal cord. The PNS, peripheral nervous system, connects the CNS to the sensory organs and other organs and the rest of the body.

 (CPAP) Continuous Positive Airways Pressure.
This is a device with  small pump that delivers a continuous supply of compressed air through a mask that either covers your nose or your nose and mouth. The compressed air prevents your throat closing. It is used for the relief of OSA - Obstructive sleep apnea.

 (CSF) Cerebrospinal fluid
CSF is a clear, colorless fluid found in the brain and spinal cord. CSF obtained by lumbar puncture from the spinal. The analysis of CSF can be  useful  for the diagnosis of various neurological and other conditions. The  particular relevance of CSF in relation to narcolepsy is to send a sample for laboratory analysis to detect the level of hypocretin in the fluid and hence in the brain. There are 2  types of hypocretin molecule, called hypocretin 1 and hypocretin 2 (also known as  orexin A and orexin B). It is possible to test for hypocretin 1 in the CSF, but not for hypocretin 2. The absence of, or significantly low level of,  hypocretin 1 in the CSF is strongly indicative of narcolepsy.

(EDS) Excessive daytime Sleepiness
Excessive Daytime Sleepiness, often referred to as EDS,  is one of the classic symptoms of narcolepsy.

EDS manifests itself as periodic, overwhelming, irresistible urges to sleep during the day, often in inappropriate places  and times, such as at work, in school, while driving etc. People have been known to fall asleep while swimming! These episodes of falling asleep can obviously be extremely dangerous for the person involved and sometimes for others, e.g. passengers in a vehicle like a  car or bus. These irresistible sleep periods can last for a number of seconds,  a number of minutes or up to an hour or more.

EDS is very often one of the first symptoms of narcolepsy to appear and is commonly initially ignored as being a real problem at all, even by the person affected. It is frequently misdiagnosed by medical professionals as being due to other factors which can also be associated with fatigue e.g depression, or even lifestyle. The reason that the PWN has these  irresistible urges to sleep are complex but it is now generally agreed by researchers that it is ultimately due to the lack of the normal control of the sleep pattern exerted by the hypocretin neurotransmitter, the absence of which is the fundamental cause of narcolepsy. In more simple terms, undoubtedly one of the main reasons for EDS is because of the extremely poor quality of the PWN’s  night-time sleep, which is again caused by the absence of the controlling neurotransmitter, hypocretin. 

(EEG) Electroencephalogram:
This is a test that detects electrical activity in the brain. It is non-invasive and carried out by attaching electrodes to the scalp and recording brain activity as a line on a moving paper roll. It is used for diagnosing brain disorders such as epilepsy and sleep disorders. It is also used to diagnose “absence seizure” (also known as petit mal) which can be provoked by rapid breathing during the test. Cataplexy in children has been known to be misdiagnosed as absence seizures.

 (ESS) Epworth Sleepiness Scale:    (see also - SNS- Swiss Narcolepsy Scale)
The Epworth Sleepiness Scale (ESS) was developed by Murray Johns in 1990 and published in 1991. Its name derived from Epworth Hospital in Australia, where Johns worked [1]. The ESS provides a simple standardised means of measuring general levels of sleepiness. It can be used by healthcare professionals to assist diagnosis or by anyone who suspects they may have sleep problem.

http://www.sleepmed.com.au/epworth-calculator.html

Hallucinations - Hypnagogic and Hypnopompic:
These are typically experienced while falling asleep or waking up and are often described as extremely vivid dreams that are indistinguishable from reality. The key feature of these hallucinations is that the person experiencing them feels that they are actually real life. This can be extremely disturbing and frightening for adults and particularly terrifying for children. It is believed by many authorities that this phenomenon is caused by the almost immediate onset of REM sleep in persons with narcolepsy. Hallucinations which occur  when falling asleep are known as “Hypnagogic hallucinations” and those that occur when waking up are known as “Hypnopompic hallucinations”.  

“HIS ACE”
This is a useful memory aid (mnemonic) which will help people easily remember the main symptoms of narcolepsy. If you remember the words “HIS ACE” then you have the first letters of the 6 main symptoms of narcolepsy type 1.

The HIS deals with nighttime symptoms; the ACE deals with daytime symptoms:

H         Hallucinations (Hypnagogic and Hypnopompic)
I           Interrupted Nighttime Sleep.
S         Sleep paralysis.
A         Automatic behaviour.
C         Cataplexy.
E         Excessive daytime Sleepiness.

(HLA) Human Leukocyte Antigen
Leukocyte is a fancy name for “White blood cells” (WBCs). These are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders.

HLA complex, as they are known, are  molecules found on the surface of almost all the body’s cells and they serve to identify and distinguish between the body’s own molecules  and those of invaders such as a viruses or bacteria - i.e. they distinguish between “self” and “non-self”, between what should be there and what should not be there.

HLA is one of our most polymorphic genes  (i.e. can have different forms). It can have literally thousands of variations that allows the body to defend itself against a vast array of invaders. The downside of such polymorphism is that the possibility of some variations actually mistaking some of the body’s own cells for invaders, and killing them. This is what happens in an autoimmune disease where the body’s defence mechanism turns on itself.

Different types, or subsets, or variations,  of the multitude of the HLA complexes have been found to be associated with different autoimmune diseases. There is a one variation which is called HLA-DBQ1*0602, often referred to as  the “DQ-Beta1 0602 variation”. This variation has been shown to be associated with narcolepsy. Approximately 25% of the population have this HLA variation. It has been found that over 90% of persons with narcolepsy carry this  HLA-DQB1*0602 variation. This makes this  particular HLA variation a very strong marker for having a predisposition for narcolepsy. It clearly does not mean that everyone who carries this variation will get narcolepsy, otherwise a quarter of the population would have narcolepsy. But it does mean that people who carry this variation are more likely to contract narcolepsy than those who do not. Testing blood for the DQB1*0602 marker is relatively simple and would be a standard preliminary test in diagnosing narcolepsy. It is not definitive either way, but it is a helpful pointer.

Hypothalamus
The hypothalamus is a small region deep in the brain which is one of the control centres for the autonomic nervous system. “Autonomic” means involuntary or automatic - i.e.  things we don’t have to consciously think about. For example, you don’t “decide” to feel tired or decide to “feel” hungry. The hypothalamus generates chemicals (neurotransmitters) to communicate such information to the brain when appropriate. It automatically regulates  things like the sleep cycle, arousal, blood pressure and appetite. There is a small region in the hypothalamus where there are cells (neurons) which  generate and secrete hypocretin molecules into the brain which specifically control the sleep cycle and appetite. In narcolepsy those cells in the hypothalamus which produce the hypocretin molecules have been destroyed and thus the automatic control of the sleep cycle which all humans and animals have, has also been destroyed.

Hypocretin  (also called Orexin):
Hypocretins are large molecules which are produced in a small region in the hypothalamus. These molecules / chemicals are neurotransmitters. There are 2 types - called hypocretin 1 and hypocretin 2. The hypocretins control in particular, the sleep cycle, and appetite. In narcolepsy the cells in the hypothalamus which produce the hypocretin molecules have been destroyed and thus the automatic control of the sleep cycle which all humans  have, has also been destroyed.

These molecules, or chemicals, were discovered in 1998 by two teams of researchers working independently. One teams called then hypocretin - the “hypo” part coming from the hypothalamus and the “cretin” because this chemical bears a weak resemblance to another messenger chemical in the body called secretin, which is a hormone produced in the duodenum, located i the intestinal glands.

The other group of researchers called the same molecules Orexin A and Orexin B. So Orexin A refers to  exactly the same molecule / chemical /  neurotransmitter as Hypocretin 1, and Orexin B is the same as Hypocretin 2.  The researchers used the name Orexin after the Greek word “orexis” which means “appetite”,  as they were aware of the molecules role in controlling appetite.

 (IH) Idiopathic Hypersomnia
Idiopathic” means “of unknown cause” ; “Hyper” is a prefix that means things like “excessive”, “a lot”, “above”, etc, and “somnia” refers to sleep. So Idiopathic Hypersomnia means excessive sleep for unknown reasons. It differs from narcolepsy inasmuch as it is not associated with hypocretin absence or deficiency. The symptom is very similar to the EDS of narcolepsy, although not identical,  but the cause is unknown. Also, persons with idiopathic hypersomnia will not fulfill the diagnostic requirements for confirmation of narcolepsy as standardised on a MSLT.

(ICSD-3)

International Classification of Sleep Disorders, edition 3

ICSD-3 criteria for diagnosis of narcolepsy type 1

  1. The patient has daily periods of irrepressible need to sleep or daytime lapses into sleep occurring for at least 3 months. (Basically the presence of EDS)

  2. The presence of one or both of the following:

a)    Cataplexy and a mean sleep latency of 8 minutes or less and 2 or more sleep onset rapid eye movement periods (SOREMPs) on a multiple sleep latency test (MSLT). A SOREMP (within 15 min of sleep onset) on the preceding nocturnal polysomnogram (PSG) may replace one of the SOREMPs on the MSLT.
b)    Cerebrospinal fluid (CSF) hypocretin-1 concentration, measured by immunoreactivity, is either 110 pg/mL or less, or less than one-third of mean values obtained in normal subjects with the same standardized assay. 

Interrupted night-time sleep:
Contrary to the common misconception that sufferers of narcolepsy sleep long and soundly, the actual reality is that their night time sleep is of extremely poor quality and is interrupted, disrupted and punctuated by continuous wake / sleep periods and that it does not include any significant periods of the deep restorative sleep that non sufferers have. The consequence of this is that the PWN feels in the morning as one would feel if one had little or no sleep at all - in other words, totally exhausted.

Very poor quality, continually interrupted night-time sleep is one of the key features of narcolepsy. It is worth stressing this fact because the average person who has any knowledge of narcolepsy at all will almost always feel that narcolepsy involves long periods of sleep which they equate with peaceful rest.

The most common misunderstanding of narcolepsy is that it simply means that the person who suffers from narcolepsy sleeps a lot more than normal. This has led to  narcolepsy being seen as an almost enviable trait and to it being treated in films and other media as a bit of a joke. We should be able to explain to people who innocently hold this belief that narcolepsy is very far from being a joke.

(LP) Lumbar Puncture
Lumbar Puncture, sometimes referred to as Spinal Tap, is the process of drawing CSF (cerebrospinal fluid) from the lower spine by means of inserting a hollow needle between two vertebrae in the lower back, the lumbar region. The significance of LP in  in relation to narcolepsy is to draw CSF for laboratory analysis to determine  the level of hypocretin in the fluid and hence in the brain. There are 2  types of hypocretin molecule, called hypocretin 1 and hypocretin 2 (also known as  orexin A and orexin B). It is possible to test for hypocretin 1 in the CSF, but not for hypocretin 2. The absence of, or significantly low level of,  hypocretin 1 in the CSF is strongly indicative of narcolepsy.

(MSLT) Multiple Sleep Latency Test
“Latency” here means - “the time it takes”, so  “Sleep Latency” means “the time it takes to fall asleep”. An MSLT is a test where a person undergoes a measurement  5 times  (hence the word “multiple”) of how long it takes them to fall asleep. Measurements are made at 2 hour intervals. The test is usually carried out in a quiet, peaceful environment in e.g. a sleep laboratory, starting in the morning and continuing throughout the day, during which the person is wired to numerous electrodes in order to measure such things as brain waves, REM (rapid eye movement), and muscle tone. The process may look intimidating due to all the electronics but is totally painless and is  considered the single most vital tool in diagnosing narcolepsy. The time it takes the person to fall asleep and to enter REM is a positive or negative indicator of narcolepsy. If a person enters REM sleep within 15 minutes or less, this is called a SOREMP (sleep onset rapid eye movement period).

Highly Indicative of narcolepsy: Cataplexy and a mean sleep latency of 8 minutes or less and 2 or more sleep onset rapid eye movement periods (SOREMPs) on a multiple sleep latency test (MSLT). A SOREMP (within 15 min of sleep onset) on the preceding nocturnal polysomnogram (PSG) may replace one of the SOREMPs on the MSLT.

 Or, put more simply:

If the person has already been diagnosed with Cataplexy, and  then during an MSLT falls asleep in less than 8 minutes on average over the five naps, this is indicative of EDS -  excessive daytime sleepiness.  If REM sleep happens within 15 minutes at least two times out of the five naps or once during the 5 naps and once during the preceding PSG this is considered highly indicative of narcolepsy.

(NREM) Non Rapid Eye Movement
Refers to the non-rapid eye movement stages of sleep. 

Neurotransmitter
A Neuron is a nerve cell. A transmitter sends signals - like a radio transmitter. So a neurotransmitter is a chemical  that enables signals to pass between nerve cells. Hypocretin is a neurotransmitter.

(PWN) Person With Narcolepsy. The accepted way to describe a person who suffers from narcolepsy is a “person with narcolepsy”. This is often abbreviated to PWN both in writing and speaking. To say someone is narcoleptic or cataplectic is not acceptable to some sufferers as it defines a person by their condition rather than by defining them as a person with many attributes, including a particular condition, in this case narcolepsy.

Orexin  (also called Hypocretin)
See Hypocretin, above.

(OSA) Obstructive Sleep Apnea

Petit Mal ( from the French - “little illness”) - see Absence Seizures

(PLMD)      Periodic Limb Movement Disorder

(PSG)  Polysomnography (pronounced: polly-som-nog-raphy) Polysomnogram.
A polysomnography is an overnight sleep study which is used to diagnose or identify various sleep disorders. It typically records such things as brain waves, heart beat, blood oxygen levels, eye movements (REM), analyses your sleep cycles, monitors sleep disruption, breathing stoppages (e.g. as in obstructive sleep apnea (OSA), and other parameters. The result of such a sleep study is called a Polysomnogram. A PSG  generally immediately  precedes the daytime MSLT in the diagnosis of narcolepsy.

 (PWN)  Person With Narcolepsy.
The accepted way to describe a person who suffers from narcolepsy is a “person with narcolepsy”. This is often abbreviated to PWN both in writing and speaking. To say someone is narcoleptic or cataplectic is not acceptable to some sufferers as it defines a person by their condition rather than by defining them as a person with many attributes, including a particular condition, in this case narcolepsy. 

 (REM) Rapid Eye Movement
Refers to one of the stages of the sleep cycle characterised by the rapid movement of the eyes from side to side, although the eyes remain closed. . For a fuller discussion on REM see Sleep Cycle, but in brief: during REM sleep stage the wave pattern of the brain more closely resembles that waking, as do breathing patterns heart rate and blood pressure. REM sleep is strongly associated with dreaming and during REM sleep the person’s main muscles become temporarily paralysed to prevent them acting out their dreams. Refer back to cataplexy to see the relevance of this in narcolepsy.

(SOREMP) Sleep onset REM Period
Normally a person will not enter the REM sleep phase until about 90 minutes from falling asleep. It varies, and can happen sooner, but if it happens within 15  minutes or less it is considered to indicative of a sleep disorder and is supportive of a diagnosis of narcolepsy  if repeated under sleep study conditions, An onset of REM sleep within 15 minutes or less is called a SOREMP. 

Highly Indicative of narcolepsy: Cataplexy and a mean sleep latency of 8 minutes or less and 2 or more sleep onset rapid eye movement periods (SOREMPs) on a multiple sleep latency test (MSLT). A SOREMP (within 15 min of sleep onset) on the preceding nocturnal polysomnogram (PSG) may replace one of the SOREMPs on the MSLT.

(RLS) - Restless Legs Syndrome.

(SNS) Swiss Narcolepsy Scale:    (see also - ESS- Epworth Sleepiness Scale)
The SNS is a 5-question patient-reported scale that screens for the occurrence of several behavioral symptoms linked to narcolepsy with cataplexy.The following link is to a combined ESS (Epworth Sleepiness Scale) and SNS (Swiss Narcolepsy Scale) calculator  which can be used by healthcare professionals to assist diagnosis or by anyone who suspects they may have sleep problem.

http://www.narcolepsylink.com/narcolepsy-symptom-screener#sns

 (SP) Sleep Paralysis
Sleep Paralysis is one of the classic symptoms of narcolepsy. Sleep Paralysis  is usually confined to times when the sufferer is waking up or going to sleep. Although still awake and fully conscious, the person finds they cannot move. This can be very frightening and can last for seconds or for as long as several minutes. The fact that interrupted night-time sleep generally involves the sufferer waking on multiple occasions through the night means that they can have  multiple experiences of sleep paralysis every night. It is believed by that this phenomenon is caused by the onset of the normal muscle paralysis associated with REM sleep occuring while the person is still awake. It is similar in this regard to one of the other main symptoms of narcolepsy, which is cataplexy.