“There are the 4 primary features of narcolepsy”
Although narcolepsy was the first condition of excessive daytime sleepiness to be recognised and named, in fact, it only constitutes about 0.5% of cases of excessive daytime sleepiness. However, it is still important to recognise, and the physiology is fascinating.
Sleep is generally divided into 4 stages, namely stage I, stage II, stage III (also referred to as Slow Wave Sleep) and REM (Rapid Eye Movement) sleep. Normally during sleep, we cycle through the stages roughly every 60 to 90 minutes. During REM sleep all the muscles become paralysed. This is thought to prevent us from acting out emotionally laden dreams, which might otherwise cause violence, particularly with the bed partner.
Narcolepsy can be seen as a problem with REM sleep: the REM stage sleep will occur when it should not, the paralysis will occur when it should not, and the dreams will occur when they should not.
It appears as though the sleep cycles do not “switch off” during the day in these sufferers. This causes the individual to be pushed into sleep between every 60 and 90 minutes. The sleep onsets can be irrepressible, but may then be followed by a latent period of about an hour during which time the sufferer will not fall asleep.
The dreams may occur inappropriately while the person is still awake before falling asleep (hypnagogic hallucinations), or after they have woken up (hypnopompic hallucinations). These are strange experiences, with the feeling of a “double reality”. The individual will be aware of the surroundings, but, at the same time, still, be dreaming. This can be very confusing to the medical practitioner so that people have been misdiagnosed as having schizophrenia.
The paralysis may occur in one of 2 settings: it can typically occur as people wake when it is known as “sleep paralysis”. This is a very frightening experience. It generally lasts just a few seconds, or until someone touches them. This is frequently what brings people to medical attention. The 2nd situation is on exposure to an emotional episode. Strangely, this is more often humour than other emotions. People may then completely lose muscle tone and fall to the ground, or it may be a lesser loss of tone, involving the dropping of the jaw, or a kinking of the legs. In severe cases, this can become socially debilitating, as it becomes a bit of a “party joke” for people to see if they can get the sufferer to fall down. Sufferers will not infrequently become completely socially isolated. This is a condition known as “cataplexy”.
These are the 4 primary features of narcolepsy, namely
- Excessive daytime sleepiness
- sleep paralysis
- hypnagogic or hypnopompic hallucinations
When all 4 of these are present, we refer to it as being “narcolepsy type I”. These patients have a particular gene complex associated with their narcolepsy. On the other hand, when cataplexy is absent, the condition is referred to as “narcolepsy type II”, and the genetic association is less clear. Type I narcolepsy has been associated with low Orexin (Hypocretin), whereas Type II does not appear to have this association.
The diagnosis is made with a Multiple Sleep Latency Test. This is a procedure where the patient is given either 4 or 5 chances during the day to sleep for 20 minutes, at 2 hourly intervals. The normal individual might get into sleep during one of these, but there will not be any REM sleep. The narcoleptic will have an average time into REM sleep of fewer than 8 minutes.
However, any condition resulting in excessive daytime sleepiness can mimic the Multiple Sleep Latency Test abnormality. This would include breathing disorders such as Obstructive Sleep Apnoea, as well as movement disorders, such as Periodic Limb Movement Disorder. In order to exclude these, it is important that there is objective confirmation of good quality sleep the night before. For this reason, a polysomnogram is usually done overnight, and then the following day is followed by the Multiple Sleep Latency Test.
A further problem is that people with narcolepsy not infrequently have a 2nd sleep disorder. This can obviously cause confusion for the treating practitioner.
The overnight test the previous night is very important. A number of years ago the drug addicts in the USA realised that if they stayed awake for a few nights the Multiple Sleep Latency Test would show up as abnormal, and they would legally be allowed to use amphetamines. A more recent issue is that cannabis can also mimic narcolepsy on the testing procedures. It has now become routine in the USA to check the urine for cannabis prior to doing the testing.
Treatment is usually the use of stimulants. In countries where amphetamines are available, these work very well. Otherwise, methylphenidate is frequently the drug of the first choice. The dosage may vary very widely depending on the needs of the individual. Timed naps can help to reduce the medication requirements.
Provigil (modafinil) is frequently very useful, but some patients will not respond at all to it. Occasionally a combination of methylphenidate with modafinil is useful.
More recently an Orexin analogue has become available in other countries, but it is not yet available here. This is probably the only available medication which will work for all 4 of the primary symptoms of narcolepsy. The stimulants will generally be useful for the excessive daytime sleepiness, and to a certain extent for the hallucinations and the sleep paralysis. They generally do not work very well for the cataplexy, for which a serotonergic agent is usually the best.
Matters become difficult when a patient also has REM sleep disorder, which can put him or her at risk by acting out dreams at night. The problem is that serotonergic agents can worsen REM sleep disorder.
The object of treatment is to control the patient to the extent that they can live a normal life, but need to take pills every day. Because this treatment will be lifelong, the dosage schedule has to be as simple as possible, preferably just twice a day. This will often involve the use of short-acting medications together with long-acting medications. Unfortunately, at this stage of our knowledge, we cannot talk about a “cure”. Early diagnosis and treatment are important because the condition is socially disabling, can be dangerous if the patient is driving in an untreated condition, and will seriously affect any efforts to study. It will also exclude any job involving working at heights, or with potentially dangerous equipment.
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