Thread by @DrMikeFarquhar

Today is #WorldNarcolepsyDay, aiming to raise awareness about a sleep disease which is often misunderstood by both the general public, and many doctors

Narcolepsy often seen as a “funny” illness, the punchline of a joke, or as a “good” thing (“I wish *I* could fall asleep anywhere/time!”)

It absolutely isn’t

Narcolepsy is a serious neurological disease which can cause significant disability and impair quality of life

Narcolepsy is a primary sleep disease, meaning it is sleep itself which is the source of the problems associated with it

Sleep is the foundation of our physical and mental health; when sleep is impaired, the consequences can affect every aspect of health and wellbeing

Narcolepsy is a spectrum illness, meaning people with the condition can have a huge range of severity of symptoms.

Even at the milder end of the spectrum though, narcolepsy can have a subtle but profound impact on health, wellbeing and function

Narcolepsy is a rare disease, but it is commoner than many realise - though because of the nature of the illness, it’s difficult to know exactly how common!

I usually quote an incidence figure of about 1 in 2500; similar to diseases like cystic fibrosis

Because the public and doctors don’t have a good understanding of narcolepsy, affected people can have their symptoms unrecognised, or even diagnosed as other conditions

On average, it still takes 10 years after symptom onset for a correct diagnosis of narcolepsy to be made

So, what is narcolepsy?

When I started medical school (in 1994) while we knew the symptoms, we understood very little of the pathophysiology of the disease

Over the last 25 years, our understanding has grown significantly

What we call narcolepsy covers a range of conditions, with a broad split into two main types: type 1 and type 2

I’ll mainly talk about type 1 just now

Narcolepsy type 1 is (almost certainly) an autoimmune condition: one where the body’s own immune system makes a mistake and causes damage to part of the body.

(Type 1 diabetes mellitus is an example of an autoimmune disease)

In narcolepsy 1, the part of the body which becomes damaged is a very small part of the brain which produces a hormone called hypocretin/orexin. Hypocretin has several roles, but plays a key role in regulation of wake and sleep, by promoting wakefulness and stabilising wake/sleep

Hypocretin also has a role in helping to regulate appetite and metabolism, which is one reason why people diagnosed with narcolepsy have often had an unexpected increase in weight following the time of symptom onset. It may also have a role in affecting mood.

With the loss of hypocretin, several physiological consequences cascade that explain the main symptoms of narcolepsy

Normally, as we sleep at night, we move (fairly!) smoothly between the different stages of sleep, shifting gears without being aware of it

We need all the stages of sleep to get all of the benefits of sleep

In narcolepsy, night-time sleep becomes unstable and fragmented, meaning the quality of that sleep becomes severely decreased

People can wake having nominally been asleep, but not having had the benefits.

It can be a bit like waking with a hangover every day

That fragmentation of sleep also means that people with narcolepsy are much more likely to have other sleep disorders as well: sleepwalking, periodic limb movements, sleep terrors, sleep disordered breathing ...

In particular though, people with narcolepsy are much more likely to have symptoms of sleep paralysis and hypnagogic hallucinations

These are related to the REM/dream stage of sleep

As we dream, we are all naturally paralysed - this stops us acting out our dreams and keeps us safe!

Most people, at least once in their lives, will have the experience of waking and feeling as if they can’t move, often associated with a feeling of absolute fear: sleep paralysis

All that has happened here is you’ve woken “too soon” and the normal REM paralysis has persisted, briefly, into the (semi-)waking state.

Although terrifying, it doesn’t cause harm in itself

Sleep paralysis is often accompanied by very vivid images which FEEL real, and as if they’re happening in your bedroom - these are hypnagogic/pompic hallucinations

They probably explain many alien abduction stories!

People with narcolepsy often have these episodes, and they can be utterly terrifying, making further good sleep even more difficult

Because of their hallucinatory nature, they have been misdiagnosed as psychosis by the unwary, and treated with drugs incorrectly

Imagine being a child and having episodes like this frequently!

Unless people (paediatricians especially) have an awareness of the symptoms, the significance can be missed

Narcolepsy doesn’t just affect night-time sleep though

Poor quality night sleep means people with narcolepsy can feel tired in the day but, more than this, they will often suddenly fall asleep with relatively little warning

Without the normal regulatory system of wake/sleep acting as it should, the “sleep trigger” can switch on suddenly and unexpectedly - a “nap attack”

People with narcolepsy can fall asleep while doing activities such as eating, walking ... driving

(“What is the weirdest place you’ve ever fallen asleep?” is one of my standard questions in clinic when I’m thinking about a possible diagnosis of narcolepsy)

Characteristically, short periods of sleep can be disproportionately refreshing for people with narcolepsy - even a few minutes can make a big difference

We prescribe “power naps” as part of treatment

(This thread got cut in half :) - the second half continues here:

https://twitter.com/drmikefarquhar/status/1175701940971429889?s=21

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