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And how to try to
describe it to them.
I found, over time, it's
really difficult for people
to understand it.
It's just very complicated with
this tiredness, the cataplexy,
the fragmented sleep at night.
If you're a normal
person, you've got sleep,
and you've got your waking life.
And occasionally, they'll
overlap a little bit.
For me, I live in
this world that
is, very rarely am I fully
awake, and very rarely am I
fully asleep.
I live in the in-between.
I'm Tom Scammell.
I'm a professor of neurology
at Harvard Medical School.
Narcolepsy is a
neurologic disorder.
It is one of the most
common sleep disorders
and affects about
1 in 2,000 people.
It doesn't matter how much
sleep they get at night.
They're going to
sleep every day.
People also can have a
variety of other symptoms.
These include hypnagogic
hallucinations,
where they could have very vivid
dreamlike hallucinations just
as they're drifting off to
sleep or just when they awaken.
They could have something
called sleep paralysis, where,
as they're falling asleep or
sometimes when they wake up,
they can't move.
And then there's
cataplexy, which
is similar to sleep paralysis.
The distinction is that
cataplexy occurs right
in the middle of the day and is
triggered by strong emotions.
And then the last
thing, which is perhaps
in sort of one of
the strangest of all,
is that, for considering
that somebody with narcolepsy
is often very sleepy
through the day,
they often have
fragmented sleep at night.
They could wake up four
or five times for 10 or 20
minutes for no clear reason.
And so in the same way that
they have trouble maintaining
wakefulness through
the day, they
can have trouble maintaining
sleep through the night.
Somewhere between age
10 and age 20 or so
is when narcolepsy begins.
People usually start
off with sleepiness,
and then the other
symptoms follow.
So there's a number
of different systems
in the brain that are
involved in promoting arousal
or wakefulness and sleep.
Up here's the cortex.
This is the front,
near the forehead.
Here's the back.
This is the brain
stem coming down here.
And this is the cerebellum,
which was involved in balance.
The brain stem is
the site that most
of these arousal-promoting
signals come from.
And those cells
send connections up
throughout the whole
front part of the brain,
and they help turn on the cortex
and other parts of the brain
when you're awake.
There's also some
cells in a small region
called the hypothalamus that
are involved in promoting sleep.
And these sleep-promoting
cells, one of the things they do
is they actually turn off
the wake-promoting cells.
And so that allows you to be
fully asleep without any hint
of consciousness.
This is called the
mammillary body.
And just about it right here,
is where the hypocretin neurons
sit.
And this is a really
critical collection
of neurons, brain cells,
that makes very particular
and special neurotransmitters
known as hypocretin, or orexin.
Those are just two names
for the same thing.
The hypocretin-producing
cells help
activate and sustain activity in
the other wake-promoting brain
regions across the day.
The brain contains
billions of neurons.
And only a very, very
small number of these
produce hypocretin.
It's probably somewhere
between 100,000 and 200,000,
which sounds like
a large number.
But when you compare it
to 10 billion neurons,
it's really very small.
In narcolepsy, those
hypocretin-producing producing
cells die off.
When you look closely at
the brain of somebody who
has narcolepsy, what you
see is about a 90% to 95%
loss of the
hypocretin-producing neurons.
So there's two broad themes that
are being pursued in narcolepsy
research right now.
One theme is to understand
what goes wrong in the brain
when the hypocretin-producing
cells die off.
How does that lead
to sleepiness and
cataplexy and other symptoms?
Another big theme is trying to
understand what actually kills
the hypocretin neurons
in the first place,
because if we could understand
that, then it's possible
that one could diagnose
and recognize narcolepsy
right at the earliest stages.
We might be able to get
in and stop that process.
As we've discovered
more and more
about what's actually causing
the hypocretin neurons to die
off, and as we've discovered
more about the consequences
of that for the
brain, it's really
given us a lot of hope for new
opportunities for coming up
with better therapies for
people with narcolepsy.
If we could get hypocretin
back in the brain somehow,
that would be potentially
as great as giving insulin
to people with diabetes.
It would really be the missing
factor coming back into play.
And it could, in theory,
cure their sleepiness
and cure their cataplexy in
the most thorough fashion.
Right now, scientists
are working
with a variety of techniques to
try to get hypocretin signaling
back into the brain.
But the hope is that
in 5, 10, or 15 years,
we may see those hypocretin
replacement therapies coming
into clinical practice.
