Incidence & symptoms
• Usually begins in adolescence or early adulthood, continues through the person’s life
• About 1 in 2000 people suffer from narcolepsy but this is an estimate as some people only have mild symptoms or just don’t go to their doctors
– sudden and uncontrollable attacks of sleep, at any time
– Several times a day
– Last 10-20 mins
– Sudden loss of muscular control – collapse, several times a day
– Auditory or visual hallucinations as falling asleep or waking up
– Sleep paralysis
Explanations of narcolepsy 1 – AO1
• Polysomnography (i.e brain activity, body & eye movements, heart rate, BP, O2 levles) show REM sleep occurs at the onset of sleep in narcoleptics – they don’t go through stages.
• This explains some of the symptoms e.g. the loss of muscle tone leading to collapse, hallucinations (seen as REM-type sleep and dreams intruding into the day).
• Suggest narcolepsy is due to abnormality in control of REM sleep mechanism but WHY .....!
• Dement 1970’s investigated some dogs who develop narcolepsy, if they are bred together they are very vulnerable to cataplexy (sudden collapse when excited).
• In the 1990’s it was found they had a problem with a gene on chromosome 12 which controls a neurotransmitter called hypocretin, thought to be vital in maintaining wakefulness.
• Lin et al (1999) found that narcoleptic dogs had low levels of hypocretin.
• Thannickal et al 2000: narcoleptic humans had less hypocretin producing cells in the hypothalamus.
• Research also suggested a link with a gene on chromosome 6 (the HLA complex gene) which regulates the immune system.
• It seems that this leads to the immune system attacking and destroying the hypocretin neurones in the…