Narcolepsy

Narcolepsy

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

•       Symptoms:

–      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…