Narcolepsy
What is Narcolepsy?
Narcolepsy is a rare condition caused by a failure of the sleep regulating system in the brain. People with narcolepsy feel an overwhelming urge to sleep at inappropriate times despite an apparently night-time sleep - that is to say they are excessively sleepy. Narcolepsy is a rare cause of day-time sleepiness; the commonest cause is poor nocturnal sleep, for example due to obstructive apnoea. Narcolepsy however is distinguished by uncontrolled day-time naps that happen at times when someone who is just a little sleepy would be able to resist the urge to nap. Sometimes these naps are so unpredictable they are termed ‘sleep attacks’. For example sufferers may fall asleep in the middle of an activity such as eating a meal, whilst driving or during a conversation. Such involuntary behaviour is clearly very disruptive and disabling and if undiagnosed may lead to problems in work, school or home life.
There are other features of narcolepsy that help to distinguish it from other causes of excessive daytime sleepiness. These include:
· Cataplexy: this unusual phenomenon involves sudden loss of muscular control triggered by emotional arousal. Triggers may include amusement, anger or excitement. The sufferer may fall to the floor due to total loss of muscle control or the muscle weakness may be limited to a certain part of the body e.g. the face may droop. Not uncommonly cataplexy is misdiagnosed as epilepsy or fainting episodes. What distinguishes cataplexy is the complete retention of consciousness and recall of the event as well as rapid full recovery. The triggers are usually predictable.
·Sleep paralysis: While muscle relaxation is a normal healthy part of sleep it usually happens in dream sleep when we are not aware of our ‘paralysis’. If woken from dream sleep, rapid return of muscle tone occurs. Sleep paralysis describes the intrusion of muscular paralysis with retention of consciousness. This can be a very alarming experience as the sufferer awakes from sleep and is completely unable to move. It is usually short lived and spontaneously resolves but nonetheless can leave a lasting sense of anxiety. It can occur independent of narcolepsy so does not necessarily point to this diagnosis unless associated with other characteristic phenomena.
· Hypnagogic and hypnopompic hallucinations: These are characteristic of narcolepsy and are vivid, often disturbing, images or sounds experienced when falling asleep or waking from sleep. The content of these hallucinations can be very frightening and threatening and generally recur. One sufferer described an old hag who climbed through the window and sat on the bed. So vivid are these experiences that many sufferers fear they are mentally ill and may be afraid to disclose their experiences to their family or doctors. Others are misdiagnosed as having mental illness.
Children with narcolepsy may not initially present with all the symptoms and diagnosis may not be made until late adolescence when more characteristic features appear. They may not be able to describe their hallucinations and young children may simply appear phobic about going to bed. Adults may misinterpret their hallucinations as ‘bad dreams’ or emotional disturbance.
Polysomnography can help to confirm the diagnosis of narcolepsy. Investigations take place both overnight and over the following day. Treatment can alleviate symptoms of day-time sleepiness. This is an area of active research and as we better understand the molecular mechanisms underlying the disease new treatments may emerge.
Periodic Limb movement
& Restless Legs Syndrome
Periodic limb movement disorder (PLMD) - which occurs at night, and restless leg syndrome (RLS) - which describes symptoms in the day, can exist independently but commonly co-exist. 70-90% of RLS sufferers have PLMD but may be unaware of their night-time symptoms. They may however suffer the consequences of leg movements in their sleep and complain of day-time tiredness and lack of concentration.
Restless legs syndrome: RLS is surprisingly common in adults -affecting between 5-15% of the population and can run in families. It can also occur in children and be mistaken for ‘growing pains’. People suffering from RLS typically describe unpleasant sensations in their legs (occasionally in their arms) characteristically when they are at rest in the day. Sensations are variously described as ‘tingling’. ‘aching’, ‘creepy-crawly’ feelings. What is common to all cases, however, is the strong impulse to move the limb and relief of symptoms with movement so that the sufferer appears to others to be ‘unable to sit still’. The sensations may be particularly troublesome at bedtime when the sufferer is trying to settle down to sleep. Generally the cause of restless legs syndrome is unknown, however, in some cases it can be attributed to specific factors such as anaemia, medical disorders (e.g. diabetes), some drugs, alcohol and caffeine. It is more common in the 3rd trimester of pregnancy and 1 in 7 women who develop this condition in pregnancy may continue to have symptoms after having their child.
Periodic Limb movement Disorder (PLMD): Periodic limb movement occurs during sleep and causes repeated episodes of leg movements through the night. Typically the toes and ankles are extended. These limb movements may cause subtle disturbance of sleep quality. While the sufferer may not be aware of these movements they may describe daytime RLS and almost certainly their bed partner will complain! Children with attention deficit hyperactivity disorder are more likely to suffer from PLMD and it is associated with some medications such as anti-depressants. PLMD can be diagnosed by an overnight sleep study and severe cases that have no known cause can be treated with medication.