Sleep and sleep disorders

Published on 09/04/2015 by admin

Filed under Neurology

Last modified 22/04/2025

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Sleep and sleep disorders

Sleep problems are common. Almost everyone has disturbed sleep at some time, but usually the cause is self-evident and self-diagnosed. Some patients have significant sleep problems. Most can be diagnosed from the history from the patient and their sleep partner. Sometimes further investigations are needed to confirm or clarify the diagnosis.

Background

Normal sleep

The amount of sleep which is normal varies from person to person and it is important to establish if there has been a change in a patient’s total time spent asleep. Normal sleep is divided into a number of stages, primarily on the associated EEG patterns:

image Light sleep – stages 1 and 2 (55–65% of sleep).
image Deep sleep – stages 3 and 4 – slow-wave sleep (10–20%).
image Rapid eye movement sleep (REM sleep) (15–25%). In REM sleep, there is loss of tone in all muscles apart from the external ocular muscles which produce rapid eye movements.

Through a normal night of sleep there are repeated cycles of light to deep to REM sleep.

There are a number of normal phenomena that occur in sleep and that are usually readily recognized, such as dreams, nightmares or sleep talking. Other normal phenomena can lead to medical referral, for example hypnic jerks (or sleep starts) which are sudden movements that occur on falling asleep, or sleep paralysis which occurs when awaking during REM sleep with marked loss of muscle tone. While sleep paralysis is normal, it does occur more often in patients with narcolepsy (see below).

Taking a sleep history

Once the patient has described the problem in their own words and with as little prompting as possible, it is important to take a sleep history. Establish from patients: the time they go to bed; how long till they fall asleep; when they wake; how often they wake through the night and what they do when they wake; how they feel on waking in the morning; whether they sleep again through the day, when and where and for how long; and if and when they feel sleepy – the Epworth sleepiness scale can be used to measure the degree of daytime sleepiness. A parallel history should be taken from any sleep partner, but also asking whether they snore or move when asleep. There may be significant differences in what the patient describes and what is observed.

A number of factors can interfere with sleep (Table 1) and these factors should be explored.

Table 1 Some factors that can interfere with sleep

Factor affecting sleep Effect
Previous sleep history Helps determine ‘normal’ amount of sleep for that person
Work pattern/domestic circumstances Long hours or shift work may disrupt sleep
Babies or young children or partner may cause repeated awakenings
Exercise Has an alerting effect but aids sleep if exercise is earlier in the day
Psychiatric history Anxiety – makes going to sleep more difficult
Depression – results in early morning waking
Alcohol Makes people sleepy but reduces sleep quality
Caffeine May cause difficulty going to sleep
Medication Most cause sedation
Pain, arthritis, carpal tunnel syndrome Lead to recurrent awakening
Nocturia Recurrent awakening
Daytime naps Reflect daytime sleepiness but may also contribute to difficulty sleeping at night

Sleep disorders

Sleep disorders can be simply classified as:

image disrupted sleep
image inability to sleep (insomnia)
image excessive sleepiness
image abnormal events during sleep.

Most patients will recognize they have a sleep disturbance, though sometimes they can present with other symptoms (Box 1).

Box 1 Symptoms that can relate to excessive daytime sleepiness

image Lethargy
image Poor concentration
image Memory loss
image Depression
image Personality change – irritability

Disrupted sleep

Disrupted sleep is usually caused by non-neurological problems, as summarized in Table 1. Treatment is of the underlying disorder.

While most patients recognize their sleep is disrupted and complain of difficulty sleeping, some are more troubled by the consequent excess sleep during the day and therefore complain of sleepiness. This should become clear from the sleep history.

Sleep disorders can present with repeated awakening, particularly periodic limb movement of sleep and sleep apnoea (see below).

Insomnia (too little sleep or inability to sleep)

Most patients who complain of difficulty sleeping have either disrupted sleep (see above), or poor ‘sleep hygiene’ or idiopathic insomnia. In some patients, a poor sleep pattern is lifelong and can become more troublesome as the normal sleep reduces with age.

Patients can be helped by eliminating sleep disruption and strategies to improve sleep hygiene – ensuring the patient has the best chance to get the best quality sleep at night, by avoiding naps and optimizing the timing of their sleep and their sleeping environment. Nocturnal sedatives can be useful if there is a short-term reversible cause for poor sleep, for example anxiety or bereavement, but should generally be avoided as the reduced effects wear off and they tend not to produce sustained benefit.

Excessive sleepiness

Sleepiness needs to be distinguished from fatigue. Fatigue is a common symptom, often with no specific cause but which relates to many medical disorders such as anaemia, diabetes and hypothyroidism. Most patients who complain of being sleepy have disrupted sleep or obstructive sleep apnoea. Narcolepsy and other causes are much rarer.

Obstructive sleep apnoea (OSA)

OSA is the most common cause of sleepiness, affecting 1–4% of men and 1–2% of women. Risk factors include obesity, upper airways disorders, neuromuscular disorders, neurodegenerative disease or sedative medication. Most patients are obese with a narrow oropharynx and thick necks and snore loudly. OSA occurs when the upper airways collapse during deep sleep resulting in apnoea, which is followed by arousal and expansion of the upper airways. This occurs repeatedly through the night. The patient often reports that they sleep well but wake feeling drowsy, perhaps with a headache. They fall asleep easily through the day. Their sleep partner will describe snoring and may observe apnoeic spells and may have moved to another room because of loud snoring. Most patients will complain primarily of sleepiness, though will often have other symptoms (see Box 1) which can be the patient’s primary complaint.

Diagnosis

Many patients with OSA can be diagnosed using overnight oximetry. The oxygen saturation is continuously monitored overnight and frequent ‘dips’ corresponding to apnoeic spells can be recorded. If this is not diagnostic, more formal sleep studies, which can include EEG monitoring and recording of respiratory function (e.g. intrathoracic pressure), may be needed.

Treatment

Weight loss is effective if it can be achieved. Continuous positive airway pressure therapy delivered by a facial mask is very effective. However, some patients find this difficult to tolerate. Some patients are helped by modafenil. Driving is restricted until symptoms are controlled.

Narcolepsy

This is a much rarer condition occurring in 25–50 per 100 000 and seems to relate to a deficiency in hypocretin, a neurotransmitter, and loss of hypocretin-associated neurones. In normal REM sleep, several things happen: deep sleep, dreaming, rapid eye movements and the suppression of tone in other muscle groups. The symptoms of narcolepsy can be seen as an incoordination of these elements and are summarized in Table 2.

Table 2 Features of narcolepsy

Symptom Description Pathophysiology
Excessive daytime sleepiness Bouts of uncontrollable sleepiness, e.g. while eating, and refreshing naps of 20–60 min Intrusion of sleep into daytime
Cataplexy Sudden collapse often triggered by emotion, with twitching face muscles REM atonia while awake
Hypnagogic hallucinations Vivid dreams on falling asleep or on waking Dreaming out of deep sleep
Sleep paralysis Terrifying feeling of being unable to move on waking, usually for 20–30 s Atonia persisting into waking

About 95% of patients with narcolepsy have HLA type DQB*602, but it is also seen in about 20% of the general population, so the test is limited. The diagnosis can be confirmed by a multiple sleep latency test, when the mean time to fall asleep is measured on a series of occasions throughout the day. Patients with narcolepsy fall asleep in less than 8 min and tend to progress quickly to REM sleep. The hypocretin levels in the CSF can be measured and are low – though this is not yet a routine test.

Treatment

Modafenil is the first-line treatment, which usually helps sleepiness. Some patients will require fluoxetine or clomipramine, which are useful to control cataplexy. For some, these agents provide inadequate control and dexamfetamine can be used. Sodium oxybate is a newer alternative.

In some patients, no specific explanation for excessive sleepiness is found and these are diagnosed as having idiopathic hypersomnia. Stimulants used in narcolepsy provide some symptomatic benefit.

Things that happen during sleep

Parasomnias

Parasomnias are very common. They can be categorized according to the phase of sleep in which they occur.

Non-REM sleep disorders

These disorders arise in childhood but may persist into adult life. They are generally in the earlier part of the night, when non-REM sleep predominates. Sleep terrors are usually brief and are often in the first hour after going to sleep; the patient typically sits up and screams and appears bewildered, then goes back to sleep and has no recollection of the episode the next day. Sleep walking usually lasts longer and may be associated with more complicated automatic behaviours, for example going to the fridge and eating (often unusual foods). These may be helped by avoiding sleep deprivation and alcohol. Benzodiazepines can help in some patients.

Hypnic jerks are brief generalized jerks on falling asleep. The ‘exploding head syndrome’ is a sensation of painless explosion on falling asleep. Both are benign phenomena.

Periodic limb movements of sleep are brief repeated movements predominantly of the legs. This is often associated with restless legs syndrome (p. 93). This can be sufficient to disturb the patient’s sleep leading to daytime sleepiness. Treatments are as for restless legs; first line is a dopamine agonist such as ropinirole or pramipexole.

REM sleep disorders

In REM sleep behaviour disorders, the patient may only have limited recall of a dream but may complain of injuries sustained during the night. However, their partner will describe episodes of vigorous and at times violent behaviour when they hit out or kick, often in a purposeful way. In these patients, there is a failure of the CNS mechanism which turns off motor activity during dreaming. Most patients are elderly and many will go on to develop Parkinson’s disease or dementia. The REM sleep disorder often responds to clonazepam.

Nocturnal seizures

Seizures may occur during sleep and some forms of epilepsy may manifest exclusively in sleep, such as benign epilepsy with centrotemporal spikes of childhood or types of frontal lobe seizures (FLSs). There may be diagnostic clues, such as tongue biting, but generally diagnosis will depend on a witness, who often makes recognition straightforward. However, some cases, particularly FLS, can be difficult to distinguish from parasomnias, although FLSs are more stereotyped, generally briefer (usually <2 min) and occur at any stage of sleep.

Sleep that happens at the wrong time

Generally the circadian rhythm works to a 24-h clock. There are some disorders where the sleep rhythm is disrupted. Most common is jet lag, which will normally resolve in days. Some patients will have delayed-phase sleep disorder, where they run on a 25-h internal clock so they go to sleep later and wake later. Some have an advanced-phase sleep disorder, with a 23-h internal clock. Treatment options include improving sleep hygiene, behavioural interventions and phototherapies. Patients with neurodegenerative diseases often develop disrupted sleep patterns; sleeping in the day and waking at night.

Sleep and sleep disorders

image Sleep disorders are common.
image Most patients can be diagnosed from the history – from the patient and their sleep partner.
image Many of these conditions are treatable.

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