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REM (DREAMING) SLEEP AND ITS DISORDERS
Phenomenology
The newborn baby spends nearly half of sleep in rapid-eye movement (REM) sleep. In one-month premature babies this rises to 67%, and up to 80% at two-months prematurity. In the first year, REM sleep falls dramatically (in both relative and absolute terms), from around 8 hours a day in the first week to around half this level by the first birthday. Although one might argue that the decline is because of the overall drop in total daily sleep length over the year, this sleep is not halved as is REM sleep, but only reduced by about a quarter. Such findings are difficult to reconcile with the idea that the function of REM sleep is to consolidate the memories of the waking day. The first year of life must be one of the most intense periods of learning in our development. This, coupled with the lengthening of daily wakefulness, with the further potential for learning, suggest that if the memory consolidation idea has substance, then REM sleep ought to increase in this first year, not decrease. There is no qualitative change to REM sleep over this period and, for example, it does not become more intense.
The high levels of REM sleep in early life led to the Ontogenetic hypothesis. Within the uterus there is little of the sensory stimulation that the growing cerebrum needs to develop properly. So REM sleep is seen to be a substitute stimulation, which, to a lesser extent is also periodically necessary for the sleeping brain after birth. The key element of REM sleep providing the brain with stimulation seems to be the spike discharges of the pontine-geniculate-occipital (PGO) areas.
REM sleep is naturally accompanied by a paralysis of most muscles responsible for body and limb movements ("motor inhibition"), including the face and neck. This paralysis also prevents one from acting out one's dreams, although this does not always happen (see below).
Nightmares
For most children dreams are pleasant experiences of everyday events. Whilst nightmares ("mare" is an old english term for "demon") are infrequent, often very real, and soon forgotten, for some children they are very disturbing, particularly if frequent or the child dwells on them for several days. That is: repetitive acting out of the nightmare with toys; a dread of sleep; struggling to stay awake etc. So the impact of nightmares should be weighed up with the effect these have on the child's life in general. Often, of course, the reverse is true, or there is a two-way interaction, with frequent nightmares being a sign of an unhappy mind or home. Nightmares tend to become a more serious problem when parents fail to confront and deal with their child's worries. Whether or not one should place much reliance on trying to analyse the content of the dream in these respects is a matter for debate. One should be circumspect about this approach as the result is often no more than inspired guesswork; the time might well be better spent in developing greater rapport with the child and delving into its conscious rather than unconscious mind. Tranquillisers should be no more than a stop-gap at best. Lastly, some nightmares are not always what they seem and may turn out to be night-terrors (see below), or, if accompanied by repetitive stereotyped motor activity often of short duration, then epilepsy or nocturnal paroxysmal dystonia (see below) might be suspected.
Sleep Paralysis
Paralysis can occur in children when they wake up suddenly out of a nightmare and find that they can not move or call out for their parents. The motor inhibition of REM sleep is still active (see above), and may take from seconds to minutes to lift; all the sufferer can do is to breathe, move the eyes and possibly, moan. This is alarming and adds to the child's distress, especially if the dream imagery continues into this wakefulness, as can happen. Younger children may have difficulty in explaining these events and this adds to the parents' concern. Such experiences, which have a neurological basis, usually remit by early adolescence. True familial sleep paralysis is much rarer, and typically happens at sleep onset and/or on awakening, and may well be a symptom of narcolepsy, although, it can occur in isolation. However, narcolepsy seldom appears before adolescence. Both forms of sleep paralysis can often be terminated prematurely by sustained voluntary eye-movement or, if possible, by touch from someone else.
REM Sleep Behaviour Disorder
During REM sleep voluntary muscle are paralysed in order to stop dreams being enacted. In rare circumstances, the paralysis is absent, and if a dream is violent, then harm may come to the sleeper and nearby persons. Although these behaviours are usually correctly diagnosed by patients or their parents, as violent nightmares, they are misunderstood. This disorder has been more frequently reported in adults, but has been found in children. More careful examination usually discloses hindbrain lesions of REM sleep control mechanisms. The most effective treatment is by drugs, for example, non-sedating tricyclics (whichsuppress REM sleep) or by Clonazepam. But in children, at least, such approaches are not encouraged if the incidence is infrequent. Cases of serious assault by children during have been attributed to slow wave sleep (below), but in the absence of EEG records it is likely as not that the basis is a REM sleep behaviour disorder.
Slow Wave Sleep and its Disorders
Phenomenology
Slow wave sleep (SWS) is the deepest form of sleep, and consists of stages 3 and 4 sleep. The other sleep stages are 1 and 2 ("light sleep"), and REM sleep; there being five stages in all. Most of the daily output of growth hormone in a child is confined to sleep, and in particular to SWS. Thus it is often thought that SWS is essential to growth. But other hormones necessary for growth, such as insulin, show no sleep-related release. The role sleep has for growth is a contentious one, as the evidence is circumstantial. Nevertheless, children with chronic sleep disturbance, as in severe asthma and obstructive sleep apnea (see above), have retarded growth, as do emotionally deprived children who have little SWS. But whether these growth problems are due to the impaired sleep, is another matter. Often, for example, cortisol output is raised, which suppresses growth.
The organ for which sleep does seem vital is the cerebrum and this is clearly demonstrated by sleep loss studies. Whereas most of the body can physically relax and recover in wakefulness, to levels similar to those of sleep, the cerebrum cannot do this. Even when the eyes are closed and the mind is blank, the waking brain remains in a state of high activity and quiet readiness. Waking cerebral metabolic rate is particularly high in the 3-8 year old child, which suggests that this organ may be in need of even greater recovery during sleep at this time. The type of sleep that seems most closely associated with cerebral recovery appears not to be REM sleep, as is commonly thought, but SWS. Again, the evidence is circumstantial. If a reduced cerebral metabolic rate of sleep is indicative of recovery, then SWS, not REM sleep is the better candidate, as in REM sleep this rate is as high if not higher than that of alert wakefulness. Recent findings with cerebral protein synthesis (an index of growth and repair) show it to be higher during SWS than in REM sleep.
Sleepwalking
When children are forcibly roused out of stage 2 sleep, a lighter form of non-REM sleep, "thinking" is often reported, which contrasts with the gross visual imagery, unrealism, and more vivid actions of dreaming usually found (but not wholly) in REM sleep. Such thinking is less prevalent in SWS. Sometimes, more disturbing mental events can occur during SWS, with the most notable being sleepwalking (somnambulism) and night terrors (pavor nocturnus- see below), with the latter being quite distinct from the nightmares of dreaming sleep. These SWS phenomena can be found together. They mainly occur in childhood and tend have some hereditary basis. Sleepwalking peaks in adolescence, but declines rapidly by the late teens. Episodes are often triggered by anxiety; in susceptible children, the worry can be trivial - the loss of a favourite toy, or just a frustrating day. Only in serious cases, when sleepwalking occurs most nights, might there be severe distress and underlying emotional conflict, requiring intervention. One of the best treatments for children is simply to reassure the parents, as the more worried they become, the more this will be sensed by the child, the more anxious he or she gets, and the more sleepwalking will happen. If the child is given greater parental support, then the episodes often resolve themselves. Sometimes the sleepwalking just becomes a benign habit that can be broken by altering the child's sleeping circumstances, for example, by changing its bedroom for a few days.
Children are particularly difficult to arouse from SWS, and even very loud sounds of 123 dB can have no effect. It is difficult to wake up a sleepwalking child, and is unwise to do so, as distress or a wild and emotional outburst may set in. It is best to guide or carry them back to bed. As many sleepwalking episodes occur within the first two hours of sleep (when SWS is most prolific), parents are usually still up. Some unenlightened parents see their wandering child's unresponsiveness as disobedience, particularly if it does some unsocial act such as urinating on the floor, and may slap the child in return. The resultant commotion may then be seen as a tantrum, and the child is sent back to bed in disgrace. This not uncommon scenario, of course, only worsens the situation. The mind of a sleepwalker is unresponsive to what is going on around and seems steeped in thought. The sleepwalker behaves like an automaton with a limited repertoire of behaviour, but does not walk about with the hands out in front, as is commonly portrayed. There is no memory of the nocturnal activities the next day. Episodes can last up to 30 minutes, but usually average 5-15 minutes. Sleepwalking and night terrors, together with nocturnal bedwetting (enuresis), all reflect some form of disordered arousal from stage 4 sleep. But this conclusion is now strongly contested. Sleep EEG recordings of sleepwalkers show that they usually remain in SWS whilst sleepwalking, with few signs of arousal.
Typically, in a sleepwalking episode the child will sit up quietly, get out of bed and move about in a confused and clumsy manner. Although behaviour becomes more coordinated, the sleepwalker tends to remain in the bedroom, often preoccupied by searching for something in drawers, cupboards or under the bed. It is almost impossible to attract their attention; however, if left alone they normally go back to bed. Navigation is done mostly by memory of the layout of the room and house; the eyes are unseeing and usually it is dark. If the sleepwalker is asked to repeat the act the next day, in wakefulness and blindfolded, then he or she will soon come to grief as recall of the houshold layout is now poor, but somehow heightened during sleep. Difficulties and sometimes injuries occur to sleep-walkers at night if they think they are somewhere else, when walls, doors, staircases and windows are not where they should be.
More adventurous activities may occur, such as dressing, going to the fridge for food or walking outdoors. But if the behaviour is more complex, with the individual seemingly alert and organised and, for example, able to get dressed, get on a bike and pedal off down the road, then this is not sleepwalking per se, but probably a confused, waking, amnesic state. It can also arise from stage 4 sleep. Such states, which are not sleepwalking episodes as such, can last for several hours, and are more common between 10 years of age and puberty.
Night Terrors
These are another phenomenon of deep sleep (SWS) and are sometimes associated with sleep-walking. They are quite distinct from the visually vivid, prolonged nightmare, and are not just bad dreams, but sudden and horrifying sensations accompanying fleeting mental images that shock the sleeper into immediate wakefulness. Night-terrors are also more common in older children than in adults, where, in the latter, the problem is more serious. Typically, the child sits abruptly up in bed, screams and appears to be staring wide-eyed at some imaginary object - maybe "a monster". When this part of the episode passes the child appears to awaken somewhat (the EEG studies are unclear about this, as there is so much artefact on the record) but is confused and disoriented. They may well remain like this for many minutes until sleep returns, having little or no recollection of the event next morning. Night terrors can be combined with sleepwalking, particularly in adolescence, when the terrified child may run around the house in an inconsolable and incommunicable state for many minutes; half an hour or more is not uncommon. Again, morning recollection is fragmentary at best.
If the child is otherwise untroubled, then night terrors are seldom a matter for serious concern. One approach is one of pre-emption, by waking up the child before the night-terror. Initially, over a week or so, a record is kept of the exact time the night terrors occur, which is often around two hours into sleep and fairly constant. Then, for the next few nights the child is gently woken about 15 minutes beforehand, for about five minutes, and allowed to return to sleep. The likelihood of a night terror occurring on these nights is reduced and, with the pattern having been broken, it is claimed that the night-terrors are less likely to return on the following nights when the child sleeps through the night without interruption. However, all that may happen is for the night-terror to re-schedule itself elsewhere in sleep.
Epilepsy in Sleep
Epilepsies have various bases and classifications, and in infants and children may well have an incidence of 1% or more. Many forms of epilepsy have a clear relationship with sleep. Attacks can occur throughout sleep but, depending on the form of epilepsy, more typically appear: during the first two hours of sleep, often associated with SWS; during lighter sleep towards the end of the night; or, within the first hour after awakening. Around half of febrile convulsions happen during sleep, and another 25% when falling asleep or awakening.
Most forms of epilepsy are not typified by "grand mal" (tonic-clonic generalised) convulsions but are more subtle, as in some complex partial seizures arising in the temporal lobe or supplementary motor cortex. These can be mistaken for bizarre types of dreaming, sleepwalking, night-terror, etc. For one reason or another, children with epilepsy often have additional emotional disturbances. Thus, sleep disturbances are fairly common among these children, and can confound the diagnosis of epilepsy. For this reason, a detailed and accurate clinical assessment of the child is essential in order to unravel these factors, and enable the appropriate treatments.
One other form of nocturnal epilepsy is termed a "complex partial seizure of frontal origin", which is often bizarre and includes vocalisations (shouts, laughs, swearwords), facial gestures, leg movements (e.g. flexing and pedalling) and other automatisms. Although these are usually initially misdiagnosed as "nightmares", this can soon be ruled out as the events are typically very frequent, often happening several times a night and have a very abrupt onset and termination, with the whole episode lasting less than a minute. Whilst conventional EEG recordings are of limited value, in some patients recordings during sleep, emphasising frontal electrode placements, might be useful. These phenomena are not so rare as was first thought, and are referred to by some investigators as, "hypogenic or nocturnal paroxysmal dystonia" . Although some doubt has been cast as to whether these episodes are a form of epilepsy, they usully are, and are often responsive to the antiepileptic drug Carbamazepine.
Other Parasomnias
Headbanging, Headrolling and Bodyrocking
Headbanging (Jactatio Capitis Nocturna) is the most common of this related trio, and is a forward-backward banging of the head into the pillow or mattress, or sometimes into a more solid object such as a wall or side of the crib (head protection may be needed). Head-rolling is a repetitive side to side head movement, and bodyrocking is usually performed on the hands and knees, with a backwards-forwards pushing of the head into the pillow. All usually occur at sleep onset and during light non-REM sleep stages (1 and 2), as well as in drowsiness, and sometimes in wakefulness. Although headbanging is more common among mentally retarded children, on its own it is not a sign of retardation, as it is found in healthy, normal infants.
These rhythmic events usually appear nightly, last around 15 minutes or less per bout (often with several bouts per night), and have a movement frequency of around 45/minute. They tend to appear around 8 months of age and probably have a neurophysiological rather than a psychiatric basis, usually spontaneously remitting by the age of four years. The activity seems to be a pleasurable experience and may be a form of vestibular stimulation that has become a learned habit. Most cases do not need treatment, although parental reassurance is necessary. But if any of these conditions persist well into childhood or adolescence, then the basis may well be anxiety or psychological distress, requiring specific behavioural treatment. Some forms of epilepsy (see above) do have symptoms that can be mistaken for these movements.
Bedwetting
Sleep-related enuresis is a common sleep-related problem of childhood. Children are not born with bladder control, but have to learn to acquire it. Therefore, whether bedwetting can be considered as a disorder depends on where one draws the line for the number of wet beds per month. In general, children should have full control over their bladders by the age of 4. Bedwetting occurs to what seems to be an abnormal degree in around 15% of children aged 5-6 years, with this level falling by about 2-3 % per year thereafter. If one or both parents suffered from the disorder when young, then the incidence in the child increases by factors of about three and five respectively. But what exactly is inherited or acquired from the parents remains a matter for debate. Whilst bedwetting is commonly thought to have an emotional basis, this is usually not the case, unless it disappears for say, 6-12 months and then reappears in associaton with clear emotional upset. Often the emotion displayed by a bedwetter is a reasonable response to the bedwetting itself. Unusually, bedwetting can be a sign of urinary tract infection, diabetes, epilepsy and even sleep apnoea; disorders that should be eliminated initially.
Bedwetting occurs in all stages of sleep, and is not, as is sometimes thought, another example of an arousal disorder of stage 4 sleep, or due to a child's unusually deep sleep. Sleep-enuretic children can have one or more of the following: a small bladder capacity; a weak external urethral sphincter; have not learned to recognise the signals from a distended bladder that should arouse the child. Psychological factors can be important, such as inappropriate toilet training, excessive teasing about the problem by siblings, or parents who inadvertently reinforce bladder immaturity by continuing to keep an older child in a nappy (diaper) at night.
Treatment should be symptomatic, for example: bladder and/or sphincter training exercises; conditioning by the "pad and buzzer" technique to enable the sleeping child to recognise a full bladder; star charts for dry nights. Medication (e.g. Imipramine) is seldom the answer but could be an occasional adjunct during the treatment period (which can last several weeks) to give the child reassurance if sleeping away from home, for example.
Sleeptalking
This is the most minor of the peculiar mental events of sleep and is a muttering of jumbled words or phrases, with no real content, occurring in light sleep, which seldom has anything to do with dreaming (i.e. REM sleep). Sleeptalking, like sleepwalking, cannot normally occur in REM sleep because of the general paralysis of voluntary muscles (see above) at this time. Sleeptalking is common in adults and even more so in children. In fact, almost all children will do this if they are talked to during light sleep. Then there is some sort of confused reply that has little relevance to what was originally said. If two or more children share a bedroom, and one starts sleeptalking, then the curtain goes up on the bizarre theatre of the mind, as often the other sleepers will join in. But none of the participants will be listening to the ramblings of another, as each will be in a world of their own.
Toothgrinding
Bruxism is a minor disorder usually found in stages 1 and 2 sleep, and has a tendency to be related to anxiety and/or stressing days. It can occur in children soon after the first dentition has erupted and may lead to tooth damage and misalignment. For this reason a night-time rubber mouthguard is often used. If anxiety is indicated, then relaxation treatments can be successful.
Conclusions
Often, sleep problems in children are not of child but of the parents, who may have unwittingly created the problem in the first place, or worry unduly about a relatively minor matter that is inflated out of all proportion, or transmit their anxiety to the child whose sleep perturbation is exacerbated into a real problem. In these cases, it can be the parents rather than the child who really need the treatment (i.e. advice and reassurance). On the other hand, as has been seen, there are more serious sleep disorders that can all-too easily be dismissed by the parents as "nightmares" or "snoring", for example. It is remarkable how the more behavioural problems of children's sleep can be resolved so quickly, by the right approach, and frequently to the amazement of the parents who over months of anguish may have become desperate for a "good nights sleep" for themselves as well. Parents easily forget that infants and children are usually much more adaptable than themselves, and very forgiving of what may seem to be short but harsh treatments.
