Introduction

Sleep medicine is often considered the domain of respiratory medicine, rather than neurology. This reflects the fact that Colin Sullivan is credited with recognising the benefits of continuous positive air pressure (CPAP) as an effective treatment for obstructive sleep apnoea (OSA).¹ What is less known is that the identification of OSA as a diagnostic entity was consequent to video telemetric evaluation of epilepsy. Nocturnal episodes were seen and appreciated to be breathing-related abnormal behaviour rather than a seizure.² Until that time, the concept of OSA had not reached the radar screens of those interested in sleep.

Obstruction of the upper respiratory tract, especially in rapid eye movement (REM) sleep, is, more likely than not, the reason why sleep medicine is seen as belonging to pulmonology, especially when one realises the benefits of CPAP. What is largely overlooked is the fact that sleep is a neurological state of being with defined electroencephalographic (EEG) patterns that reflect the stages of sleep emanating from the brain.³ It follows that sleep is an integral part of neurology rather than being of transient interest.

The purpose of this chapter is not to teach family physicians to be sleep physicians but rather to introduce general practitioners to the concepts of sleep medicine, as seen through the eyes of a neurologist. One most salient area of concern is that of the person with significant sleep disorder, be it OSA or narcolepsy, who continues to drive a motor vehicle. The general practitioner plays a vital role in advising the patient and/or the licensing authority if the patient drives contrary to advice. This responsibility exists irrespective of whether the general practitioner is conversant with sleep medicine or not.

What is Sleep Medicine?

As the name implies, sleep medicine is the study of how sleep affects health or, alternatively, the interface of sleep and health. Sleep medicine is much more than OSA, although OSA represents a very important part of sleep medicine because of its impact on activities such as driving. OSA is a potentially fatal condition because it is associated with an increase in hypertension, stroke and cardiovascular disease.⁴ Should death occur it is usually attributed to one of these associated conditions, thereby bypassing and camouflaging the serious implications of OSA.

Sleep medicine includes: chronobiology and the impact of shiftwork on biorhythms; insomnia (be it initial at the onset of sleep or late with early morning waking—as often associated with psychological factors such as depression); various movement disorders associated with sleep, such as periodic leg or limb movement in sleep (PLMS), which itself may cause arousal (PLMA) as well as being associated with the restless leg syndrome (RLS); narcolepsy; the sleepiness and fatigue often associated with many systemic diseases, including infections or neoplasia but also with other neurological conditions such as multiple sclerosis (MS); and altered behaviour during sleep such as REM behaviour disorder (RBD) that may be increased in Parkinson’s disease. The role of the sleep physician may be as simple as to evaluate the impact of poor sleep hygiene, which itself might be highly intrusive to quality of life.

It can be seen that sleep medicine covers a magnitude of conditions in which sleep and good health are intertwined. As sleep is an integral component of the lives of all patients who attend general practitioners, it is very important that practitioners have at least a superficial understanding of sleep medicine. Without this, general practitioners are deprived of the capacity to help their patients whose complaints emanate from sleep.

Where to Start?

As with all neurology, the starting point necessitates the need to have a high index of suspicion, for without it, it is impossible to take an adequate history. This should be tempered with some specialised knowledge that includes an understanding of what causes sleep disturbance and the consequences of poor sleep.

Often it is the experienced receptionist who will alert the doctor to the potential for a patient to have OSA. Office staff may play a pivotal role in advising the doctor about a patient who has been nodding off in the waiting room. Once alerted to the possibility, it is much more likely that the doctor will ask the right questions to make the diagnosis.

The patient’s partner is also a great source of diagnostic information, such as the history of loud and intrusive snoring, a restless sleep pattern or gasping for air during the night. The pattern of snoring punctuated by gaps of silence in which nothing is heard, followed by violent sucking in of air to compensate for the lack of oxygen, should provide the doctor with a red flag to suspect OSA.

Sleep is often a neglected and ignored component of medical history that translates into a third of the patient’s life being ignored and taken for granted. The patient’s size might provide the incentive to explore sleep. The Pickwickian obese, middle-aged Caucasian male or the obese, more senior Caucasian female should herald the ringing of warning bells for OSA. It should be appreciated that OSA is associated with a particular habitus⁵ that is quite different for Caucasians and Occidentals,⁶ with less emphasis on obesity in Asian people who experience OSA. OSA more frequently occurs in slim Occidental people, rather than the obese, as is the case with Caucasians.

Accidents that occur while driving should alert the doctor to question the patient, and their partner, concerning a sleep-related history. Assessment of sleep, sleep hygiene and related factors, such as disturbed sleep for whatever reason, or sufficiency of sleep, both in quality and quantity of time, should become part of the routine history taking. Daytime somnolence or excessive sleepiness or fatigue need to be explored. One such question relates to the capacity to fall asleep at traffic lights. This is a most important question and, if the patient admits to this, it is grounds for serious concern both about sleep disorders and the patient continuing to drive. An overall assessment of sleep should ultimately become part of routine patient evaluation for the conscientious general practitioner.

The family doctor should have some understanding of their patient’s sleep pattern to allow a more informed referral to an appropriate specialist should sleep-related issues arise. As has already been stated, sleep can impact on a host of medical conditions as diverse as headaches, Parkinson’s disease, MS or epilepsy. It is not by accident that sleep-deprived EEGs are routinely ordered to enhance the diagnostic yield when assessing patients with possible epilepsy. Lack of sleep, drifting off to sleep or waking up from sleep may be sufficient to provoke an epileptic seizure in a susceptible patient. The Sleep Centre at St Luke’s Hospital in Sydney will often combine a sleep deprived, full 10/20 electrode placement, prolonged EEG video telemetric recording with an all-night diagnostic polysomnograph (PSG) to assist in cases in which the differentiation between epilepsy and parasomnia is difficult to determine. This is an area where the neurologist has the advantage as the semiology of the event is important for making the diagnosis. An example of this may be found with possible rapid onset and arrest of a nocturnal episode favouring epilepsy over parasomnia.

Taking a History

Much of the above discussion of ‘where to start’ covered aspects of history taking, but the following will offer a more systematic approach.

The general practitioner should specifically ask about: the sleep pattern; what time the patient retires; sleep quality; duration of sleep; possible nocturia; insomnia; snoring; time(s) of waking; and comments from sleeping partners. The patient should be asked about how restful or invigorating sleep has been and how energetic they feel the following morning.

Daytime sleepiness, clarity of thinking and daytime efficiency should be explored. A history of work-related factors, such as shiftwork, stress, responsibility and efficiency, may shed extra light on quality of sleep. A patient who is often criticised due to poor work performance may have a sleep disorder as its root cause. It is axiomatic that if one does not ask the questions one cannot expect to get the answers. Doctors need to appreciate that their patients must have enough good quality sleep so that they can recharge their batteries, to be able to function efficiently and effectively.

Examination

There is nothing specific to the examination of the patient with regards to the neurology of sleep that necessitates special consideration. Pulmonologists may well explore, endoscopically, the upper airways to seek evidence of allergies that may impact upon sleep-related breathing. This is an area in which pulmonologists have an advantage over neurologists who are generally not trained in such endoscopic techniques.

Ear, nose and throat surgeons may focus much greater attention upon the tonsils and adenoids as a source of intrusive obstruction to breathing in sleep. Routine neurological examination when assessing cranial nerves includes examination of the pharynx and mouth. This would identify enlarged tonsils that may play a role in poor sleep, especially OSA and especially in the young.

Routine neurological examination should also include cardiac and respiratory auscultation, which would identify such breathing disorders as asthma or lung infections that might adversely affect sleep. Similarly, blood pressure determination and measurement of the patient’s weight are components of the assessment of the patient’s vital statistics. These should be routinely recorded, acknowledging that they may have increased relevance when assessing sleep. Not infrequently one is surprised to find that a patient thought to be of average height and weight is significantly overweight, which then provides the initial focus of therapy. As with history, suspicion and a thorough approach is the key to better patient care.

Sleep Apnoea

Sleep apnoea may be either OSA or sleep apnoea caused by a central origin, namely a brain-related cause as may occur with a lesion in the brainstem affecting the reticular formation.⁷ When considering sleep apnoea, most people only consider REM-related OSA, although OSA may occur in non-REM sleep and in some patients non-REM OSA may dominate the pattern.

In REM sleep muscles lose their intrinsic tone, which may cause the respiratory tract to collapse, blocking the upper airways. Once the respiratory pathway has collapsed, air can no longer reach the lungs. As a consequence, oxygen cannot fuel the vital organs, such as the heart and brain—thus the increased risk of myocardial infarction or stroke in patients with OSA.

A heightened awareness of the potential for OSA, particularly in overweight, middle-aged male Caucasians, will prompt the general practitioner to ask about snoring, excessive daytime sleepiness or hypersomnolence. The sleep partner is an invaluable source of history and can describe the apnoeic episodes. There are a variety of features favouring OSA (see Table 12.1).

TABLE 12.1 Features of obstructive sleep apnoea

Once suspicion of OSA has been raised, it is appropriate to refer the patient to an accredited sleep physician. This should establish a chain of events in which the physician takes an appropriate history to confirm the suspicion and refers the patient for a PSG. Should this confirm the presence of OSA the patient will be referred for further PSG, known as all-night CPAP titration PSG. This will determine the type of CPAP mask that best suits the patient’s facial features and temperament, and the amount of CPAP set in centimetres of water pressure required to maintain a patent respiratory pathway, so significantly reducing the apnoea–hypopnoea index (a measure of the frequency of disturbed sleep as a consequence of altered breathing).

There is a growing industry of home assessment for OSA that bypasses the sleep physician and, while cheaper, it reinforces the maxim that ‘you get what you pay for!’ There are also oral devices that resist closure of the airways, prepared by dental mould and worn at night. These too take second place to the gold standard of CPAP with proper hospital assessment. With OSA, the role of the general practitioner stops once there is a heightened suspicion of the diagnosis, as this should lead to a referral to an appropriate specialist to confirm the diagnosis and instigate treatment. It recommences once the patient has been provided with appropriate treatment, as general practitioners are vital in maintaining compliance and encouraging patients to persevere with the CPAP.

Insomnia

By far the most common cause for a patient to attend the general practitioner for disturbed sleep is insomnia. The most common cause for insomnia is emotional stress, such as anxiety, depression or worry for whatever reason.⁸ Often the patient will present complaining of a headache, because society considers it more socially acceptable to have an organic problem rather than openly confess to having difficulty coping. The patient will often present complaining of a migraine, and a good history should exclude migraine as a realistic option with the more common type of headache being tension-type headache (see Ch 6). Once this is diagnosed, the general practitioner can take a more detailed history of potential sleep disturbance.

This is an area in sleep medicine in which a competent general practitioner will be able to solve the problem without the need to refer the patient to a consultant. The issues may resolve with appropriate counselling, although pharmaceutical intervention may also assist. A favoured medication is one of the tricyclic antidepressants, amitriptyline (Endep®), which acts as an hypnotic as well as an analgesic, as an antidepressant and anxiolytic. The dosage usually starts with 25 mg nocte and may increase to satisfy need. It is important to realise that it may take up to 10 days to 2 weeks before the response is appreciated, and possible side-effects need to be discussed with the patient. Should the patient also have nocturia contributing to a disturbed sleep pattern, the anticholinergic properties of the tricyclics may also provide symptomatic relief for this complaint. This will enhance sleep quality while relieving the headaches. The goal is to use the medication only as a ‘stop-gap’, to relieve symptoms while helping the patient sort out a better approach with which to deal with the issues causing concern. The general practitioner is pivotal in this relationship.

Should the insomnia be a consequence of stress or altered sleep pattern, from whatever cause, that has resulted in a pattern of inappropriate wakening through the night, it is important to investigate sleep hygiene. The patient should be questioned about timing of going to bed and whether or not they get up through the night for whatever reason. Instituting correct sleep hygiene will often go a long way to correct the insomnia provoked by its disturbance. This may be complemented by the use of hypnotics, such as benzodiazepines in the form of diazepam (Valium®), nitrazepam (Mogadon®) or temazepam (Normison®). Such hypnotics should be taken for three nights in a row to re-establish the body-clock, while at the same time avoiding the potential for habituation and tolerance that attaches to the benzodiazepines. Some patients may complain of a feeling of being ‘hung over’ with the benzodiazepines, in which case zolpidam (Stilnox®) may offer a viable alternative. It must be acknowledged that there have been reports of bizarre nocturnal behaviour associated with Stilnox®, such as binge eating or somnambulism, so the patient needs to be warned.

If these simple remedies fail to achieve the desired outcome then it is time to refer the patient to a sleep physician to be assessed in greater detail, including PSG.

Somnambulism

Somnambulism (sleepwalking) is one of the parasomnias and is a condition in which the patient may execute very deliberate and, at times, very dangerous activities during sleep.⁹ It is associated with an abnormality of slow wave sleep rather than REM sleep.

To highlight the potential dangers associated with somnambulism, there is the case of a sailor who walked off the stern of a battleship during his sleep, luckily while the ship was in port rather than at sea, and was aroused once underwater. He could recount the sensation of seeing lights in the distance as they passed through the water, and swimming towards them. Once he reached the surface, he had significant difficulty getting out of the water as the port was not designed for casual swimmers. Had this event occurred at sea, he would have been lost and perished.

Somnambulism is more often encountered in children, especially in the peri-pubertal period. They are often described as growing out of it, although it may resurface in later life at times of significant stress. The sleepwalking need not entail actually getting out of bed and walking; it may be as simple as talking in one’s sleep, singing or just sitting up for no obvious reason. In some circumstances, the somnambulism may be confused with epilepsy and may require full investigation, thus necessitating referral to a neurologist.

The simple treatment for somnambulism is to protect the patient from the potential of causing harm to themselves or to others. Should there be an association with stress or other emotional factors, these need to be addressed, but this can usually happen at the level of the general practitioner.

Night Terrors

Night terrors¹⁰ are also one of the parasomnias that may be confused and misdiagnosed as epilepsy. They are often very frightening for parents, who feel impotent as they are powerless to stop them and equally powerless to comfort the distressed child.

Night terrors are far more prevalent in children, particularly aged two to six, rather than adults and they are unlike bad dreams. Night terrors are associated with the feeling of apparently unprovoked fear rather than frightening imagery, as may occur in nightmares. More often than not, they occur in non-REM sleep. No specific treatment is available although ensuring that the child has adequate sleep is said by some to be beneficial, but this is debatable. Comfort, reassurance and protecting the distraught child from harm remain the mainstay of any intervention.

Referral to a specialist is advisable, and EEG is often performed if only to exclude epilepsy while at the same time reassuring the parents.

Narcolepsy

Narcolepsy¹¹ has its associated tetrad of symptoms including: excessive sleepiness (with the rapid onset of REM sleep); sleep paralysis in which the patient may actually be conscious but cannot move until stimulated by something as innocuous as a light touch; cataplexy with sudden loss of muscle tone which results in collapse that may be provoked by emotional activity (as simple as laughter associated with hearing a joke); and hypnagogic (drifting off to sleep) or hypnopompic (awakening) hallucinations, namely vivid and realistic dreams associated with REM sleep although the patient is sufficiently awake to recall the experience.

The diagnostic process requires the patient to undergo a multiple sleep latency test (MSLT) to ascertain the frequency and rapidity of the onset of REM sleep. Tests of wakefulness may also be undertaken. Both tests require referral to a sleep laboratory, and hence referral to a sleep physician or neurologist.

An introductory overview such as this, aimed at the non-neurologist, does not lend itself to the discussion of the role of genetics nor the recent finding that narcolepsy is a result of a deficiency in hypocretin, also known as orexin transmission. Orexin enhances wakefulness and inhibits REM sleep, and its deficiency may be measured in a specialised laboratory using the lumbar puncture and cerebral spinal fluid. This is offered merely to whet the appetite of any reader wishing to explore the matter further.¹²

In the past the mainstay of treatment was the use of stimulants or antidepressants, either tricyclics or serotonin reuptake inhibitors. More recently modafinil (Modavigil®) has become the drug of choice for narcolepsy, as well as for shiftworkers reporting excessive sleepiness. Gamma hydroxybutyrate (often called GHB), widely recognised as the ‘date-rape’ drug, has proven efficacy for cataplexy. Prior to these medications being prescribed, the patient will have been referred to a neurologist or sleep physician so the actual choice of medication will be at their discretion. If the diagnostic tests necessitate referral to a sleep laboratory, it is appropriate to refer the patient once the diagnosis is suspected.

REM Behaviour Disorder (RBD)

Discussion of RBD should probably be beyond the scope of this chapter, but it also is offered to whet the appetite. RBD represents a form of behaviour that occurs in REM sleep in which the patient may act out and even become quite aggressive.¹³ Sleep partners may describe all manner of strange behaviour provoked by RBD, including being physically attacked by the patient. The patient may vehemently deny it as they will have no recollection of behaving in this manner.

RBD may be confused with epilepsy, and it could take a considerable time for the correct diagnosis to be made. This may necessitate prolonged video-telemetric EEG recording coupled with all-night diagnostic PSG, so is obviously outside the domain of the average general practitioner. It is treated with low dosage clonazepam (Rivotril®) and is increased with some neurological conditions such as Parkinson’s disease.

Conclusion

Sleep disorders are far more prevalent than might be thought if one is not actively seeking to define them while taking a history. Sleep apnoea, particularly OSA, is often considered the hallmark of sleep medicine and clearly requires PSG, and hence referral to a consultant. Insomnia, which is frequently referred to a specialist, can often be adequately managed by the general practitioner with judicious use of counselling, instigating proper sleep hygiene, and the judicious short-term use of hypnotics. Sleep walking and night terrors are parasomnias for which the general practitioner may be able to offer sufficient support and assistance to obviate the need to involve a specialist. Conditions, such as narcolepsy and RBD, are better treated with early referral to a specialist.

As with all such brief overviews, it is impossible to be all-inclusive, so it is hoped that this chapter offers an introduction to sleep medicine as seen through the eyes of a neurologist that will whet the appetite of the general practitioner to delve further into this fascinating area. Sleep disorders are far more prevalent than we have thought in the past. Sleep occupies a third of the patient’s life, yet it is often overlooked both when taking a history and when managing patients. Awareness is the key, and it is hoped that this chapter has stimulated such awareness.