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.