1
The Sleep History

Paul Reading1 and Sebastiaan Overeem2,3

1 Department of Neurology, James Cook University Hospital, Middlesbrough, UK

2 Centre for Sleep Medicine 'Kempenhaeghe', Heeze, The Netherlands

3 Eindhoven University of Technology, Eindhoven, The Netherlands

Introduction

It is a commonly held misperception that practitioners of sleep medicine are highly dependent on sophisticated investigative techniques to diagnose and treat sleep-disordered patients. However, it is relatively rare for detailed tests to add indispensable diagnostic information, provided a detailed, credible and accurate 24-hour sleep-wake history is available. In fact, there can be few areas of medicine where a good, directed history is of more diagnostic importance. In some situations, this can be extremely complex due to interacting social, environmental, medical and psychological factors. Furthermore, obtaining an accurate sleep history often requires collateral or corroborative information from bed partners or close relatives, especially in the assessment of parasomnias.

In sleep medicine, neurological patients can present particular diagnostic challenges. It can often be difficult to determine whether a given sleep-wake symptom arises from the underlying neurological disorder and perhaps its treatment or whether an additional primary sleep disorder is the main contributor. The problem is compounded by the relative lack of formal training in sleep medicine received by the majority of neurology trainees that often results in reduced confidence when faced with sleep-related symptoms. However, it is difficult to underestimate the potential importance of disordered sleep in many chronic and diverse neurological conditions such as epilepsy, migraine, multiple sclerosis and parkinsonism.

The following framework is a personal view on how to approach sleep-wake complaints from a neurological perspective. Although the focus is on individual or particular symptoms, it should be realised that several conditions can produce a variety of symptoms across the full 24-hour sleep-wake period. In Chapters 2 and 3, the various ways in which sleep and sleepiness can be recorded are discussed. Then, in Chapter 4, an 'integrative' approach to diagnosis is outlined, illustrated by case examples.

Excessive Daytime Sleepiness

Excessive daytime sleepiness (EDS) is an increasingly recognised symptom that is deemed worthy of assessment. It is relatively prevalent and disabling both in general and neurological populations [1]. Many excessively sleepy patients may present to the medical profession indirectly, most often due to adverse indirect effects on cognition, motivation or mood. Indeed, the inability to focus or maintain concentration is often the most disabling aspect of conditions causing EDS, described as 'brain fog' or even masquerading as dementia. A not uncommon question posed to general neurologists is whether a sleepy patient might have narcolepsy or a similar primary, presumed 'central' sleep disorder. Furthermore, 'secondary' or 'symptomatic' narcolepsy is evolving as a valid concept given recent major advances in unravelling the neurobiology of sleep regulation. In particular, a variety of pathologies predominantly affecting the hypothalamus can mimic elements of idiopathic (primary) narcolepsy [2].

It is widely perceived that EDS is a normal phenomenon associated with the ageing process. In fact, objective measures of sleepiness suggest that healthy elderly subjects are actually less prone to falling asleep when unoccupied during the day compared with their younger counterparts. Although afternoon planned naps are probably a normal phenomenon with many elderly people in all cultures, evidence for EDS beyond this level should be taken seriously in all age groups.

In the initial assessment of EDS, it is essential to gain an impression of the severity of symptoms and how they are impacting on an individual subject. It is also crucial to confirm that the complaint is that of true excessive somnolence rather than simple fatigue or lethargy. Although sleepiness questionnaires are widely used and can act as an effective screening tool in this respect (Chapter 4), they rarely help with actual diagnosis. Directly asking a subject about particularly unusual, unplanned or inappropriate sleep episodes can therefore provide valuable insight. Habitual mid-afternoon or late evening naps when unoccupied could be considered normal phenomena whereas regularly dropping to sleep mid-morning or in public places usually indicates a problem. A history of invariably napping as a car passenger for journeys of over an hour may suggest pathological levels of sleepiness as may a complete inability to watch any film all the way through. In narcolepsy, the subject may describe sleep onset even whilst engaged in physical activities such as writing or standing. Furthermore, in severe EDS, the subject may report awakening from naps unaware of any prior imperative to sleep. So-called 'sleep attacks' are recognised in narcolepsy and have been widely reported in sleepy parkinsonian patients. Regarding the latter population, recent evidence suggests that they may be particularly poor at monitoring their levels of subjective sleepiness, making the history from relatives particularly important [3].

The commonest causes of mild and severe EDS are probably insufficient sleep and poor quality overnight sleep, respectively. A directed history, perhaps backed by a sleep diary, usually helps in diagnosing the former and can indicate causes of the latter. If a subject regularly and reliably reports at least seven or eight hours of continuous sleep, yet remains significantly somnolent during the day, it is most likely that there is a disturbance of sleep architecture and, usually, that insufficient deep or restorative sleep is being obtained. An overabundance of light (stage N2) sleep compared with deep non-rapid eye movement (REM) sleep (stage N3) is frequently seen in sleep-related breathing disorders and periodic limb movement disorder. These diagnoses can easily be missed from the history if the subject is not a typical phenotype for the former or if they sleep alone. However, leading questions such as 'do you invariably awake with a dry mouth?' or 'are the bed clothes usually disrupted on waking?' can provide diagnostic pointers. Morning headaches or general sensations of 'heaviness' are traditionally associated with obstructive sleep apnoea although are equally common in a variety of sleep disorders.

A drug history including alcohol habit is also clearly relevant in assessing EDS as numerous agents given before bed may appear to induce drowsiness and aid sleep onset but actually worsen nocturnal sleep quality overall. Tricyclic preparations and benzodiazepines are frequently associated with unrefreshing sleep yet are frequently given primarily as hypnotic agents. It is worth noting that most antidepressants will potentially worsen restless legs syndrome or periodic limb movement disorder (Chapter 13).

Less recognised causes of disturbed nocturnal sleep may be picked up by a focused history. Nocturnal pain, frequent nocturia, persistent wheeze and acid reflux are usually fairly obvious 'toxins' to sleep and are generally readily reported. However, more subtle phenomena such as teeth grinding (bruxism) may not be recognised by the subject and only suspected if direct questions are asked about teeth wear, temporomandibular joint dysfunction or jaw pain, especially on waking.

A number of primary neurological disorders, including narcolepsy, disrupt the continuity of nocturnal sleep, most likely as a result of pathology in various brain regions intimately involved in sleep-wake control. A new symptom of sleep fragmentation and daytime somnolence in a patient with inflammatory brain disease such as multiple sclerosis, for example, might sometimes suggest inflammatory pathology in the pontomedullary area [4] or around the hypothalamus [5]. Idiopathic Parkinson's disease is strongly associated with EDS, especially in the advanced stages. Although there are many potential causes, including dopaminergic medication, primary Lewy body brainstem pathology itself is a likely substrate for most of the sleep-wake dysregulation, especially with regards to REM sleep [6]. If a neurological patient complains of significant EDS and no obvious cause such as Parkinson's disease is determined after a detailed history and subsequent sleep investigations, magnetic resonance brain imaging can be justified to exclude unexpected inflammatory or even structural pathology. This may particularly apply to sleepy, overweight children, for example [7].

There are usually sufficient clues from a patient's history to suggest a specific diagnosis of narcolepsy, the quintessential primary disorder of sleep-wake dysregulation (Chapter 8). Typically, narcolepsy causes symptoms from early adolescence and profound delays in receiving a diagnosis are still commonplace. A detailed history, therefore, exploring issues of excessive sleepiness around schooling can be illuminating. Apart from its severity, the nature of sleepiness is not particularly exceptional or unique in narcolepsy. However, even short naps, planned or unplanned, tend to be restorative, allowing a 'refractory' wakeful period of...