Epilepsy


Epilepsy and Sleep Disorders Matthew C Walker1


and Sofia H Eriksson2


1. Professor of Neurology, and Consultant Neurologist; 2. Consultant Neurologist, Department of Clinical and Experimental Epilepsy, National Hospital for Neurology and Neurosurgery, and Institute of Neurology, University College London


Abstract


There is a close association between sleep and epilepsy. In some epilepsy syndromes, seizures occur predominantly (or even exclusively) during sleep or on awakening. Excessive daytime sleepiness is common in patients with epilepsy and may be due not only to medication but also to nocturnal seizures or concomitant sleep disorders. Sleep disorders such as obstructive sleep apnoea can worsen epilepsy, with improvement of seizure control following appropriate treatment of the sleep disorder. Conversely, epilepsy and antiepileptic medication can worsen sleep disorders. Nocturnal epileptic seizures may be difficult to differentiate from parasomnias, in particular non-rapid eye movement parasomnias such as night terrors, sleepwalking and confusional arousals, on history alone since there are semiological similarities between the two disorders. Schemes have been developed to facilitate differential diagnosis, although this remains a challenge even using the gold standard, video-electroencephalography telemetry.


Keywords Frontal lobe epilepsy, nocturnal seizures, non-rapid eye movement parasomnia, sleep apnoea, sleepwalking, night terrors


Disclosure: Matthew C Walker has received consultancy and/or speaker fees from UCB Pharma, Eisai and GSK. Sofia H Eriksson has no conflicts of interest to declare. Acknowledgements: This work was undertaken at University College London Hospitals/University College London, which receives a proportion of funding from the Department of Health’s National Institute for Health Research Biomedical Research Centres funding scheme. Received: 18 October 2010 Accepted: 26 November 2010 Citation: European Neurological Review, 2011;6(1):60–3 Correspondence: Matthew C Walker, University College London Institute of Neurology, Queen Square, London, WC1N 3BG, UK. E: mwalker@ion.ucl.ac.uk


Throughout the ages, sleep has been considered akin to death; indeed, Homer referred to sleep as the ‘brother of death’. However, the advent of electroecephalography (EEG) has expelled this misconception and sleep is now recognised as consisting of active brain states during which many biological processes occur, such as synaptic plasticity and memory consolidation.1


Sleep can be broadly


divided into rapid eye movement (REM) sleep and non-REM (NREM) sleep. These sleep states cycle over 90 minutes throughout the night. NREM can be subdivided into light (stages I/II) and deep (stages III/IV) sleep (see Figure 1). As sleep progresses, deep sleep periods become shorter and are absent towards the morning; conversely, REM sleep time increases.2


19th and early 20th centuries determined that 20% of patients with epilepsy have nocturnal seizures only.5,6


Importantly, the occurrence


of seizures predominantly during sleep is a characteristic of specific epilepsy syndromes. In particular, nocturnal seizures are typical of frontal lobe epilepsy, in which seizures usually cluster and can occur many times in a night.7


Nocturnal seizures occur throughout all stages


of NREM sleep and are distributed proportionately, so that they occur more frequently during light stages rather than deep stages (see Figure 2).8,9


Since different conditions occur in different sleep stages/states, the timing of events during the night is important for diagnosis. Epilepsy and sleep have an important temporal association and can interact (i.e. lack of sleep can precipitate seizures and seizures can disrupt sleep). Moreover, nocturnal epileptic seizures can be misdiagnosed as sleep disorders and vice versa.


It is also striking that, in some people, seizures can occur exclusively at night, an observation mentioned in ancient texts. Indeed, Aristotle stated that “the beginning of this malady [epilepsy] takes place with many during sleep, and their subsequent habitual seizures occur in sleep, not in waking hours”.4


Temporal Association of Epilepsy with Sleep Perhaps the best established relationship between epilepsy syndromes and sleep is in idiopathic generalised epilepsy syndromes, in which seizures occur shortly after waking. This is especially evident in the myoclonic jerks and tonic–clonic seizures in juvenile myoclonic epilepsy.3


Later studies from the 60


Although temporal lobe epilepsy does not show this diurnal variation, if temporal lobe seizures occur during the night, they are more likely to be secondary generalised.7,9


Similarly, seizures in benign focal epilepsy with centrotemporal spikes (BECTS) show a predilection for sleep or drowsiness.10


ESES is associated with certain epilepsy syndromes, including Landau–Kleffner syndrome, Lennox–Gastaut syndrome, continuous spikes and waves during sleep and benign epilepsy of childhood with rolandic spikes, and is associated with autistic/language regression.


Certain epileptic encephalopathies also show marked diurnal variation in seizure manifestation and electrographic activity. This is a particular feature of electrical status epilepticus during sleep (ESES), which is characterised by spike and wave discharges in 85–100% of NREM sleep.11


Interictal epileptiform discharges (IEDs) on the EEG increase with depth of NREM sleep and are often seen over a wider field than IEDs occurring during wakefulness.12,13


generated in similar circuits to those involved in the generation of spike-wave discharges in generalised epilepsies14


(however, this © TOUCH BRIEFINGS 2011


Sleep spindles and K complexes are


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