Written by M C Walker, S M Sisodiya
Institute of Neurology, University College London, National Hospital for Neurology and Neurosurgery, Queen Square, London, and National Society for Epilepsy, Chalfont St Peter, Bucks. London, and National Society for Epilepsy, Chalfont St Peter, Bucks. September 2005. This article can be reproduced for educational purposes.
Epilepsy has a complex association with sleep. Certain seizures are more common during sleep, and may show prominent diurnal variation. Rarely, nocturnal seizures are the only manifestation of an epileptic disorder and these can be confused with a parasomnia. Conversely, certain sleep disorders are not uncommonly misdiagnosed as epilepsy. Lastly, sleep disorders can exacerbate epilepsy and epilepsy can exacerbate certain sleep disorders. This chapter is thus divided into four sections: normal sleep physiology and the relationship to seizures; the interaction of sleep disorders and epilepsy; and the importance of sleep disorders in diagnosis.
Normal sleep physiology and the relationship to seizures
Adults require on average 7 – 8 hours sleep a night. This sleep is divided into two distinct states – rapid eye movement (REM) sleep and non-REM sleep. These two sleep states cycle over approximately 90 minutes throughout the night with the REM periods becoming progressively longer as sleep continues. Thus there is a greater proportion of REM sleep late on in the sleep cycles. REM sleep accounts for about a quarter of sleep time. During REM sleep, dreams occur; hypotonia or atonia of major muscles prevents dream enactment. REM sleep is also associated with irregular breathing and increased variability in blood pressure and heart rate. Non-REM sleep is divided into four stages (stages I – IV) defined by specific EEG criteria. Stages I/II represent light sleep, while stages III/IV represent deep, slow-wave sleep.
Gowers noted that in some patients, epileptic seizures occurred mainly in sleep. Sleep influences cortical excitability and neuronal synchrony. Surveys have suggested that 10 – 45% of patients have seizures that occur predominantly or exclusively during sleep or occur with sleep deprivation. EEG activation in epilepsy commonly occurs during sleep, so that sleep recordings are much more likely to demonstrate epileptiform abnormalities. These are usually most frequent during non-REM sleep and often have a propensity to spread so that the epileptiform discharges are frequently observed over a wider field than is seen during the wake state. Sleep deprivation (especially in generalised epilepsies) can also ‘activate’ the EEG, but can induce seizures in some patients. Thus many units perform sleep EEGs with only moderate sleep deprivation (late night, early morning), avoidance of stimulants (e.g. caffeine-containing drinks) and EEG recording in the afternoon. Sleep-induced EEGs in which the patient is given a mild sedative (e.g. chloral hydrate) are also useful.
Sleep and generalised seizures
Thalamocortical rhythms are activated during non-REM sleep giving rise to sleep spindles. Since similar circuits are involved in the generation of spike-wave discharges in primary generalised epilepsy, it is perhaps not surprising that non-REM sleep often promotes spike-wave discharges. Epileptiform discharges and seizures in primary generalised epilepsies are both commonly promoted by sleep deprivation. Furthermore, primary generalised seizures often occur within a couple of hours of waking, whether from overnight sleep or daytime naps. This is most notable with juvenile myoclonic epilepsy in which both myoclonus and tonic-clonic seizures occur shortly after waking, and the
syndrome of tonic-clonic seizures on awakening described by Janz. Seizure onset in this syndrome is from 6 – 35 years and the prognosis for eventual remission is good.
Certain epileptic encephalopathies show marked diurnal variation in seizure manifestation and electrographic activity. An example is the generalised repetitive fast discharge during slow-wave sleep occurring in Lennox-Gastaut syndrome. Another example is electrical status epilepticus during sleep (ESES). This is characterised by spike and wave discharges in 85 – 100% of non-REM sleep. This phenomenon is associated with certain epilepsy syndromes, including Landau-Kleffner, Lennox-Gastaut syndrome, continuous spikes and waves during sleep and benign epilepsy of childhood with rolandic spikes. ESES can thus be a component of a number of different epilepsy syndromes with agedependent onset, many seizure types, and varying degrees of neuropsychological deterioration. Indeed, ESES has been described in the setting of an autistic syndrome alone with no other
manifestation of epilepsy.
Sleep and partial epilepsies
Inter-ictal epileptiform abnormalities on the EEG occur more frequently during sleep, especially stage III/IV sleep (slow-wave sleep). The discharges have a greater propensity to spread during sleep, and thus are often seen over a wider field than discharges occurring during wakefulness. Temporal lobe seizures are relatively uncommon during sleep, while frontal lobe seizures occur often predominantly (sometimes exclusively) during sleep. Nocturnal frontal lobe seizures can be manifest as: brief stereotypical, abrupt arousals; complex stereotypical, nocturnal movements; or episodic nocturnal wanderings with confusion. Inherited frontal lobe epilepsies can manifest with only nocturnal events that can be confused with parasomnias (see below). Autosomal dominant nocturnal frontal lobe epilepsy is such an epilepsy. This has been associated with mutations in alpha-4 and beta-2 subunits of the neuronal nicotinic acetylcholine receptor. Onset is usually in adolescence with seizures occurring frequently, sometimes every night. The seizures are provoked by stress, sleep deprivation and menstruation, and often respond well to carbamazepine.
The interaction of sleep disorders and epilepsy
Seizures can disrupt sleep architecture. Complex partial seizures at night disrupt normal sleep patterns, decrease REM sleep and increase daytime drowsiness. Daytime complex partial seizures can also decrease subsequent REM sleep, which may contribute to impaired function. Antiepileptic drugs (AEDs) can also disrupt normal sleep patterns, although there are conflicting data (this is partially due to drugs having different short-term and long-term effects). Carbamazepine, for example, given acutely reduces and fragments REM sleep, but these effects are reversed after a month of treatment. The GABAergic drugs can have a profound effect on sleep; phenobarbitone and benzodiazepines prolong non-REM sleep and shorten REM sleep, while tiagabine increases slow-wave sleep and sleep efficiency. Gabapentin and lamotrigine may both increase REM sleep.
Certain sleep disorders are more common in patients with epilepsy. This is particularly so with obstructive sleep apnoea which is more common in patients with epilepsy and can also exacerbate seizures. Indeed, sleep apnoea is approximately twice as common in those with refractory epilepsy than in the general population. The reasons why this is so are unknown, but may relate to increased body weight, use of AEDs, underlying seizure aetiology or the epilepsy syndrome itself.
Patients with obstructive sleep apnoea often find that seizure control improves with treatment of the sleep apnoea. Topiramate may also be a particularly useful drug in these cases.
The importance of sleep disorders in differential diagnosis
On occasions nocturnal seizures can be misdiagnosed as a primary sleep disorder (see above). Conversely, certain sleep disorders can be misdiagnosed as epilepsy and the more common of these will be discussed below. Sleep disorders tend to occur during specific sleep phases and thus usually occur at specific times during the night, while seizures usually occur at any time during the night. There may also be other clues in the history, including age of onset, association with other symptoms (see below) and the stereotypy of the episodes (seizures are usually stereotypical).
In cases where there is some uncertainty, video-EEG polysomnography is the investigation of choice. There are, however, instances in which the diagnosis can be difficult even after overnight video-EEG telemetry as frontal lobe seizures can be brief with any EEG change obscured by movement artefact, and it is often the stereotypy of the episodes that confirms the diagnosis.
Abnormalities of sleep are divided into three main categories: 1) dysomnias or disorders of the sleepwake cycle; 2) parasomnias or disordered behaviour that intrudes into sleep, and 3) sleep disorders associated with medical or psychiatric conditions. Although there is an extensive list of conditions within each of these categories, we will confine ourselves to the clinical features of the more common conditions that can be confused with epilepsy.
Narcolepsy is a specific, well-defined disorder with a prevalence of approximately one in 2000. It is a life-long condition usually presenting in late teens or early 20s. Narcolepsy is a disorder of REM sleep and has as its main symptom excessive daytime sleepiness. This is manifest as uncontrollable urges to sleep, not only at times of relaxation (e.g. reading a book, watching television), but also at inappropriate times (e.g. eating a meal or while talking). The sleep is itself usually refreshing. The other typical symptoms are cataplexy, sleep paralysis and hypnagogic/hypnopompic hallucinations. These represent REM sleep phenomena such as hypotonia/atonia, and dreams occurring at inappropriate times. Cataplexy is a sudden decrease in voluntary muscle tone (especially jaw, neck and limbs) that occurs with sudden emotion like laughter, elation, surprise or anger. This can manifest as jaw dropping, head nods or a feeling of weakness or, in more extreme cases, as falls with ‘paralysis’ lasting sometimes minutes. Consciousness is preserved. Cataplexy is a specific symptom of narcolepsy, although narcolepsy can occur without cataplexy. Sleep paralysis and hypnagogic hallucinations are not particularly specific and can occur in other sleep disorders and with sleep deprivation (especially in the young). Both these phenomena occur shortly after going to sleep or on waking.
Sleep paralysis is a feeling of being awake, but unable to move. This can last minutes and is often very frightening, so can be associated with a feeling of panic. Hypnagogic/hypnopompic hallucinations are visual or auditory hallucinations occurring while dozing/falling asleep or on waking; often the hallucinations are frightening, especially if associated with sleep paralysis.
Narcolepsy is associated with HLA type. Approximately 90% of all narcoleptic patients with definite cataplexy have the HLA allele HLA DQB1*0602 (often in combination with HLA DR2), compared with approximately 25% of the general population. The sensitivity of this test is decreased to 70% if cataplexy is not present. The strong association with HLA type has raised the possibility that narcolepsy is an autoimmune disorder. Recently loss of hypocretin-containing neurons in the hypothalamus has been associated with narcolepsy, and it is likely that narcolepsy is due to deficiency in hypocretin (orexin).
Since narcolepsy is a life-long condition with possibly addictive treatment, the diagnosis should always be confirmed with multiple sleep latency tests (MSLT). During this test five episodes of sleep are permitted during a day; rapid onset of sleep and REM sleep within 15 minutes in the absence of sleep deprivation are indicative of narcolepsy.
The excessive sleepiness of narcolepsy can be treated with modafinil, methylphenidate or dexamphetamine and regulated daytime naps. The cataplexy, sleep paralysis and hypnagogic/hypnopompic hallucinations respond to antidepressants (fluoxetine or clomipramine are the most frequently prescribed). People with narcolepsy often have fragmented, poor sleep at night, and good sleep hygiene can be helpful.
Sleep apnoea can be divided into the relatively common obstructive sleep apnoea and the rarer central sleep apnoea. Obstructive sleep apnoea is more common in men than women and is associated with obesity, micrognathia and large neck size. The prevalence may be as high as 4% in men, and 2% in women. The symptoms suggestive of obstructive sleep apnoea are loud snoring, observed nocturnal apnoeic spells, waking at night fighting for breath or with a feeling of choking, morning headache, daytime somnolence, personality change and decreased libido. Although the daytime somnolence can be as severe as narcolepsy, the naps are not usually refreshing and are longer. Obstructive sleep apnoea and central sleep apnoea can be associated with neurological disease, but central sleep apnoea can also occur as an idiopathic syndrome. The correct diagnosis requires polysomnography with measures of oxygen saturations and nasal airflow or chest movements. To be pathological a sleep apnoea or hypopnoea (a 50% reduction in airflow) has to last ten seconds and there need to be more than five apnoeas/hypopnoeas per hour (the precise number to make a diagnosis varies from sleep laboratory to sleep laboratory).
Uncontrolled sleep apnoea can lead to hypertension, cardiac failure, pulmonary hypertension and stroke. In addition, sleep apnoea has been reported to worsen other sleep conditions, such as narcolepsy, and to worsen seizure control.
Treatment of sleep apnoea should include avoidance of alcohol and sedatives and weight reduction. Pharmacological treatment is not particularly effective, although REM suppressants such as protriptyline can be helpful. The mainstays of treatment are surgical and include tonsillectomies, adenoidectomy and procedures to widen the airway, and the use of mechanical devices. Dental appliances to pull the bottom jaw forward can be effective in mild cases, but continuous positive airway pressure administered by a nasal mask has become largely the treatment of choice for moderate/severe obstructive sleep apnoea. In cases associated with neuromuscular weakness intermittent positive pressure ventilation is often necessary.
Restless legs syndrome/periodic limb movements in sleep
Restless legs syndrome (RLS) and periodic limb movements in sleep (PLMS) can occur in association or separately. Most people with RLS also have PLMS, but the converse is not true and most people with PLMS do not have RLS. RLS is characterised by an unpleasant sensation in the legs, often described as tingling, cramping or crawling, and an associated overwhelming urge to move the legs. These sensations are usually worse in the evening, and movement only provides temporary relief. RLS affects about 5% of the population. Periodic limb movements in sleep are brief, repetitive jerking of usually the legs that occur every 20 – 40 seconds. These occur in non-REM sleep and can cause frequent arousals. PLMS occurs in about 50% of people over 65 years. These conditions can also be associated with daytime jerks. Both RLS and PLMS can be familial, but can be secondary to peripheral neuropathy (especially diabetic, uraemic and alcoholic neuropathies), iron deficiency, pregnancy and rarely spinal cord lesions.
Symptomatic relief can be achieved with benzodiazepines, gabapentin and opioids, but L-DOPA and dopamine agonists are the mainstay of treatment.
Sleep-wake transition disorders
The most common of these are hypnic jerks or myoclonic jerks that occur on going to sleep or on waking. They are entirely benign in nature, and require no treatment. They can occur in association with other sleep disorders. Rhythmic movement disorder is a collection of conditions occurring in infancy and childhood characterised by repetitive movements occurring immediately prior to sleep onset that can continue into light sleep. One of the most dramatic is headbanging or jactatio capitis nocturna. Persistence of these rhythmic movements beyond the age of ten years is often associated with learning difficulties, autism or emotional disturbance. Sleep-talking can occur during non-REM and REM sleep, but is often seen with wake-sleep transition and is a common and entirely benign phenomenon.
Nocturnal enuresis is a common disorder that can occur throughout the night. Although diagnosis is straightforward, it can recur in childhood, and also occurs in the elderly, with approximately 3% of women and 1% of men over the age of 65 years having the disorder. Thus, on occasions, it can be misdiagnosed as nocturnal epilepsy.
Non-REM parasomnias usually occur in slow-wave (stage III/IV) sleep. These conditions are often termed arousal disorders and indeed can be induced by forced arousal from slow-wave sleep. There are three main non-REM parasomnias – sleepwalking, night terrors and confusional arousal. These disorders often have a familial basis, but can be brought on by sleep deprivation, alcohol and some drugs. They can also be triggered by other sleep disorders such as sleep apnoea, medical and psychiatric illness. Patients are invariably confused during the event, and are also amnesic for the event. These conditions are most common in children, but do occur in adults.
Sleepwalking may occur in up to 25% of children, with the peak incidence occurring from age 11 – 12 years. The condition is characterised by wanderings often with associated complex behaviours such as carrying objects, and eating. Although speech does occur, communication is usually impossible. The episode usually lasts a matter of minutes. Aggressive and injurious behaviour is uncommon, and should it occur then polysomnography may be indicated to exclude an REM sleep parasomnia (see below), and to confirm the diagnosis. Night terrors are less common and are characterised by screaming, and prominent sympathetic nervous system activity – tachycardia, mydriasis and excessive sweating. Both these conditions are usually benign and rarely need treatment. If dangerous behaviour occurs, then treatment may be indicated. Benzodiazepines, especially clonazepam, are usually very effective.
Nightmares are REM phenomena that can occur following sleep deprivation, with certain drugs (e.g. L-DOPA) and in association with psychological and neurological disease. Sleep paralysis (see narcolepsy) is also an REM parasomnia, and may be familial.
Of more concern are REM sleep behaviour disorders. These consist of dream enactment. They are often violent, and tend to occur later in sleep when there is more REM sleep. These are rare and tend to occur in the elderly. In over one-third of cases, REM sleep behaviour disorders are symptomatic of an underlying neurological disease such as dementia, multisystem atrophy, Parkinson’s disease, brainstem tumours, multiple sclerosis, subarachnoid haemorrhage and cerebrovascular disease. In view of this, a history of possible REM sleep behaviour disorder needs to be investigated by polysomnography, and if confirmed, then possible aetiologies need to be investigated. REM sleep behaviour disorders respond very well to clonazepam.
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ABOUT THE THOMAS HAYDN TRUST
The Thomas Haydn Trust is The Paediatric Epilepsy Charity that aims to serve the needs of Young People, Parents, Carers and Medical Professionals. But to know who we are you need to know why we are.
Providing local services and sharing the rewards globally is the core of THT’s work, weather newly diagnosed or not, you will find THT a valuable source of support, knowledge and news for the epilepsies.
The Thomas Haydn Trust was set up in the wake of Thomas Haydn Smith’s diagnosis of Lennox-Gastaut Syndrome – One of the Most severe forms of Childhood Onset Epilepsies, affecting 1 in 1,000,000 epilepsy sufferer’s worldwide.
In setting up THT our aim was to combat many of the hurdles that Thomas and his family come across while living with LGS. THT strives to ‘Give Something Back’ to organisations that help families and children with severe epilepsies.
We work towards our goals in the following manner:
Raising the need profile for both basic and clinical research into Lennox-Gastaut Syndrome and other childhood Epilepsies.
By providing a free and open forum for sufferers, family and carers’, allowing them to share experiences, build relationships and facilitate peer learning. THT also provides details of leading specialist support organisations of specific Epilepsy conditions – Supporting the specific needs of the child.
Developing an ever-expending resource of research findings and educational materials for the public and medical professionals.
Where possible, fund individuals and organisations involved in support, development and care of families with sick children.
Raising awareness of childhood Epilepsies through various mediums including the internet, press, radio and television. Highlighting the effects of LGS and other childhood onset Epilepsies through our live events – Raising awareness is the key principle on which THT works.
Promoting the advancement of individuals with Epilepsy to speak out against ignorance, predjudice and bigotry that still surrounds conditions of Epilepsy.
Developing links with other national and international organisations to create a coalition of information sharing networks.