Sleep and epilepsy

Seizures commonly occur during sleep. Some types of epilepsy are brought on by sleep and sleep disorders can trigger seizures.

There is a two-way relationship between sleep and epilepsy.  In people with epilepsy it is important that coexistent sleep disorders are treated as they can exacerbate epilepsy and make seizures more likely.  For those with sleep problems the associated sleepiness and chronic sleep disturbance can increase the risk of seizures.  There are also some sleep disorders such as parasomnias that can be hard to distinguish from sleep-related epilepsy or seizures.

What type of seizures can occur during sleep?

Any seizures can occur during sleep.  They can be generalised seizures, which are usually obvious, with rhythmical jerking of arms and legs.  A bed partner will often be awoken by movements or grunting when this happens and it can be very distressing to watch.  However, seizures can be more subtle and occur during sleep with no outward physical manifestations.  They can, however, disturb the restorative nature of sleep and leave people feeling tired and unrefreshed.  There are also forms of seizures during sleep such as nocturnal frontal lobe epilepsy that can result in behaviours occurring during sleep but can be hard to distinguish from sleep walking or sleep talking.

Nocturnal frontal lobe epilepsy (NFLE)

Nocturnal frontal lobe epilepsy was first described in 1994 by Professor Ingrid Scheffer in the journal Lancet.  The difficult description of NFLE is of stereotypical behaviours arising from sleep and causing sleep disturbance.  They are often noticed by a partner or parent or people report that they are waking feeling unrefreshed.  NFLE can be difficult to distinguish from parasomnias such as sleep walking or sleep talking. A scale has been developed to help but differentiate nocturnal seizures such as NFLE from parasomnias.  It uses clinical characteristics and the appearance of behaviours on video to calculate the FLEP scale and estimate the likelihood of episodes being either epilepsy or parasomnias.  Interestingly the criteria do not include electroencephalographic (EEG) characteristics as often with these seizures the electrical activity recorded from the surface of the brain, as is done during a sleep study, can remain normal throughout.

What should I do if I have had a seizure during sleep?

Obviously anyone who has had a seizure should seek help from a healthcare professional.  They will then evaluate your clinical situation to see if there is anything that may have triggered a seizure from sleep.  Sometimes these are predictable and do not necessarily require further investigation such as with the use of illicit medications, binge drinking or in someone with known epilepsy.  However, usually seizures arising from sleep will require investigation by a health professional.

Look for causes of seizures – In terms of evaluating causes of epilepsy usually people would have some form of brain imaging such as a CT or MRI scan under the supervision of a neurologist.  They would also generally have an electroencephalogram (EEG) which can be done over around 45 minutes whilst awake.  However, there are also prolonged EEG recordings such as a sleep-deprived EEG or a prolonged EEG for four to five hours.  Even longer EEG monitoring over four to five days in hospital continuously including during sleep and with continuous video recording is very helpful in differentiating nocturnal epilepsies from parasomnias and other behaviours.

Exclude co-existent sleep disorders – In people who have had a seizure arising during sleep it is also important to exclude other sleep disorders.  Sleep disorders such as sleep apnoea can be a trigger for seizures arising from sleep.  Sleep apnoea, where the upper airway either partially or completely blocks during sleep can result in lowered oxygen levels in the brain and the associated increase in sympathetic nervous system activity when the airway opens up can be a trigger for seizures.  Other sleep disorders such as insomnia, restless legs syndrome and circadian rhythm disorders can also make nocturnal seizures more likely.  I commonly see people referred by their neurologists with seizures arising from sleep to look for coexistent sleep disorders.  My usual evaluation is taking a clinical history to look for symptoms of sleep disorders and accompany this with a polysomnogram (overnight sleep study) in a laboratory with continuous video monitoring and extended electroencephalography (EEG).  I do not usually use home sleep studies in this clinical situation as they are generally used for confirming a diagnosis of sleep apnoea in people with a high likelihood of severe obstructive sleep apnoea, and often don’t include high quality EEG recordings.

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