Epilepsy and Sleep: A Close Relationship
It has always been known that there is a special relationship between seizures and sleep. The ancient Babylonians noticed it as did Aristotle and many other historical figures after them. However, these intuitive historical accounts were mostly inaccurate because they could not differentiate between epileptic seizures and non-epileptic seizures.
With the advent of electroencephalography (EEG) a hundred years ago, the connection between epileptic seizures and sleep was quickly established on a scientific footing.
Approximately 20% of people with epilepsy have seizures only during the night, while 40% only during the day, and 35% during both the day and the night. Importantly, children with epilepsy mostly have seizures while asleep or upon wakening from sleep. Moreover, epileptic seizures that are associated with sleep are more likely to be treatment resistant.
Clinically, the relationship between sleep and epilepsy is bi-directional – this means that epilepsy can cause sleep problems and sleep problems can lead to or exacerbate epileptic seizures.
Effects of epilepsy on sleep
Epilepsy is associated with more than 12 times higher rate of sleep disorders in children even without the disruption of seizures themselves.
Common sleep disorders associated with epilepsy include:
Excessive daytime drowsiness – this often occurs even in the absence of seizures. Additionally, a seizure can also be followed by very excessive drowsiness for up to more than a day.
Breathing disorders in sleep, most commonly obstructive sleep apnea (OSA), are widespread among people with epilepsy. Conversely, it has been shown that reduction of OSA can improve the ability to control epileptic seizures.
Insomnia can be caused either by the epilepsy itself or by the action of anti-epileptic drugs.
Epilepsy can disrupt or alter the normal phases of sleep. Normal sleep phase structure is important for essential processes that take place during sleep such as learning processes and memory formation.
Effects of sleep on epilepsy
Many observations have been made that may point toward why epileptic seizures are triggered at night and in relation to sleep. Three of the more common ones are:
The high degree of synchronization of brain waves (as measured by EEG) during non-rapid-eye-movement sleep (NREM sleep or deep sleep) could explain the observation that epileptiform discharges are more frequent during this sleep phase.
Arousal from sleep is also associated with a high degree of synchronization of brain waves ancould explain why certain kinds of epileptic seizures, particularly in children, are activated as they wake up.
Circadian cycles (internal body clocks) have also been linked to observed patterns of epileptic seizures.
Some common ways that sleep can affect epilepsy include:
Sleep deprivation has been directly connected with seizure activation. Given that insomnia can result from epilepsy, this can become a vicious cycle.
Parasomnias such as sleep walking, sleep terrors, and confusion upon waking, can be very difficult to differentiate from epileptic seizures without EEG.
SUDEP or sudden unexpected death in epilepsy is not very well understood, but its association with sleep or arousal from sleep has been well established.
The bi-directional relationship described in the above paragraphs can become a perpetuating vicious cycle. Therefore, it is essential to understand, monitor, and treat epilepsy within the context of sleep and vice versa.