Sleep Studies, Parasomnias and Nocturnal Events

When something strange happens during sleep, how do doctors know whether it is epilepsy?

Sleep is not a period when the brain simply switches off.

Throughout the night, the brain moves repeatedly through different stages of:

• non-REM sleep

• REM sleep

• brief awakenings

• and transitions between sleep and wakefulness.

Many perfectly normal or non-epileptic events can happen during those transitions.

People may:

• jerk

• talk

• shout

• sit up

• walk

• thrash

• appear frightened

• act out dreams

• grind their teeth

• kick repeatedly

• or briefly seem confused.

Epileptic seizures can also occur during sleep.

The difficulty is that some sleep disorders can look remarkably similar to nocturnal epilepsy.

NICE therefore recommends urgent neurological assessment for adults and children with symptoms suggesting new-onset epileptic seizures during sleep.

“Nocturnal event” is a description, not a diagnosis

If somebody says:

“Something happens to me at night,”

there are many possibilities.

These can include:

• epileptic seizures

• sleepwalking

• night terrors

• confusional arousals

• REM sleep behaviour disorder

• nightmares

• sleep paralysis

• normal sleep-start jerks

• periodic limb movements

• restless legs-related movements

• obstructive sleep apnoea

• narcolepsy-related phenomena

• medication effects

• or other sleep disorders.

Sometimes more than one condition is present.

The aim is therefore to identify:

what happens

when it happens

how stereotyped it is

how long it lasts

what sleep stage it arises from

and, when necessary:

what the EEG and other body signals are doing at the same time.

What is a sleep seizure?

A sleep seizure is an epileptic seizure that begins during sleep.

Some people have:

• seizures only while asleep

• seizures both awake and asleep

• or seizures that occur particularly soon after waking.

Epilepsy Action reports that around 10 to 15 in every 100 people with epilepsy have sleep-related epilepsy, although patterns differ widely between individuals and epilepsy syndromes.

Almost any seizure type can potentially occur during sleep.

Why does sleep affect epilepsy?

Sleep changes the electrical organisation of the brain.

Different sleep stages alter:

• neuronal synchronisation

• cortical excitability

• communication between brain networks

• and the likelihood of epileptiform activity appearing.

For some epilepsies, particular sleep stages make epileptic activity easier to detect.

This is one reason clinicians sometimes request:

• sleep EEG

• sleep-deprived EEG

• overnight EEG

• ambulatory EEG

• or prolonged video telemetry.

NICE recommends considering a sleep-deprived EEG when routine EEG is normal but epilepsy is still suspected, and ambulatory EEG when uncertainty persists after routine and sleep-deprived EEG.

Sleep and epilepsy affect each other

The relationship works in both directions.

Poor sleep can make seizures more likely in some people.

Seizures can then:

• disturb sleep

• cause repeated awakenings

• reduce restorative sleep

• and contribute to daytime fatigue.

Epilepsy Action describes this as a two-way relationship between sleep and epilepsy.

This is different from saying poor sleep is necessarily the underlying cause of epilepsy.

How might somebody know they are having seizures in sleep?

Possible clues include:

• a partner witnessing a typical seizure

• repeated unusual movements

• waking with unexplained injuries

• waking confused

• unexplained blood on the pillow from injury

• finding bedding or furniture unusually disturbed

• unexplained incontinence

• waking somewhere other than the bed

• feeling markedly different from usual on waking

• or events captured on video.

Epilepsy Action lists unexplained injuries, confusion, unusual movements, waking out of bed and other changes as possible signs that sleep seizures may be occurring.

None of these signs proves epilepsy by itself.

For example, tiredness on waking has many possible causes.

Not every twitch during sleep is a seizure

Normal sleep contains movement.

One particularly common phenomenon is the hypnic jerk, sometimes called a sleep start.

This is a sudden brief movement as someone falls asleep.

It may involve:

• one leg

• an arm

• the whole body

• or a sensation of suddenly falling.

NICE specifically says adults with isolated brief jerks on falling asleep do not routinely need neurological referral.

A single sleep-start jerk is therefore very different from repeated stereotyped nocturnal seizures.

What is a parasomnia?

Parasomnia is an umbrella term for unusual behaviours or experiences occurring:

• during sleep

• while falling asleep

• or while waking.

Parasomnias include conditions such as:

• sleepwalking

• night terrors

• confusional arousals

• REM sleep behaviour disorder

• nightmares

• and sleep paralysis.

Specialist NHS sleep services assess parasomnias alongside conditions such as nocturnal epilepsy because the appearances can overlap.

Non-REM parasomnias

Several familiar parasomnias arise from non-REM sleep, particularly deep sleep.

These include:

• sleepwalking

• night terrors

• and confusional arousals.

North Bristol NHS Trust describes sleepwalking and sleep terrors as non-REM parasomnias arising from deep sleep.

They often occur earlier in the night, when deep sleep is more abundant.

Sleepwalking

During sleepwalking, a person may:

• sit upright

• get out of bed

• walk

• dress

• eat

• move around the house

• or perform other apparently organised behaviours.

Their eyes may be open.

They may look awake.

But they are not fully awake and may not respond normally.

The NHS notes that sleepwalking generally occurs in the first part of the night, can last several minutes and is usually not remembered the following morning.

Sleepwalking can look surprisingly complex

A person may appear to:

• navigate a room

• open doors

• move objects

• speak

• or carry out familiar routines.

That apparent purposefulness does not mean they are fully conscious.

This can make sleepwalking particularly difficult to distinguish from some focal seizures involving:

• automatisms

• wandering

• impaired consciousness

• or unusual motor behaviour.

The whole pattern matters.

What is a night terror?

During a night terror, somebody may suddenly:

• scream

• shout

• sit upright

• thrash

• appear terrified

• jump from bed

• or move around.

Their eyes may be open even though they remain asleep.

The NHS states that night terrors typically occur during the earlier part of the night and are often not remembered afterwards.

Children are affected much more often than adults.

A night terror is not the same as a nightmare

A nightmare is a disturbing dream from which the person usually wakes and may remember the dream.

A night terror typically involves:

• behavioural arousal

• apparent fear

• limited awareness

• and little or no memory afterwards.

The NHS notes that nightmares more commonly occur later in the night, whereas night terrors tend to happen earlier.

That distinction can help, but real sleep patterns do not always fit textbook timing perfectly.

Why can night terrors look like seizures?

Both can include:

• sudden screaming

• abnormal movement

• apparent unresponsiveness

• open eyes

• agitation

• and amnesia afterwards.

But clinicians may look for differences in:

• duration

• timing within the night

• stereotypy

• frequency

• exact motor sequence

• and how clearly the event starts and stops.

No single feature is perfect.

What makes a nocturnal epileptic seizure more suspicious?

Features that can raise suspicion include:

• highly stereotyped events

• almost identical movement each time

• very abrupt onset

• brief duration

• several events in one night

• occurrence at various points during the night

• clear focal features

• evolution into a larger epileptic seizure

• or a characteristic postictal state.

NICE's supporting evidence highlights stereotyped behaviour and events beginning focally and progressing as important clues to nocturnal epilepsy.

Research comparing nocturnal seizures and sleep disorders has similarly found that short, highly stereotyped repeated attacks are particularly suggestive of sleep-related epilepsy.

What makes a parasomnia more likely?

A non-REM parasomnia may be more likely when events:

• arise mainly from deep sleep

• commonly occur in the first part of the night

• are relatively prolonged

• vary somewhat from one episode to another

• involve confused or partially organised behaviour

• and have no sharply defined ending.

Epilepsy Society notes that epileptic seizures often follow a similar pattern each time and may have a clearer beginning and end, whereas parasomnias can be more variable and less sharply bounded.

These are patterns, not absolute diagnostic rules.

Stereotypy is particularly useful

Stereotyped means that the event looks remarkably similar each time.

For example:

sudden sitting → right arm stiffens → head turns → brief kicking movement → immediate stop

happening repeatedly in the same order is more suspicious for epilepsy than many very different night-time behaviours.

The repeated sequence may reveal a consistent seizure network.

But some parasomnias can also become repetitive, so stereotypy alone is not proof.

Duration can help

Some sleep-related epileptic seizures are very brief.

They may last:

• seconds

• or less than a few minutes.

Non-REM parasomnias can sometimes continue longer.

But duration overlaps.

A short event is not automatically epilepsy.

A long event is not automatically a parasomnia.

Video timing is more reliable than a frightened witness's estimate.

Frequency during one night can be useful

Some nocturnal epilepsies can produce clusters, meaning multiple brief events during one night's sleep.

Repeated nearly identical attacks several times in one night can increase suspicion of epilepsy.

Parasomnias can also recur, so again this is one feature rather than a standalone diagnostic test.

Sleep-related hypermotor epilepsy

One important epilepsy that can be confused with parasomnias is sleep-related hypermotor epilepsy — SHE.

This was previously called nocturnal frontal lobe epilepsy.

The name changed because:

• seizures are strongly related to sleep rather than simply clock time;

• and similar hypermotor seizures can sometimes arise outside the frontal lobes.

A major consensus process therefore renamed the syndrome sleep-related hypermotor epilepsy.

What can sleep-related hypermotor seizures look like?

Possible manifestations include:

• abrupt vigorous movement

• kicking

• rocking

• cycling-type leg movements

• twisting

• unusual postures

• sudden sitting or jumping up

• vocalisation

• shouting

• or apparently bizarre motor behaviour.

These seizures can be:

• very brief

• frequent

• clustered

• and highly stereotyped.

Because of the dramatic behaviour, they have historically been confused with:

• night terrors

• sleepwalking

• psychiatric events

• and other parasomnias.

A normal routine EEG does not rule out sleep-related epilepsy

Some focal seizures can be difficult to detect using ordinary scalp EEG.

Reasons include:

• deep seizure origin

• rapid movement creating artefact

• limited scalp representation

• or simply no seizure occurring during the short routine recording.

So somebody with convincing nocturnal focal seizures may still have:

• normal routine EEG

• or non-diagnostic interictal EEG.

NICE explicitly advises that EEG must not be used to exclude epilepsy.

REM sleep behaviour disorder

REM sleep behaviour disorder — RBD is very different from sleepwalking.

During normal REM sleep, the brain usually suppresses most skeletal muscle activity.

In REM sleep behaviour disorder, that normal muscle inhibition is reduced.

The person may physically act out their dreams.

They may:

• shout

• talk

• punch

• kick

• reach

• defend themselves

• or leap from bed.

North Bristol NHS Trust describes dream-enactment behaviour with vocalisation and limb movement as characteristic of RBD.

REM behaviour disorder often has dream content

If awakened, somebody with RBD may sometimes remember a vivid dream that matches the movement.

For example:

they may remember defending themselves from an attacker while their partner observed them punching during sleep.

That can help distinguish RBD from:

• some non-REM parasomnias

• and some epileptic seizures.

But diagnosis should not be based on one remembered dream.

Timing may help with REM behaviour disorder

REM sleep becomes more abundant later in the night.

North Bristol NHS Trust notes that the first REM period usually begins roughly 90 minutes after sleep onset and that REM becomes more prominent during the later part of the night.

Therefore recurrent dream-enactment events predominantly later in the night may support an REM-related parasomnia.

Again, timing is not definitive by itself.

How is REM behaviour disorder confirmed?

A specialist may request polysomnography.

An important finding is abnormal persistence of muscle activity during REM sleep, sometimes called REM sleep without atonia.

North Bristol NHS Trust describes overnight polysomnography as a method for measuring muscle activity during REM when RBD is suspected.

Sleep paralysis

Sleep paralysis occurs when somebody becomes conscious while the body remains temporarily in the muscle-inhibited state associated with REM sleep.

They may:

• know they are awake

• be unable to move

• be unable to speak

• feel frightened

• and occasionally experience vivid sensory phenomena.

North Bristol NHS Trust describes recurrent isolated sleep paralysis as waking while temporarily unable to speak or move.

NICE says isolated brief episodes of sleep paralysis do not normally require routine neurological referral.

Sleep paralysis can feel frighteningly neurological

Someone may wonder whether they have:

• had a seizure

• become paralysed

• or experienced a stroke.

The relationship to falling asleep or waking and the transient inability to move can strongly suggest sleep paralysis.

But new neurological weakness that persists after waking is a different situation and should not automatically be attributed to sleep paralysis.

What about nightmares?

Nightmares can cause:

• fear

• sweating

• rapid heartbeat

• sudden awakening

• and vivid remembered experiences.

They do not themselves represent epileptic seizures.

But someone with both:

• epilepsy

• and frequent nightmares

can obviously experience both disorders.

The fact that one night-time event is a nightmare does not classify every other night-time event.

Periodic limb movements

Some people repeatedly move their legs during sleep.

Movements can include:

• extension of the big toe

• ankle movement

• knee bending

• or repeated leg kicks.

When clinically significant, this may be part of periodic limb movement disorder.

Sleep services may use leg EMG — electromyography to record muscle activity during a sleep study.

Repeated leg movements are not automatically nocturnal seizures.

Restless legs syndrome is different again

Restless legs syndrome usually produces an uncomfortable urge to move the legs while:

• resting

• sitting

• or lying down.

Movement may temporarily relieve the sensation.

It generally occurs while the person is awake rather than as a sudden episode of altered consciousness.

It can, however, severely disturb sleep.

Sleep apnoea can create alarming night-time behaviour

Obstructive sleep apnoea causes repeated narrowing or closure of the airway during sleep.

The NHS lists night-time features including:

• breathing that stops and starts

• loud snoring

• gasping

• snorting

• choking noises

• and repeated waking.

Daytime symptoms may include:

• severe tiredness

• poor concentration

• mood changes

• and morning headache.

These symptoms can sometimes be noticed by a partner before the person realises anything is wrong.

Gasping during sleep does not automatically mean seizure activity

A witness seeing somebody:

• stop breathing

• gasp

• snort

• or suddenly move

may understandably fear a seizure.

But obstructive sleep apnoea can produce repeated breathing disturbances without epilepsy.

Conversely, seizures can also alter breathing.

The sequence and accompanying features therefore matter.

If breathing repeatedly stops and starts during ordinary sleep, sleep apnoea assessment may be appropriate.

Sleep apnoea can coexist with epilepsy

The possibilities are not:

sleep apnoea OR epilepsy.

Someone may have both.

Epilepsy Action notes that people with epilepsy can also have separate sleep disorders such as sleep apnoea, and appropriate investigation and treatment of sleep disorders can improve sleep and quality of life.

We will cover this fully in the separate planned page:

Sleep Apnoea and Epilepsy

rather than repeat all its treatment here.

Narcolepsy can also be mistaken for epilepsy

Narcolepsy is a neurological sleep disorder involving excessive daytime sleepiness.

Some people also experience:

• cataplexy

• sleep paralysis

• vivid dream-like experiences around sleep

• and disturbed night-time sleep.

NICE recommends specialist assessment for people with suspected narcolepsy.

Epilepsy Society also notes that some symptoms of narcolepsy may be mistaken for epilepsy.

What is cataplexy?

Cataplexy is a sudden loss of muscle tone associated with narcolepsy.

It may be triggered by emotion such as:

• laughter

• surprise

• excitement

• or anger.

Depending on severity, somebody may experience:

• jaw dropping

• head dropping

• knees buckling

• or complete collapse.

Consciousness is typically preserved.

A sudden collapse can therefore occasionally be confused with:

• an atonic seizure

• syncope

• or another neurological event.

The complete history is essential.

Why home video is particularly useful at night

A person having the event may be:

• asleep

• confused

• amnesic

• or completely unaware it occurred.

A partner's description helps.

A video can preserve:

• exactly how the event began

• movement pattern

• duration

• vocalisation

• position in bed

• and what happened afterwards.

Epilepsy Society recommends keeping a record or video because nocturnal seizures and parasomnias can be difficult to distinguish.

Home video cannot show brain activity

A camera may show:

what the body did.

It cannot show:

whether epileptic electrical activity occurred in the brain.

This distinction becomes especially important when:

• movements are unusual

• episodes are subtle

• or epilepsy and parasomnia remain equally plausible.

That is when simultaneous physiological recording may be needed.

What is a sleep EEG?

A sleep EEG records brain electrical activity while somebody sleeps.

The NHS lists sleep EEG as one of the specialist forms of EEG used when appropriate.

Sleep can reveal epileptiform abnormalities that may not appear during an ordinary awake EEG.

But recording an interictal abnormality is not necessarily the same as recording the person's actual night-time event.

What is a sleep-deprived EEG?

A sleep-deprived EEG is performed after the person has been deliberately asked to sleep less than usual before the test.

Sleep deprivation serves two purposes:

• making it easier for the person to fall asleep during the recording;

• and sometimes increasing the chance of epileptiform abnormalities becoming apparent.

NICE recommends considering sleep-deprived EEG after a normal routine EEG when epilepsy remains suspected.

Sleep deprivation should be performed according to the testing service's instructions rather than deliberately attempted independently to trigger a seizure.

What is polysomnography?

Polysomnography — PSG is a detailed overnight sleep study.

Unlike a simple EEG, polysomnography measures several body systems simultaneously.

Depending on the study, this can include:

• brain waves — EEG

• eye movements — EOG

• muscle activity — EMG

• breathing

• airflow

• oxygen levels

• heart rate and rhythm — ECG

• chest and abdominal movement

• sound

• and video.

NHS information describes this multichannel approach to sleep assessment.

Why record so many signals?

The combination helps answer different questions.

EEG

What stage of sleep is the brain in?

Is epileptic activity present?

Eye movements

Is the person in REM sleep?

Muscle activity

Does normal REM muscle inhibition occur?

Are repeated limb movements present?

Breathing and oxygen

Is sleep apnoea occurring?

ECG

What is the heart rhythm doing?

Video and audio

What behaviour actually occurred?

Combining these signals can make it possible to connect an unusual movement with the exact sleep stage and physiology in which it occurred.

Polysomnography and epilepsy monitoring are not exactly the same test

A standard sleep study may be designed primarily to investigate:

• sleep apnoea

• parasomnias

• limb movements

• narcolepsy

• or REM behaviour disorder.

Epilepsy video telemetry is primarily designed to investigate seizures.

In difficult night-time cases, specialist services can combine video EEG telemetry with polysomnography, allowing detailed sleep measurements and epilepsy EEG recording together.

This combined approach is particularly useful when the question is:

parasomnia or seizure?

Reviews of nocturnal motor events specifically identify video EEG polysomnography as valuable in difficult differential diagnosis.

One normal night does not always settle the diagnosis

Night-time events may be intermittent.

Some people:

• have several events every night;

• others have one every few weeks.

If no typical event occurs during the study, the result may still provide useful information about:

• sleep architecture

• EEG abnormalities

• breathing

• limb movements

but may not completely answer what the habitual event is.

A negative recording therefore needs interpretation in context.

Why might doctors request prolonged video EEG instead?

If the main concern is epilepsy, prolonged video EEG may increase the chance of recording a habitual seizure.

The NHS describes video telemetry EEG as simultaneous EEG and video recording, usually over several days in hospital.

This may be more useful than one ordinary night's sleep study when seizures are:

• frequent enough to capture

• diagnostically unclear

• or part of presurgical evaluation.

Related Information Hub page:
Video Telemetry: Recording Seizures in Hospital

Can several different events happen in the same person?

Yes.

Someone might have:

• focal seizures during sleep

• ordinary sleep-start jerks

• sleepwalking

• and obstructive sleep apnoea.

Finding one explanation does not automatically explain everything.

Research and specialist reviews specifically recognise that parasomnias and epilepsy can coexist.

If there are clearly different night-time events, describe each separately.

Why medication history matters

Medicines can affect sleep.

Possible effects include:

• sleepiness

• insomnia

• vivid dreams

• altered REM sleep

• abnormal movements

• or worsening of an existing sleep disorder.

Some antiseizure medicines can also cause daytime drowsiness.

Therefore specialists may need to determine whether tiredness is due to:

• seizures

• poor sleep

• medication

• sleep apnoea

• another sleep disorder

• or several factors together.

The timing of events can provide clues

Keeping track of when within the night events occur can be useful.

For example:

Mainly first part of night

may support some non-REM parasomnias.

Mainly later in the night with remembered dreams

may support REM-related phenomena.

Brief highly stereotyped attacks occurring repeatedly at varying points through sleep

may increase suspicion of sleep-related epilepsy.

Timing is helpful, but no diagnosis should be made from clock time alone.

What should a sleep-event diary include?

Record:

• date

• approximate time

• how long after falling asleep

• whether the person had recently awakened

• exactly what happened

• first movement or sound

• responsiveness

• whether eyes were open

• whether movements were identical to previous events

• duration

• how the event ended

• whether they were confused afterwards

• whether they remembered anything

• injury

• incontinence if relevant

• breathing changes

• medication

• sleep deprivation or illness

• and whether video exists.

This is far more useful than:

“Bad night again.”

Describe rather than diagnose

Instead of:

“Night seizure at 02:15.”

if the diagnosis is uncertain, write:

“02:15 — sat suddenly upright, shouted twice, pushed bedding away, walked towards door, did not answer normally, returned to bed after approximately three minutes, no memory next morning.”

The specialist can then decide whether this looks more like:

• parasomnia

• seizure

• or another event.

Record stereotypy

If episodes are nearly identical, say so.

For example:

“All six events this month began with exactly the same sudden right-arm posture followed by approximately 20 seconds of repeated leg movement.”

That is clinically useful information.

If events are very different each time, record that too.

Record clusters

If five events occur within one night, record:

• each time

• approximate duration

• whether the person recovered between them

• and whether the movements were the same.

Repeated brief stereotyped clusters can be important when considering sleep-related epilepsy.

Record what happens immediately after the event

Ask:

• Does the person immediately lie back down?

• Do they continue wandering?

• Are they confused?

• Can they speak?

• Can they recognise people?

• Do they wake fully?

• Do they remember it?

• Do they fall into deep sleep?

• Is there temporary weakness?

The recovery pattern may help distinguish seizure from parasomnia.

Avoid aggressively waking somebody just to test them

During some parasomnias, trying to wake the person forcefully can increase:

• confusion

• fear

• agitation.

The NHS advises remaining calm during night terrors and not trying to wake the person unnecessarily unless safety requires intervention.

For sleepwalking, gentle guidance back to bed is generally advised, with gentle waking only if necessary.

Safety takes priority.

Bedroom safety matters regardless of the diagnosis

Until unusual night-time behaviour is understood, practical measures may be needed if there is a risk of injury.

Depending on the event, examples might include:

• removing sharp furniture near the bed

• keeping floors clear

• reducing fall hazards

• protecting access to stairs

• securing dangerous external exits when appropriate

• avoiding top bunks for people who sleepwalk

• or discussing individual seizure safety with the epilepsy team.

The correct measures depend heavily on the actual diagnosis.

Do not physically restrain a suspected seizure

If an event appears epileptic:

• protect from injury

• do not pin the person down

• do not put anything in their mouth

• and follow their seizure care plan.

If an event is prolonged or meets emergency criteria, seek urgent help.

Related Information Hub page:
Seizure First Aid

When should new night-time events be medically assessed?

NICE recommends urgent neurological assessment when an adult or child develops symptoms suggesting new-onset epileptic seizures during sleep.

Assessment is particularly important when events are:

• new

• recurrent

• stereotyped

• associated with injury

• associated with prolonged unresponsiveness

• followed by significant confusion

• accompanied by clear focal features

• or evolving into bilateral convulsive seizures.

When should sleepwalking be assessed?

The NHS advises seeing a GP when sleepwalking:

• disrupts sleep

• creates concern about accidents or injuries

• occurs alongside excessive daytime tiredness

• or is associated with symptoms such as breathing stopping and starting during sleep.

Referral to a sleep clinic may be appropriate when episodes are severe, dangerous or diagnostically uncertain.

When should night terrors be assessed?

Night terrors are common in younger children.

NICE recommends referral for:

• children over 5 with new-onset night terrors;

• and children whose night terrors persist beyond age 12.

This is partly because new or persistent unusual nocturnal episodes may need another explanation considered.

When should sleep apnoea be considered?

The NHS recommends assessment when someone has symptoms including:

• breathing repeatedly stopping and starting during sleep

• gasping, choking or snorting

• loud snoring

• or persistent daytime tiredness.

A sleep clinic may arrange overnight monitoring of:

• breathing

• oxygen

• heart rate

• and other signals.

What if an event only happens once?

A single unusual movement in sleep does not automatically indicate epilepsy.

Normal people:

• move

• jerk

• talk

• dream

• and partially wake.

The significance increases when events:

• recur

• are highly stereotyped

• cause injury

• impair breathing

• produce prolonged confusion

• or include convincing seizure features.

Context matters.

What if somebody sleeps alone?

Diagnosis can be harder because nobody sees the event.

Possible evidence may come from:

• home video

• audio

• movement monitors

• injuries

• disturbed bedding

• unusual waking locations

• or formal overnight monitoring.

But indirect clues should not automatically be labelled seizures.

For example:

waking tired

alone is not enough.

Related Information Hub page:
Seizure Diaries and Videos: How to Record Useful Evidence

What if a home camera records movement?

Keep the original clip if possible.

Useful information includes:

• what happened immediately before movement

• exact duration

• whether the movement is rhythmic

• whether it repeats identically on other nights

• body position

• vocalisation

• and what happens afterwards.

Avoid judging a two-second clip without its context.

Seizure alarms cannot diagnose nocturnal epilepsy

Some devices can detect:

• repeated movement

• changes in heart rate

• or other physiological signals.

They may be useful for selected people with particular seizure types.

But a movement alarm cannot determine by itself whether an event was:

• epilepsy

• parasomnia

• ordinary sleep movement

• or another condition.

We will cover this separately under:

Seizure Detection Devices, Alarms and Wearables

Why sleep disorders matter even when epilepsy is already confirmed

A sleep disorder can worsen:

• daytime fatigue

• concentration

• memory

• mood

• quality of life

• and sometimes seizure control.

Therefore the question should not always be:

“Is this epilepsy instead of a sleep disorder?”

It may be:

“Does this person with epilepsy also have a treatable sleep disorder?”

Epilepsy Action specifically recommends considering separate sleep disorders when people with epilepsy have disrupted sleep or excessive tiredness.

Questions to ask a neurologist

Useful questions include:

Do these events look stereotyped enough to suggest seizures?

Could this be sleep-related hypermotor epilepsy?

Do I need a sleep EEG?

Would a sleep-deprived EEG help?

Would ambulatory EEG be more useful?

Do I need video telemetry?

Would a combined video EEG and sleep study be better?

Could my normal routine EEG have missed nocturnal epilepsy?

Should I record the events at home?

Could I have both epilepsy and a parasomnia?

Questions to ask a sleep specialist

Useful questions include:

Does this pattern fit sleepwalking or another non-REM parasomnia?

Could it be REM behaviour disorder?

Do I need polysomnography?

Will my study include EEG and video?

Could sleep apnoea be contributing to my symptoms?

Could limb movements be disrupting my sleep?

Could my medication be affecting my sleep?

Do I need neurological assessment as well as sleep assessment?

How the different night-time events can differ

Sleep-related epileptic seizures are often very stereotyped. This means the same sequence of movements or behaviour may happen in almost exactly the same way each time. They can begin abruptly, are often relatively brief and may occur several times during the same night. Some people have no memory of them afterwards. EEG may show epileptic activity, although scalp EEG can sometimes fail to detect focal seizures arising from deep or small brain regions.

Non-REM parasomnias, such as sleepwalking, night terrors and confusional arousals, commonly arise from deeper non-REM sleep and therefore often happen during the earlier part of the night. Episodes may last several minutes and behaviour can be more variable from one event to another. The person may appear awake, have their eyes open or move around, but may respond poorly and remember little or nothing the following morning.

REM sleep behaviour disorder occurs during REM sleep, which becomes more frequent later in the night. Instead of the normal muscle relaxation that occurs during REM sleep, the person may move, shout, kick or appear to act out a dream. If awakened, they may sometimes remember dream content that corresponds with their behaviour. Video polysomnography can demonstrate abnormal muscle activity during REM sleep and help confirm the diagnosis.

There is considerable overlap between these conditions. Timing, duration or appearance alone cannot reliably determine the diagnosis. When events remain unclear, specialists may need to combine the history, witness descriptions, home video, EEG and video polysomnography.

The most important message

Strange behaviour during sleep does not automatically mean epilepsy.

People can:

• walk

• shout

• jerk

• thrash

• appear frightened

• act out dreams

• stop breathing

• kick repeatedly

• or briefly become paralysed

because of several different sleep phenomena.

At the same time, epileptic seizures can occur entirely during sleep and may be missed for a long time.

Features that can increase suspicion of sleep-related epilepsy include:

• very abrupt onset

• short duration

• repeated highly stereotyped episodes

• several similar events during one night

• focal seizure features

• and characteristic postictal changes.

Non-REM parasomnias such as sleepwalking and night terrors tend to arise from deep sleep and are often more variable.

REM behaviour disorder involves acting out dreams because normal REM muscle inhibition is lost.

Sleep apnoea produces repeated disturbances of breathing and can coexist with epilepsy.

And normal phenomena such as occasional brief jerks while falling asleep do not usually indicate epilepsy.

When the distinction remains uncertain, the answer may come from combining:

• detailed history

• witness reports

• home video

• sleep diary

• EEG

• prolonged video telemetry

• and, when needed, video polysomnography.

The purpose is not simply to decide:

“seizure or not?”

It is to identify exactly what is happening during sleep, because epilepsy, parasomnias and other sleep disorders require very different treatment.

Sources and further reading

NICE — Suspected neurological conditions: recognition and referral (NG127).
NICE recommends urgent neurological assessment for adults and children with symptoms suggesting new-onset epileptic seizures during sleep. It also provides guidance on ordinary sleep-start jerks, sleep paralysis, night terrors, narcolepsy and sleep apnoea.

NICE — Epilepsies in children, young people and adults (NG217).
Current UK epilepsy guidance recommends sleep-deprived EEG after a normal routine EEG when epilepsy remains suspected and ambulatory EEG when diagnostic uncertainty persists.

Epilepsy Action — Sleep seizures.
Current UK information on seizures occurring during sleep or around waking, possible signs of unrecognised nocturnal seizures, the relationship between sleep and epilepsy and consideration of coexisting sleep disorders. Last modified November 2025.

Epilepsy Society — Sleep and epilepsy.
Discusses parasomnias, sleepwalking, night terrors and difficulties distinguishing sleep phenomena from epilepsy, including the value of home video and stereotyped seizure patterns.

NHS — Sleepwalking.
Current NHS guidance describes sleepwalking as partial arousal from sleep, usually occurring in the first part of the night, with open eyes, impaired responsiveness and little or no later memory. Last reviewed April 2025.

NHS — Night terrors and nightmares.
Explains differences between night terrors and nightmares, typical timing and the behavioural features of night terrors.

North Bristol NHS Trust — REM Sleep Behaviour Disorder.
Current specialist NHS information covering REM sleep, dream enactment, muscle activity during REM and the role of polysomnography.

NHS — Sleep apnoea.
Current information on repeated pauses in breathing, snoring, choking or gasping, disrupted sleep, daytime tiredness and sleep-clinic assessment.

NHS — Narcolepsy diagnosis.
Explains full polysomnography and the simultaneous recording of EEG, eye movements, muscle tone, breathing, oxygen, ECG, sound and video during detailed sleep assessment.

Tinuper and colleagues — Sleep-related motor events and differential diagnosis.
Peer-reviewed literature describes the difficulty distinguishing nocturnal seizures from non-epileptic parasomnias and the value of video EEG polysomnography, particularly for brief stereotyped nocturnal motor events.

Information reviewed: September 2026.

This page provides general educational information. New recurrent nocturnal events, injuries during sleep, prolonged unresponsiveness or symptoms suggesting new-onset epileptic seizures should receive appropriate medical assessment.