Strange behaviour during sleep is not always epilepsy. Parasomnias and nocturnal seizures can both involve sudden sitting up, vocalisation, movement, fear, confusion or apparently purposeful behaviour.
What is a parasomnia?
Parasomnias are unwanted behaviours or experiences arising from sleep. Examples include sleepwalking, confusional arousals, night terrors and REM sleep behaviour disorder.
What is a nocturnal seizure?
A nocturnal seizure is an epileptic seizure arising during sleep. Some epilepsies are strongly sleep-related, including sleep-related hypermotor epilepsy.
Why they can look similar
Both can involve incomplete awareness, unusual movements, sudden arousal, vocal sounds and amnesia afterwards. Descriptions such as “thrashing” or “acting strangely” are not enough on their own.
Features specialists consider
Clinicians look at timing within the night, duration, frequency, stereotypy, clustering, age of onset, injuries, sleep stage and whether the same sequence happens each time.
Stereotypy can be an important clue
Epileptic seizures are often highly stereotyped. Parasomnias can also recur, but the behaviour may be longer and more variable.
Timing during sleep matters
Some non-REM parasomnias commonly arise from deep non-REM sleep, often earlier in the night. Nocturnal seizures can occur at different points and may cluster.
Home video can help
A safe home recording can show sequence, duration and responsiveness, but it cannot show the brain’s electrical activity.
EEG and sleep studies
Specialists may use video-EEG monitoring, ambulatory EEG, polysomnography or combined sleep and EEG studies. A routine EEG may be normal even in someone with epilepsy.
Do not assume every night-time event is epileptic
Sleep apnoea, parasomnias, periodic limb movements, reflux and other conditions can disturb sleep and may coexist with epilepsy.
Related reading
- Sleep-Related Hypermotor Epilepsy
- Sleep and Epilepsy
- Recovery After Nocturnal Seizures
- A Normal EEG Does Not Rule Out Epilepsy
Sources and further reading
- Strange episodes during sleep — epilepsy or parasomnia?. 2024. PMID: 38506017.
- Sleep and Epilepsy, Clinical Spectrum and Updated Review. 2021. PMID: 33985663.
- Standard procedures for the diagnostic pathway of sleep-related epilepsies and comorbid sleep disorders. 2020. PMID: 32959446.
Evidence checked: September 2026.