Virginia Thornley, M.D.
February 1, 2019
Night terrors can be terrifying events. But happens exactly?
There are 3 states of arousal: wakefulness, non-REM (rapid eye movement) and REM sleep.
Non-REM has 4 stages. Stages 1 and 2 are light sleep. Stage 1 is characterized by attenuation of the posterior dominant rhythm and vertex waves can occur centrally. Stage 2 sleep is characterized by the presence of sleep spindles which are seen symmetrically in the central regions. Stage 3 is the deeper stage also called slow wave sleep. Stage 3 has delta wave activity.
When do parasomnias occur?
Parasomnias or disorders of sleep usually occur when one transitions from non-REM slow wave sleep. Night terror is a type of parasomnia. Night terrors are a disorder of the usual transition. The mechanism of this dysfunctional transition is not clear.
This is in contrast to nightmares which occur during REM when dreaming occurs.
One study found that when there are frequent arousals or complex behaviors in a polysomnogram this might correlate with night terrors. It might be a potential marker for occurrence of disorders of arousal such as night terrors (1).
- Lopez, R., Shen, Y., Chenini, S., Rassu, A.L., Evangelista, E., Barateau, L., Jaussent, I., Dauvilliers, Y., Diagnostic criteria for disorders of arousal: a video polysomnographic assessment. Ann. Neurol. 2018, Feb; 83(2):341-351