Arousal disorders, such as sleepwalking (somnambulism) and sleep terrors (pavor nocturnus), typically occur during non-REM (NREM) sleep, particularly during the first third of the night. Sleepwalking involves complex motor behaviors such as walking, eating, or even driving while asleep, often with little to no memory of the event upon waking. Sleep terrors, on the other hand, are marked by sudden arousal from sleep with intense fear, screaming, or thrashing, usually accompanied by a rapid heart rate and sweating. These episodes are difficult to awaken from and are often not remembered in detail.
Sleep-wake transition disorders, such as confusional arousals and sleepwalking, occur during the partial arousal from sleep, particularly during the transition between NREM stages 3 and 4 (slow-wave sleep) and lighter sleep. Confusional arousals involve disorientation, slow speech, and difficulty focusing upon waking, but without the full-blown motor activity seen in sleepwalking.
Parasomnias associated with REM sleep include REM sleep behavior disorder (RBD), where individuals physically act out vivid dreams, often with violent or aggressive movements. This disorder is linked to an absence of normal muscle atonia (paralysis) during REM sleep. Other REM-related parasomnias include sleep paralysis, where a person is temporarily unable to move or speak upon waking or falling asleep, and recurrent isolated sleep paralysis.
Other parasomnias include nightmares, which are disturbing dreams occurring during REM sleep, and sleep-related eating disorder, where individuals consume food while asleep without awareness. Parasomnias can be influenced by factors such as stress, sleep deprivation, irregular sleep schedules, and certain medications. Diagnosis typically involves a detailed sleep history, polysomnography (sleep study), and sometimes a sleep diary. Treatment may include improving sleep hygiene, addressing underlying causes, and, in severe cases, medication.