Parasomnias: sleep disorders and how to manage them

“The term ‘parasomnias’ refers to a group of sleep disorders characterized by abnormal behaviors occurring during sleep, often accompanied by unusual movements,” explains Prof. Ferini Strambi.

Their manifestation varies depending on the stage of sleep in which they occur, which leads to a distinction into two main categories:

1. Parasomnias related to deep non-REM sleep

Deep non-REM sleep, typical of the first part of the night, is characterized by very slow brain activity and a general state of hypometabolism, meaning reduced glucose metabolism in the brain. It is in this context that so-called arousal disorders occur, including:

• night terrors;
• sleepwalking.

These parasomnias are much more common in children than in adults.

Night terrors in children

“Night terrors affect about 20% of children between the ages of 2 and 3, and 10% between 6 and 7. They should not be confused with nightmares, as they are not related to dreaming: the child is not dreaming, since the phenomenon occurs during non-REM sleep,” the specialist continues.

During an episode, the child:

• wakes up suddenly;
• cries inconsolably;
• shows tachycardia and rapid breathing;
• is not responsive, because the brain is in a hypometabolic state and does not respond to external stimuli.

After the episode, the child quickly falls back asleep and does not remember anything the next morning.

Sleepwalking in children

The same applies to sleepwalking, a condition that affects about 5% of children and around 1% of adults. During an episode, the individual may walk, sit up in bed, talk, or perform more or less complex actions, then return to sleep with no memory of what occurred.

This happens because the hippocampus, which is responsible for memory, is temporarily underactive.

Certain factors, such as poor sleep quality the previous night, fever, or infections that increase the proportion of deep non-REM sleep, can raise the likelihood of these episodes.

Family history also plays an important role: often, a parent experienced the same disorders in childhood.

2. Parasomnias related to REM sleep

Among REM sleep parasomnias, we find:

Frightening dreams

“Frightening dreams occur in the second part of the night, when REM sleep predominates. People who wake from a frightening dream are immediately alert and clearly remember the dream content,” the specialist explains.

REM sleep behavior disorder (RBD)

REM sleep behavior disorder (RBD) is typical of adults, especially after the age of 50. During this phase, the body is normally in a state similar to paralysis; however, in individuals with RBD, muscle tone remains active.

The person “acts out” their dreams with sudden movements, kicks, or punches, often linked to dreams involving aggression or defense. This can also pose a risk to a bed partner.

This disorder is of particular clinical interest because it may precede, by years, the onset of certain neurodegenerative diseases known as alpha-synucleinopathies, including Parkinson’s disease, Lewy body dementia, and multiple system atrophy.

Parasomnias mainly present as episodes of nighttime agitation:

• if they occur in the first part of the night, they are more likely to be non-REM parasomnias, such as night terrors or sleepwalking;
• if they occur in the second part, they are more likely related to REM sleep, such as frightening dreams or REM sleep behavior disorder.

“The causes of parasomnias can be multiple,” adds the specialist:

• genetic factors, especially in night terrors and sleepwalking;
• environmental factors that increase deep non-REM sleep, such as sleep deprivation, fever, or infections;
• stress or traumatic events, which may favor frightening dreams;
• medications that alter REM sleep structure, facilitating intense or disturbed dream episodes.

The primary diagnostic test is overnight video polysomnography, which simultaneously records:

• movements;
• brain activity;
• physiological parameters;
• video images to observe the episodes.

This is the key test for accurately distinguishing the type of parasomnia.

“For non-REM parasomnias, such as night terrors and sleepwalking, management is mainly behavioral,” the neurologist explains, including:

• avoiding sleep deprivation;
• correcting any contributing factors.

In cases of frequent episodes, a specialist consultation is required and, if indicated, video polysomnography should be performed.

For REM sleep behavior disorder, symptomatic treatments such as melatonin or clonazepam are available and can help control nighttime behaviors. Research is ongoing to develop preventive treatments aimed at reducing the risk of progression to neurodegenerative diseases.

“It is advisable to consult a specialist when episodes become more frequent, more intense, or potentially dangerous,” concludes Prof. Ferini Strambi.

The specialist can assess the clinical history, recommend specific tests, and establish an accurate diagnosis.

In recurrent cases, an overnight study is essential to define the disorder and determine the most appropriate treatment.