Disorders involving movement or perception, during and around sleep
There are many disorders involving movement and perception around the time of sleep. During sleep our body goes through a system of changes in order to shift between stages of sleep and in order to move appropriately during these stages, whether it be to get comfortable or in order to not act out dreams. Problems with these systems mix in with the state of consciousness you are in while they happen to create a wide variety of possible movements and behaviours.
There are two major categories of movement disorder:
Sleep related movement disorders
Sleep related movement disorders are movements during sleep which disturb your rest. You may or may not be aware that these movements are occurring, but, unlike normal movements during sleep, they can result in sleep disturbances causing them to be classified as a sleep related movement disorder. Movements that do not interrupt sleep or do not affect sleep quality are not categorised as sleep related movement disorders (but may be considered parasomnias, which are covered below). A well-known example of a sleep related movement disorder would be restless leg syndrome.
Parasomnias are complex: they often encompass movements made during sleep but can also involve a person’s perception and emotion and can also occur during entry into or exit from a state of sleep. They include conditions such as sleepwalking, as well as more bizarre movements, seemingly purposeful behaviour and violent thrashing, punching and kicking. Patients usually present with concerns that they may injure themselves or others.
There are many different types of parasomnia, including, but not limited to, sleep walking, eating, night terrors, sleep paralysis, nightmare disorder and REM sleep behaviour disorder. Three major groups are thought to exist, based on the stage of sleep you are in when you experience them.
Rapid Eye Movement related
These parasomnias occur during rapid eye movement (REM) sleep. This type of sleep is typically when we dream, and when our muscles are selectively paralysed to stop us acting these dreams out. Disorders here can involve paralysis during sleep: it can be too strong and affect you after sleep, or be too weak and result in you acting out dreams and nightmares. REM related disorders can also involve dreams themselves: dreams and nightmares may be too vivid or you may experience a lack of REM sleep altogether.
Non Rapid Eye Movement related
These parasomnias involve incomplete awakening from sleep, resulting in a wide range of disorders including sleepwalking, sleep terrors and confusion. Generally episodes repeat and involve effects on responsiveness, cognition and memory.
Non sleep stage related
Some parasomnias are not related to the stage of sleep you are in, these include both hallucinations and parasomnias caused by factors external to sleep, such as drugs or another medical conditions.