Effect on the Central Nervous System

Many neurological and psychiatric disorders cause daytime sleepiness. Some of the most important symptoms (excessive sleepiness, fatigue, nocturnal behavioral disorders) of different sleep disorders originate in the central nervous system (CNS). Examples of primary neurological sleep disorders include narcolepsy and other CNS hypersomnias. Different theories exist about the purpose of sleep. Among them is a theory that one of the main functions of sleep is for recuperation of the CNS and filling of the energy stores of the brain and body. The effects of hypersomnia on the CNS are multiple, but perhaps the most important effects are related to lack of energy of the brain. The first signs of lack of sleep (either too little sleep or poor sleep quality) can usually be seen in dysfunction of the frontal lobe. Effects of hypersomnias on the CNS include sleepiness, fatigue, cognitive symptoms, including problems of concentration, attention, impulsiveness, and memory. Also, dizziness, troubles with vision (diplopia), hallucinations, aggressiveness, challenging behavior, and dissociative symptoms may be associated with narcolepsy or another type of underlying primary hypersomnia disorder. The mode of onset of narcolepsy is in childhood and adolescence (9–17 years of age). The diagnosis of narcolepsy is made often several years later in adulthood. For this reason, various CNS effects of hypersomnias should be kept in mind especially in the differential diagnosis of problematic psychiatric symptoms among children and adolescents. The treatment of the effects on the CNS consists of stimulants. Sodium oxybate may be used in narcolepsy. It is important to avoid consuming rapidly absorbed carbohydrates (with a high glycemic index) during the daytime because they tend to aggravate sleepiness. Physical exercise is beneficial.