Kleine–Levin syndrome (KLS) is a rare disorder characterized by persistent episodic hypersomnia and cognitive or mood changes. Many patients also experience hyperphagia, hypersexuality and other symptoms. Patients generally experience recurrent episodes of the condition for more than a decade and may return at a later age. Individual episodes generally last more than a week, sometimes lasting for months. The condition greatly affects the personal, professional, and social lives of those with KLS. The severity of symptoms and the course of the syndrome vary between those with KLS. Patients commonly have about 20 episodes over about a decade. Several months generally elapse between episodes. The onset of the condition usually follows a viral infection; several different viruses have been observed to trigger KLS. It is generally only diagnosed after similar conditions have been excluded; MRI, CT scans, lumbar puncture, and toxicology tests are used to rule out other possibilities. The syndromes mechanism is not known, but the thalamus is thought to possibly play a role. SPECT has shown thalamic hypoperfusion of patients during episodes. KLS is very rare, occurring at a rate of 1 in 1 million, which limits research into genetic factors. The condition primarily affects adolescent males, though females can also be affected and the age of onset varies. There is no known cure, and there is little evidence supporting drug treatment. Lithium has been reported to have limited effects in case reports, decreasing the length of episodes and duration between them in some patients.
The use of electroencephalography (EEG) can exclude temporal status epilepticus from consideration. EEGs are normal in about 70% of KLS patients, but background slowing may sometimes be detected. In addition, low-frequency high-amplitude waves can be observed during waking hours.Initially, KLS appears similar to bipolar depression. Patients with frontal-lobe syndromes and Klüver–Bucy syndrome also display similar symptoms, but these conditions can be differentiated by the presence of brain lesions. KLS should also be distinguished from very rare cases of menstruation-caused hypersomnia. Prevention
Lithium is the only drug that appears to have a preventive effect. In two studies of more than 100 patients, lithium helped prevent recurrence of symptoms in 20% to 40% of cases. The recommended blood level of lithium for KLS patients is 0.8–1.2 mEq/ml. It is not known if other mood stabilizers have an effect on the condition. Anti-depressants do not prevent recurrence. Treatment
Several drug therapies have been used on patients with KLS, but none of them have been subject to randomized controlled trials. A 2016 Cochrane Review concluded that "No evidence indicates that pharmacological treatment for Kleine–Levin syndrome is effective and safe".In several cases, stimulants, including modafinil, have been reported to have a limited effect on patients, often alleviating sleepiness. They can cause behavioral problems, but they may pose fewer issues if used in older patients with mild symptoms. In some case reports, lithium has been reported to decrease the length of episodes and the severity of their symptoms and to increase the time between episodes.