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Kleine-Levin Syndrome

The Kleine-Levin syndrome is a medical condition, in which the patient suffers from episodes of hypersomnia, accompanied by changes in the cognitive function or mood. This condition is also known as the Sleeping Beauty syndrome, being considered a rare sleep disorder. Apart from the changes already mentioned, many patients also present an enhanced appetite and frequent sexual urges. The episodes are recurrent and they may last for more than a decade. The duration of one episode varies from one person to the other (in general, it can last between one week and one month).

Due to the recurrent episodes, the patient’s quality of life is affected, including at personal and professional level. However, it should be mentioned that, in the majority of the cases, the condition goes away on its own and it does not cause permanent damage. As you will have the opportunity to read below, the prognosis of the condition depends on the severity of the symptoms. It has been estimated that one can suffer approximately twenty episodes in one decade. There are a lot of people who have an episode once every few months. Different factors can trigger the condition, including viral infections. The diagnosis is often made only after other potential causes have been excluded.

At the moment, the mechanism behind this condition is not thoroughly understood, even though it is believed that the thalamus might be involved. The condition is extremely rare, affecting approximately one in one million people. In general, it affects young man, although it has been diagnosed in older people and women as well. The condition cannot be cured and the treatment methods that are available might prove out to be limited. It was in the 20th Century that the condition was described for the first time, being added to the International Classification of Sleep Disorders in 1990. The syndrome was named after the two people who made the discovery, meaning Will Kleine and Max Levin.


These are the most common symptoms that appear in the patients diagnosed with this condition:

  • Hypersomnia (prolonged sleep)
  • Excessive tiredness (episodic)
  • Active episode – sleep duration varies between 15 and 21 hours per day
  • Excessive appetite – can be accompanied by cravings that unusual, affecting a large percent of the patients
  • Frequent sexual urges (hypersexuality – especially in males)
  • Mood swings
  • Changes in the cognitive function
  • The patient no longer perceives the world as real, suffering from extreme apathy
  • Hallucinations or delusions can also be present among the symptoms
  • Depression and anxiety (not in all patients)
  • No recollection of what happened during the episode
  • Repetitive behavior
  • Headaches
  • Improper behavior during the episodes (childlike)
  • During the episode, the communication abilities, as well as the coordination might be impaired
  • Malfunctioning of the autonomic nervous system
  • The first episode is accompanied by flu-like symptoms (viral infection)


The exact cause that leads to the appearance of this syndrome has yet to be identified. However, these are the causes that have been suggested so far:

  • Hypothalamic or circadian dysfunction
  • Dysfunction of the temporal lobe (especially in the patients who present cognitive impairment)
  • Frontal lobe dysfunction (in patients who are disinhibited or in those who present severe apathy)
  • Problems related to the brain neurotransmitters (dopamine, serotonin) – imbalance in the pathways through which these substances are transmitted
  • Viral infections – most commonly with: adenovirus, influenza A virus, herpes zoster, varicella zoster and Epstein-Barr
  • Genetics or environment (the condition has been diagnosed in members belonging to the same family)

These are considered to be triggers for the syndrome:

  • Alcohol consumption
  • Head injury
  • International travel
  • Not sleeping enough
  • Sleep


These are the most common methods used for the diagnosis of the Kleine-Levin syndrome:

  • Diagnosis of exclusion – the patient is tested for other conditions and the diagnosis is confirmed only after excluding other potential causes
  • MRI – can be useful in determining whether the patient is suffering from stroke, multiple sclerosis or brain tumors
  • Lumbar puncture – exclusion of encephalitis diagnosis
  • Toxicology testing – exclusion of substance abuse diagnosis
  • Electroencephalography (EEG) – exclusion of temporal status epilepticus diagnosis
  • Other investigations
    • Sleep studies – multiple sleep latency test
    • CT scan
    • SPECT (Single-photon emission computer tomography)
    • Serum biology
    • C-Reactive protein
    • Lectins
    • Cerebrospinal fluid analysis


These are the treatment measures that have been proposed for patients diagnosed with this syndrome:

  • Stimulants – modafinil (reduce the hypersomnia but can lead to behavioral problems)
  • Lithium – reduce the length, intensity and frequency of the episodes (may have side-effects, affecting the kidneys or the thyroid gland)
  • Antipsychotics and benzodiazepines – these are useful in alleviating the symptoms that may appear due to the psychosis or anxiety
  • Carbamazepine – not effective in all patients
  • Sleep hygiene


These are the most important facts you should know on the Kleine-Levin syndrome:

  • A person diagnosed with the Kleine-Levin syndrome can sleep more than 20 hours per day (when having an episode)
  • Teenage boys are commonly affected by this syndrome
  • The symptoms that were described above can re-appear all of a sudden, without any warning
  • In between episodes, the patients diagnosed with KLS present a normal state of health
  • The sleep pattern between the episodes is normal
  • Due to the increased sexual appetite, the patient might engage in excessive masturbation, being promiscuous or making inappropriate sexual advances
  • The condition is also known as the familial hibernation syndrome or the periodic somnolence and morbid hunger syndrome
  • During the episode, the individual might wake up only to eat and go to the toilet
  • The compulsive eating that appears during an episode can lead to weight gain on a long-term basis
  • There are approximately 500 cases of this syndrome recorded in the medical literature


If the condition appears in the adolescent period, it will generally disappear (with or without treatment) until the person reaches the 3rd decade of life. The patients who experience intense or frequent sexual urges do not have the best prognosis. If the patient hasn’t presented an episode in six years, he/she is considered to have been cured of this syndrome.

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