Kleine Levin Syndrome


Kleine-Levin Syndrome: A rare condition characterized by periods of excessive sleepiness (up to 20 hours a day), increased hunger, irritability and disorientation.


The first episode is triggered by infection in 72% of cases. 

Patients experience 7-19 neurological episodes with a duration of 10-13 days/episode and relapses every 3.5 months. 

Episodes recurr more frequently in patients with childhood onset. 

  • all patients experience hypersomnia with sleep periods typically lasting 15-21 hours per day
  • cognitive impairment (apathy, confusion, slowness, amnesia)
  • derealization (dream-like state of altered perception)
  • hyperhagia
  • hypersexuality
  • anxiety
  • compulsive or mood disorders
  • depression 
  • increased BMI


Newly identified susceptibility factors include perinatal and developmental problems. Familial clustering (5% of cases involve multiplex families, suggesting autosomal recessive transmission) and a potential Jewish founder effect support a role for genetic susceptibility factors. An association of KLS with HLA-DQ2 positivity was found in a small series but was not replicated in a larger independent sample group. There is no family history of neuropsychiatric disorders. In 10% of cases, KLS arises secondary to various genetic, inflammatory, vascular or paraneoplastic conditions.


Structural brain imaging, cerebrospinal fluid and serological inflammatory markers are unremarkable. EEG slowing is noted in 70% of cases during episodes, without epileptic activity. Sleep structure varies from harmonious hypersomnia to hypoarousal with low sleep efficiency. Brain scintigraphy may show hypoperfusion, mainly focused in the thalamic, hypothalamic and frontotemporal areas, especially when compared to images obtained between episodes. 


Patients generally show a poor response to medical treatment.