Introduction

Kleine-Levin Syndrome (KLS), also referred to as ‘sleeping beauty syndrome’ or ‘familial hibernation syndrome’, is a rare disorder characterised by recurrent episodes of hypersomnia, during which individuals sleep for extended periods, typically 16 to 20 hours per day.¹ In addition to excessive sleepiness, KLS affects behaviour and cognitive function, often resulting in emotional disturbances such as confusion, depersonalisation, hallucinations, anger, aggression, anxiety, depression, amnesia, or apathy. Disorders of eating behaviour, typically excessive appetite or compulsive eating (hyperphagia or megaphagia), and increased sex drive (hypersexuality) can also occur in patients.^1,2 On average, episodes of KLS last about 10 days but can range from a few days to several weeks. ³In between episodes, individuals typically return to their normal behaviour and do not show signs of the condition, though some may continue to experience modest cognitive abnormalities. The exact cause of KLS remains unknown.^4,5

According to statistics, KLS is regarded as a very rare condition.^1-5 Its estimated incidence ranges from 1 to 2 cases per million people, though some insights indicate it could be as high as 5 to 7 cases per million. Until 2014, only about 200 cases had been documented in the literature. Although it can affect anyone, males are more likely to have it than females; gender ratios show that boys are four times more likely than girls to develop the condition.^2,4 Although there is currently no officially established cure for KLS, numerous pharmacological and non-pharmacological approaches have been explored to control symptoms and lessen the frequency and severity of episodes.^1,4 This article reviews the current treatment practices for KLS, including medication, lifestyle alterations, and emerging management techniques, to provide a clearer understanding of best strategies and directions for future research.

Understanding Kleine-Levin syndrome

KLS is characterised by behavioural and cognitive abnormalities, as well as frequent episodes of extreme drowsiness that often persist for extended periods. Although some may suffer from slight memory loss, people with KLS usually resume their regular behavioural patterns in between episodes and show no indications of the disorder.^1,4,5

Symptoms and diagnostic criteria

Early adolescence is typically when symptoms first appear, and they tend to recur periodically. Over time, episodes become less frequent and less severe. Common signs include:

Recurrent hypersomnia

Recurrent episodes of extreme daytime sleepiness, or hypersomnia, are the main symptom of KLS.^1-5 People with KLS typically sleep 16 to 20 hours a day during these episodes, while some studies suggest that sleep duration might reach 12 to 24 hours.^1,2,4 Even though they sleep a lot, they are extremely drowsy and have trouble staying awake. During an episode, the need for sleep is said to be extremely strong.⁴ Patients usually resume their regular sleep schedules when an episode ends; however, some may temporarily experience sleeplessness.^2,4

Cognitive and behavioural disturbances

KLS episodes are characterised by notable behavioural abnormalities and cognitive impairment in addition to hypersomnia.^1-5 96–100% of patients experience issues such as memory disturbances, confusion, and impaired attention during episodes.⁴ Depersonalisation, a sensation that the environment appears incorrect, warped, unreal, or dreamlike, is a common and prominent symptom.^2,4,5 Patients may also experience sensations of strangeness, alienation with themselves or their surroundings. Memory loss, or amnesia, is another frequently reported symptom; many individuals experience partial amnesia or struggle to recall events during an episode.¹

Diagnostic process and exclusion of other conditions

Due to the lack of a definitive test, KSL is challenging to diagnose.^1,4 To diagnose KLS, medical professionals must rule out other illnesses that present with comparable symptoms.^1,4 A thorough patient history, including the duration and intensity of symptoms, is the first step in the diagnostic process.¹ Early in the course of the disease, patients are frequently misdiagnosed with mental illnesses such as bipolar disorder or atypical depression. This is because the energy spike that follows a KLS episode can resemble mania, while the episodes themselves, distinct by withdrawal, hyperphagia, and somnolence, may mimic patterns of depressive phases. Other types of primary hypersomnia, narcolepsy, sleep-disordered breathing, temporal lobe epilepsy, Klüver-Bucy syndrome, metabolic encephalopathies, Lyme disease, and acute intermittent porphyria are additional disorders that need to be taken into account in the differential diagnosis.^2,4 

Aetiology and pathophysiology

Potential causes

Even though the cause of KLS is still uncertain, several hypotheses and possible contributing factors are being examined:

1. Neurological/Hypothalamic dysfunction: given the importance of the hypothalamus in controlling hunger, sleep, and sexual behaviour, an underlying hypothalamic pathology is proposed.⁴ According to specific research, a disease or trauma may harm the hypothalamus, the area of the brain that controls sleep^1,2
2. Autoimmune mechanisms: because KLS episodes often precede infection, an autoimmune mechanism has been proposed.^1,2,4 According to research, KLS may trigger an immunological reaction in which the body misinterprets healthy tissue as an invasive organism, impairing the healthy brain tissue's ability to function normally¹
3. Genetic theories: reports of familial KLS instances suggest a potential degree of heightened genetic susceptibility. ^2,4,5 Some research points to a potential connection to alterations or mutations in the LMOD3 and TRANK1 genes^1,3
4. Neurotransmitter imbalance: in certain instances, abnormalities in the metabolism of serotonin and dopamine have been documented, indicating a possible imbalance in these pathways⁴

Triggers

Before symptoms appear, patients frequently report a triggering event.² According to one study, infection and fever are the most frequent triggers, occurring before symptoms in up to 72% of cases and 96.6% of initial episodes.^2,4 Before episodes, upper respiratory tract infections or flu-like illnesses are commonly recorded.^1-4

Among the other known triggers are: 

• Alcohol consumption^1,2,4,5 
• Being sleep deprived^1,2,5 
• Trauma to the head^1,2,4,5 
• Strenuous physical activity⁴
• Stress (atypical psychological occurrences or stress)^1,2,4,5 

Medical treatment options

KLS does not have a proven cure.^1,2,4 Since the condition's source is unknown, prevention is not possible.¹ The ailment usually resolves on its own over time, and treatment methods typically focus on alleviating the symptoms.^1,4 Various drugs have been utilised based on case reports, frequently with unpredictable results given the lack of high-quality evidence.^4,5

Stimulants for hypersomnia

During episodes, excessive daytime sleepiness is sometimes treated with stimulants such as amphetamines, methylphenidate, and modafinil.^1,2,4,5 If taken early in the symptomatic cycle, stimulants are proven to be effective in reducing the symptoms.² Particularly, amphetamines, which have a reported response rate of 40-71% in case series compared to other stimulants, may shorten the duration of the symptomatic period.⁴ However, according to some reports, amphetamines have no long-term effects on the rate of symptom recurrence. They may also help to lessen sleepiness, but they do not improve cognitive or behavioural symptoms. One of the possible adverse effects is the possibility of paradoxical agitation brought on by stimulants, which is more likely to happen near the end of an episode.² Additionally, there is a significant chance of dependency.¹

Mood stabilisers and antipsychotics

Several mood stabilisers have been explored, including lamotrigine, gabapentin, phenytoin, carbamazepine, lithium, and valproic acid. For prolonged psychotic symptoms that may arise during episodes, antipsychotics such as risperidone, haloperidol, chlorpromazine, levomepromazine, trifluoperazine, thioridazine, and clozapine have been utilised.^2,4,5 However, published case reports and clinical series suggest that these treatments are generally not effective for treating KLS.⁴

Antidepressants

KLS episodes can cause temporary depression symptoms that can be treated with antidepressants such as tricyclics, selective serotonin reuptake inhibitors (SSRIs), and serotonin-norepinephrine reuptake inhibitors (SNRIs).^1,2 

Other medications

In one instance, a novel experimental noninvasive treatment using methylene blue and red light intranasal photobiomodulation was tried. Within a week of beginning treatment, the patient in this instance went into remission, and two years later, there had been no relapse. This strategy is thought to affect mitochondrial function and offer neuroprotection, which may help address the cerebral hypoperfusion and hypometabolism seen in KLS.³

Non-pharmacological management strategies

Sleep hygiene and lifestyle adjustments

Supportive treatment is frequently advised unless KLS episodes are particularly severe. While the episode is ongoing, the patient should be permitted to sleep in a secure, comfortable, and familiar setting.² Patients may wake up to eat or use the restroom, but their severe drowsiness limits their ability to move.¹ During an episode, it is dangerous to handle heavy machinery or drive a car, as the patient may nod off, endangering both themselves and others.^1,2 Patients should not be allowed to use heavy equipment or wander unsupervised. It is recommended that patients stick to regular sleep-wake patterns and abstain from alcohol and sick days in between episodes.²

Psychological and psychiatric support

Your healthcare provider may recommend supportive therapy to help manage symptoms such as behavioural changes, hypersexuality, anxiety, and low mood by working with a mental health professional.¹ If there are signs of anxiety or sadness, they should be addressed and constantly watched.² KLS may impact your mental health, so you should speak with your provider if you feel hopeless, have suicidal thoughts, or exhibit signs of anxiety or despair.¹ During episodes, temporary anxiety and despair may strike.^2,4 The preferred course of action is frequently to educate parents and avoid using harsh methods. You can navigate each day securely during or after an episode by forming a network of friends and family.^1,2

Educational and occupational planning

To allow you to get as much sleep as your body requires during episodes, your healthcare professional can assist you in arranging accommodations, such as time off from work or school. Activities related to work and school should be rescheduled or delayed until the symptoms have subsided.^1,2 During episodes, patients frequently avoid social contact. Patients who are awake during an episode often exhibit apathy and report difficulties with memory, communication, and concentration. Partial amnesia of the incidents may also occur. Due to these symptoms, daily obligations and routines must be modified. If you experience an episode while alone, it is a good idea to let people know by wearing a medical ID tag or carrying an emergency ID card in your wallet.¹

Monitoring and long-term management

Tracking episodes and symptoms

Recording episodes and related symptoms is the first step towards effective long-term management of KLS. Patients are advised to record information about the frequency, length, and triggers of their episodes using sleep diaries or electronic tools. This approach makes it easier for individuals and medical professionals to comprehend how the condition develops and spot any trends.¹

Wearable technology and digital apps are becoming increasingly helpful in tracking symptoms associated with hypersomnia. Compared to conventional techniques, these instruments can provide more accurate data collection, increasing patient self-awareness and enabling more flexible treatment planning.³ 

Individualised treatment plans

Depending on the frequency and intensity of an individual's episodes, treatment plans must be customised to meet their needs. Mood stabilisers like valproate or lithium may help lessen the frequency of episodes, while stimulant drugs like modafinil may be provided to some individuals during episodes to encourage wakefulness.² However, the effectiveness of these drugs can vary considerably, and many patients experience only limited alleviation from their symptoms.

Because KLS episodes are unpredictable, treatment methods must be adaptable and heavily emphasise patient and caregiver education to modify therapies as symptoms change over time.¹

Multidisciplinary care approach

Due to the multifaceted nature of KLS, a multidisciplinary approach is necessary for optimal management. Neurologists, psychiatrists, and sleep specialists must work together to address it. From treating the disorder's psychological and social effects to managing neurological symptoms, each doctor offers a distinct perspective.⁴ This kind of cooperation guarantees comprehensive treatment, including cognitive behavioural therapy, medication, and social support networks, in addition to increasing diagnostic precision.

Challenges and future directions

Gaps in research and evidence

Despite growing awareness, many unanswered questions remain about KLS and its management. Large-scale clinical studies are rare, and the majority of currently available material consists of case reports and retrospective reviews.² Because of this, there is not a single, widely recognised standard of care, and therapy choices are frequently decided on an individual basis. Furthermore, the pathogenesis of KLS remains unknown. The results are insufficiently definitive to direct targeted therapy, despite several neuroimaging studies detecting thalamic and hypothalamic dysfunctions during episodes.⁴

Promising avenues for future treatment

New studies have begun investigating the potential genetic and immunological causes of KLS. According to specific case studies and observational reports, autoimmune mechanisms may be at play, particularly in patients who have previously experienced viral infections before the onset.⁵ Immunomodulatory treatments have gained attention as a result, even though clinical validation is still in its infancy. Additionally, although no specific gene has been identified yet, genetic research is being conducted to investigate potential hereditary components. To develop trustworthy diagnostic instruments that can detect or forecast KLS episodes before the onset of clinical symptoms, research is being done on biomarkers, such as those identified through proteome analysis.³

Summary

KLS is an uncommon and complex neurological condition characterised by periodic attacks of hypersomnia, mental impairment, and behavioural abnormalities. No definitive treatment exists, but several treatment approaches (e.g., the use of stimulants to provoke wakefulness, mood stabilisers to reduce episode frequency, and antipsychotics for behavioural control) can provide symptomatic benefits depending on the individual requirements of patients. Long-term care requires meticulous documentation of episodes, including sleep diaries or devices, and is best supported by a multidisciplinary team of neurologists, psychiatrists, and sleep specialists. Awareness among medical personnel and the general population is crucial to ensure early diagnosis, reduce misdiagnosis, and support individuals and their families affected by the condition. While ongoing research remains in its infancy, promising fields such as immunotherapy, genetic studies, and the discovery of biomarkers are creating new hope for future advances in diagnosis and treatment. With continued scientific inquiry and public awareness, growing optimism exists regarding better control and improved quality of life in individuals with KLS.