Kleine–Levin syndrome in a 14-year-old girl: CSF hypocretin-1 measurements

Kleine-Levin syndrome. Clinical boarderlands based on a thorough analysis of 475 case reports

OBJECTIVE/BACKGROUND

Kleine-Levin syndrome (KLS) is a rare sleep disorder characterized by recurrent episodes of severe hypersomnolence in association with various degrees of cognitive impairment, perceptive abnormalities, apathy, behavioral disturbances. Some of these symptoms, hypersomnolence, compulsive eating and increased sexual drive may be replaced by their opposites or alternate with them. Remarkably enough, these « atypical symptoms » have never been enlighted nor compared in frequency with corresponding typical symptoms. Besides, KLS is more frequent in males than in females but no review has ever compared the frequency of precipitating factors and symptoms in males and females.

PATIENTS/METHODS

To uncover these as yet uninvestigated aspects of KLS, a predesigned template was used to extract precipitating factors and symptoms, in 475 case reports of KLS, comprising 364 males and 111 females.

RESULTS

Precipitating factors were more frequently recorded in males (67.31 %) than in females (49.55 %). Recurrent episodes of hypersomnolencee were present in 94.32 % of cases, recurrent insomnia in 1.05 % and alternation of hypersomnolence and insomnia in 4.63 %. Cognitive impairment was present in 67.37 % of cases and absent in 6.95 %. Derealization/altered perception was present in 38.32 % of cases and absent in 1.68 %. Severe apathy was present in 44.63 % of cases. Compulsive eating was present in 59.58 % of cases, absent in 13.26 %, replaced by anorexia in 9.05 %, alternation of compulsive eating and anorexia in 5.68 % and alternation of compulsive eating and no compulsive eating in 8.42 %. Increased sexual drive was present in 33.68 % of cases, absent in 22.74 %, replaced by decreased sexual drive in 1.47 %, alternation of increased sexual drive and no increased sexual drive in 2.95 %. Odd behaviors were present in 45.05 % of cases. Psychiatric features were present in 71.58 % of cases, absent in 2.95 %. Finally, the percentages of precipitating factors and of sleep disorder, apathy, sexual disorder, irritability/agressivity, were higher in males than in females.

CONCLUSIONS

The frequency of the opposites of hypersomnolence, compulsive eating and increased sexual drive appears to be quite significant. In addition, a systematic comparison of precipitating factors and symptoms in males and females has shown limited differences between sexes.

Sleep medicine, sleep research, and sleep education: a whole life devoted to sleep

This article describes my participation in sleep medicine, sleep research, and sleep education, mainly in Europe, between the years 1970 and 2000.

The orexin story, sleep and sleep disturbances

The orexins, also known as hypocretins, are two neuropeptides (orexin A and B or hypocretin 1 and 2) produced by a few thousand neurons located in the lateral hypothalamus that were independently discovered by two research groups in 1998. Those two peptides bind two receptors (orexin/hypocretin receptor 1 and receptor 2) that are widely distributed in the brain and involved in the central physiological regulation of sleep and wakefulness, orexin receptor 2 having the major role in the maintenance of arousal. They are also implicated in a multiplicity of other functions, such as reward seeking, energy balance, autonomic regulation and emotional behaviours. The destruction of orexin neurons is responsible for the sleep disorder narcolepsy with cataplexy (type 1) in humans, and a defect of orexin signalling also causes a narcoleptic phenotype in several animal species. Orexin discovery is unprecedented in the history of sleep research, and pharmacological manipulations of orexin may have multiple therapeutic applications. Several orexin receptor antagonists were recently developed as new drugs for insomnia, and orexin agonists may be the next-generation drugs for narcolepsy. Given the broad range of functions of the orexin system, these drugs might also be beneficial for treating various conditions other than sleep disorders in the near future.

The orexin/hypocretin system in neuropsychiatric disorders: Relation to signs and symptoms

Hypocretin-1 and 2 (or orexin A and B) are neuropeptides exclusively produced by a group of neurons in the lateral and dorsomedial hypothalamus that project throughout the brain. In accordance with this, the two different hypocretin receptors are also found throughout the brain. The hypocretin system is mainly involved in sleep-wake regulation, but also in reward mechanisms, food intake and metabolism, autonomic regulation including thermoregulation, and pain. The disorder most strongly linked to the hypocretin system is the primary sleep disorder narcolepsy type 1 caused by a lack of hypocretin signaling, which is most likely due to an autoimmune process targeting the hypocretin-producing neurons. However, the hypocretin system may also be affected, but to a lesser extent and less specifically, in various other neurological disorders. Examples are neurodegenerative diseases such as Alzheimer's, Huntington's and Parkinson's disease, immune-mediated disorders such as multiple sclerosis, neuromyelitis optica, and anti-Ma2 encephalitis, and genetic disorders such as type 1 diabetus mellitus and Prader-Willi Syndrome. A partial hypocretin deficiency may contribute to the sleep features of these disorders.

Kleine-Levin syndrome: clues to aetiology

Kleine-Levin syndrome (KLS) is the commonest recurrent sleep disorder, with a prevalence of 1-2 per million population. Clear diagnostic criteria are now defined, but effective treatment remains elusive. The significant body of published literature allows consideration of possible aetiological mechanisms, an understanding of which could guide the development of therapeutic strategies. Functional imaging studies have been inconclusive; although diencephalic abnormalities are a common finding, no consistent pattern has emerged, and these studies have not revealed the mechanism(s) underlying the development of the abnormalities detected. An autoimmune aetiology is consistent with the available data. In this review, we argue that, in order to further our understanding of KLS, there needs to be a co-ordinated international effort to standardise approaches to functional imaging studies, genetic analyses that specifically address the possibility of an autoimmune aetiology, and clinical trials of immunosuppressive therapies.

The "Known Unknowns" of Kleine-Levin Syndrome: A Review and Future Prospects

Kleine-Levin syndrome (KLS) is a rare, homogeneous, debilitating sleep disorder characterized by episodic hypersomnia, cognitive impairment, and behavioral changes. The etiology, pathophysiology, and optimal management of KLS remain uncertain. We identify the 5 key areas requiring urgent attention: KLS immunopathogenesis studies, next-generation genetics, multimodal functional imaging, biomarker discovery, and clinical drug trials. A centralized registry of afflicted individuals must be established. Disease uniformity should make the identification of associated genetic or imaging biomarkers easier, but clinical efforts require laboratory-based research to model the disease and generate preclinical data for clinical translation.

Cerebrospinal Fluid Orexin A Levels and Autonomic Function in Kleine-Levin Syndrome

STUDY OBJECTIVES

Kleine-Levin syndrome (KLS) is a rare disorder of relapsing sleepiness. The hypothesis was that the syndrome is related to a change in the vigilance peptide orexin A.

METHODS

From 2002 to 2013, 57 patients with relapsing hypersomnolence were clinically assessed in a referral academic center in Beijing, China, and 44 (28 males and 16 females; mean age 18.3 ± 8.9 y (mean ± standard deviation, range 9-57 y) were determined to have clinical and behavioral criteria consistent with KLS. Cerebrospinal fluid orexin A levels and diurnal blood pressure were measured in relapse versus remission in a subgroup of patients.

RESULTS

Presenting symptoms included relapsing or remitting excessive sleepiness-associated parallel complaints of cognitive changes (82%), eating disorders (84%); depression (45%); irritability (36%); hypersexuality (18%); and compulsions (11%). Episodes were 8.2 ± 3.3 days in duration. In relapse, diurnal values for blood pressure and heart rate were lower (P < 0.001). In a subgroup (n = 34), cerebrospinal fluid orexin A levels were ∼31% lower in a relapse versus remission (215.7 ± 81.5 versus 319.2 ± 95.92 pg/ml, P < 0.001); in three patients a pattern of lower levels during subsequent relapses was documented.

CONCLUSIONS

There are lower orexin A levels in the symptomatic phase than in remission and a fall and rise in blood pressure and heart rate, suggesting a role for orexin dysregulation in KLS pathophysiology.

SPECT in the Kleine-Levin Syndrome, a Possible Diagnostic and Prognostic Aid?

Introduction: Kleine–Levin syndrome (KLS) is a rare syndrome of periodic hypersomnia and behavioral and cognitive symptoms based on clinical criteria. In the setting of differential diagnosis of hypersomnia disorders, an objective diagnostic aid is desirable. A promising modality is single photon emission computed tomography (SPECT). As intraepisodal investigations are difficult to perform, an interepisodal investigation would be very helpful. Another aim of the study was to correlate SPECT findings to prognosis.

Methods and Materials: Twenty-four KLS-patients were categorized as severe or non-severe based on clinical characteristics. The clinical characteristics were analyzed in relation to SPECT-examinations performed between hypersomnia periods (interepisodal) or after remission, as a clinical routine investigation.

Results: Forty-eight percent of the KLS-patients have hypoperfusion in the temporal or fronto-temporal regions. In patients that have undergone remission, 56% show that pattern. There were no specific findings related to prognosis.

Discussion/Conclusion: SPECT might be a diagnostic aid, in a setting of hypersomnia experience. With a sensitivity of 48%, interepisodal SPECT alone cannot be used for diagnosing KLS.

Cerebrospinal fluid hypocretin-1 levels during the active period of cluster headache

Background: Hypocretins (orexins) are hypothalamic neuropeptides which are involved in a wide range of physiological processes in mammals including central pain processing. Genetic studies in humans evidenced a role for the hypocretinergic system in cluster headache (CH).

Patients and methods: We tested cerebrospinal fluid (CSF) hypocretin-1 (orexin-A) levels in 10 CH patients during an active cluster period. CSF hypocretin-1 levels were measured by radioimmunoassay.

Results: CSF hypocretin-1 levels were within the normal range (mean 457.3 ± 104.98 pg/ml, range 304–639) in our 10 patients, with a slight reduction in one case (304 pg/ml). There were no associations between CSF hypocretin-1 levels and the clinical features of CH. A trend towards higher hypocretin-1 levels was disclosed in patients with chronic CH compared to episodic CH.

Conclusions: CSF hypocretin-1 levels seem not to influence the clinical course of CH, but our results cannot completely exclude a functional involvement of the hypothalamic hypocretinergic system in the pathogenesis of CH.