A patient with coexisting narcolepsy and morbid jealousy showing favourable response to fluoxetine

The familial risk and HLA susceptibility among narcolepsy patients in Hong Kong Chinese

STUDY OBJECTIVES

To explore the familial aggregation and HLA susceptibility of narcolepsy in Hong Kong Chinese by objective sleep measurements and HLA typing.

DESIGN

Case control design

PARTICIPANTS

Twelve narcoleptic probands, 34 first-degree relatives, and 30 healthy controls.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Each subject underwent a standardized nocturnal polysomnogram (PSG), followed by a daytime multiple sleep latency test (MSLT). HLA typing was performed for all subjects. One relative (2.9%) was diagnosed as suffering from narcolepsy with cataplexy. Nearly 30% of the relatives fulfilled the criteria of narcolepsy spectrum disorder (shortened mean sleep latency [MSL] and/or the presence of sleep onset REM periods [SOREMPs]). When using the population data for comparison, the relative risk of narcolepsy in first-degree relatives was 85.3. The odds ratio of narcolepsy spectrum disorder in first-degree relatives was 5.8 (95% CI: 1.2 - 29.3) when compared to healthy controls. There existed 6 multiplex families, in which all 10 relatives with narcolepsy spectrum disorders, including all 3 relatives with multiple SOREMPs, were positive for HLA DQB1*0602.

CONCLUSIONS

Our study demonstrated a definitive familial aggregation of narcolepsy, narcolepsy spectrum disorders, and possibly cataplexy in Hong Kong Chinese. This familial aggregation supported an inherited basis for narcolepsy spectrum. The tight co-segregation of HLA DQB1*0602 and narcolepsy spectrum disorders might suggest that HLA typing, especially DQB1*0602, at least partly confer the familial risk of narcolepsy. In addition, our study suggested that the subjective questionnaire measurements including Ullanlinna Narcolepsy Scale and Epworth Sleepiness Scale were unable to detect the presence of narcolepsy spectrum disorders among the relatives. A stringent objective measurement-based design for family studies is suggested for future study. Further studies are indicated for the determination of the mode and molecular level of narcolepsy transmission.

Sodium oxybate for the treatment of narcolepsy

Narcolepsy, a lifelong disease with diverse symptoms, poses a therapeutic challenge to physicians. Psychomotor stimulants are used to provide some relief from excessive sleepiness, whereas a variety of other medications have traditionally been used to treat the other symptoms of this disorder. Cataplexy, consisting of sudden episodes of bilateral skeletal muscle weakness, has long been treated with tricyclic antidepressants or selective serotonin re-uptake inhibitors. Although these drugs have brought relief to some patients, they cause intolerable adverse effects in others, whereas still others become tolerant to their beneficial effects. In July of 2002, sodium oxybate was approved by the US FDA for the treatment of cataplexy, representing a significant advance in the treatment of this unusual disease. The following drug evaluation summarises the role of this novel medication in the practice of sleep medicine.

Pharmacotherapy for cataplexy

A variety of medications representing several major drug classes improve cataplexy in patients with narcolepsy. These include aminergic reuptake inhibitors such as venlafaxine and clomipramine as well as sodium oxybate. This review is intended to familiarize readers with the safety and efficacy of these medications, thus enabling clinicians to optimize their management of cataplexy.

A review of sex differences in sexual jealousy, including self-report data, psychophysiological responses, interpersonal violence, and morbid jealousy

The specific innate modular theory of jealousy hypothesizes that natural selection shaped sexual jealousy as a mechanism to prevent cuckoldry, and emotional jealousy as a mechanism to prevent resource loss. Therefore, men should be primarily jealous over a mate's sexual infidelity and women over a mate's emotional infidelity. Five lines of evidence have been offered as support: self-report responses, psychophysiological data, domestic violence (including spousal abuse and homicide), and morbid jealousy cases. This article reviews each line of evidence and finds only one hypothetical measure consistent with the hypothesis. This, however, is contradicted by a variety of other measures (including reported reactions to real infidelity). A meta-analysis of jealousy-inspired homicides, taking into account base rates for murder, found no evidence that jealousy disproportionately motivates men to kill. The findings are discussed from a social-cognitive theoretical perspective.

The prevalence of narcolepsy among Chinese in Hong Kong

Narcolepsy is a lifelong, crippling sleep disorder. Although the discovery of the hypocretin system has been a breakthough in genetics, the epidemiological aspects of narcolepsy remain elusive. Ethnic predisposition was suggested to partially account for the 2,500-fold difference in the reported prevalence rates of narcolepsy between Japanese (0.59%) and Israeli Jews (0.00023%). We carried out a general population study, conducting a random telephone survey with a structured questionnaire, which included a validated screening instrument (a Chinese version of the Ullanlinna Narcolepsy Scale). It was followed by clinical-polysomnographic-HLA confirmation of the subjects determined to be positive for narcolepsy based on the questionnaire. Of 9,851 subjects interviewed, 28 subjects (0.28%, 58% female) were screened positive. Ninety percent had a second detailed interview, 64% had HLA typing, and over half of them had a sleep assessment. Only three subjects were found to have genuine narcolepsy. The most common nonnarcolepsy diagnoses were sleep apnea syndrome and sleep-wake schedule disorder. The prevalence rate of narcolepsy in Southern (Hong Kong) Chinese was found to be 0.034% (95% confidence interval = 0.010-0.117%). All available narcoleptic subjects were HLA DRB1-1501 positive and 50% were DQB1-0602 positive. The prevalence rate of narcolepsy among Chinese is comparable to the rates for other populations in studies with stringent epidemiological designs, suggesting that major cross-ethnic differences in the prevalence rates of narcolepsy previously reported likely resulted from methodological limitations.

HLA DR2 and DQ1 frequency among narcoleptic patients in Hong Kong Chinese

Narcolepsy is a life-long crippling sleep disorder with significant physical and psychosocial impairments. Although its exact etiology and neuropathology is not clear, a strong association with specific human leucocyte antigen (HLA) subtype, particularly DR2 (DRw15) and DQw1 (DQw6), has been demonstrated across different ethnic groups including Caucasians and Japanese. The presence of 100% association with HLA DR2 in a series of Hong Kong Chinese narcoleptic patients has previously been reported. The report can now be extended, and as far as could be ascertained in the available subjects, all were HLA DQw1 (DQw6)-positive. This is concordant with the experiences of Japanese narcoleptic patients who are 100% HLA DR2- and DQw1-positive. However, the definitive account of the population prevalence of narcolepsy in Chinese could be determined only by a well-conducted epidemiological study with laboratory confirmation.

Successful treatment of post-traumatic narcolepsy with methylphenidate: a case report

Narcolepsy is a rare sequela of brain injury. We report the case of a 27-yr-old male with post-traumatic narcolepsy who was successfully treated with methylphenidate. This patient sustained moderate brain injury from a motorcycle accident. Subsequently, he manifested the classic tetrad of narcolepsy: cataplexy, excessive daytime sleepiness, sleep paralysis, and hypnogogic hallucinations. There was no premorbid seizure or sleep disorder. There was no family history of sleep disorders. Polysomnography and Multiple Sleep Latency Test confirmed the diagnosis of narcolepsy. Sleep latency (time to sleep onset), rapid eye movement sleep latency (time from sleep onset to rapid eye movement sleep onset), and mean multiple sleep latency were all pathologically shortened (2.5, 66, and 1.2 min, respectively). Twenty-four hour electroencephalographic monitoring and magnetic resonance imaging of the brain were normal, as were serum chemistries. Treatment with caffeine was unsuccessful. He was then started on methylphenidate, 10 mg twice daily, which was increased to 30 mg twice daily over a 4-mo period. Cataplexy and excessive daytime sleepiness started to improve 1 mo after adjustments in methylphenidate dosing. Six months after the initiation of methylphenidate therapy, the patient is completely asymptomatic.

Narcolepsy in Hong Kong Chinese--a preliminary experience

BACKGROUND

Narcolepsy is a sleep disorder of unknown aetiology. Despite the widely reported strong association with HLA DR2 among different ethnic groups and their varying prevalence rates, there has never been any series of laboratory documented narcolepsy in Chinese.

AIMS

To report the preliminary experience with Chinese narcoleptic patients and their HLA typing.

METHODS

The records of 342 patients who presented to our sleep laboratory for various sleep problems from 1986 to 1992 were examined. Both clinical and polysomnographic data were analysed. The criteria for a diagnosis of narcolepsy is based on shortened mean sleep latency of less than 5 minutes and presence of rapid eye movement (REM) sleep in two or more of the five 20-minute naps during multiple sleep latency test (MSLT).

RESULTS

There were five narcoleptic patients documented resulting in an overall laboratory prevalence of 1.5% or 2.3% of patients presenting with hypersomnia. All patients were HLA DR2 positive.

CONCLUSION

There is 100% association with HLA DR2 in Hong Kong Chinese narcoleptic patients. Based on the laboratory prevalence, the prevalence rate of narcolepsy among Hong Kong Chinese population is estimated to be within the range of four in 10,000 to one in 100,000.