HLA DR2 in narcolepsy with sleep-onset REM periods but not cataplexy

A validity study of Ullanlinna Narcolepsy Scale in Hong Kong Chinese

OBJECTIVE

To validate the Chinese version of Ullanlinna Narcolepsy Scale (CUNS).

METHODS

A total of 234 subjects [163 male (69.7%) and 71 female (30.3%)] including 17 patients with narcolepsy, 21 normal controls and 196 patients with various sleep and psychiatric disorders were studied. The diagnoses of these patients were independently ascertained with sleep laboratory confirmation whenever indicated. All the subjects were interviewed through the telephone by a trained lay interviewer who was blind to the diagnosis. The questionnaire included demographic information, sleep habits and CUNS.

RESULTS

Narcoleptic patients had a significantly higher CUNS score (18.6+/-4.7; 95% confidence interval (CI) 16.2-21.0) and differentiated well from all the other groups (F(6,227)=28.4, P<0.001). The CUNS has a satisfactory internal consistency with Cronbach's alpha of 0.75. The principal component analysis with varimax rotation revealed two factors, namely sleepiness and cataplexy factors, which accounted for 45.5% of the total variance. The best cut-off point for the CUNS scale was found to be at 13/14 with high specificity (93.5%), sensitivity (94.1%), negative predictive value (NPV, 99.5%) and modest positive predictive value (PPV, 53.3%). The AUC of receiver operating characteristic (ROC) analysis was 0.97 (95% CI 0.95-0.99).

CONCLUSIONS

The CUNS was validated with satisfactory psychometric properties. The cross-cultural validation of UNS scale suggested that it could be used across the ethnic groups.

Sleep onset REM periods during multiple sleep latency tests in patients evaluated for sleep apnea

Although 2 or more sleep onset rapid eye movement (REM) periods (2omSOREMPs) on a Multiple Sleep Latency Test (MSLT) raise the possibility of narcolepsy, patients with obstructive sleep apnea (OSA) also can have 2omSOREMPs, which may then cause diagnostic uncertainty. To explore what features among OSA patients predict 2omSOREMPs on an MSLT that follows nocturnal polysomnography, we reviewed data from 1,145 consecutively studied patients suspected or confirmed to have OSA rather than narcolepsy. Overall, 4.7% of the subjects had 2omSOREMPs. Variables that were independently predictive of 2omSOREMPs in logistic regression models included male gender (OR = 4.4, 95% CI = 1.9 to 12.7), a 5-min decrease in the MSLT-derived mean sleep latency (OR = 1.9, 95% CI = 1.3 to 2.8), a 90-min decrease in nocturnal latency to REM sleep (OR = 1.6, 95% CI = 1.1 to 2.5), and a 15-unit decrease in minimal recorded oxygen saturation (OR = 1.6, 95% CI = 1.3 to 2.0). We conclude that among patients suspected or confirmed to have OSA, one or more of these four variables-male sex, sleepiness, nocturnal REM sleep latency, and extent of oxygen desaturation-could reflect neurophysiological mechanisms responsible for 2omSOREMPs. Consideration of these variables, and especially gender, may be useful in clinical practice when 2omSOREMPs are found unexpectedly.

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.

Pharmacological aspects of human and canine narcolepsy

Narcolepsy-cataplexy is a disabling neurological disorder that affects 1/2000 individuals. The main clinical features of narcolepsy, excessive daytime sleepiness and symptoms of abnormal REM sleep (cataplexy, sleep paralysis, hypnagogic hallucinations) are currently treated using amphetamine-like compounds or modafinil and antidepressants. Pharmacological research in the area is facilitated greatly by the existence of a canine model of the disorder. The mode of action of these compounds involves presynaptic activation of adrenergic transmission for the anticataplectic effects of antidepressant compounds and presynaptic activation of dopaminergic transmission for the EEG arousal effects of amphetamine-like stimulants. The mode of action of modafmil is still uncertain, and other neurochemical systems may offer interesting avenues for therapeutic development. Pharmacological and physiological studies using the canine model have identified primary neurochemical and neuroanatomical systems that underlie the expression of abnormal REM sleep and excessive sleepiness in narcolepsy. These involve mostly the pontine and basal forebrain cholinergic, the pontine adrenergic and the mesolimbic and mesocortical dopaminergic systems. These studies confirm a continuing need for basic research in both human and canine narcolepsy, and new treatments that act directly at the level of the primary defect in narcolepsy might be forthcoming.