Narcolepsy with cataplexy and pregnancy: a case–control study

This was a retrospective case–control study in 25 patients with narcolepsy with cataplexy and 75 women in the control group. Patients completed the questionnaire by Maurovich‐Horvat et al. (J. Sleep Res., 2013, 22: 496–512). We personally interviewed 25 patients with narcolepsy with cataplexy using the administered questionnaire regarding conception, pregnancy, delivery, perinatal and breastfeeding periods. Patients with narcolepsy with cataplexy reported 59 pregnancies versus 164 in the control group. In 16 cases (27.1%), a disease before pregnancy was present compared with eight cases (4.9%) in the control group (P < 0.001); among them, extrinsic asthma was reported 11 times in the narcolepsy with cataplexy group (P < 0.005). Patients with narcolepsy with cataplexy more often had a single pregnancy compared with controls (P < 0.05). Gestational diabetes was more frequent in patients with narcolepsy with cataplexy (P < 0.05). Induced deliveries were higher in controls (P < 0.009). No differences were found between the groups in terms of duration of pregnancies and complications during and after delivery, as during the puerperium. Neonates from patients had heavier birth weight (P < 0.015). The breastfeeding period was longer in patients (P < 0.01). Modafinil and methylphenidate were the drugs administered in six pregnancies. No significant differences in depression during pregnancy and during puerperium were found between patients and controls. This is the first case–control study in women with narcolepsy with cataplexy related to pregnancy, delivery, childbirth and puerperium. Data suggest that patients have pregnancy outcomes similar to controls. The prevalence of gestational diabetes was higher in women with narcolepsy with cataplexy. Caesarean sections, complications during delivery and normal perinatal period for infants were similar in both groups. Breastfeeding was longer in patients.     

A critical role of hypocretin deficiency in pregnancy

Hypocretin/orexin peptides are known for their role in the control of the wake–sleep cycle and narcolepsy–cataplexy pathophysiology. Recent studies suggested that hypocretin peptides also have a role in pregnancy. We tested this hypothesis by conducting a retrospective analysis on pregnancy complications in two different mouse models of hypocretin deficiency. We recorded 85 pregnancies of mice lacking either hypocretin peptides (knockout) or hypocretin‐releasing neurons (transgenic) and their wild‐type controls. Pregnancy was associated with unexplained dam death before delivery in 3/15 pregnancies in knockout mice, and in 3/23 pregnancies in transgenic mice. No casualties occurred in wild‐type pregnant dams (P < 0.007 versus hypocretin‐deficient mice as a whole). Hypocretin deficiency did not impact either on litter size or the number of weaned pups per litter. These data provide preliminary evidence of a critical role of hypocretin deficiency in pregnancy.     

Effect of sodium oxybate on disrupted nighttime sleep in patients with narcolepsy

This post hoc analysis evaluated the dose‐related effects of sodium oxybate on sleep continuity and nocturnal sleep quality in patients with narcolepsy–cataplexy. Polysomnography data, including shifts to Stage N1/Wake, were from a randomized, placebo‐controlled trial of sodium oxybate. Patients were ≥16 years old with a diagnosis of narcolepsy including symptoms of cataplexy and excessive daytime sleepiness. Treatment was for 8 weeks with placebo or sodium oxybate 4.5, 6 or 9 g administered as two equally divided nightly doses. Relative to baseline, significant dose‐dependent reductions in the number of shifts per hour from Stages N2/3/rapid eye movement and Stages N2/3 to Stage N1/Wake were observed at week 8 with sodium oxybate (P < 0.05); sodium oxybate 6‐ and 9‐g doses also resulted in similar reductions in shifts per hour of rapid eye movement to Stage N1/Wake (both P < 0.05). Across all shift categories, the shift reductions with sodium oxybate 9 g were significantly greater than those observed with placebo (P < 0.05). Improvements from baseline in reported sleep quality were significantly greater with sodium oxybate 4.5 and 9 g at week 8 (P < 0.05). Correlations between change from baseline in number of shifts per hour to Stage N1/Wake and cataplexy frequency, patient‐reported nocturnal sleep quality, and excessive daytime sleepiness assessed using the Epworth Sleepiness Scale were numerically highest for the sodium oxybate 9‐g dose across all sleep stage shift categories. In these patients with narcolepsy, sodium oxybate showed improvements in the sleep continuity and nocturnal sleep quality that are characteristic of disrupted nighttime sleep ( ClinicalTrials.gov identifier NCT00049803).     

Narcolepsy with cataplexy and comorbid immunopathological diseases

Evidence suggests that autoimmune diseases tend to co‐occur so that patients with an autoimmune disorder are at higher risk of a second autoimmune disease. The association between allergic and autoimmune diseases is also of considerable interest. There are no reports on the association between sporadic or familial narcolepsy with cataplexy and other non‐neurological immune‐mediated diseases. This study reported on the comorbid immunopathological diseases associated with narcolepsy. One‐hundred and fifty six narcoleptic patients with a mean age at diagnosis of 39.1 ± 17.8 years (range, 6–70 years) were assessed using the clinical history, physical and neurological examinations, sleep questionnaires, neuroimaging and human leucocyte antigen typing. Diagnosis was confirmed by polysomnography followed by a multiple sleep latency test or by measuring hypocretin‐1 levels. Patients with immunopathological diseases were matched for gender and age at the onset of narcoleptic symptoms with narcoleptic patients without immunopathological diseases. Twenty‐six patients (16.6%; 50% women; one familial, 25 sporadic) had one or more immunopathological diseases associated: autoimmune diseases, such as idiopathic thrombocytopenic purpura, multiple sclerosis, systemic lupus erythematosus, psoriasis, Crohn's disease, ulcerative colitis, autoimmune thyroid disease, Peyronie's disease and idiopathic recurrent facial palsy; other immunopathological diseases, like atopic dermatitis, allergic asthma and allergic rhinitis. Although not significant, the age at diagnosis of narcolepsy was 9.3 years earlier in patients with narcolepsy + immunopathological diseases. The results demonstrate that the prevalence of comorbid immunopathological diseases is high in narcolepsy, and cataplexy is significantly more severe in patients with narcolepsy + immunopathological diseases.     

Multiple sleep latency test in narcolepsy type 1 and narcolepsy type 2: A 5‐year follow‐up study

Excessively sleepy teenagers and young adults without sleep‐disordered breathing are diagnosed with either narcolepsy type 1 or narcolepsy type 2, or hypersomnia, based on the presence/absence of cataplexy and the results of a multiple sleep latency test. However, there is controversy surrounding this nomenclature. We will try to find the differences between different diagnoses of hypersomnia from the results of the long‐term follow‐up evaluation of a sleep study. We diagnosed teenagers who had developed excessive daytime sleepiness based on the criteria of the International Classification of Sleep Disorders, 3rd edition. Each individual received the same clinical neurophysiologic testing every year for 5 years after the initial diagnosis of narcolepsy type 1 (n = 111) or type 2 (n = 46). The follow‐up evaluation demonstrated that narcolepsy type 1 (narcolepsy‐cataplexy) is a well‐defined clinical entity, with very reproducible clinical neurophysiologic findings over time, whereas patients with narcolepsy type 2 presented clear clinical and test variability. By the fifth year of the follow‐up evaluation, 17.6% of subjects did not meet the diagnostic criteria of narcolepsy type 2, and 23.9% didn't show any two sleep‐onset rapid eye movement periods in multiple sleep latency during the 5‐year follow‐up. Therefore narcolepsy type 1 (narcolepsy‐cataplexy) is a well‐defined syndrome, with the presentation clearly related to the known consequences of destruction of hypocretin/orexin neurons. Narcolepsy type 2 covers patients with clinical and test variability over time, thus bringing into question the usage of the term “narcolepsy” to label these patients.     

Diurnal changes in blood pressure and heart rate in children with narcolepsy with cataplexy

The hypocretin neurons in the lateral hypothalamus are connected not only to brain alertness systems but also to brainstem nuclei that regulate blood pressure and heart rate. The premise is that regulation of blood pressure and heart rate is altered and affected by methylphenidate, a stimulant drug in children with narcolepsy with cataplexy. The changes in 24-hr ambulatory systolic and diastolic blood pressure and heart rate were compared among pre-treated narcolepsy with cataplexy patients (40 males, 10 females), with mean age 10.4 ± 3.5 years (M ± SD, range 5–17 years) with values from 100 archival age–sex–body mass index matched controls. Patients had a lower diurnal systolic blood pressure (−6.5 mmHg; p = 0.000) but higher heart rate (+11.0 bpm; p = 0.000), particularly evident in the waketime, while diastolic blood pressure was comparable. With methylphenidate (18 mg sustained release at 08:00 hours), patients with narcolepsy with cataplexy had higher systolic blood pressure (+4.6 mmHg, p = 0.015), diastolic blood pressure (+3.3 mmHg, p = 0.005) and heart rate (+7.1 bpm, p = 0.028) during wake time, but nighttime cardiovascular values were unchanged from pre-treated values; amplitude variation in cardiovascular values was unchanged over 24 hr. In conclusion, children with narcolepsy with cataplexy had downregulation blood pressure profile but a higher heart rate, and lesser non-dipping profiles. Daytime methylphenidate treatment increases only waketime blood pressure and further elevated heart rate values.     

Improved vigilance after sodium oxybate treatment in narcolepsy: a comparison between in‐field and in‐laboratory measurements

This two‐centre observational study of vigilance measurements assessed the feasibility of vigilance measurements on multiple days using the Sustained Attention to Response Task and the Psychomotor Vigilance Test with portable task equipment, and subsequently assessed the effect of sodium oxybate treatment on vigilance in patients with narcolepsy. Twenty‐six patients with narcolepsy and 15 healthy controls were included. The study comprised two in‐laboratory days for the Maintenance of Wakefulness Test and the Oxford Sleep Resistance test, followed by 7‐day portable vigilance battery measurements. This procedure was repeated for patients with narcolepsy after at least 3 months of stable treatment with sodium oxybate. Patients with narcolepsy had a higher Sustained Attention to Response Task error count, lower Psychomotor Vigilance Test reciprocal reaction time, higher Oxford Sleep Resistance test omission error count adjusted for test duration (Oxford Sleep Resistance test_OMIS/MIN), and lower Oxford Sleep Resistance test and Maintenance of Wakefulness Test sleep latency compared with controls (all P < 0.01). Treatment with sodium oxybate was associated with a longer Maintenance of Wakefulness Test sleep latency (P < 0.01), lower Oxford Sleep Resistance test_OMIS/MIN (P = 0.01) and a lower Sustained Attention to Response Task error count (P = 0.01) in patients with narcolepsy, but not with absolute changes in Oxford Sleep Resistance test sleep latency or Psychomotor Vigilance Test reciprocal reaction time. It was concluded that portable measurements of sustained attention as well as in‐laboratory Oxford Sleep Resistance test and Maintenance of Wakefulness Test measurements revealed worse performance for narcoleptic patients compared with controls, and that sodium oxybate was associated with an improvement of sustained attention and a better resistance to sleep.     

The clinical diagnosis of the narcoleptic syndrome

Sleep–wake habits and control of postural muscle tone were investigated by self-report questionnaire in 183 subjects considered to have the narcoleptic syndrome, 62 subjects with hypersomnia and 10 with obstructive sleep apnoea. Results were compared with those in a group of 188 control subjects with normal sleep–wake habits. Excessive daytime sleepiness, determined by the Epworth Sleepiness Scale (ESS), was five times greater in the narcoleptic syndrome than in control subjects (score range 0–24, mean scores ±SD 19.6±3.0; and 4.5±3.3 respectively; P<0.001). The propensity to cataplexy, as determined by a rating scale developed to estimate the likelihood of loss of postural tone in response to sudden emotional stimuli, including laughter, was 10 times greater in narcoleptic syndrome than in control subjects (postural atonia total score range 0–600; mean±SD 334±122 and 28±45, respectively; P<0.001). Narcoleptics had more disturbances of night sleep than controls with episodes of muscle jerking, sleep walking, sleep talking and sleep terrors, as well as sleep paralysis, and higher insomnia self-rating scores. Sleep latency from bedtime to sleep-onset time was shorter in narcoleptics than controls. The hypersomniac group of 62 subjects was heterogeneous. Subsequent investigation showed that 18 subjects (29%) had idiopathic hypersomnia, four (6%) ‘incomplete’ narcolepsy without cataplexy and 10 (16%) hypersomnia accompanying a mood disorder. The mean ESS scores in this group and in subjects with obstructive sleep apnoea were comparable to those of the narcoleptic syndrome subject group. Mean postural atonia scores were similar to those of control subjects.     

Body Mass Index-Independent Metabolic Alterations in Narcolepsy with Cataplexy

Study Objectives:

To contribute to the anthropometric and metabolic phenotyping of orexin-A–deficient narcoleptic patients, and to explore a possible risk of their developing a metabolic syndrome.

Design:

We performed a cross-sectional study comparing metabolic alterations in patients with narcolepsy with cataplexy (NC) and patients with idiopathic hypersomnia without long sleep time.

Setting:

University hospital.

Patients:

Fourteen patients with narcolepsy with cataplexy and 14 sex and age-matched patients with idiopathic hypersomnia without long sleep time.

Interventions:

N/A.

Measurements and results:

Metabolic parameters were evaluated by measuring body mass index (BMI), waist circumference (also with abdominal computed tomography), blood pressure, and daily calorie intake (3-day diary). Chronotypes were assessed through the morningness-eveningness questionnaire. Lumbar puncture for cerebrospinal fluid orexin-A determination and HLA typing were performed. Patients with narcolepsy with cataplexy (all HLA DQB1*0602 positive and with cerebrospinal fluid orexin-A levels < 110 pg/mL) had a higher BMI and BMI-independent metabolic alterations, namely waist circumference, high-density lipoprotein cholesterol, and glucose/insulin ratio (an insulin resistance index), with respect to patients with idiopathic hypersomnia without long sleep time (cerebrospinal fluid orexin-A levels > 300 pg/mL). Despite lower daily food intake, patients with narcolepsy with cataplexy displayed significant alterations in metabolic parameters resulting in a diagnosis of metabolic syndrome in more than half the cases.

Conclusions:

BMI-independent metabolic alterations and the relative hypophagia of patients with narcolepsy with cataplexy, as compared with patients with idiopathic hypersomnia without long sleep time, suggest that orexin-A influences the etiology of this phenotype. Moreover, considering that these dysmetabolic alterations are present from a young age, a careful metabolic follow-up of patients diagnosed with narcolepsy with cataplexy is mandatory.

Citation:

Poli F; Plazzi G; Dalmazi GD; Ribichini D; Vicennati V; Pizza F; Mignot E; Montagna P; Pasquali R; Pagotto U. Body mass index-independent metabolic alterations in narcolepsy with cataplexy. SLEEP 2009;32(11):1491-1497.     

Facing emotions in narcolepsy with cataplexy: haemodynamic and behavioural responses during emotional stimulation

Narcolepsy with cataplexy is a complex sleep disorder that affects the modulation of emotions: cataplexy, the key symptom of narcolepsy, is indeed strongly linked with emotions that usually trigger the episodes. Our study aimed to investigate haemodynamic and behavioural responses during emotional stimulation in narco‐cataplexy. Twelve adult drug‐naive narcoleptic patients (five males; age: 33.3 ± 9.4 years) and 12 healthy controls (five males; age: 30.9 ± 9.5 years) were exposed to emotional stimuli (pleasant, unpleasant and neutral pictures). Heart rate, arterial blood pressure and mean cerebral blood flow velocity of the middle cerebral arteries were continuously recorded using photoplethysmography and Doppler ultrasound. Ratings of valence and arousal and coping strategies were scored by the Self‐Assessment Manikin and by questionnaires, respectively. Narcoleptic patients' haemodynamic responses to pictures overlapped with the data obtained from controls: decrease of heart rate and increase of mean cerebral blood flow velocity regardless of pictures' content, increase of systolic blood pressure during the pleasant condition, and relative reduction of heart rate during pleasant and unpleasant conditions. However, when compared with controls, narcoleptic patients reported lower arousal scores during the pleasant and neutral stimulation, and lower valence scores during the pleasant condition, respectively, and also a lower score at the ‘focus on and venting of emotions’ dimensions of coping. Our results suggested that adult narcoleptic patients, compared with healthy controls, inhibited their emotion‐expressive behaviour to emotional stimulation, and that may be related to the development of adaptive cognitive strategies to face emotions avoiding cataplexy.     

The clinical spectrum of narcolepsy with cataplexy: a reappraisal

In the absence of a golden standard for the diagnosis of narcolepsy, the clinical spectrum of disorder remains controversial. The aims of this study were (1) to determine frequency and characteristics of sleep-wake symptoms in patients with narcolepsy with cataplexy, (2) to compare clinical characteristics with results of ancillary tests, and (3) to identify factors that discriminate narcolepsy from other conditions with excessive daytime sleepiness (EDS). We prospectively studied 57 narcoleptics with cataplexy, 56 patients with non-narcoleptic hypersomnia (H), and 40 normal controls (No). Based on suggested and published criteria, we differentiated between narcoleptics with definite cataplexy (N) and narcoleptics without definite cataplexy (possible cataplexy, NpC). Assessment consisted of questionnaires [all patients and controls, including the Ullanlinna Narcolepsy Score (UNS)], polysomnography (all patients), multiple sleep latency test (MSLT) and human leukocyte antigen typing (in most narcoleptics). A new narcolepsy score based on five questions was developed. Data were compared with those of 12 hypocretin-deficient narcoleptics (N-hd). There were significant differences between N and NpC (including mean sleep latency on MSLT), but none between N and N-hd. A score of sleep propensity during active situations (SPAS) and the frequency of sleep paralysis/hallucinations at sleep onset, dreams of flying, and history of sleep shouting discriminated N from H and No (P < 0.001). Cataplexy-like symptoms in H (18%) and No (8%) could be discriminated from 'true' cataplexy in N on the basis of topography of motor effects, triggering emotions and triggering situations (P < 0.001). Our narcolepsy score had a similar sensitivity (96% versus 98%) but a higher specificity (98% versus 56%) than the UNS. Analysis of co-occurring symptoms in narcolepsy revealed two symptom complexes: EDS, cataplexy, automatic behaviors; and sleep paralysis, hallucinations, parasomnias. Low/undetectable cerebrospinal fluid hypocretin-1 levels and a history of definite cataplexy identify similar subgroups of narcoleptics. Specific questions on severity of EDS (SPAS score) and characteristics of cataplexy allow the recognition of subgroups of narcoleptics and their differentiation from non-narcoleptic EDS patients, including those reporting cataplexy-like episodes. The existence of co-occurring symptoms supports the hypothesis of a distinct pathophysiology of single narcoleptic symptoms.     

Altered skin-temperature regulation in narcolepsy relates to sleep propensity

STUDY OBJECTIVES: In healthy subjects, sleep propensity increases when the distal skin temperature increases relative to the proximal skin temperature. This increase results from increased blood flow in the skin of the extremities and is, among other factors, controlled by the hypothalamic circadian clock, as is sleep. Because narcolepsy is characterized by hypothalamic alterations, we studied skin temperature in narcoleptic patients in relation to their characteristically increased sleep propensity during the day. DESIGN: Distal and proximal skin temperature and their gradient (DPG) were measured during a Multiple Sleep Latency Test. This allowed temperature to be studied during wakefulness, at sleep onset and during sleep. SETTING: Tertiary narcolepsy referral center in a university hospital. PATIENTS: Fifteen unmedicated narcolepsy patients with cataplexy and 15 controls. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: In subjects in the waking state, DPG was higher in narcoleptics than in controls throughout the day (time by group interaction, p < .0001), due to increased distal skin temperature and decreased proximal skin temperature. The increase in DPG was related to a shorter subsequent sleep-onset latency (p = .02). Once asleep, narcoleptics maintained their elevated distal skin temperature and DPG (p < .0001), whereas proximal skin temperature increased to reach normal levels. CONCLUSIONS: This is the first demonstration of a dramatic alteration of daytime skin temperature control in narcolepsy. Even awake narcoleptic patients showed a DPG higher than that which healthy controls achieve when asleep. This observation suggests that hypocretin deficiency in narcolepsy affects skin-temperature regulation and invites further examination. Skin-temperature control might ultimately even have therapeutic implications for the alleviation of narcoleptic symptoms.     

Is narcolepsy a REM sleep disorder? Analysis of sleep abnormalities in narcoleptic Dobermans

Narcolepsy is a chronic sleep disorder marked by excessive daytime sleepiness, cataplexy, sleep paralysis, and hypnagogic hallucinations. Since the discovery of sleep onset REM periods (SOREMPs) in narcoleptic patients, narcolepsy has often been regarded as a disorder of REM sleep generation: REM sleep intrudes in active wake or at sleep onset, resulting in cataplexy, sleep paralysis, or hypnagogic hallucinations. However, this hypothesis has not been experimentally verified. In the current study, we characterized the sleep abnormalities of genetically narcoleptic-cataplectic Dobermans, a naturally occurring animal model of narcolepsy, in order to verify this concept. Multiple sleep latency tests during the daytime revealed that narcoleptic Dobermans exhibit a shorter sleep latency and a higher frequency of SOREMPs, compared to control Dobermans. The total amount of time spent in wake and sleep during the daytime is not altered in narcoleptic dogs, but their wake and sleep patterns are fragmented, and state transitions into and from wake and other sleep stages are altered. A clear 30 min REM sleep cyclicity exists in both narcoleptic and control dogs, suggesting that generation of the ultradian rhythm of REM sleep is not altered in narcoleptics. In contrast, cataplexy displays no cyclicity and can be elicited in narcoleptic animals anytime with emotional stimulation and displays no cyclicity. Stimulation of a cholinoceptive site in the basal forebrain induces a long-lasting attack of cataplexy in narcoleptic dogs; however, bursts of rapid eye movements during this state still occur with a 30 min cyclicity. Sites and mechanisms for triggering cataplexy may therefore be different from those for REM sleep. Cataplexy and a dysfunction in the maintenance of vigilance states, but not abnormal REM sleep generation, may therefore be central to narcolepsy.     

Segregation of HLA genes in multicase narcolepsy families

In the past 15 years, 411 sporadic narcolepsy patients have been diagnosed in the Hephata Klinik, Schwalmstadt, Germany. They were explored for presence or absence of excessive daytime sleepiness and narcolepsy in their relatives. A subset of 39 patients were explored for presence or absence of parasomnias. Six patients had more than one relative affected by narcolepsy-cataplexy. Forty-seven family members were investigated with the Stanford Center for Narcolepsy Sleep Inventory and a standardized parasomnia questionnaire. Twenty-four relatives had nocturnal polysomnographies and Multiple Sleep Latency Tests. HLA class I typing was performed in all sporadic and familial cases, class II and microsatellite typing was performed in all members of multicase families. Based on the Finnish prevalence study by Hublin et al., 1994, the relative risk for first degree relatives to develop narcolepsy-cataplexy was in our sample 16.5, 34.2 for excessive daytime sleepiness and 426.9 for parasomnias. Cataplexy, excessive daytime sleepiness and single narcoleptic symptoms in the multicase families segregate with the DRB1*1501, CARII:200, CARI:103, DQB1*0602 haplotype. In two families, members with narcolepsy and isolated symptoms have inherited the DRB1*1501/DQB1*0602 haplotype from the non-affected parent. The observed segregations in these two families may support the view that narcoleptic symptoms are expressed by DRB1*1501/DQB1*0602 carriers, independent of haplotype origin. Parasomnias do not segregate with a specific haplotype. The frequency of parasomnias in narcolepsy is much higher than in the general population. The empirical risk for first degree family members of narcolepsy patients to develop cataplexy seems to be low, whereas it is higher for EDS and highest for parasomnias.     

Narcolepsy-cataplexy: deficient prepulse inhibition of blink reflex suggests pedunculopontine involvement

Hypocretin (orexin) deficiency plays a major role in the pathophysiology of narcolepsy–cataplexy. In animal models, hypocretinergic projections to the pedunculopontine nucleus are directly involved in muscle tone regulation mediating muscle atonia – a hallmark of cataplexy. We hypothesized that pedunculopontine nucleus function, tested with prepulse inhibition of the blink reflex, is altered in human narcolepsy–cataplexy. Twenty patients with narcolepsy–cataplexy and 20 healthy controls underwent a neurophysiological study of pedunculopontine nucleus function. Blink reflex, prepulse inhibition of the blink reflex and blink reflex excitability recovery were measured. Blink reflex characteristics (R1 latency and amplitude, and R2 and R2c latency and area under the curve) did not differ between patients and controls (P > 0.05). Prepulse stimulation significantly increased R2 and R2c latencies and reduced R2 and R2c areas in patients and controls. However, the R2 and R2c area suppression was significantly less in patients than in controls (to 69.8 ± 14.4 and 74.9 ± 12.6%, respectively, versus 34.5 ± 28.6 and 43.3 ± 29.5%, respectively; each P < 0.001). Blink reflex excitability recovery, as measured by paired‐pulse stimulation, which is not mediated via the pedunculopontine nucleus, did not differ between patients and controls (P > 0.05). Our data showed that prepulse inhibition is reduced in narcolepsy–cataplexy, whereas unconditioned blink reflex and its excitability recovery are normal. Because the pedunculopontine nucleus is important for prepulse inhibition, these results suggest its functional involvement in narcolepsy–cataplexy.     

White matter alterations in narcolepsy patients with cataplexy: tract‐based spatial statistics

Functional imaging studies and voxel‐based morphometry analysis of brain magnetic resonance imaging showed abnormalities in the hypothalamus–thalamus–orbitofrontal pathway, demonstrating altered hypocretin pathway in narcolepsy. Those distinct morphometric changes account for problems in wake–sleep control, attention and memory. It also raised the necessity to evaluate white matter changes. To investigate brain white matter alterations in drug‐naïve narcolepsy patients with cataplexy and to explore relationships between white matter changes and patient clinical characteristics, drug‐naïve narcolepsy patients with cataplexy (n = 22) and healthy age‐ and gender‐matched controls (n = 26) were studied. Fractional anisotropy and mean diffusivity images were obtained from whole‐brain diffusion tensor imaging, and tract‐based spatial statistics were used to localize white matter abnormalities. Compared with controls, patients showed significant decreases in fractional anisotropy of white matter of the bilateral anterior cingulate, fronto‐orbital area, frontal lobe, anterior limb of the internal capsule and corpus callosum, as well as the left anterior and medial thalamus. Patients and controls showed no differences in mean diffusivity. Among patients, mean diffusivity values of white matter in the bilateral superior frontal gyri, bilateral fronto‐orbital gyri and right superior parietal gyrus were positively correlated with depressive mood. This tract‐based spatial statistics study demonstrated that drug‐naïve patients with narcolepsy had reduced fractional anisotropy of white matter in multiple brain areas and significant relationship between increased mean diffusivity of white matter in frontal/cingulate and depression. It suggests the widespread disruption of white matter integrity and prevalent brain degeneration of frontal lobes according to a depressive symptom in narcolepsy.     

High bicarbonate levels in narcoleptic children

The objective of this study was to evaluate the levels of plasma bicarbonate levels in narcoleptic children. Clinical, electrophysiological data and bicarbonate levels were evaluated retrospectively in children seen in our paediatric national reference centre for hypersomnia. The cohort included 23 control subjects (11.5 ± 4 years, 43% boys) and 51 patients presenting de‐novo narcolepsy (N) (12.7 ± 3.7 years, 47% boys). In narcoleptic children, cataplexy was present in 78% and DQB1*0602 was positive in 96%. The control children were less obese (2 versus 47%, P = 0.001). Compared with control subjects, narcoleptic children had higher bicarbonate levels (P = 0.02) as well as higher PCO₂ (P < 0.01) and lower venous pH gas (P < 0.01). Bicarbonate levels higher than 27 mmol L^?1 were found in 41.2% of the narcoleptic children and 4.2% of the controls (P = 0.001). Bicarbonate levels were correlated with the Adapted Epworth Sleepiness Scale (P = 0.01). Narcoleptic patients without obesity often had bicarbonate levels higher than 27 mmol L ^?1 (55 versus 25%, P = 0.025). No differences were found between children with and without cataplexy. In conclusion, narcoleptic patients had higher bicarbonate plasma levels compared to control children. This result could be a marker of hypoventilation in this pathology, provoking an increase in PCO₂ and therefore a respiratory acidosis, compensated by an increase in plasma bicarbonates. This simple screening tool could be useful for prioritizing children for sleep laboratory evaluation in practice.     

Cataplexy: An affair of pleasure or an unpleasant affair?

Narcolepsy, cataplexy and emotions form an intriguing triad that fascinates sleep researchers. A novel aspect of narcoleptic patients’ behaviours now appears depending on the emotional valence of the context: how can we explain the fact that narcoleptic patients may experience pleasant-triggered (e.g. laughing) cataplexy as well as unpleasant-related drawback performance (Tucci, V., Stegagno, L., Vandi, S., Ferrillo, F., Palomba, D., Vignatelli, L., Ferini-Strambi, L., Montagna, P., Plazzi, G., Emotional information processing in patients with narcolepsy: a psychophysiologic investigation, Sleep 26 (2003) 558–564; Khatami, R., Birkmann, S., Bassetti, C.L., Amygdala dysfunction in narcolepsycataplexy, J. Sleep Res. 16 (2007) 226–229)? With this in mind we postulate that narcolepsy with cataplexy is a complex sleep disorder that, among others, affects the modulation of emotions at different levels: structural, cellular and molecular.     

Criteria for gauging response to sodium oxybate for narcolepsy

Our objective was to define responder criteria using an anchor‐based approach for frequency of cataplexy attacks and excessive daytime sleepiness in patients with narcolepsy undergoing sodium oxybate treatment. We used pooled data from two randomized, placebo‐controlled, double‐blind, multicentre 4‐ and 8‐week trials of sodium oxybate for narcolepsy with cataplexy and analysed using receiver operator characteristics analysis. The percentage change in frequency of weekly cataplexy attacks and the Epworth Sleepiness Scale outcomes were compared with Clinical Global Impression of Change ratings, used as the anchor to define true response. Participants (n = 336) were 39% male, 89% white, with a mean age of 41.5 (15.3) years, reporting a median of 20.5 cataplexy attacks per week and a mean Epworth Sleepiness score of 17.5 at baseline. A majority (51%) were Much Improved or Very Much Improved based on Clinical Global Impression of Change ratings, considered a true response to treatment. Area under the curve values for % reduction in cataplexy attacks (77%) and % change in sleepiness score (78%) supported response definition thresholds of 46% and 12%, respectively. Classification using either response definition agreed with the anchor for approximately 71% of participants. Cataplexy response definition was more sensitive (cataplexy = 0.77, Epworth Sleepiness Scale = 0.69), while sleepiness was more specific (cataplexy = 0.66, Epworth Sleepiness Scale = 0.75). Both responder definitions showed a dose–response relationship with sodium oxybate, demonstrating their validity using an external criterion. Weekly cataplexy attacks and Epworth Sleepiness Scale can be used to help document clinical response to narcolepsy treatment using criteria of 46% and 12% reductions, respectively.