Widespread white matter changes in post-H1N1 patients with narcolepsy type 1 and first-degree relatives

Cortical thickness and sub-cortical volumes in post-H1N1 narcolepsy type 1: A brain-wide MRI case-control study

OBJECTIVE

There was more than a 10-fold increase in the incidence of narcolepsy type 1 (NT1) after the H1N1 mass vaccination in 2009/2010 in several countries. NT1 is associated with loss and increase of cell groups in the hypothalamus which may be associated with secondary affected sub-cortical and cortical gray matter. We performed a case-control comparison of MRI-based global and sub-cortical volume and cortical thickness in post-H1N1 NT1 patients compared with controls.

METHODS

We included 54 post-H1N1 NT1 patients (51 with confirmed hypocretin-deficiency; 48 H1N1-vaccinated with Pandemrix®; 39 females, mean age 21.8 ± 11.0 years) and 114 healthy controls (77 females, mean age 23.2 ± 9.0 years). 3T MRI brain scans were obtained, and the T1-weighted MRI data were processed using FreeSurfer. Group differences among three global, 10 sub-cortical volume measures and 34 cortical thickness measures for bilateral brain regions were tested using general linear models with permutation testing.

RESULTS

Patients had significantly thinner brain cortex bilaterally in the temporal poles (Cohen's d = 0.68, p = 0.00080), entorhinal cortex (d = 0.60, p = 0.0018) and superior temporal gyrus (d = 0.60, p = 0.0020) compared to healthy controls. The analysis revealed no significant group differences for sub-cortical volumes.

CONCLUSIONS

Post-H1N1(largely Pandemrix®-vaccinated) NT1 patients have significantly thinner cortex in temporal brain regions compared to controls. We speculate that this effect can be partly attributed to the hypothalamic neuronal change in NT1, including loss of function of the widely projecting hypocretin-producing neurons and secondary effects of the abnormal sleep-wake pattern in NT1 or could be specific for post-H1N1 (largely Pandemrix®-vaccinated) NT1 patients.

Microstructural White Matter Abnormalities in Children and Adolescents With Narcolepsy Type 1

BACKGROUND

In 2010, the H1N1 Pandemrix vaccination campaign was followed by a sudden increase in narcolepsy type 1 (NT1). We investigated the brain white matter microstructure in children with onset of NT1 within two years after the Pandemrix vaccination.

METHODS

We performed diffusion-weighted magnetic resonance imaging (MRI) on 19 children and adolescents with NT1 and 19 healthy controls. Imaging was performed at a median of 4 years after the diagnosis at a median age of 16 years. For the MRI, we used whole-brain tractography and tract-based spatial statistics (TBSS). We compared these results with medical records and questionnaire data.

RESULTS

Narcoleptic children showed a global decrease in mean, axial, and radial diffusivity and an increase in planarity coefficient in the white matter TBSS skeleton and tractography. These differences were widespread, and there was an increased asymmetry of the mean diffusivity in children with NT1. The global microstructural metrics were reflected in behavior, and especially the axial diffusion levels correlated with anxiety and depression symptoms and social and behavioral problems.

CONCLUSIONS

In pediatric patients with Pandemrix-associated NT1, several global changes in the brain white matter network skeleton were observed within five years after the onset of NT1. The degree of changes correlates with behavioral problems.

Larger hypothalamic volume in narcolepsy type 1

STUDY OBJECTIVES

Narcolepsy type 1 (NT1) is a neurological sleep disorder. Postmortem studies have shown 75%-90% loss of the 50 000-70 000 hypocretin-producing neurons and 64%-94% increase in the 64 000-120 000 histaminergic neurons and conflicting indications of gliosis in the hypothalamus of NT1 patients. The aim of this study was to compare MRI-based volumes of the hypothalamus in patients with NT1 and controls in vivo.

METHODS

We used a segmentation tool based on deep learning included in Freesurfer and computed the volume of the whole hypothalamus, left/right part of the hypothalamus, and 10 hypothalamic subregions. We included 54 patients with post-H1N1 NT1 (39 females, mean age 21.8 ± 11.0 years) and 114 controls (77 females, mean age 23.2 ± 9.0 years). Group differences were tested with general linear models using permutation testing in Permutation Analysis of Linear Models and evaluated after 10 000 permutations, yielding two-tailed P-values. Furthermore, a stepwise Bonferroni correction was performed after dividing hypothalamus into smaller regions.

RESULTS

The analysis revealed larger volume for patients compared to controls for the whole hypothalamus (Cohen's d = 0.71, p = 0.0028) and for the left (d = 0.70, p = 0.0037) and right part of the hypothalamus (d = 0.65, p = 0.0075) and left (d = 0.72, p = 0.0036) and right tubular-inferior (d = 0.71, p = 0.0037) hypothalamic subregions.

CONCLUSIONS

In conclusion, patients with post-H1N1 NT1 showed significantly larger hypothalamic volume than controls, in particular in the tubular-inferior subregions which could reflect several processes as previous studies have indicated neuroinflammation, gliosis, and changes in the numbers of different cell types.

Associations between psychiatric comorbid disorders and executive dysfunctions in hypocretin-1 deficient pediatric narcolepsy type1

OBJECTIVE/BACKGROUND

Psychiatric symptoms and cognitive deficits add significantly to impairment in academic achievement and quality of life in patients with narcolepsy. The primary aim of this study was to evaluate the prevalence of psychiatric disorders and executive dysfunctions, secondly to explore the association between psychiatric comorbidity, executive dysfunctions, subjective and objective sleep measures, and severity of cerebrospinal fluid (CSF) hypocretin-1 deficiency in pediatric narcolepsy type 1 (PNT1).

PATIENTS/METHODS

Cross-sectional study of 59 consecutively included PNT1 patients (age: 6-20 years; 34:25 girls: boys; 54/59 H1N1 (Pandemrix®)-vaccinated). Core narcolepsy symptoms including subjective sleepiness, polysomnography and multiple sleep latency test results, CSF hypocretin-1 levels, psychiatric disorders (by semistructured diagnostic interview Kaufmann Schedule for Affective Disorders and Schizophrenia Present and Lifetime version (KSADS)), and executive dysfunction (by Behavior Rating of Executive Function (BRIEF)) were assessed.

RESULTS

52.5% of the patients had one or more psychiatric comorbid disorder, and 64.7% had executive dysfunction in a clinically relevant range, with no sex difference in prevalence, while older age was associated with poorer executive function (p=0.013). Having any psychiatric comorbid disorder was associated with poorer executive functions (p=0.001). CSF hypocretin-1 deficiency severity was significantly associated with presence of psychiatric comorbidity (p=0.022) and poorer executive functions (p=0.030), and poorer executive functions was associated with subjective sleepiness (p=0.009).

CONCLUSIONS

The high occurrence of, and association between, psychiatric comorbidity and executive dysfunction underlines the importance of close attention to both these comorbidities in clinical care of NT1.

Novel Objective Measures of Hypersomnolence

Purpose of review

To provide a brief overview of current objective measures of hypersomnolence, discuss proposed measure modifications, and review emerging measures.

Recent findings

There is potential to optimize current tools using novel metrics. High-density and quantitative EEG-based measures may provide discriminative informative. Cognitive testing may quantify cognitive dysfunction common to hypersomnia disorders, particularly in attention, and objectively measure pathologic sleep inertia. Structural and functional neuroimaging studies in narcolepsy type 1 have shown considerable variability but so far implicate both hypothalamic and extra-hypothalamic regions; fewer studies of other CDH have been performed. There is recent renewed interest in pupillometry as a measure of alertness in the evaluation of hypersomnolence.

Summary

No single test captures the full spectrum of disorders and use of multiple measures will likely improve diagnostic precision. Research is needed to identify novel measures and disease-specific biomarkers, and to define combinations of measures optimal for CDH diagnosis.

Assessment of glymphatic function in narcolepsy using DTI-ALPS index

INTRODUCTION

Sleep is a modulator of glymphatic activity which is altered in various sleep disorders. Narcolepsy is a sleep disorder characterized by excessive daytime sleepiness (EDS), rapid onset of rapid eye movement (REM) sleep, cataplexy, disturbed night sleep with fragmentation. It is categorized into two types, type 1 (NT1) and type 2 (NT2) depending on the presence of cataplexy and/or absence of orexin. We sought for alterations in glymphatic activity in narcoleptic patients using diffusion tensor imaging (DTI) along perivascular space (ALPS) index on magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Adult patients diagnosed with NT1 or NT2 who had polysomnography (PSG) and MRI with DTI were included in the study. Sleep recording included Epworth Sleepiness Scale (ESS) score, sleep latency during multiple sleep latency test (MSLT), sleep efficiency during night PSG, wake after sleep onset (WASO), REM sleep latency during PSG, percentage of non-REM (NREM), REM sleep and wakefulness during night PSG. DTI-ALPS index was calculated for each patient and age-sex matched healthy control(HC)s.

RESULTS

The study group was composed of 25 patients [F/M = 15/10, median age = 34 (29.5-44.5)], 14 with NT1 and 11 with NT2 disease. ESS, WASO and percentage of wakefulness were significantly higher in NT1 patients (p < 0.05). Mean DTI-ALPS was not significantly different neither between narcoleptic patients and HCs, nor between NT1 and NT2 patients (all, p > 0.05). However, DTI-ALPS was negatively correlated with WASO (r = -0.745, p = 0.013) and percentage of wakefulness (r = -0.837, p = 0.005) in NT1 patients. DTI-ALPS correlated negatively with percentage of N1 sleep (r = -0.781, p = 0.005) but positively with REM percentage (r = 0.618, p = 0.043) in NT2 patients.

CONCLUSION

In this study, DTI-ALPS was not significantly different in narcoleptic patients than the HCs. However, the glymphatic index as assessed by DTI-ALPS correlated with PSG parameters; negatively with WASO, percentage of wakefulness in NT1, percentage of N1 sleep in NT2, and positively with REM sleep in NT2. A tendency for a reduction in DTI-ALPS in NT1 patients compared to both NT2 patients and HCs was also found. These findings might show the first evidence of an alteration of glymphatic activity, especially in NT1 patients, thus warrant further prospective studies in larger size of narcoleptic patient cohorts.

Changed Cerebral White Matter Structural Network Topological Characters and Its Correlation with Cognitive Behavioral Abnormalities in Narcolepsy Type 1

OBJECTIVE

In the current study we investigated topological abnormalities of the cerebral white matter networks in narcolepsy type 1 (NT1) patients and its relationship with their cognitive abnormalities using diffusion tensor imaging (DTI) technology.

METHODS

DTI and the Beijing version of the Montreal Cognitive Assessment (MoCA-BJ) were applied to 30 NT1 patients and 30 age-matched healthy controls. DTI studies were also carried using the 3T MRI system. Next, DTI data was used to establish a cerebral white matter network for all subjects and graph theory was applied to analyze the topological characteristics of the white matter structural network. Topographical parameters (such as local efficiency (Eloc), global efficiency (Eglob) and small-world (σ)) between NT1 patients and controls were then compared. The correlation between MoCA-BJ scores and topological parameters was also analyzed.

RESULTS

MoCA-BJ scores in NT1 patients were lower than those in the healthy controls. Compared with healthy controls, the global efficiency of the white matter network and attributes of the small world network were significantly reduced in NT1 patients. Finally, the global efficiency of the white matter structural network was related to the MoCA-BJ score of NT1 patients.

CONCLUSION

The abnormal topological characteristics of the white matter structural network in NT1 patients may be associated with their cognitive impairment.

High nocturnal sleep fragmentation is associated with low T lymphocyte P2Y11 protein levels in narcolepsy type 1

STUDY OBJECTIVES

Narcolepsy type 1 (NT1) is associated with hypocretin neuron loss. However, there are still unexplained phenotypic NT1 features. We investigated the associations between clinical and sleep phenotypic characteristics, the NT1-associated P2RY11 polymorphism rs2305795, and P2Y11 protein levels in T lymphocytes in patients with NT1, their first-degree relatives and unrelated controls.

METHODS

The P2RY11 SNP was genotyped in 100 patients (90/100 H1N1-(Pandemrix)-vaccinated), 119 related and 123 non-related controls. CD4 and CD8 T lymphocyte P2Y11 protein levels were quantified using flow cytometry in 167 patients and relatives. Symptoms and sleep recording parameters were also collected.

RESULTS

We found an association between NT1 and the rs2305795 A allele (OR = 2, 95% CI (1.3, 3.0), p = 0.001). T lymphocyte P2Y11 protein levels were significantly lower in patients and relatives homozygous for the rs2305795 risk A allele (CD4: p = 0.012; CD8: p = 0.007). The nocturnal sleep fragmentation index was significantly negatively correlated with patients' P2Y11 protein levels (CD4: p = 0.004; CD8: p = 0.006). Mean MSLT sleep latency, REM-sleep latency, and core clinical symptoms were not associated with P2Y11 protein levels.

CONCLUSIONS

We confirmed that the P2RY11 polymorphism rs2305795 is associated with NT1 also in a mainly H1N1-(Pandemrix)-vaccinated cohort. We demonstrated that homozygosity for the A risk allele is associated with lower P2Y11 protein levels. A high level of nocturnal sleep fragmentation was associated with low P2Y11 levels in patients. This suggests that P2Y11 has a previously unknown function in sleep-wake stabilization that affects the severity of NT1.

Narcolepsy type 1 patients have lower levels of effector memory CD4+ T cells compared to their siblings when controlling for H1N1-(Pandemrix™)-vaccination and HLA DQB1∗06:02 status

STUDY OBJECTIVES

Evidence suggests a cell-mediated autoimmune pathogenesis for narcolepsy type 1 (NT1), but it is not clear whether the disease is associated with overall changes in T cell subsets. The increase in NT1 incidence after H1N1 vaccination campaign with the Pandemrix™ vaccine suggests that disease-relevant changes in the immune system following this vaccination were important. In this study, we aimed to investigate differentiated T cell subsets and levels of CD25 and CD69 activation markers in a cohort of mainly Pandemrix™-vaccinated NT1 patients compared with their vaccinated and unvaccinated siblings.

METHODS

Peripheral blood mononuclear cells were collected in parallel and analysed with flow cytometry in 31 NT1 patients with disease onset after the 2009 influenza A (H1N1) pandemic and/or Pandemrix™ vaccination and 45 of their non-narcoleptic siblings (29/31 and 34/45 vaccinated, respectively).

RESULTS

We observed significantly lower effector memory CD4⁺ T cell levels in NT1 patients compared to their siblings, when controlling for HLA DQB1∗06:02 and vaccination status. Further, within the sibling group, vaccination status significantly affected frequencies of central memory and CD8⁺CD25⁺ T cells, and HLA DQB1∗06:02 status significantly affected frequencies of CD4⁺CD25⁺ T cells.

CONCLUSION

We confirm that NT1 is associated with lower levels of effector memory CD4⁺ T cells in peripheral blood. Importantly, this finding was only significant when controlling for vaccination and HLA status in both patients and controls. We thus demonstrate the importance of characterizing such factors (eg HLA and vaccination) when studying T cell subsets in NT1. This might explain earlier conflicting results.

Abnormal Brain Network Topology During Non-rapid Eye Movement Sleep and Its Correlation With Cognitive Behavioral Abnormalities in Narcolepsy Type 1

Objective: Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) were applied to investigate the abnormalities in the topological characteristics of functional brain networks during non-rapid eye movement(NREM)sleep. And we investigated its relationship with cognitive abnormalities in patients with narcolepsy type 1 (NT1) disorder in the current study. Methods: The Beijing version of the Montreal Cognitive Assessment (MoCA-BJ) and EEG-fMRI were applied in 25 patients with NT1 and 25 age-matched healthy controls. All subjects participated in a nocturnal video polysomnography(PSG)study, and total sleep time (TST), percentage of TST (%TST) for each sleep stage and arousal index were calculated. The Epworth Sleepiness Score (ESS) was used to measure the degree of daytime sleepiness. The EEG-fMRI study was performed simultaneously using a 3T MRI system and a 32-channel MRI-compatible EEG system during sleep. Visual scoring of EEG data was used for sleep staging. Cognitive function was assessed for all subjects using the MoCA-BJ. The fMRI data were applied to establish a whole-brain functional connectivity network for all subjects, and the topological characteristics of the whole-brain functional network were analyzed using a graph-theoretic approach. The topological parameters were compared between groups. Lastly, the correlation between topological parameters and the assessment scale using Montreal Cognition was analyzed. Results: The MoCA-BJ scores were lower in patients with NT1 than in normal controls. Whole-brain global efficiency during stage N2 sleep in patients with NT1 displayed significantly lower small-world properties than in normal controls. Whole-brain functional network global efficiency in patients with NT1 was significantly correlated with MoCA-BJ scores. Conclusion: The global efficiency of the functional brain network during stage N2 sleep in patients with NT1 and the correspondingly reduced small-world attributes were associated with cognitive impairment.

Neuroimaging of Narcolepsy and Primary Hypersomnias

Advances in neuroimaging open up the possibility for new powerful tools to be developed that potentially can be applied to clinical populations to improve the diagnosis of neurological disorders, including sleep disorders. At present, the diagnosis of narcolepsy and primary hypersomnias is largely limited to subjective assessments and objective measurements of behavior and sleep physiology. In this review, we focus on recent neuroimaging findings that provide insight into the neural basis of narcolepsy and the primary hypersomnias Kleine-Levin syndrome and idiopathic hypersomnia. We describe the role of neuroimaging in confirming previous genetic, neurochemical, and neurophysiological findings and highlight studies that permit a greater understanding of the symptoms of these sleep disorders. We conclude by considering some of the remaining challenges to overcome, the existing knowledge gaps, and the potential role for neuroimaging in understanding the pathogenesis and clinical features of narcolepsy and primary hypersomnias.

Resting-state brain network topological properties and the correlation with neuropsychological assessment in adolescent narcolepsy

Study Objectives

To evaluate functional connectivity and topological properties of brain networks, and to investigate the association between brain topological properties and neuropsychiatric behaviors in adolescent narcolepsy.

Methods

Resting-state functional magnetic resonance imaging (fMRI) and neuropsychological assessment were applied in 26 adolescent narcolepsy patients and 30 healthy controls. fMRI data were analyzed in three ways: group independent component analysis and a graph theoretical method were applied to evaluate topological properties within the whole brain. Lastly, network-based statistics was utilized for group comparisons in region-to-region connectivity. The relationship between topological properties and neuropsychiatric behaviors was analyzed with correlation analyses.

Results

In addition to sleepiness, depressive symptoms and impulsivity were detected in adolescent narcolepsy. In adolescent narcolepsy, functional connectivity was decreased between regions of the limbic system and the default mode network (DMN), and increased in the visual network. Adolescent narcolepsy patients exhibited disrupted small-world network properties. Regional alterations in the caudate nucleus (CAU) and posterior cingulate gyrus were associated with subjective sleepiness and regional alterations in the CAU and inferior occipital gyrus were associated with impulsiveness. Remodeling within the salience network and the DMN was associated with sleepiness, depressive feelings, and impulsive behaviors in narcolepsy.

Conclusions

Alterations in brain connectivity and regional topological properties in narcoleptic adolescents were associated with their sleepiness, depressive feelings, and impulsive behaviors.

Obesity and other medical comorbidities among NT1 patients after the Norwegian H1N1 influenza epidemic and vaccination campaign

Study Objectives

Narcolepsy type 1 (NT1) may be complicated by comorbidities. We aimed to study the extent of obesity and other medical comorbidities in a Norwegian population of NT1 patients with debut of symptoms after the 2009 H1N1 influenza epidemic and vaccination campaign. We also aimed to explore factors associated with obesity.

Methods

Ninety-one patients (48 children and 43 adults) were included in this cross-sectional study, 80 of whom were H1N1-vaccinated. All participants were hospitalized and underwent sleep investigation and physical examination, and completed a semi-structured clinical interview.

Results

In children, 16 females (70%) and 10 males (40%) were classified as overweight or obese. Twenty children (42%) had a co-existing medical disorder. Medical comorbidity was significantly positively associated with BMI in children (p = .032). In adults, 19 females (58%) and 7 males (70%) were classified as overweight or obese. Twenty-six adults (61%) had a co-existing medical disorder. We found no factors significantly associated with BMI in adults. On a fatigue scale from 0 to 100, lower scores indicating more fatigue, we found a mean (SD) total fatigue score of 50 (17) in children and 39 (16) in adults.

Conclusion

In a cohort of predominantly H1N1-vaccinated NT1 patients, we found a high prevalence of overweight or obesity. Half of the cohort presented with one or more additional medical comorbidities, and patients reported a clinically relevant degree of fatigue. Our findings highlight the importance of carefully monitoring patients with NT1 with regard to the development of obesity, which is a significant risk factor for cardiovascular disorders.

Widespread white matter connectivity abnormalities in narcolepsy type 1: A diffusion tensor imaging study

Narcolepsy type 1 is caused by a selective loss of hypothalamic hypocretin-producing neurons, resulting in severely disturbed sleep-wake control and cataplexy. Hypocretin-producing neurons project widely throughout the brain, influencing different neural networks. We assessed the extent of microstructural white matter organization and brain-wide structural connectivity abnormalities in a homogeneous group of twelve drug-free patients with narcolepsy type 1 and eleven matched healthy controls using diffusion tensor imaging with multimodal analysis techniques. First, tract-based spatial statistics (TBSS) was carried out using fractional anisotropy (FA) and mean, axial and radial diffusivity (MD, AD, RD). Second, quantitative analyses of mean FA, MD, AD and RD were conducted in predefined regions-of-interest, including sleep-wake regulation-related, limbic and reward system areas. Third, we performed hypothalamus-seeded tractography towards the thalamus, amygdala and midbrain. TBSS analyses yielded brain-wide significantly lower FA and higher RD in patients. Localized significantly lower FA and higher RD in the left ventral diencephalon and lower AD in the midbrain, were seen in patients. Lower FA was also found in patients in left hypothalamic fibers connecting with the midbrain. No significant MD and AD differences nor a correlation with disease duration were found. The brain-wide, localized ventral diencephalon (comprising the hypothalamus and different sleep- and motor-related nuclei) and hypothalamic connectivity differences clearly show a heretofore underestimated direct and/or indirect effect of hypocretin deficiency on microstructural white matter composition, presumably resulting from a combination of lower axonal density, lower myelination and/or greater axon diameter.

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Patients with narcolepsy type 1 have brain-wide microstructural white matter disruptions.

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Patients have overall lower fractional anisotropy and higher radial diffusivity.

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Fractional anisotropy was most prominently lower in the left ventral diencephalon.

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Lower fractional anisotropy was seen in patients in tracts connecting the left hypothalamus with the midbrain.

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Patients suffer from a combination of lower axonal density, lower myelination and/or greater axon diameter.

Autoantibodies in Pandemrix®-induced narcolepsy: Nine candidate autoantigens fail the conformational autoantibody test

Study objectives: Narcolepsy type 1 (NT1) is a chronic sleep disorder characterized by loss of hypocretin-producing neurons. Increased NT1 incidence was observed in Sweden following mass-vaccination with Pandemrix^®. Genetic association to HLA DQB1*06:02 implies an autoimmune origin, but target autoantigen remains unknown. Candidate autoantigens for NT1 have previously been identified in solid-phase immunoassays, while autoantibodies against conformation-dependent epitopes are better detected in radiobinding assays. The aims are to determine autoantibody levels against nine candidate autoantigens representing (1) proteins of the hypocretin transmitter system; Preprohypocretin (ppHypocretin), Hypocretin peptides 1 and 2 (HCRT1 and HCRT2) and Hypocretin receptor 2 (HCRTR2); (2) proteins previously associated with NT1; Tribbles homologue 2 (TRIB2), Pro-opiomelanocortin/alpha-melanocyte-stimulating-hormone (POMC/α-MSH) and Prostaglandin D2 Receptor DP1 (DP1); (3) proteins suggested as autoantigens for multiple sclerosis (another HLA DQB1*06:02-associated neurological disease); ATP-dependent Inwardly Rectifying Potassium Channel Kir4.1 (KIR4.1) and Calcium-activated chloride channel Anoctamin 2 (ANO2). Methods: Serum from post-Pandemrix^® NT1 patients (n = 31) and their healthy first-degree relatives (n = 66) were tested for autoantibody levels in radiobinding assays separating autoantibody bound from free labelled antigen with Protein A-Sepharose. ¹²⁵I-labelled HCRT1 and HCRT2 were commercially available while ³⁵S-methionine-labelled ppHypocretin, HCRTR2, TRIB2, α-MSH/POMC, DP1, KIR4.1 or ANO2 was prepared by in vitro transcription translation of respective cDNA. In-house standards were used to express data in arbitrary Units/ml (U/ml). Results: All radiolabelled autoantigens were detected in a concentration-dependent manner by respective standard sera. Levels of autoantibodies in the NT1 patients did not differ from healthy first-degree relatives in any of the nine candidate autoantigens. Conclusions: None of the nine labelled proteins proposed to be autoantigens were detected in the radiobinding assays for conformation-dependent autoantibodies. The results emphasise the need of further studies to identify autoantigen(s) and clarify the mechanisms in Pandemrix^®-induced NT1.

Structural anomaly in the reticular formation in narcolepsy type 1, suggesting lower levels of neuromelanin

The aim of this study was to investigate structural changes in the brain stem of adolescents with narcolepsy, a disorder characterized by excessive daytime sleepiness, fragmented night-time sleep, and cataplexy. For this purpose, we used quantitative magnetic resonance imaging to obtain R1 and R2 relaxation rates, proton density, and myelin maps in adolescents with narcolepsy (n = 14) and healthy controls (n = 14). We also acquired resting state functional magnetic resonance imaging (fMRI) for brainstem connectivity analysis. We found a significantly lower R2 in the rostral reticular formation near the superior cerebellar peduncle in narcolepsy patients, family wise error corrected p = .010. Narcolepsy patients had a mean R2 value of 1.17 s^-1 whereas healthy controls had a mean R2 of 1.31 s^-1, which was a large effect size with Cohen d = 4.14. We did not observe any significant differences in R1 relaxation, proton density, or myelin content. The sensitivity of R2 to metal ions in tissue and the transition metal ion chelating property of neuromelanin indicate that the R2 deviant area is one of the neuromelanin containing nuclei of the brain stem. The close proximity and its demonstrated involvement in sleep-maintenance, specifically through orexin projections from the hypothalamus regulating sleep stability, as well as the results from the connectivity analysis, suggest that the observed deviant area could be the locus coeruleus or other neuromelanin containing nuclei in the proximity of the superior cerebellar peduncle. Hypothetically, the R2 differences described in this paper could be due to lower levels of neuromelanin in this area of narcolepsy patients.