The role of tissue biopsy as a biomarker in REM sleep behavior disorder.

Patients with idiopathic REM-sleep behavior disorder (iRBD) are at substantial risk of progressive neurodegenerative disease of α-synuclein pathology. Longitudinal studies have demonstrated that abnormal α-synuclein deposition occurs early in the course of disease and may precede the appearance of motor symptoms by several decades. This provides rationale for the use of a reliable biomarker to both follow disease progression and to assess treatment response, once disease-modifying treatments become available. Tissue α-synuclein has emerged as a promising candidate, however the utility of α-synuclein detection in tissues accessible to biopsy in iRBD remains unclear. This article summarizes the current literature on the role of tissue biopsy in iRBD, with specific focus on its potential role as a biomarker of disease progression and its role in future clinical trials.

Peripheral Blood Inflammatory Cytokines in Idiopathic REM Sleep Behavior Disorder.

BACKGROUND: Although previous research provides insight into the role of neuroinflammation in idiopathic REM sleep behavior disorder, the association of this disorder with peripheral blood inflammatory markers remains unclear. OBJECTIVE: To investigate inflammatory cytokines in plasma samples in patients with idiopathic rapid eye movement sleep behavior disorder and to explore whether these markers are associated with prodromal symptoms of α-synucleinopathies. METHODS: We collected plasma from patients with polysomnographically confirmed idiopathic rapid eye movement sleep behavior disorder without parkinsonism or dementia (n = 54) and from healthy controls (n = 56). The following cytokines were measured: interleukin-1ß, interleukin-2, interleukin-6, interleukin-10, and tumor necrosis factor-α. The idiopathic REM sleep behavior disorder patients underwent sleep, motor, cognitive, olfactory, and autonomic testing. RESULTS: The anti-inflammatory cytokine, interleukin-10, levels in the idiopathic rapid eye movement sleep behavior disorder group were significantly upregulated compared to the control group (P = 0.022), but this difference did not withstand Bonferroni correction. The other proinflammatory cytokine levels did not differ between the groups. No correlation was found between the cytokine levels and any clinical variable. CONCLUSIONS: Our data do not provide evidence supporting the role of peripheral inflammation in idiopathic rapid eye movement sleep behavior disorder. However, considering the limited statistical power because of the small sample size, further large-scale longitudinal studies with a broader spectrum of cytokines are needed to clarify this issue. © 2019 International Parkinson and Movement Disorder Society.

Biomarkers for REM sleep behavior disorder in idiopathic and narcoleptic patients.

To search for discriminating biomarkers, 30 patients with idiopathic rapid-eye-movements sleep behavior disorder (iRBD) were compared with 17 patients with RBD within narcolepsy type 1. Both groups underwent extensive examinations, including skin biopsy searching for phosphorylated α-synuclein deposits and whole-night video-polysomnography. Skin biopsy was positive for phosphorylated α-synuclein deposits in 86.7% of iRBD patients and in none of narcoleptic patients. The analysis of video-polysomnographic motor events showed differences in their occurrence throughout the night in the two groups. iRBD and RBD due to narcolepsy do have different clinical and pathological findings, confirming a different pathophysiology.

Abnormal α-synuclein deposits in skin nerves: intra- and inter-laboratory reproducibility.

BACKGROUND AND PURPOSE: Visualization of phosphorylated α-synuclein at serine 129 (p-syn) in skin nerves is a promising test for the in vivo diagnosis of synucleinopathies. Here the aim was to establish the intra- and inter-laboratory reproducibility of measurement of intraneural p-syn immunoreactivity in two laboratories with major expertise (Würzburg and Bologna). METHODS: In total, 43 patients affected by Parkinson's disease (PD 21 patients), dementia with Lewy bodies (DLB 1), rapid eye movement sleep behaviour disorder (RBD 11), multiple system atrophy (MSA-P 4) and small fibre neuropathy (SFN 6) were enrolled. Skin biopsy was performed at the C7 paravertebral spine region and distal skin sites (thigh or leg). The analysis was standardized in both laboratories and carried out blinded on a single skin section double stained with antibodies to p-syn and the pan-axonal marker protein gene product 9.5. Fifty skin sections were randomly selected for the analysis: 25 from C7 and 25 from distal sites. Differently classified sections were re-evaluated to understand the reasons for the discrepancy. RESULTS: The intra-laboratory analysis showed an excellent reproducibility both in Würzburg (concordance of classification 100% of sections; K = 1; P < 0.001) and Bologna (96% of sections; K = 0.92; P < 0.001). Inter-laboratory analysis showed reproducibility in 45 sections (90%; K = 0.8; P < 0.001) and a different classification in five sections, which was mainly due to fragmented skin samples or weak fluorescent signals. CONCLUSIONS: Analysis of p-syn showed excellent inter- and intra-laboratory reproducibility supporting the reliability of this technique. The few ascertained discordances were important to further improve the standardization of this technique.

Alpha-synuclein aggregates in the parotid gland of idiopathic REM sleep behavior disorder.

BACKGROUND: The neuropathological hallmark of Parkinson's disease (PD) is the presence of aggregates of phosphorylated alpha-synuclein (pAS) in the nervous system. METHOD: We report a patient with video-polysomnography-confirmed idiopathic REM sleep behavior disorder that underwent parotidectomy because of parotid gland cancer. Immunohistochemistry of the gland tissue revealed abundant pAS deposits. One year after surgery the patient was diagnosed with PD. Prompted by this observation we examined the parotid gland in 10 consecutive individuals that underwent elective parotidectomy irrespective of their clinical condition. RESULTS: One had PD and another had mild parkinsonian signs plus reduced dopamine transporter uptake in the striatum. Both had pAS deposits in the parotid gland. The remaining eight subjects had no neurological signs and pAS was found in one of them. CONCLUSION: Our study shows that the parotid gland may contain pAS pathology in the prodromal stage of PD and in manifested PD.

Rapid eye movement sleep behavior disorder and the link to alpha-synucleinopathies.

Rapid eye movement (REM) sleep behavior disorder (RBD) involves REM sleep without atonia in conjunction with a recurrent nocturnal dream enactment behavior, with vocalizations such as shouting and screaming, and motor behaviors such as punching and kicking. Secondary RBD is well described in association with neurological disorders including Parkinson's disease (PD), multiple system atrophy (MSA), and other conditions involving brainstem structures such as tumors. However, RBD alone is now considered to be a potential harbinger of later development of neurodegenerative disorders, in particular PD, MSA, dementia with Lewy bodies (DLB), and pure autonomic failure. These conditions are linked by their underpinning pathology of alpha-synuclein protein aggregation. In RBD, it is therefore important to recognize the potential risk for later development of an alpha-synucleinopathy, and to investigate for other potential causes such as medications. Other signs and symptoms have been described in RBD, such as orthostatic hypotension, or depression. While it is important to recognize these features to improve patient management, they may ultimately provide clinical clues that will lead to risk stratification for phenoconversion. A critical need is to improve our ability to counsel patients, particularly with regard to prognosis. The ability to identify who, of those with RBD, is at high risk for later neurodegenerative disorders will be paramount, and would in addition advance our understanding of the prodromal stages of the alpha-synucleinopathies. Moreover, recognition of at-risk individuals for neurodegenerative disorders may ultimately provide a platform for the testing of possible neuroprotective agents for these neurodegenerative disorders.

Rapid eye movement sleep behaviour disorder and striatal dopamine depletion in patients with Parkinson's disease.

BACKGROUND AND PURPOSE: Rapid eye movement sleep behaviour disorder (RBD) is related to striatal dopamine depletion. This study was performed to confirm whether clinically probable RBD (cpRBD) in patients with Parkinson's disease (PD) is associated with a specific pattern of striatal dopamine depletion. METHODS: A prospective survey was conducted using the RBD Screening Questionnaire (RBDSQ) in 122 patients with PD who had undergone dopamine transporter (DAT) positron emission tomography scan. RESULTS: Patients with cpRBD (RBDSQ ≥ 7) exhibited greater motor deficits, predominantly in the less-affected side and axial symptoms, and were prescribed higher levodopa-equivalent doses at follow-up than those without cpRBD (RBDSQ ≤ 4), despite their similar disease and treatment durations. Compared to patients without cpRBD, those with cpRBD showed lower DAT activities in the putamen, particularly in the less-affected side in all putaminal subregions, and a tendency to be lower in the ventral striatum. In addition, greater motor deficits in patients with cpRBD than in those without cpRBD remained significant after controlling for DAT binding in the putamen and other confounding variables. CONCLUSIONS: These results demonstrated that the presence of RBD in patients with PD is associated with different patterns of both motor deficit distribution and striatal DAT depletion, suggesting that the presence of RBD represents a distinct PD subtype with a malignant motor parkinsonism.

Skin nerve phosphorylated α-synuclein deposits in idiopathic REM sleep behavior disorder.

OBJECTIVE: To test if phosphorylated α-synuclein (p-α-syn) deposits can be detected by means of skin biopsy in patients with idiopathic REM sleep behavior disorder (iRBD) as a potential early histopathologic marker of impending synucleinopathy. METHODS: Proximal (cervical) and distal (legs) samples of skin biopsy were obtained from 12 patients with polysomnographically confirmed iRBD and 55 sex- and age-matched healthy controls (HC). P-α-syn deposits were assessed with a monoclonal antibody against p-α-syn at serine 129, disclosed by an immunofluorescence method. In addition, patients underwent an extensive workup in order to search for nonmotor symptoms and neuroimaging findings usually associated with impending neurodegeneration and to exclude subtle motor or cognitive signs. RESULTS: P-α-syn deposits were detected in 9 (75%) out of 12 patients with iRBD and none of the HC. In iRBD, the sensitivity of the test was higher at the cervical site (67%) when compared to the leg site (58%). CONCLUSIONS: Our preliminary findings suggest that skin biopsy in patients with iRBD might be a safe and sensitive procedure to be further tested in order to detect p-α-syn deposits in the premotor stage of synucleinopathies. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that p-α-syn skin deposits identify patients with iRBD.

Dermal phospho-alpha-synuclein deposits confirm REM sleep behaviour disorder as prodromal Parkinson's disease.

Phosphorylated alpha-synuclein (p-alpha-syn) deposits, one of the neuropathological hallmarks of Parkinson's disease (PD), have recently been detected in dermal nerve fibres in PD patients with good specificity and sensitivity. Here, we studied whether p-alpha-syn may serve as a biomarker in patients with a high risk of developing PD, such as those with REM sleep behaviour disorder (RBD). We compared the presence and distribution of p-alpha-syn deposits in dermal nerve fibres in 18 patients with RBD, 25 patients with early PD and 20 normal controls. Skin biopsy was taken at C7, Th10, and the upper and lower leg. Presynaptic dopamine transporter imaging using FP-CIT-SPECT was performed in all patients with RBD and in 11 patients with PD. All RBD patients underwent olfactory function testing. The likelihood ratio (LR) for prodromal PD was calculated for each patient based on published research criteria. Skin serial sections were assessed by double-immunofluorescence labelling with antibodies to pSer129-alpha-syn under blinded conditions. P-alpha-syn was visualized in 10/18 patients with RBD (sensitivity of 55.6%) and in 20/25 early PD patients (sensitivity of 80%) but in none of the controls (specificity of 100%). The percentage of dermal structures innervated by p-alpha-syn-positive fibres was negatively correlated with dopamine transporter binding in the FP-CIT-SPECT (ρ = -0.377, p = 0.048), with olfactory function (ρ = -0.668, p = 0.002), and positively correlated with the total LR for RBD to present prodromal PD (ρ = 0.531, p = 0.023). Dermal p-alpha-syn can be considered a peripheral histopathological marker of synucleinopathy and can be detected in a subgroup of RBD patients presumably representing prodromal PD. Dermal p-alpha-syn is detectable in RBD patients without PD motor symptoms, thereby stratifying a patient group that is of great interest for clinical trials testing disease-modifying drugs.

Assessment of α-synuclein in submandibular glands of patients with idiopathic rapid-eye-movement sleep behaviour disorder: a case-control study.

BACKGROUND: The histological feature of Parkinson's disease is the presence of intraneuronal aggregates of phosphorylated α-synuclein (αSyn). In patients with Parkinson's disease, deposits of αSyn are found in the autonomic nerve fibres of the submandibular gland. Since patients with idiopathic rapid-eye-movement sleep behaviour disorder (IRBD) can develop Parkinson's disease and other synucleinopathies, we investigated whether αSyn deposits could also be detected in their submandibular gland nerve fibres. METHODS: We did a case-control study at the Hospital Clinic de Barcelona (Barcelona, Spain) in patients with polysomnographic-confirmed IRBD, patients with clinically diagnosed Parkinson's disease, and controls matched by age with the IRBD group. The controls were either healthy, had had elective neck surgery in the clinic, or were patients who had died in the clinic and had an autopsy. We did a transcutaneous core needle biopsy of the submandibular gland with ultrasound guidance in patients with IRBD or Parkinson's disease, and healthy controls, and without ultrasound guidance in the other controls. We assessed the presence of αSyn with immunohistochemistry using 129-phosphorylated antiserine monoclonal antibody, and analysed quantitative variables with Kruskall-Wallis tests and qualitative variables with Fisher's exact tests. FINDINGS: We did our study between July 16, 2014, and May 16, 2015, and recruited 21 patients with IRBD, 24 patients with Parkinson's disease, and 26 controls (seven healthy, 11 patients undergoing neck surgery, and eight autopsies). We obtained submandibular biopsy material containing glandular parenchyma in nine (43%) of 21 patients with IRBD, 12 (50%) of 24 patients with Parkinson's disease, and all (100%) of the 26 controls. αSyn aggregates were detected in nerve fibres of the glandular parenchyma in eight (89%) of nine patients with IRBD and eight (67%) of 12 with Parkinson's disease, but none of the controls. Of the individuals whose biopsy samples did not contain glandular parenchyma, deposits of αSyn were found in extraglandular tissues in an additional three (25%) of 12 patients with IRBD and five (42%) of 12 patients with Parkinson's disease. None of the controls showed αSyn immunoreactivity in extraglandular tissues. Of the 52 participants who had ultrasonography-guided biopsy, 11 (21%) reported mild-to-moderate local pain, and nine (17%) developed a subcutaneous haematoma; however, these adverse events were transient and did not need treatment. INTERPRETATION: Our findings suggest that, in patients with IRBD, submandibular gland biopsy is a safe procedure for the detection of αSyn aggregates. αSyn detection could be useful for histological confirmation in individuals clinically diagnosed with Parkinson's disease. FUNDING: Centre for Networked Biomedical Research in Neurodegenerative Disorders (CIBERNED), Barcelona, Spain.

Investigation on Abnormal Iron Metabolism and Related Inflammation in Parkinson Disease Patients with Probable RBD.

OBJECTIVE: To investigate potential mechanisms involving abnormal iron metabolism and related inflammation in Parkinson disease (PD) patients with probable rapid eye movement sleep behavior disorder (PRBD). METHODS: Total 210 PD patients and 31 controls were consecutively recruited. PD patients were evaluated by RBD Screening Questionnaire (RBDSQ) and classified into PRBD and probable no RBD (NPRBD) groups. Demographics information were recorded and clinical symptoms were evaluated by series of rating scales. Levels of iron and related proteins and inflammatory factors in cerebrospinal fluid (CSF) and serum were detected. Comparisons among control, NPRBD and PRBD groups and correlation analyses between RBDSQ score and levels of above factors were performed. RESULTS: (1) The frequency of PRBD in PD patients is 31.90%. (2) PRBD group has longer disease duration, more advanced disease stage, severer motor symptoms and more non-motor symptoms than NPRBD group. (3) In CSF, levels of iron, transferrin, NO and IL-1ß in PRBD group are prominently increased. RBDSQ score is positively correlated with the levels of iron, transferrin, NO and IL-1ß in PD group. Iron level is positively correlated with the levels of NO and IL-1ß in PD group. (4) In serum, transferrin level is prominently decreased in PRBD group. PGE2 level in PRBD group is drastically enhanced. RBDSQ score exhibits a positive correlation with PGE2 level in PD group. CONCLUSIONS: PRBD is common in PD patients. PRBD group has severer motor symptoms and more non-motor symptoms. Excessive iron in brain resulted from abnormal iron metabolism in central and peripheral systems is correlated with PRBD through neuroinflammation.

Evaluation of brain iron content in idiopathic REM sleep behavior disorder using quantitative magnetic resonance imaging.

BACKGROUND: Neuroimaging studies in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) show similar structural and functional changes to alpha-synucleinopathies, including PD. Until now, there have been few attempts to characterize brain iron deposition in iRBD. The aim of this study was to investigate brain iron content in patients with iRBD using quantitative magnetic resonance imaging (MRI). METHODS: 3-T MRI was performed in 15 patients with iRBD and 20 age-matched healthy control subjects. In order to evaluate the iron-related neurodegenerative changes, we assessed volume and transverse relaxation rate (R2*) simultaneously. We used both region-based and voxel-based analysis. RESULTS: No significant differences in R2* values were found between iRBD groups and healthy control subjects. There were no areas of significantly reduced or increased gray matter and white matter volume in the iRBD group. Instead, lateral ventricle volumes measured automatically by FreeSurfer were significantly larger in patients with iRBD than in healthy controls (P < 0.05). CONCLUSION: The present study suggests that iron-related R2* values may not be an imaging biomarker for neurodegeneration in iRBD.

Unimpaired postprandial pancreatic polypeptide secretion in Parkinson's disease and REM sleep behavior disorder.

BACKGROUND: Pancreatic polypeptide is released immediately after food ingestion. The release is operated by vagal-abdominal projections and has therefore been suggested as a test for vagal nerve integrity. Pathoanatomical and clinical studies indicate vagal dysfunction in early Parkinson's disease (PD). METHODS: We assessed the postprandial secretion of pancreatic polypeptide and motilin in healthy controls (n = 18) and patients with idiopathic rapid-eye-movement sleep behavior disorder (iRBD, n = 10), a potential premotor stage of PD, as well as in drug-naive (n = 19) and treated (n = 19) PD patients. RESULTS: The postprandial pancreatic polypeptide secretion showed a physiological pattern in all groups and even an enhanced response in drug-naive PD and iRBD. Motilin concentrations correlated with pancreatic polypeptide concentrations. CONCLUSIONS: Postprandial pancreatic polypeptide secretion is not a suitable test for vagal nerve integrity in PD. The unimpaired pancreatic polypeptide response in iRBD and PD might be explained by partially intact vagal-abdominal projections or compensatory mechanisms substituting a defective neuronal brain-gut axis.

Rapid eye movement sleep deprivation induces changes in the high-affinity binding of [3H]-ouabain to the rat cortical membranes.

Rapid eye movement sleep (REMS) suppresses seizures. On the other hand, REMS deprivation (REMSD) increases brain susceptibility to seizures. Sodium-potassium/ATPase is involved in the control of brain excitability. Ouabain, a cardiotonic glycoside, binds to a regulatory extracellular allosteric site in the sodium-potassium/ATPase inhibiting/stimulating its activity depending on its concentration. Endogenous ouabain-like substances exist in the brain; therefore, changes in the ouabain binding site may be involved in the increased brain excitability induced by REMSD. Adult, Wistar male rats were deprived of REMS for 96 hours by the flower-pot method (REMSD). A stress control group was kept in the same environment on a larger platform (LP). A third group of rats was kept in the same room in their home-cages (CONTROL). After REMSD all rats were sacrificed by decapitation and their cerebral cortex dissected. High-affinity [3H]-ouabain binding was carried out in cortical crude membrane preparation using 8 concentrations of [3H]-ouabain (1-24 nM). The results show a statistically significant increase of KD in the REMSD rats compared to both CONTROL and LP groups. There were no statistically significant differences in the Bmax among the experimental groups. There was also no change either in cortical activity of K+ stimulated p-nitrophenylphosphatase, the dephosphorylation reaction of phosphorylated sodium-potassium/ATPase or in Mg2+-stimulated p-nitrophenylphosphatase. An increase in the KD of [3H]-ouabain binding to the sodium-potassium/ATPase in REMSD rats indicates a lower affinity to the endogenous inhibitors/stimulators of the enzyme. Therefore, this decreased affinity of the endogenous ouabain-like substances may be involved in the increased excitability induced by REMSD.

[REM Sleep behavioral disorder]. / Troubles du comportement en sommeil paradoxal.

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia which occurs only during REM sleep. RBD is characterized by the loss of skeletal muscle atonia, which is the principal feature of REM sleep, and by abnormal behavior representing the attempted enactment of dreaming. Clinically, it consists of abnormal behavior, frequently violent, that may lead to injuries. A polysomnographic study is necessary to assess the diagnosis showing the absence of REM sleep atonia and related abnormal behavior. RBD usually affects older men. Its exact etiological factors remain unknown. However, RBD is sometimes linked with drug use or exposure to toxic conditions. Moreover, the association with neurological disorders is frequently reported, particularly cerebrovascular, tumoral or neurodegenerative disease. Neurodegenerative disorders with parkinsonism are frequently involved. In Lewy body dementia, RBD is particularly frequent. In many cases, RBD may have a predictive value, preceding other symptoms of neurodegenerative disorders with parkinsonism. The biochemical mechanisms underlying RBD still remain unclear but could involve the dopamino-cholinergic balance and the serotoninergic pathway.