Restless legs syndrome in multiple system atrophy

Orexin and Sleep Disturbances in Alpha-Synucleinopathies: a Systematic Review

PURPOSE OF REVIEW

Sleep disturbances are amongst most frequent non-motor symptoms of Parkinson's Disease (PD), and they are similarly frequently reported in other alpha-syncleinopathies, such as Dementia with Lewy Bodies (DLB) and Multiple System Atrophy (MSA). More recently, the orexin system has been implicated in control of arousal based on salient environmental set points, and its dysregulation in sleep issues in alpha-synucleinopathies suggested by the findings from the translational animal models. However, its role in the patients with alpha-synucleinopathies remains unclear. We thus set to systematically review, and to critically assess, contemporary evidence on the association of the orexinergic system and sleep disturbances in alpha-synucleinopathies. In this systematic review, studies investigating orexin and sleep in alpha-synucleinopathies (Rapid Eye Movement (REM) Behaviour Disorder (RBD), Parkinson's Disease (PD), Dementia with Lewy Bodies (DLB), Multiple System Atrophy (MSA)) were identified using electronic database searches of PubMed, Web of Science and PsychINFO using MeSH terms, keywords, and title words such as "Alpha-synucleinopathies" AND "Orexin" AND "Sleep Disturbances".

RECENT FINDINGS

17 studies were included in this systemic review, of which 2 studies on RBD, 10 on PD, 4 on DLB, and 1 on MSA patients. Taken together, RBD and PD studies suggest a potential adaptive increase in orexin levels in early stages of the neurodegenerative process, with reduced levels more often reported for later, more advanced stages of illness. To date, no differences in orexin levels were demonstrated between MSA patients and healthy controls. There is a dearth of studies on the role of orexin levels in alpha-synucleinopathies. Moreover, significant methodologic limitations in the current body of work, including use of non-standardised research protocols and lack of prospective, multi-centre studies, disallow for any finite conclusion in regards to underlying pathomechanisms. Nonetheless, a picture of a complex, multifaceted relationship between the dysregulation of the orexinergic pathway and sleep disturbances in alpha-synucleinopathies is emerging. Hence, future studies disentangling orexinergic pathomechanisms of alpha-syncleinopathies are urgently needed to obtain a more comprehensive account of the role of orexinergic pathway in alpha-synucleinopathies. Pharmacological manipulations of orexins may have multiple therapeutic applications in treatment strategies, disease diagnosis, and might be effective for treating both motor and non-motor symptoms.

Sleep-related symptoms in multiple system atrophy: determinants and impact on disease severity

Background:

Sleep disorders are common but under-researched symptoms in patients with multiple system atrophy (MSA). We investigated the frequency and factors associated with sleep-related symptoms in patients with MSA and the impact of sleep disturbances on disease severity.

Methods:

This cross-sectional study involved 165 patients with MSA. Three sleep-related symptoms, namely Parkinson's disease (PD)-related sleep problems (PD-SP), excessive daytime sleepiness (EDS), and rapid eye movement sleep behavior disorder (RBD), were evaluated using the PD Sleep Scale-2 (PDSS-2), Epworth Sleepiness Scale (ESS), and RBD Screening Questionnaire (RBDSQ), respectively. Disease severity was evaluated using the Unified MSA Rating Scale (UMSARS).

Results:

The frequency of PD-SP (PDSS-2 score of ≥18), EDS (ESS score of ≥10), and RBD (RBDSQ score of ≥5) in patients with MSA was 18.8%, 27.3%, and 49.7%, respectively. The frequency of coexistence of all three sleep-related symptoms was 7.3%. Compared with the cerebellar subtype of MSA (MSA-C), the parkinsonism subtype of MSA (MSA-P) was associated with a higher frequency of PD-SP and EDS, but not of RBD. Binary logistic regression revealed that the MSA-P subtype, a higher total UMSARS score, and anxiety were associated with PD-SP; that male sex, a higher total UMSARS score, the MSA-P subtype, and fatigue were associated with EDS; and that male sex, a higher total UMSARS score, and autonomic onset were associated with RBD in patients with MSA. Stepwise linear regression showed that the number of sleep-related symptoms (PD-SP, EDS, and RBD), disease duration, depression, fatigue, and total Montreal Cognitive Assessment score were predictors of disease severity in patients with MSA.

Conclusions:

Sleep-related disorders were associated with both MSA subtypes and the severity of disease in patients with MSA, indicating that sleep disorders may reflect the distribution and degree of dopaminergic/non-dopaminergic neuron degeneration in MSA.

Current Management and Emerging Therapies in Multiple System Atrophy

Multiple system atrophy (MSA) is a progressive neurodegenerative disease variably associated with motor, nonmotor, and autonomic symptoms, resulting from putaminal and cerebellar degeneration and associated with glial cytoplasmic inclusions enriched with α-synuclein in oligodendrocytes and neurons. Although symptomatic treatment of MSA can provide significant improvements in quality of life, the benefit is often partial, limited by adverse effects, and fails to treat the underlying cause. Consistent with the multisystem nature of the disease and evidence that motor symptoms, autonomic failure, and depression drive patient assessments of quality of life, treatment is best achieved through a coordinated multidisciplinary approach driven by the patient's priorities and goals of care. Research into disease-modifying therapies is ongoing with a particular focus on synuclein-targeted therapies among others. This review focuses on both current management and emerging therapies for this devastating disease.

New tricks for an old dog: A repurposing approach of apomorphine

Apomorphine is a 150-year old nonspecific dopaminergic agonist, currently indicated for treating motor fluctuations in Parkinson's disease. At the era of drug repurposing, its pleiotropic biological functions suggest other possible uses. To further explore new therapeutic and diagnostic applications, the available literature up to July 2018 was reviewed using the PubMed and Google Scholar databases. As many of the retrieved articles consisted of case reports and preclinical studies, we adopted a descriptive approach, tackling each area of research in turn, to give a broad overview of the potential of apomorphine. Apomorphine may play a role in neurological diseases like restless legs syndrome, Huntington's chorea, amyotrophic lateral sclerosis, Alzheimer's disease and disorders of consciousness, but also in sexual disorders, neuroleptic malignant(-like) syndrome and cancer. Further work is needed in both basic and clinical research; current developments in novel delivery strategies and apomorphine derivatives are expected to open the way.

Multiple System Atrophy: An Oligodendroglioneural Synucleinopathy1

Multiple system atrophy (MSA) is an orphan, fatal, adult-onset neurodegenerative disorder of uncertain etiology that is clinically characterized by various combinations of parkinsonism, cerebellar, autonomic, and motor dysfunction. MSA is an α-synucleinopathy with specific glioneuronal degeneration involving striatonigral, olivopontocerebellar, and autonomic nervous systems but also other parts of the central and peripheral nervous systems. The major clinical variants correlate with the morphologic phenotypes of striatonigral degeneration (MSA-P) and olivopontocerebellar atrophy (MSA-C). While our knowledge of the molecular pathogenesis of this devastating disease is still incomplete, updated consensus criteria and combined fluid and imaging biomarkers have increased its diagnostic accuracy. The neuropathologic hallmark of this unique proteinopathy is the deposition of aberrant α-synuclein in both glia (mainly oligodendroglia) and neurons forming glial and neuronal cytoplasmic inclusions that cause cell dysfunction and demise. In addition, there is widespread demyelination, the pathogenesis of which is not fully understood. The pathogenesis of MSA is characterized by propagation of misfolded α-synuclein from neurons to oligodendroglia and cell-to-cell spreading in a "prion-like" manner, oxidative stress, proteasomal and mitochondrial dysfunction, dysregulation of myelin lipids, decreased neurotrophic factors, neuroinflammation, and energy failure. The combination of these mechanisms finally results in a system-specific pattern of neurodegeneration and a multisystem involvement that are specific for MSA. Despite several pharmacological approaches in MSA models, addressing these pathogenic mechanisms, no effective neuroprotective nor disease-modifying therapeutic strategies are currently available. Multidisciplinary research to elucidate the genetic and molecular background of the deleterious cycle of noxious processes, to develop reliable biomarkers and targets for effective treatment of this hitherto incurable disorder is urgently needed.

Hypersomnia in Neurodegenerative Diseases

Hypersomnia is a common complaint in many patients with neurodegenerative diseases and a major cause of decreased quality of life. This article discusses the prevalence and factors associated with hypersomnia in patients with a variety of neurodegenerative diseases affecting the central nervous system, including tauopathies, synucleinopathies, and other conditions. Common nocturnal sleep problems that may result in daytime hypersomnia are delineated. A clinical approach to hypersomnia in patients with neurodegenerative diseases, recommended diagnostic testing, and available treatment options are also discussed.

Selective Serotonin Reuptake Inhibitor/Serotonin-Norepinephrine Reuptake Inhibitor Use as a Predictor of a Diagnosis of Restless Legs Syndrome

OBJECTIVE/BACKGROUND

Because restless legs syndrome (RLS) is a problematic syndrome, demonstrating an association between use of selective serotonin reuptake inhibitors (SSRIs)/serotonin-norepinephrine reuptake inhibitors (SNRIs) and RLS may help direct patient care. The goals of this study were (1) to establish the incidence of RLS in mental health patients being treated with SSRIs or SNRIs in a local Veterans Affairs medical center and (2) to evaluate the frequency with which certain SSRIs or SNRIs are associated with RLS and the trend in frequency of the diagnosis since the revision of the criteria for RLS offered by the International Restless Leg Syndrome Study Group (IRLSSG), the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and the International Classification of Sleep Disorders, Revised (ICSD-3).

METHODS

A retrospective chart review was used to evaluate the number of patients receiving SSRI/SNRI therapy with and without a diagnosis of RLS, with the date of the RLS diagnosis and initiation of SSRI/SNRI therapy noted. The frequency with which certain SSRIs/SNRIs were associated with RLS, and the frequency of RLS diagnoses since January 2012 were also noted. Descriptive statistics and logistic regression were used for data analysis.

RESULTS

A total of 254 charts were reviewed. A majority of the patients (89.8%) were male, and 14 (5.5%) were diagnosed with RLS. A logistic regression equation approached significance in predicting RLS (P=0.053). Age and sex emerged as significant predictors of RLS. The prevalence of any individual SSRI or SNRI being associated with RLS was indeterminable. No difference was seen in the number of RLS diagnoses since the refining of the IRLSSG, DSM-5, and ICSD-3 criteria.

CONCLUSIONS

The use of SSRIs/SNRIs does not seem to be associated with a diagnosis of RLS. In addition, the diagnosis of RLS does not seem to have become more common since the revision of the diagnostic criteria for the disorder.

Mechanisms and prevention of sudden death in multiple system atrophy

BACKGROUND

Sudden death in multiple system atrophy (MSA) usually occurs during sleep and was therefore attributed to suffocation resulting from vocal cord abductor paralysis, a characteristic laryngeal finding of MSA. This led to the use of tracheostomy and noninvasive positive pressure ventilation (NPPV) for the prevention of sudden death. However, neither method has been able to prevent sudden death, and both have occasionally precipitated treatment-related complications, including central sleep apneas and exacerbation of floppy epiglottis. Therefore, it is important to determine the mechanisms and prevention of sudden death in MSA.

METHODS

We reviewed the literature on the mechanisms and prevention of sudden death in patients with MSA.

RESULTS

Sudden death in MSA is hypothesized to be a consequence of disordered central respiration, suffocation caused by sputum and food, upper airway obstruction from NPPV acting on a floppy epiglottis, cardiac autonomic disturbance, or a combination of these factors.

CONCLUSION

Various factors may be involved in the mechanism of sudden death in MSA. A multidisciplinary approach is needed to prevent sudden death, and this requires an organized system of several medical specialties. Neurologists require a cooperative network that includes experts in otorhinolaryngology, sleep medicine, dysphagia rehabilitation, and cardiology.

Current Concepts in the Treatment of Multiple System Atrophy

MSA is a progressive neurodegenerative disorder characterized by autonomic failure and a variable combination of poor levodopa-responsive parkinsonism and cerebellar ataxia (CA). Current therapeutic management is based on symptomatic treatment. Almost one third of MSA patients may benefit from l-dopa for the symptomatic treatment of parkinsonism, whereas physiotherapy remains the best therapeutic option for CA. Only midodrine and droxidopa were found to be efficient for neurogenic hypotension in double-blind, controlled studies, whereas other symptoms of autonomic failure may be managed with off-label treatments. To date, no curative treatment is available for MSA. Recent results of neuroprotective and -restorative trials have provided some hope for future advances. Considerations for future clinical trials are also discussed in this review.