Multiple system atrophy presenting as central sleep apnoea: Fig. 1.—

Sleep Dysfunction in Movement Disorders: a Window to the Disease Biology

PURPOSE OF REVIEW

To comprehensively summarize the sleep pathologies associated with movement disorders, focusing on neurodegenerative diseases.

RECENT FINDINGS

Mounting evidence has further implicated both sleep and circadian disruption in the pathophysiology of many movement disorders. In particular, recent data illuminate the mechanisms by which poor sleep quality and circadian dysfunction can exacerbate neurodegeneration. In addition, anti-IgLON5 disease is a recently described autoimmune disease with various symptoms that can feature prominent sleep disruption and parasomnia. Many movement disorders are associated with sleep and circadian rhythm disruption. Motor symptoms can cause sleep fragmentation, resulting in insomnia and excessive daytime sleepiness. Many neurodegenerative movement disorders involve brainstem pathology in regions close to or affecting nuclei that regulate sleep and wake. Further, commonly used movement medications may exacerbate sleep concerns. Providers should screen for and address these sleep symptoms to improve function and quality of life for patients and caregivers.

Diagnosis and management of central sleep apnea syndrome

Introduction: Central sleep apnea (CSA) syndrome has gained a considerable interest in the sleep field within the last 10 years. It is overrepresented in particular subpopulations such as patients with stroke or heart failure. Early detection and diagnosis, as well as appropriate treatment of central breathing disturbances during sleep remain challenging. Areas covered: Based on a systematic review of CSA in adults the clinical evidence and polysomnographic patterns useful for discerning central from obstructive events are discussed. Current therapeutic indications of CSA and perspectives are presented, according to the type of respiratory disturbances during sleep, alterations in blood gases and ventilatory control. Expert opinion: The precise identification of central events during polysomnographic recording is mandatory. Therapeutic choices for CSA depend on the typology of respiratory disturbances observed by polysomnography, changes in blood gases and ventilatory control. In CSA with normocapnia and ventilatory instability, adaptive servo-ventilation is recommended. In CSA with hypercapnia and/or rapid-eye movement sleep hypoventilation, non-invasive ventilation is required. Further studies are required as strong evidence is lacking regarding the long-term consequences of CSA and the long-term impact of current treatment strategies.

Central Apneas and REM Sleep Behavior Disorder as an Initial Presentation of Multiple System Atrophy

ABSTRACT

We present the case of a patient with multiple system atrophy who presented with central apnea as the only sleep disordered breathing, associated with REM behavior disorder and restless legs syndrome. This presentation of the disease is unusual and probably reflects more widespread involvement at the onset. With this case, we show the importance of considering this kind of disease in the differential diagnosis of central sleep apnea syndromes.

Sleep Disorders in Atypical Parkinsonism

Sleep disorders are commonly seen in atypical parkinsonism, with particular disorders occurring more frequently in specific parkinsonian disorders. Multiple systems atrophy (MSA) is a synucleinopathy often associated with nocturnal stridor which is a serious, but treatable condition highly specific to MSA. In addition, this disorder is strongly associated with rapid eye movement (REM) sleep behavior disorder (RBD), which is also seen in dementia with Lewy bodies (DLB). RBD is far less prevalent in progressive supranuclear palsy (PSP), which is a tauopathy. Insomnia and impaired sleep architecture are the most common sleep abnormalities seen in PSP. Corticobasilar degeneration (CBD) is also a tauopathy, but has far fewer sleep complaints associated with it than PSP. In this manuscript we review the spectrum of sleep dysfunction across the atypical parkinsonian disorders, emphasize the importance of evaluating for sleep disorders in patients with parkinsonian symptoms, and point to sleep characteristics that can provide diagnostic clues to the underlying parkinsonian disorder.

Breathing variability and brainstem serotonergic loss in a genetic model of multiple system atrophy

Breathing disorders like sleep apnea, stridor, and dysrythmic breathing are frequent in patients with multiple system atrophy (MSA). These observations have been related to neurodegeneration in several pontomedullary respiratory nuclei and may explain the occurrence of sudden death. In this study, we sought to determine whether these functional and neuropathological characteristics could be replicated in a transgenic model of MSA. Mice expressing human wild-type α-synuclein under the control of the proteolipid promoter (PLP-αSYN) were compared with age-matched controls. Using whole-body, unrestrained plethysmography, the following breathing parameters were measured: inspiratory and expiratory times, tidal volume, expiratory volume, peak inspiratory and expiratory flows, and respiratory frequency. For each category, the mean, coefficient of variation, and irregularity score were analyzed. Brains were then processed for stereological cell counts of pontomedullary respiratory nuclei. A significant increase in the coefficient of variation and irregularity score was observed for inspiratory time, tidal volume, and expiratory volume in PLP-αSYN mice (P < 0.05). Glial cytoplasmic inclusions were found in the medullary raphe of PLP-αSYN mice, together with a loss of serotonergic immunoreactivity in the raphe obscurus (P < 0.001) and pallidus (P < 0.01). There was a negative correlation between α-synuclein burden and raphe pallidus cell counts (P < 0.05). There was no significant neuronal loss in the pre-Botzinger complex. The PLP-αSYN mouse model replicates the breathing variability and part of the neuronal depletion in pontomedullary respiratory nuclei observed in patients with MSA. Our findings support the use of this model for future candidate drugs in the breathing disorders observed in MSA.

Multiple system atrophy: current and future approaches to management

Multiple system atrophy (MSA) is a rare neurodegenerative disorder without any effective treatment in slowing or stopping disease progression. It is characterized by poor levodopa responsive Parkinsonism, cerebellar ataxia, pyramidal signs and autonomic failure in any combination. Current therapeutic strategies are primarily based on dopamine replacement and improvement of autonomic failure. However, symptomatic management remains disappointing and no curative treatment is yet available. Recent experimental evidence has confirmed the key role of alpha-synuclein aggregation in the pathogenesis of MSA. Referring to this hypothesis, transgenic and toxic animal models have been developed to assess candidate drugs for MSA. The standardization of diagnosis criteria and assessment procedures will allow large multicentre clinical trials to be conducted. In this article we review the available symptomatic treatment, recent results of studies investigating potential neuroprotective drugs, and future approaches for the management in MSA.

Multiple-system atrophy with cerebellar predominance presenting as respiratory insufficiency and vocal cords paralysis

Background. MSA (Multiple System Atrophy) may be associated either with Parkinsonism or with cerebellar ataxia (MSA-c subtype). It is considered a rare disease, but many patients are misdiagnosed as suffering from idiopathic Parkinson's disease. In this paper, we report a case of a patient admitted with respiratory failure and vocal cords paralysis due to MSA-c. Case Report. A 79-year-old Caucasian woman was admitted in March 2010 with dyspnea, asthenia, stridor, and respiratory failure needing noninvasive ventilation. She had orthostatic blood pressure decline, constipation, insomnia, daytime sleepiness, and snoring. The neurologic examination revealed cerebellar ataxia. A laryngoscopy revealed vocal cord paralysis in midline position and tracheostomy was performed. The Brain Magnetic Resonance Imaging revealed atrophy of middle cerebellar peduncles and pons with the “hot cross bun sign.” Conclusion. Although Multiple-system atrophy is a rare disease, unexplained respiratory failure, bilateral vocal cord paralysis, or stridor should lead to consider MSA as diagnosis.

Hypoventilation syndromes

A wide variety of mechanisms can lead to the hypoventilation associated with various medical disorders, including derangements in central ventilatory control, mechanical impediments to breathing, and abnormalities in gas exchange leading to increased dead space ventilation. The pathogenesis of hypercapnia in obesity hypoventilation syndrome remains somewhat obscure, although in many patients comorbid obstructive sleep apnea appears to play an important role. Hypoventilation in neurologic or neuromuscular disorders is primarily explained by weakness of respiratory muscles, although some central nervous system diseases may affect control of breathing. In other chest wall disorders, obstructive airways disease, and cystic fibrosis, much of the pathogenesis is explained by mechanical impediments to breathing, but an element of increased dead space ventilation also often occurs. Central alveolar hypoventilation syndrome involves a genetically determined defect in central respiratory control. Treatment in all of these disorders involves coordinated management of the primary disorder (when possible) and, increasingly, the use of noninvasive positive pressure ventilation.

Depletion of medullary serotonergic neurons in patients with multiple system atrophy who succumbed to sudden death

Multiple system atrophy (MSA) is a neurodegenerative disorder characterized by prominent autonomic failure with ataxia and/or parkinsonism. The leading cause of death in MSA is sudden death. We have shown that the early development of autonomic failure is an independent risk factor for sudden death. The depletion of sympathetic preganglionic neurons in the spinal intermediolateral cell column (IML) and its afferent medullary catecholaminergic and serotonergic neurons has been proposed to be partly responsible for autonomic failure in MSA. In this study, we investigated whether the depletion of neurons in any of these autonomic neuron groups contributes to sudden death in MSA. Out of 52 autopsy-proven patients with MSA, we selected 12 individuals who had died within 3.5 years after disease onset to define the accurate levels of slices and identify early neuropathological changes of autonomic nuclei in MSA. Four patients succumbed to sudden death and eight patients died through established causes. Serial 10 mum sections were obtained from the 8th segment of the thoracic cord and the rostral medulla oblongata. Sections from the medulla oblongata were immunostained for thyrosine hydroxylase and tryptophan hydroxylase. The total cell number in the five sections was computed for comparison. Compared with the control, the MSA group showed a marked depletion of neurons in the IML (38.0 +/- 7.1 versus 75.2 +/- 7.6 cells, P < 0.001), thyrosine hydroxylase-immunoreactive neurons in the ventrolateral medulla (VLM) (17.4 +/- 5.1 versus 72.8 +/- 13.6 cells, P < 0.01) and tryptophan hydroxylase-immunoreactive neurons in the VLM (15.6 +/- 9.2 versus 60.8 +/- 17.0 cells, P < 0.01), nucleus raphe obscurus (19.3 +/- 4.4 versus 75.3 +/- 8.6 cells, P < 0.001), nucleus raphe pallidus (2.1 +/- 2.7 versus 9.0 +/- 3.4 cells, P < 0.03), and arcuate nucleus (0.4 +/- 0.8 versus 2.3 +/- 1.5 cells, P < 0.05). Moreover, in patients who succumbed to sudden death, when compared with patients who had established causes of death, we found a marked depletion of tryptophan hydroxylase-immunoreactive neurons in the VLM (7.3 +/- 3.5 versus 21.8 +/- 6.5 cells, P < 0.02) and nucleus raphe obscurus (15.0 +/- 2.0 versus 22.5 +/- 2.1 cells, P < 0.01). The results indicate that the spinal IML and medullary catecholaminergic and serotonergic systems are involved even in the early stages of MSA, and the dysfunction of the medullary serotonergic system regulating cardiovascular and respiratory systems could be responsible for sudden death in patients with MSA.

Multiple system atrophy manifesting as complex sleep-disordered breathing

A 56-year-old female presented with multiple system atrophy (MSA) and pure obstructive sleep-disordered breathing (SDB) with an apnea hypopnea index of 29.6/h. However, after the elimination of obstructive events, central apneas emerged with a central apnea index (CAI) of 45.3/h as determined by continuous positive airway pressure titration. Adaptive servoventilation titration decreased the CAI; however, it remained at 14.2/h. There are two different underlying causes of SDB in MSA patients, one is upper airway obstruction at the glottic level, and the other is central components owing to the degeneration of the pontomedullary respiratory centers. Clinicians should recognize that whether a patient has central apnea cannot be determined by diagnostic polysomnography but only after the elimination of upper airway obstruction in MSA patients.

Abnormalities of respiratory control and the respiratory motor unit

BACKGROUND

Control of ventilation depends on a brainstem neuronal network that controls activity of the motor neurons innervating the respiratory muscles. This network includes the pontine respiratory group and the dorsal and ventral respiratory groups in the medulla. Neurologic disorders affecting these areas or the respiratory motor unit may lead to abnormal breathing.

REVIEW SUMMARY

The brainstem respiratory network contains neurons critical for respiratory rhythmogenesis; this network receives inputs from peripheral and central chemoreceptors sensitive to levels of carbon dioxide (PaCO2) and oxygen (PaO2) and from forebrain structures that control respiration as part of integrated behaviors such as speech or exercise. Manifestations associated with disorders of this network include sleep apnea and dysrhythmic breathing frequently associated with disturbances of cardiovagal and sympathetic vasomotor control. Common disorders associated with impaired cardiorespiratory control include brainstem stroke or compression, syringobulbia, Chiari malformation, high cervical spinal cord injuries, and multiple system atrophy. By far, neuromuscular disorders are the more common neurologic conditions leading to respiratory failure.

CONCLUSIONS

Respiratory dysfunction constitute an early and relatively major manifestation of several neurologic disorders and may be due to an abnormal breathing pattern generation due to involvement of the cardiorespiratory network or more frequently to respiratory muscle weakness.

Idiopathic central sleep apnoea syndrome treated with zolpidem

We report the case of a 47-year-old man with idiopathic central sleep apnoeas recurring during wake-sleep transitions at night or at diurnal naps. Symptoms associated with central apnoeas were sudden awakening with shortness of breath, sleep fragmentation and daytime tiredness. Following the failure of CPAP and BiPAP, we treated the patient with zolpidem which reduced central apnoea events, improved sleep and eliminated the patient's nocturnal disturbing symptoms. Beneficial effects were still present after two years of treatment. Our case demonstrates that zolpidem may be beneficial in the long term treatment of idiopathic central sleep apnoea syndrome.

Unilateral ablation of pre-Botzinger complex disrupts breathing during sleep but not wakefulness

RATIONALE

In adult rats, bilateral ablation of pre-Bötzinger complex (preBötC) neurokinin 1-expressing (NK1R) neurons leads to a progressive and irreversible disruption in breathing pattern, initially during sleep, eventually resulting in an ataxic breathing pattern during wakefulness.

OBJECTIVES

Here we determine whether ablation of fewer preBötC NK1R neurons leads to a persistent pattern of disordered breathing during sleep but not during wakefulness.

METHODS

Adult male Sprague-Dawley rats (n = 12) were instrumented to record diaphragmatic, abdominal, and neck EMG, and EEG. Fourteen days later, a second surgery was performed to stereotaxically microinject into the preBötC on one side the toxin saporin conjugated to substance P (SP-SAP), which selectively ablates NK1R neurons.

MEASUREMENTS AND MAIN RESULTS

Postinjection, rats were monitored within a plethysmograph until they were killed (Days 21-51). At Days 6-9 post-unilateral SP-SAP injection, respiratory pattern during sleep, particularly REM sleep, became increasingly disordered, characterized by an increase in frequency of central sleep apnea and hypopneas (36.8 +/- 7.4 episodes/h of REM vs. 6 +/- 2.0 episodes/h in preinjection controls; P < 0.05), whereas breathing during resting wakefulness remained stable. Unlike bilateral SP-SAP-injected rats, an ataxic breathing pattern did not develop during wakefulness. Rats that were monitored up to 51 days post-SP-SAP injection continued to have sleep-disordered breathing; breathing during wakefulness remained relatively stable. Histologic analysis of the ventrolateral medulla confirmed that NK1R neurons within the preBötC on the injected but not on the contralateral side of the medulla were ablated.

CONCLUSIONS

Gradual loss of preBötC NK1R neurons may be an underlying factor of sleep-disordered breathing, in particular of central sleep apnea.

Ventilatory constraints and dyspnea during exercise in chronic obstructive pulmonary disease

Dyspnea (respiratory difficulty) and activity limitation are the primary symptoms of chronic obstructive pulmonary disease (COPD) and progress relentlessly as the disease advances, contributing to reduced quality of life. In COPD, the mechanisms of dyspnea are multifactorial, but abnormal dynamic ventilatory mechanics are believed to play a central role. In flow-limited patients with COPD, dynamic lung hyperinflation (DH) occurs during exercise and has serious sensory and mechanical consequences. In several studies, indices of DH strongly correlate with ratings of dyspnea intensity during exercise, and strategies that reduce resting hyperinflation (either pharmacological or surgical) consistently result in reduced exertional dyspnea. The mechanisms by which DH gives rise to exertional dyspnea and exercise intolerance are complex, but recent mechanistic studies suggest that DH-induced inspiratory muscle loading, restriction of tidal volume expansion during exercise, and consequent neuromechanical uncoupling of the respiratory system are key components. This review examines the specific derangements of ventilatory mechanics that occur in COPD during exercise and attempts to provide a mechanistic rationale for the attendant respiratory discomfort and activity limitation.

Severe sleep-disordered breathing in a patient with Brown–Vialetto–Van Laere syndrome: Polysomnographic findings

Brown-Vialetto-Van Laere (BVVL) syndrome is a rare disorder with clinical features that include progressive bilateral sensorineural deafness and a variety of cranial nerve impairments. Respiratory compromise has been observed in most familial and sporadic cases; however, few studies have been published regarding sleep-disordered breathing in this syndrome. We report the unique case of a 16-year-old girl with the clinical features of BVVL syndrome who presented with bilateral sensorineural hearing loss and then progressively developed paralysis of the 7th and 9th-12th cranial nerves. More importantly, she presented with the unusual feature of severe sleep-disordered breathing. A polysomnographic study showed evidence of dominant central sleep apnea, and the majority of apneic episodes more likely occurred in stage 2 during NREM sleep. The central sleep apnea was associated with rapid respiratory deterioration and death. This report raises the fact that a patient with BVVL syndrome may present with severe sleep-disordered breathing as a life-threatening condition, which emphasizes the need for greater attention to the early detection of potential sleep-disordered breathing in these afflicted with the BVVL syndrome for optimal clinical management.

Morphological substrate of autonomic failure and neurohormonal dysfunction in multiple system atrophy: impact on determining phenotype spectrum

Autonomic failure is a prominent clinical feature of patients with multiple system atrophy (MSA). Neurohormonal dysfunction is also a frequent accompaniment in patients with MSA. The determination of the pathological involvement of the autonomic neurons, which are responsible for circadian rhythms and responses to stress, provides new insight into autonomic failure and neurohormonal dysfunction in MSA. The disruptions of circadian rhythms and responses to stress may underlie the impairment of homeostatic integration responsible for cardiovascular and respiratory failures. These notions lead to the hypothesis that a pathological involvement of autonomic neurons is a significant factor of the poor prognosis of MSA. Beyond this perspective, endeavors to find the morphological phenotype that represents a predominant loss of autonomic neurons may elucidate the full spectrum of pathological involvements in MSA.

Sleep-related stridor due to dystonic vocal cord motion and neurogenic tachypnea/tachycardia in multiple system atrophy

Sleep-disordered breathing and sleep-related motor phenomena are part of the clinical spectrum of multiple system atrophy (MSA). Stridor has been attributed to denervation of laryngeal muscles or instead to dystonic vocal cord motion. We studied 3 patients with nocturnal stridor in the setting of MSA. All patients underwent nocturnal videopolysomnography (VPSG) with breathing and heart rate, O(2) saturation and intra-esophageal pressure recordings, and simultaneous EMG recordings of the posterior cricoarytenoid, cricothyroid, and thyroarytenoid muscles and continuous vocal cord motion evaluation by means of fiberoptic laryngoscopy. VPSG/EMG and fiberoptic laryngoscopy documented normal vocal cord motion without denervation during wake and stridor only during sleep when hyperactivation of vocal cords adductors appeared in the absence of significant O(2) desaturation. All patients had tachycardia and tachypnea and paradoxical breathing during sleep, erratic intercostalis and diaphragmatic EMG activity and Rem sleep behavior disorder. One of the patients had restless legs syndrome with periodic limb movement during sleep and excessive fragmentary hypnic myoclonus. In conclusion, our patients with MSA had nocturnal stridor due to sleep-related laryngeal dystonia. Stridor was associated with other abnormal sleep-related respiratory and motor disorders, suggesting an impairment of homeostatic brainstem integration in MSA.

Brainstem respiratory control: substrates of respiratory failure of multiple system atrophy

Multiple system atrophy may manifest with severe respiratory disorders, including sleep apnea and laryngeal stridor, which reflect a failure of automatic control of respiration. This function depends on a pontomedullary network of interconnected neurons located in the parabrachial/Kölliker Fuse nucleus in the pons, nucleus of the solitary tract, and ventrolateral medulla. Neurons in the preBötzinger complex expressing neurokinin-1 receptors are critically involved in respiratory rhythmogenesis, whereas serotonergic neurons in the medullary raphe and glutamatergic neurons located close to the ventral medullary surface are involved in central chemosensitivity to hypercapnia, hypoxia, or both. Pathological studies using selective neurochemical markers indicate that these neuronal groups are affected in multiple system atrophy. This finding may provide potential anatomical substrates for the respiratory manifestations of the disease.

Effect of bronchoscopic lung volume reduction on dynamic hyperinflation and exercise in emphysema

Endobronchial valve placement improves pulmonary function in some patients with chronic obstructive pulmonary disease, but its effects on exercise physiology have not been investigated. In 19 patients with a mean (SD) FEV(1) of 28.4 (11.9)% predicted, studied before and 4 weeks after unilateral valve insertion, functional residual capacity decreased from 7.1 (1.5) to 6.6 (1.7) L (p = 0.03) and diffusing capacity rose from 3.3 (1.1) to 3.7 (1.2) mmol . minute(-1) . kPa(-1) (p = 0.03). Cycle endurance time at 80% of peak workload increased from 227 (129) to 315 (195) seconds (p = 0.03). This was associated with a reduction in end-expiratory lung volume at peak exercise from 7.6 (1.6) to 7.2 (1.7) L (p = 0.03). Using stepwise logistic regression analysis, a model containing changes in transfer factor and resting inspiratory capacity explained 81% of the variation in change in exercise time (p < 0.0001). The same variables were retained if the five patients with radiologic atelectasis were excluded from analysis. In a subgroup of patients in whom invasive measurements were performed, improvement in exercise capacity was associated with a reduction in lung compliance (r(2) = 0.43; p = 0.03) and isotime esophageal pressure-time product (r(2) = 0.47; p = 0.03). Endobronchial valve placement can improve lung volumes and gas transfer in patients with chronic obstructive pulmonary disease and prolong exercise time by reducing dynamic hyperinflation.