Breathing disorders during sleep in myasthenia gravis

Palatal prolapse during nasal expiration in patients with myasthenia gravis

INTRODUCTION/AIMS

We have encountered patients with myasthenia gravis (MG) who exhibited palatal prolapse (PP) during nasal expiration in the supine position while awake. This may be an overlooked cause of dyspnea in MG patients. This study aimed to examine and describe the characteristics of MG patients with PP.

METHODS

We reviewed the medical records of 183 consecutive patients who were diagnosed with MG in our hospital from 2012 to 2021. Thirty-two patients underwent laryngoscopy because of bulbar symptoms. Eight of these patients (25%) exhibited PP on laryngoscopy. Clinical features of these eight patients were retrospectively characterized.

RESULTS

Median age of the eight patients with PP was 70 years. Six were men. Median body mass index was 21.6 kg/m2 . All patients exhibited PP in the supine position but not the sitting position. Although no patient had abnormal findings on spirometry nor chest computed tomography, six reported dyspnea or difficulty with nasal expiration only in the supine position. PP improved in all four patients who underwent edrophonium testing. All eight patients eventually improved after immunotherapy.

DISCUSSION

PP during nasal expiration may be a cause of dyspnea in MG patients, along with respiratory muscle impairment, lung disease, and vocal cord paralysis. Laryngoscopy in the supine position is required to confirm.

[Sleep disorders in patients with myastenia gravis]

This review analyzes publications that present data on sleep disorders in patients with myasthenia gravis (MG). The analysis is based on domestic and foreign publications that are freely available over the past 30 years. Sleep disorders, the most significant of which are sleep-related respiratory disorders, are one of the factors that cause quality of life decreasing and mortality in patients with neuromuscular diseases. The issues of prevalence of breathing disorders during sleep, relationship of these disorders with clinical and immunological characteristics of disease, demographic indicators are studied. The influence of sleep breathing disorders on quality of life and affective sphere of patients is discussed. Most studies prove that sleep-related respiratory disorders occur in patients with MG significantly more often than in general population. Some studies show a high prevalence of poor sleep quality, excessive daytime sleepiness in patients with MG, while others do not report such associations. However, studies that failed to establish an association with MG and sleep disturbances were of small sample sizes. Thus, given the inconclusive evidence and limited literature, further study of sleep disorders in patients with MG is needed. The topic is relevant and requires further development.

Sleep Disorders in Mitochondrial Diseases

PURPOSE OF REVIEW

We aim to summarize the sleep disorders reported in patients affected by primary mitochondrial dysfunctions and describe the association with their clinical and molecular characteristics.

RECENT FINDINGS

Sleep complaints are prevalent in mitochondrial disorders. Sleep-disordered breathing is the main sleep disorder reported in mitochondrial diseases. OSA and CSA are, respectively, more frequently associated with patients characterized by the prevalent involvement of the skeletal muscle and the predominant involvement of the central nervous system. Other sleep disorders, such as restless legs syndrome, have been rarely described. Sleep disorders are frequently associated with primary mitochondrial disorders, and the clinical phenotypes affect the type of sleep disturbance associated with the mitochondrial dysfunction. A polysomnographic study should be performed in every subject with this neurogenetic disorder both at diagnosis and during follow-up for the numerous adverse clinical outcomes associated with sleep disorders and the frailty of mitochondrial patients.

Myasthenia Symptom Burden, Fatigue, and Sleep: Are They Related?

OBJECTIVE

Our aim is to explore the relationship between myasthenia gravis (MG)-related symptom burden, sleep quality, and fatigue in a diverse group of self-identified MG patients.

METHODS

Patients provided relevant myasthenia disease data and completed the MG QOL-15, Epworth sleepiness scale, Pittsburgh Sleep Quality Index, and fatigue severity score (FSS) online. MG activities of daily living scale (MG-ADL) was completed on a follow-up telephone interview.

RESULTS

One hundred ninety-six patients completed the online survey and 99 provided MG-ADL data. The mean age was 52 ± 15.34 years, 88 were acetylcholine receptor antibody positive, and 21 were muscle specific kinase positive. The mean MG-ADL was 6.81, indicating a moderate MG disease burden. Forty-seven (24%) reported high Epworth sleepiness scale scores, 152 (77%) reported high Pittsburgh Sleep Quality Index scores, and 162 (82%) reported high FSS scores. Correlation analysis correcting for body mass index and sleep apnea revealed a moderate positive correlation between MGQOL-15, MG-ADL, and FSS.

CONCLUSIONS

There is a moderate positive correlation between various MG-specific outcome measures and fatigue severity.

Diagnosis of sleepiness, fatigue and depression in patients with myasthenia gravis

Introduction. Examination of excessive daytime sleepiness, fatigue and depression in patients with myasthenia gravis is important for differential diagnosis of other disorders, and adds to a comprehensive clinical assessment.

Objective. The aim is a comprehensive assessment of sleepiness, fatigue and depression and evaluation of the impact of autoimmune comorbidity on these symptoms in myasthenia gravis patients, using newly validated Russian versions of international questionnaires. The present article aims at familiarizing a wider Russian-speaking audience of specialists in the field of neuromuscular disease and sleep medicine with the main findings of our previously published work.

Materials and methods. The study included 73 patients with MG and 230 control subjects. For sleepiness, fatigue and depression evaluation were used: Fatigue Severity Scale (FSS), Fatigue Impact Scale (FIS) (cognitive / physical / psychosocial subscales), Epworth Sleepiness Scale (ESS), Beck Depression Inventory (BDI) (cognitive-affective and somatic domains), Spielberger–Khanin State Trait Anxiety Inventory (STAI).

Results. The Fatigue Severity Scale and Fatigue Impact Scale showed good psychometric properties and can be used to identify distinct aspects of fatigue in patients with myasthenia gravis. The studied patient cohort revealed clinically significant fatigue (69.9 %), excessive daytime sleepiness (15.1 %), moderate to severe depression (20.5 %), a high level of personal (64.4 %) and situational anxiety (27.4 %). Among 13 patients with myasthenia gravis and additional autoimmune comorbidity, there were no significant differences in the severity of sleepiness, fatigue and depression compared with the main group.

Conclusion. The use of self-reported scale of sleepiness, fatigue and depression combined with careful clinical-neurological characterization adds to a more comprehensive view of the patient. The identification of sleepiness, fatigue and depression can guide therapeutic decisions and contributes to a better patient care. The presence of concomitant autoimmune pathology in patients with myasthenia gravis does not seem to increase the severity of sleepiness, fatigue and depression.

Sleep-Disordered Breathing in Neuromuscular Disease: Diagnostic and Therapeutic Challenges

Normal sleep-related rapid eye movement sleep atonia, reduced lung volumes, reduced chemosensitivity, and impaired airway dilator activity become significant vulnerabilities in the setting of neuromuscular disease. In that context, the compounding effects of respiratory muscle weakness and disease-specific features that promote upper airway collapse or cause dilated cardiomyopathy contribute to various sleep-disordered breathing events. The reduction in lung volumes with neuromuscular disease is further compromised by sleep and the supine position, exaggerating the tendency for upper airway collapse and desaturation with sleep-disordered breathing events. The most commonly identified events are diaphragmatic/pseudo-central, due to a decrease in the rib cage contribution to the tidal volume during phasic rapid eye movement sleep. Obstructive and central sleep apneas are also common. Noninvasive ventilation can improve survival and quality of sleep but should be used with caution in the context of dilated cardiomyopathy or significant bulbar symptoms. Noninvasive ventilation can also trigger sleep-disordered breathing events, including ineffective triggering, autotriggering, central sleep apnea, and glottic closure, which compromise the potential benefits of the intervention by increasing arousals, reducing adherence, and impairing sleep architecture. Polysomnography plays an important diagnostic and therapeutic role by correctly categorizing sleep-disordered events, identifying sleep-disordered breathing triggered by noninvasive ventilation, and improving noninvasive ventilation settings. Optimal management may require dedicated hypoventilation protocols and a technical staff well versed in the identification and troubleshooting of respiratory events.

Home sleep study for patients with myasthenia gravis

OBJECTIVES

The objective of the study was to examine predictors for sleep-disordered breathing (SDB) in patients with myasthenia gravis (MG) using Watch-PAT.

MATERIALS AND METHODS

We prospectively studied 58 consecutive patients with MG without respiratory symptoms for a full-night Watch-PAT with concomitant recording of the MG score and acetylcholine receptor antibody concentration and analyzed potential risk factors of SDB.

RESULTS

Twenty-four patients (41%) had definitive SDB, which was mild in 12 patients, moderate in six, and severe in six. Assessing risk factors with multivariate models, we found four significant predictors (BMI, age, male gender, and use of azathioprine); BMI was the most powerful predictor. The severity and prevalence of sleep-disordered breathing had no significant association with MG score, myasthenia stage, or seropositivity of acetylcholine receptor antibody.

CONCLUSIONS

The prevalence of SDB in myasthenic patients with mild and moderate weakness was high when using the Watch-PAT. Both myasthenia-specific factors (use of azathioprine) and general predictors in terms of BMI, age, and male gender predisposed the development of SDB in patients with myasthenia gravis. Careful screening of patients with myasthenia gravis at risk of SDB using Watch-PAT might improve the quality of sleep and cardiovascular health through proper treatment of underlying SDB.

Sleep disorders in patients with myasthenia gravis: a systematic review

[Purpose] This systematic review evaluated the presence of sleep-disordered breathing in patients with myasthenia gravis and clarified the role of physiotherapy. [Subjects and Methods] We followed the PRISMA declaration criteria. The evaluation was performed in accordance with the STROBE statement for observational and cross-sectional studies and the CONSORT checklist for clinical trials. Searches were followed by hand on MEDLINE, EMBASE, SciELO, PubMed Central, and the Cochrane Central Register of Controlled Trials. [Results] Our searches yielded a total of 36 studies published between 1970 and 2014. The number of patients involved ranged from 9–490. Of the 36 studies, 19 articles were excluded because they did not meet the inclusion criteria. Therefore, 17 observational, cross-sectional, or clinical studies assessing the quality of sleep and prevalence of sleep disorders in patients with myasthenia gravis were eligible for our review. [Conclusion] Some studies of patients with MG show that patients with MG are associated with poor sleep quality, excessive daytime sleepiness, presence of restless syndrome, and a higher incidence of SDB, while other studies do not report such associations. Therefore, given the current inconclusive evidence and limited literature, further study of sleep disturbances in patients with MG is needed.

Fatigue in myasthenia gravis: is it more than muscular weakness?

Background

Few studies have focused on fatigue in myasthenia gravis (MG), and fatigue in relation to the autonomic system has never been systematically explored in these patients. The study aimed to document the prevalence of MG-related fatigue in ethnic Norwegians and to examine whether MG severity is associated with symptoms of autonomic disturbance, which in turn is associated with fatigue and functional disability.

Methods

Eighty two of the 97 who fulfilled the study inclusion criteria participated in the study. Controls were 410 age- and sex-matched subjects drawn from a normative sample (n = 2136) representative of the Norwegian population. Bivariate analyses and multivariate linear regression analyses were used to assess associations between questionnaire-reported MG severity, symptoms of autonomic disturbance, fatigue (mental and physical) and functional disability.

Results

Forty-four per cent (36/82) of patients fulfilled the criteria for fatigue compared with 22% (90/410) of controls (odds ratio 2.0; p = 0.003). Twenty-one per cent of patients (17/82) met the criteria for chronic fatigue versus 12% (48/410) of controls (odds ratio 1.96; p = 0.03). MG patients had higher total fatigue scores than controls (p < 0.001) and a high prevalence of autonomic symptoms, especially poor thermoregulation and sleep disturbance. According to multivariate analyses controlled for MG score, symptoms of autonomic disturbances were independently positively associated with fatigue (p < 0.001), and fatigue was independently negatively associated with functional level (p < 0.001).

Conclusion

Norwegian ethnic patients with MG have higher levels of fatigue and a higher prevalence of chronic fatigue than controls, even in patients in full remission. MG severity is highly suggestive to be associated with symptoms of autonomic disturbance, which in turn is associated with fatigue and the level of functional disability.

Myasthenia gravis, schizophrenia, and colorectal cancer in a patient: long-term follow-up with medication complexity

In a case of 46-year-old woman suffering from schizophrenia for over 20 years, she experienced frequent episodes of dyspnea and confirmed as superimposed with myasthenia gravis (MG). Throughout the seven-year follow-up period, after diagnosed as MG, she has been hospitalized 6 times and also diagnosed as colorectal cancer. Authors experienced various conditions associated with untoward effects of medication for myasthenia, schizophrenia, and colorectal cancer. Therefore, authors reported considerations for the pharmacotherapy of schizophrenia with myasthenia gravis.

Myasthenia gravis: sleep quality, quality of life, and disease severity

INTRODUCTION

There is much research on quality of life in myasthenia gravis (MG), and its relationship to disease severity is well-established. However, evidence regarding sleep disturbance in MG is inconclusive.

METHODS

To evaluate sleep and quality of life among clinically stable MG patients, 54 subjects were investigated by means of the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and 15-Item-Quality-Of-Life Instrument for MG (MG-QOL15).

RESULTS

A pathological PSQI score, which was observed in 59% of patients, was increased in subjects with active disease compared with patients in clinical remission [odds ratio = 4.3; confidence interval 95% (1.0-17.6); P = 0.04]. We found a relationship between PSQI and MG-QOL15 scores in patients with clinically active disease (r = 0.62; P < 0.001).

CONCLUSIONS

Our study highlights the high prevalence of sleep disturbance among MG patients. Disease severity may be considered to be a MG-specific risk factor for patient-reported sleep disturbance. The MG-QOL15 and PSQI should be used to estimate the impact of the disease on sleep and quality of life.

Long-term respiratory muscle endurance training in patients with myasthenia gravis: first results after four months of training

Myasthenia gravis (MG) is characterized by reduced muscle endurance and is often accompanied by respiratory complications. Improvement of respiratory function is therefore an important objective in MG therapy. A previous study demonstrated that respiratory muscle endurance training (RMET) over four weeks increased respiratory muscle endurance of MG patients to about 200% of baseline. The purpose of the present study was to establish an appropriate maintenance training and to test its effects over four months. Ten patients with mild to moderate MG participated in this study. During the first month, they performed five training sessions per week. For the following 3 months, training frequency was reduced to five sessions per two weeks. Myasthenia score, lung function, and respiratory endurance were determined prior to training, after the first month, and after 4 months. Myasthenia score improved from 0.71 ± 0.1 to 0.56 ± 0.1 (P = 0.007). Respiratory endurance time increased from 6.1 ± 0.8 to 20.3 ± 3.0 min (P < 0.001). In conclusion, this RMET maintenance program is feasible and is significantly beneficial for MG patients.

Airway limitation and exercise intolerance in well-regulated myasthenia gravis patients

OBJECTIVES

Myasthenia gravis (MG) is an autoimmune disease of neuromuscular synapses, characterized by muscular weakness and reduced endurance. Remission can be obtained in many patients. However, some of these patients complain of fatigue. The aim of this study was to assess exercise capacity and lung function in well-regulated MG patients.

PATIENTS AND METHODS

Ten otherwise healthy MG patients and 10 matched controls underwent dynamic spirometry, and a ramped symptom-limited bicycle exercise test. Spirometric variables included forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and maximum voluntary ventilation (MVV). Exercise variables included maximal oxygen uptake (VO(2) max), anaerobic threshold (VO(2) AT) maximum work load (W), maximum ventilation (VE max), and limiting symptom.

RESULTS

Myasthenia gravis patients had significantly lower FEV1/FVC ratio than controls. This was more marked in patients on acetylcholine esterase inhibitors. On the contrary, patients not using acetylcholine esterase inhibitors had a significantly lower exercise endurance time.

CONCLUSION

Well-regulated MG patients, especially those using pyridostigmine, tend to have an airway obstruction. The modest airway limitation might be a contributing factor to their fatigue. Patients who are not using acetylcholinesterase inhibitor seem to have diminished exercise endurance in spite of their clinically complete remission.

Long-term effect of continuous positive airway pressure therapy on inflammation markers of patients with obstructive sleep apnea syndrome

STUDY OBJECTIVES

Several lines of evidence suggest immune system derangement in obstructive sleep apnea syndrome (OSAS) patients. However, no data exist on the long-term effect of continuous positive airway pressure (CPAP) treatment on systemic immunity. Hence, we sought to evaluate this effect on various immunological parameters in OSAS patients.

DESIGN

Prospective case series.

SETTING

Sleep unit of a general hospital.

PATIENTS

Newly-diagnosed, nonsmoking, otherwise healthy OSAS male patients (n = 52) were evaluated on diagnosis and 6 months after CPAP treatment. According to compliance to CPAP use at 6-month follow-up, they were divided into 2 groups: group A (n = 32): good compliance (mean CPAP use > or = 4 h/night); and group B (n = 20): poor compliance (mean CPAP use < 4 h/night).

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Blood samples were obtained at baseline and at the 6-month follow-up. Percentage and absolute count of lymphocyte subsets (by flow cytometry), serum TNF-alpha, IL-6, and uric acid levels were measured. No differences were recorded regarding the baseline anthropometric or sleep characteristics of the 2 groups. In group A, a significant decrease in the absolute count of total lymphocytes (P = 0.003), and of CD4+ cells (P = 0.001), and a decrease in TNF-alpha levels (P = 0.001) and uric acid levels (P < 0.001) was observed after CPAP application. On the contrary, no alterations occurred in any of the tested parameters in group B patients.

CONCLUSIONS

The selective reduction of soluble and cellular immune response factors only in those OSAS patients who exhibited good compliance to CPAP therapy provides further evidence for an ongoing systemic immune process in OSAS.

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.

Sleep disordered breathing in medically stable patients with myasthenia gravis

We investigate sleep and breathing in clinically stable myasthenia gravis (MG) patients and ask weather sleep disordered breathing (SDB) is causally linked with MG. Nineteen MG patients with a mean disease duration of 9.7 years underwent sleep studies in two consecutive nights. The primary outcome measure was the respiratory disturbance index (RDI) in terms of snoring and apneas/hypopneas. Further outcome measurements were total sleep time, sleep stage distribution and the number of arousals. A clinically relevant SDB in terms of obstructive sleep apnea (OSA) (defined as RDI > 10/h) was found in four patients. There were only a few central apneas (central apnea index: 0.19 +/- 0.4/h). We did not find a relationship between maximum inspiratory pressure and SDB (r = -0.03). There is no evidence for a causal relationship between medically stable MG and SDB in terms of OSA. The extent of respiratory muscle weakness failed to correlate with SDB. Furthermore, our study does not confirm the high occurrence of central respiratory events during sleep in patients with well-controlled MG.

Sleep and Neuromuscular Disorders

Nocturnal sleep-related ventilatory alterations may occur in dis-proportion to the severity of the neuromuscular disorder. Diaphragm paralysis occurring with a neuromuscular disorder is an overlooked complication. Failure to thrive, daytime tiredness, and incapacitating fatigue may be the result of a correctable sleep-related abnormality, not the result of relentless progression of a neuromuscular condition. Polysomnographic evaluation is recommended for patients who have neuromuscular disorder who develop symptoms and signs of sleep-wake abnormality or nocturnal respiratory failure. Application of noninvasive positive airway ventilation and, in some cases, administration of supple-mental oxygen may improve quality of life and prolong survival of patients who have neuromuscular disorder.

Long-term sleep apnea as a pathogenic factor for cell-mediated autoimmune disease

BACKGROUND

Previous medical literature has shown that cell injury from hypoxia, such as that induced by sleep apnea, leads to hyperuricemia. Furthermore, a recent study has shown that when hyperuricemia reaches sufficient concentration to precipitate as monosodium urate, a T-cell immune response is triggered. The frequent repetition of this cell injury and immune response over a prolonged time, as would occur with long-term sleep apnea, may lead to the development, continuation, or aggravation of autoimmune disease.

HYPOTHESIS

Long-term sleep apnea is hypothesized to be a pathogenic factor in the development of cell-mediated autoimmune disease. Several corollaries are presented along with this general hypothesis. First, some of the diseases associated with sleep apnea may have an autoimmune etiology. Second, some autoimmune diseases not usually recognized to be associated with sleep apnea may indeed have that association. Third, resolving sleep apnea in some patients with autoimmune disease to remove that autoimmune stimulus may aid in deceleration, halt, or even reversal of the progress of the autoimmune disease. Fourth, because monosodium urate also causes gouty arthritis in some individuals, diagnosis of gout may allow for resolution of sleep apnea early enough to prevent autoimmune development. Fifth, allopurinol, which suppresses uric acid generation, may be an effective therapy for the remission or prevention of a number of autoimmune diseases.

CONCLUSION

This hypothesis strengthens the evidence pointing to the danger of unresolved sleep apnea by a mechanism previously unrecognized, namely the risk of developing an autoimmune disease. As a result of this realization, new therapies may be adopted for the treatment and prevention of autoimmune disease, specifically, resolving sleep apnea and the use of allopurinol.

Excessive daytime sleepiness and sleep disturbances in patients with neurological diseases: epidemiology and management

Up to 12% of the general population experience excessive daytime sleepiness (EDS), with increasing prevalence in the elderly. EDS may lead to cognitive impairment, resulting in inattentiveness, poor memory, mood disorders and an increased risk of accidents. As a result, quality of life is reduced in most patients with EDS as well as in their caregiving spouses. There are a variety of causes leading to EDS, including CNS pathology, neurological dysfunction, associated sleep disorders with insufficient or fragmented sleep, and drug therapy. Since EDS accompanies many neurological disorders, such as neurodegenerative and neuromuscular diseases, neurologists should be familiar with the diagnosis, its major causes and with treatment options. The main focus of this article is on movement disorders, neuromuscular diseases, multiple sclerosis, dementia, cerebrovascular diseases, head and brain trauma, pain and epilepsy. General management strategies for EDS in all these neurological diseases include sleep hygiene aspects such as extensions of noctural time in bed and frequent naps during the day. Pharmacological treatment is generally achieved with stimulants such as amphetamine, methylphenidate and pemoline, or newer compounds such as modafinil.

Pulmonary function study of myasthenia-gravis patients treated with double-filtration plasmapheresis

The aim of this study was to investigate the changes in pulmonary function tests for patients with myasthenia gravis (MG) after treatment with double filtration plasmapheresis (DFP) and to evaluate whether pulmonary function tests predict the efficacy of DFP treatment. Thirty-five MG patients (20 females and 15 males, age range 21-69 years) underwent DFP for between four and eight consecutive sessions. Vital capacity (VC), maximal inspiratory pressure (Pi(max)), and MG score were measured before and after DFP. Based on the results of pulmonary function tests, the patients were divided into dyspnea (VC < 1.0 L or Pi(max) < -25 cm H(2)O) and control groups (VC > 1.0 L and Pi(max) > -25 cm H(2)O). The dyspnea group had a significantly better response to DFP treatment, reflected in the decrease of the MG-score (P=0.0327), and the increase in VC value (P=0.0561). Higher clearance rates of acetylcholine receptor antibody (AchRAb) had a trend toward higher changes of VC. In conclusion, VC might better serve as a predictor for the effect of DFP in the dyspnea patient group because of better correlation with clinical improvement and AchRAb clearance.

Disorders of the respiratory muscles

The act of breathing depends on coordinated activity of the respiratory muscles to generate subatmospheric pressure. This action is compromised by disease states affecting anatomical sites ranging from the cerebral cortex to the alveolar sac. Weakness of the respiratory muscles can dominate the clinical manifestations in the later stages of several primary neurologic and neuromuscular disorders in a manner unique to each disease state. Structural abnormalities of the thoracic cage, such as scoliosis or flail chest, interfere with the action of the respiratory muscles-again in a manner unique to each disease state. The hyperinflation that accompanies diseases of the airways interferes with the ability of the respiratory muscles to generate subatmospheric pressure and it increases the load on the respiratory muscles. Impaired respiratory muscle function is the most severe consequence of several newly described syndromes affecting critically ill patients. Research on the respiratory muscles embraces techniques of molecular biology, integrative physiology, and controlled clinical trials. A detailed understanding of disease states affecting the respiratory muscles is necessary for every physician who practices pulmonary medicine or critical care medicine.

A review of sleep in selected immune and autoimmune disorders

Evidence for the reciprocal role of the immune system in sleep is growing. Sleep disturbances are believed to be both a cause and a consequence of various immune and autoimmune conditions.

Patterns and predictors of sleep disordered breathing in primary myopathies

BACKGROUND

Sleep disordered breathing (SDB) is common in neuromuscular diseases but its relationship to respiratory function is poorly defined. A study was undertaken to identify distinct patterns of SDB, to clarify the relationships between SDB and lung and respiratory muscle function, and to identify daytime predictors for SDB at its onset, for SDB with continuous hypercapnic hypoventilation, and for diurnal respiratory failure.

METHODS

Upright and supine inspiratory vital capacity (IVC, % predicted), maximal inspiratory muscle pressure (PImax), respiratory drive (P(0.1)), respiratory muscle effort (P(0.1)/PImax), and arterial blood gas tensions were prospectively compared with polysomnography and capnometry (PtcCO(2)) in 42 patients with primary myopathies.

RESULTS

IVC correlated with respiratory muscle function and gas exchange by day and night. SDB evolved in three distinct patterns from REM hypopnoeas, to REM hypopnoeas with REM hypoventilation, to REM/non-REM (continuous) hypoventilation, and preceded diurnal respiratory failure. SDB correlated with IVC and PImax which yielded highly predictive thresholds for SDB onset (IVC <60%, PImax <4.5 kPa), SDB with continuous hypoventilation (IVC <40%, PImax <4.0 kPa), and SDB with diurnal respiratory failure (IVC <25%, PImax <3.5 kPa).

CONCLUSION

Progressive ventilatory restriction in neuromuscular diseases correlates with respiratory muscle weakness and results in progressive SDB which, by pattern and severity, can be predicted from daytime lung and respiratory muscle function.

Sleep apnoea in infancy and childhood. Considering two possible causes: obstruction and neuromuscular disorders

Two aspects of sleep apnoea in infancy and childhood are considered. First of all the obstructive sleep apnoea syndrome is reviewed; its causes, and types, and clinical differences depending on the age of the affected patient. Difficulties of diagnosis are discussed, as well as methods used to confirm the presence of the syndrome. Then means of treatment are considered, both medical and surgical. The second part of the paper is concerned with a particular group of children, especially at risk of sleep apnoea; those suffering from neuromuscular disorders as these are likely to be of special interest to paediatric neurologists. These include neuropathies, myopathies such as Duchenne muscular dystrophy and myotonia, and disorders of the neuromuscular junction.

Skeletal advancement for the treatment of obstructive sleep apnea in children

OBJECTIVE

Maxillomandibular advancement is curative for some adult patients with obstructive sleep apnea (OSA). Little is known, however, about the efficacy of this treatment in children. The purpose of this retrospective analysis is to assess the clinical outcomes of children with medically refractory OSA who were treated with a variety of procedures to advance the maxillofacial skeleton.

METHODS

The records of eight children with OSA (five boys and three girls; mean age, 8.6 years; range, 2 to 17 years) were reviewed. Six children had identifiable syndromes associated with micrognathia, one child had mandibular ankylosis, and one child was nonsyndromic. In five of the children, conventional medical and surgical treatment of OSA had failed; therefore, these children were considered tracheostomy candidates. The remaining three children had had tracheostomies placed in infancy. Specific signs and symptoms with regard to each patient's OSA were identified and recorded. Bronchoscopy was performed preoperatively to evaluate the airway and localize the site of obstruction and again postoperatively if the patient's signs and symptoms recurred. Oxygen saturation and sleep patterns were monitored overnight in the five patients without tracheostomies, revealing a mean apnea index of 25.3 (range, 2.0 to 60.0) and mean lowest desaturation of 73% (range, 62% to 77%). All patients underwent a variety of skeletal procedures to advance the mandible, maxilla, and/or chin.

OUTCOME MEASURES

Criteria for success after treatment were twofold: (1) decannulation and (2) cessation or improvement in symptoms facilitating avoidance of tracheostomy. Criteria for failure, likewise, were (1) inability to decannulate and (2) recurrence or nonimprovement in symptoms necessitating tracheostomy.

RESULTS

To date, with a mean follow-up time of 7.2 years (range, 19 months to 19 years), the treatment of four of the eight children in our population can be considered a success. Two of the three children with previously placed tracheostomies were able to be decannulated within days of surgery and experienced no further signs or symptoms of OSA. Two other children experienced complete cessation of clinical signs and symptoms and elimination of previous oxygen requirements. Of the four patients in whom treatment failed, three had transient improvement (mean, 6 months) and, despite skeletal stability, eventually experienced relapse of symptoms: one patient with Down syndrome and tracheobronchomalacia required subsequent tracheostomy; the second had a central obstructive component and underwent a ventriculoperitoneal shunt for treatment of a Chiara I malformation; and the third experienced relapse of symptoms due to lack of mandibular growth. The fourth child could not be decannulated because of accompanying tracheal and laryngeal malacia.

CONCLUSIONS

Skeletal advancement can be an effective treatment for medically refractory OSA in children. Success, however, is dependent not only on skeletal position but also on neuromuscular adaptation. Bronchoscopy is the most valuable diagnostic and predictive tool.

Does myasthenia gravis affect the brain?

Associations between myasthenia gravis (MG) and CNS functions have been made for over 80 years. An increased incidence of psychiatric disorders, epilepsy and multiple sclerosis as well as electroencephalographic (EEG) abnormalities and abnormal evoked responses have been noted in patients with MG. Descriptions of sleep and memory disturbances in MG patients appeared as knowledge accumulated about the role of brain cholinergic systems in sleep and memory. The inference of many of these studies has been that the alleged central cholinergic effects in MG were caused either by the anticholinesterases used to treat MG or by antibodies to muscle nicotinic acetylcholine receptor (nAchR) present in the serum and cerebrospinal fluid (CSF) of MG patients. The antigenic differences between muscle nAchR and neuronal nAchRs, together with the very low concentrations of muscle nAchR antibodies in the CSF, make highly unlikely the claims that CNS cholinergic systems are affected by these muscle antibodies in MG patients. Evoked response abnormalities, if indeed present, are more likely caused by peripheral than central mechanisms, and sleep abnormalities in MG also probably originate in the periphery rather than in the CNS, the result of hypoxia caused by oropharyngeal, intercostal and diaphragmatic muscle weakness which may worsen during sleep, especially during REM sleep. Such hypoxia may account for some of the EEG abnormalities noted in MG patients, but the association of MG with epilepsy appears to be either coincidental or the result of uncontrolled MG. Significant excessive daytime sleepiness resulting from sleep disturbances can also impair memory and the performance of MG patients on neuropsychological tests, as can the presence of mental depression. The psychological aspects of MG can be attributed to the expected consequences of a chronic but unpredictable neuromuscular disease involving weakness of breathing, swallowing, talking, limb and eye movement. Considering the number and variety of claims for direct CNS involvement in MG, the evidence for this is remarkably unconvincing. The quality of MG treatment, both physical and psychological, is a presently undefined variable which might help explain the diametrically opposed results which have been obtained in some of the studies reviewed. Adequate respiratory muscle strength during sleep is an often overlooked peripheral influence upon mental functioning and general well-being of MG patients.

Sleep-disordered breathing at an early stage of amyotrophic lateral sclerosis

Eighteen amyotrophic lateral sclerosis (ALS) patients having neither respiratory complaints nor subjective symptoms of sleep disturbance were studied by using an ambulatory multi-parameter monitoring system during sleep. They were divided into two groups: 11 patients with predominantly bulbar form and seven with non-bulbar form. After performing daytime pulmonary function tests, the presence of sleep-disordered breathing (SDB) was evaluated by using a portable device. ALS patients did not show significant SDB as a whole, and the respiratory disturbance index (RDI) was not significantly different between the bulbar group and the non-bulbar group. However, three patients of the bulbar group showed significant SDB, and the patterns of apnea/hypopnea suggested that both bulbar weakness and minimal diaphragmatic weakness might cause SDB in ALS patients at an early clinical stage. Multi-parameter respiratory monitoring during sleep should be included in the routine evaluation of ALS patients at an early clinical stage, especially those with predominantly bulbar involvement, in order to predict early respiratory failure.

Respiratory aspects of neurological disease

Neurological disease may result in respiratory dysfunction; however the manifestations of respiratory dysfunction in such patients may be atypical because of wider effects of their underlying condition. In the present review we have considered separately acute neuromuscular respiratory disease (as well as aspects of respiratory muscle function relevant to intensive care), chronic neuromuscular respiratory disease, sleep related disorders, respiratory consequences of specific neurological diseases, and neurological features of respiratory disease. Approaches to specific clinical problems are discussed; in many instances this can be expedited by close cooperation with a respiratory physician. We suggest that management of respiratory dysfunction in neurological disease depends critically on three factors: firstly, knowledge of when respiratory dysfunction is likely to occur; secondly, maintaining a high index of clinical suspicion (specifically apparently vague symptoms should not be uncritically attributed to the underlying neurological condition); and, thirdly, the pursuing of appropriate investigations.