Kyoung Bin Im

Obstructive Sleep Apnea and Stroke

Obstructive sleep apnea (OSA) and stroke are frequent, multifactorial entities that share risk factors, and for which case-control and cross-sectional studies have shown a strong association. Stroke of respiratory centers can lead to apnea. Snoring preceding stroke, documentation of apneas immediately prior to transient ischemic attacks, the results of autonomic studies, and the circadian pattern of stroke, suggest that untreated OSA can contribute to stroke. Although cohort studies indicate that OSA is a stroke risk factor, controversy surrounds the cost-effectiveness of the screening for and treatment of OSA once stroke has occurred.

Management of Sleep Disorders in Stroke

Opinion statementScientific studies have proven a very strong association between stroke and obstructive sleep apnea (OSA). The prevalence of OSA is very high in patients with acute stroke, and untreated OSA is a stroke risk factor. In the stroke patient population, symptoms of OSA may atypically appear as isolated insomnia, hypersomnia, a dysfunction of circadian rhythm, a parasomnia, or a sleep-related movement disorder. Thus, we believe that in patients with acute stroke, OSA should be addressed first, using full in-laboratory, attended polysomnography (PSG), before other specific sleep disorders are aggressively addressed with specific therapeutic interventions. When OSA is diagnosed, supportive techniques including the application of continuous positive airway pressure (CPAP) therapy, positional therapies, or both should be considered first-line treatments. If OSA is ruled out by PSG, the therapeutic emphasis for sleep-related complaints is routinely based on instituting good sleep hygiene practices and using cognitive behavioral techniques (cognitive therapies, sleep restriction, stimulus control, and progressive relaxation therapies) because patients with stroke may be prone to the adverse effects of many of the medications that are otherwise routinely prescribed for a variety of specific sleep disorders.

Sleep and Stroke

In many regards, the field of medicine for sleep disorders can be considered as a branch of medicine in its infancy, in large part due to the relatively recent ready availability of polysomnography (an electrographic tool, which is now recognized as the standard method for analyzing sleep). As such, many important sleep-related phenomena, including the relationship that exists between sleep and stroke, have only just recently been identified. Through the utilization of polysomnographic studies and scientific methodology, there is now an evidence to support the hypothesis that untreated obstructive sleep apnea (OSA) is a significant risk factor for the development of ischemic stroke. Laboratory studies have shown that sleep-related obstructive respiratory events can lead to hypoxemia and hypercapnia and elevations in sympathetic and parasympathetic activity, resulting in significant variations in blood pressure, tachycardia–bradycardia, and even asystole. Termination of untreated OSA-related events is largely dependent upon the arousal response. Some experts hypothesize that a dysfunctional arousal system in a select population of patients with OSA may set the stage for a potential cause-and-effect relationship between untreated OSA and not only stroke but also cardiac dysrhythmias and even death.

Factors Associated with Cheyne-Stokes Respiration in Acute Ischemic Stroke

Background and Purpose Cheyne-Stokes respiration (CSR) is frequently observed in patients with acute stroke. There have been conflicting opinions about the associations of CSR with the location and size of the lesion. We aimed to better define the clinical relevance and pathogenesis of CSR in acute stroke. Methods We investigated patients who had been admitted with acute ischemic stroke and received an overnight sleep apnea test. We collected data on demographics, risk factors, etiologic subtypes, initial vital signs, clinical course of the stroke, and parameters associated with respiratory events during the sleep apnea test. We performed a multivariate logistic regression analysis to determine the factors associated with CSR. Results Among 182 patients, 35 patients showed CSR in sleep apnea testing. Large-artery atherosclerosis or cardioembolism, bilateral hemispheric involvement, atrial fibrillation, low left-ventricle ejection fraction (LVEF), and left atrium (LA) enlargement were all associated with the presence of CSR. Multivariate analysis revealed that the previous modified Rankin Scale (mRS) score, bilateral hemispheric involvement, low LVEF, and LA enlargement were significantly associated with CSR. Subgroup analysis with large-artery atherosclerosis without cardiac disease revealed that the previous mRS score is the only independent factor associated with CSR. Conclusions CSR frequently occurs in strokes involving large arteries or due to cardioembolism, regardless of the location and severity of the stroke. Predisposing conditions such as preexisting neurologic disability, low LVEF, and LA enlargement are associated with CSR in acute stroke.

Impact of Neurological Diseases

There is an association between neurological diseases and hypersomnia (the primary complaint of excessive sleepiness). Descriptions of the neurological disorders that have been associated with sleepiness can be found in the International Classification of Sleep Disorders , 2nd edn. (ICSD-2), under the sections that cover hypersomnias of central origin, sleep-related breathing disorders (SRBDs), and circadian rhythm sleep disorders. Although some neurological diseases are associated with parasomnias and the sleep-related movement disorders, hypersomnolence is generally not a major symptom in these cases.

Narcolepsy due to a Medical Condition

Narcolepsy due to a medical condition is a very rare condition that occurs during the course of an underlying medical or neurological disorder. Often it is difficult to clearly differentiate secondary narcolepsy from idiopathic cases. However, several clues may help distinguish between the two conditions. These include negative human leukocyte antigen (HLA) subtypes, relatively late onset, and a characteristic time course paralleling the suspected underlying condition. Low cerebrospinal fluid (CSF) hypocretin level is common and it tends to normalize as the symptoms resolve. Diagnosis is established when the causality is proven in addition to symptoms or sleep study findings consistent with narcolepsy. Treatments target the underlying pathologic process.