Idiopathic central sleep apnea: the past, the present, and the future

Idiopathic central sleep apnea or primary central sleep apnea (ICSA) has been an officially recognized sleep disorder since the 2005 International Classification of Sleep Disorders 2nd edition (ICSD-2) and remains in the International Classification of Sleep Disorders 3rd edition (ICSD-3). The literature supports the etiology as "high loop gain or increased controller gain," along with central sleep apnea (CSA) associated with common diagnoses (e.g. heart failure). Available data place the adult population prevalence at about 0.05% (men) and 0.003% (women), while up to 11% of patients diagnosed with CSA may be classified as ICSA. Symptoms may include nocturnal choking, witnessed apneas, awakenings with the sensation of shortness of breath, restless sleep, insomnia, non-restorative sleep, daytime sleepiness, fatigue, and variable degrees of snoring. Per the ICSD-3, ICSA may only be diagnosed if "The disorder [CSA] is not better explained by another current sleep disorder, medical or neurologic disorder, medication use, or substance use disorder." However, a putative diagnosis of ICSA should prompt a comprehensive search for asymptomatic left ventricular dysfunction without heart failure, atrial fibrillation, carotid artery disease, ischemic central nervous system pathology, acromegaly, and licit or illicit respiratory depressant drug use, which could be potential causes of CSA. Systematic studies are needed to determine the cost effectiveness of this approach. However, if present, ICSA is excluded and intervention can be initiated for the underlying diagnosis, which may resolve CSA and, importantly, improve outcomes specific to the causative disease. Treatment options for ICSA include devices such as adaptive servo-ventilation or transvenous phrenic nerve stimulation, medications such as acetazolamide, and sleep position training. Statement of Significance Idiopathic central sleep apnea (ICSA) has not been comprehensively reviewed in peer-reviewed journals. As many as 11% of patients with central sleep apnea (CSA) may fulfill the criteria for ICSA, although the key requirement that "The disorder is not better explained by another … medical or neurologic disorder…" is often incompletely established in published studies. Although considered a rare entity, early and more recent studies have shown that CSA could be associated with asymptomatic left ventricular dysfunction without heart failure, carotid artery disease, and asymptomatic subtle brain infarcts. Therefore, to label CSA idiopathic, these diseases should be ruled out and prompt management specific to the causative disease may improve disease-specific outcomes. It is of great importance that sleep physicians be aware of this aspect of ICSA and act accordingly.