PCR-confirmed disseminated herpes zoster initially mimicking lumbar radiculopathy in an apparently immunocompetent adult: a case report and literature review.

Cluster headache (CH) is a primary headache disorder defined by the 3rd edition of the International Classification of Headache Disorders (ICHD-3) as attacks of severe, strictly unilateral pain lasting 15–180 min, accompanied by ipsilateral autonomic symptoms and/or restlessness [], and characterized by striking circadian and circannual periodicity, excruciating pain intensity, and substantial functional impairment. It is widely regarded as one of the most disabling headache syndromes, with profound impact on quality of life and daily functioning []. CH typically has an onset in the third to fourth decade of life and shows a male predominance, with reported male-to-female ratio ranging from approximately 2:1 to 4:1 across population-based studies [,]. Obstructive sleep apnea (OSA) has been increasingly recognized as a common comorbidity in patients with CH. Previous studies have reported OSA prevalence rates ranging from approximately 58% to 80% in CH cohorts undergoing polysomnography, suggesting a potential pathophysiological link beyond shared risk factors [,,,]. Both conditions exhibit nocturnal predominance, are more common in men, and are associated with unhealthy lifestyle factors, such as smoking and alcohol consumption [,,]. Untreated OSA is associated with increased risks of cerebrovascular disease, cardiovascular morbidity [], and mortality []. Importantly, patients with CH are reported to be at an increased risk of hypertension and coronary heart disease []. They also have high smoking rates and are at risk of potential medication overuse, which may further exacerbate the consequences of unrecognized OSA. Therefore, failure to identify and manage OSA in this population may adversely affect both headache outcomes and systemic comorbidities. Although several case reports have described improvement of CH symptoms following treatment of OSA using positive airway pressure (PAP), systematic and controlled evidence remains limited [,,]. To evaluate the clinical necessity and therapeutic implications of OSA in patients with CH, it is important to identify treatment-relevant OSA rather than considering all cases of OSA equally. While an AHI of ≥15 events/hour is generally used to define moderate OSA, treatment decisions often incorporate symptom burden and comorbidities in addition to AHI. Therefore, rather than focusing solely on conventional OSA severity categories, we adopted an AHI ≥ 10 events/hour as a pragmatic definition of treatment-relevant OSA, which may better reflect real-world clinical practice in this population. Patients with CH frequently experience nocturnal attacks, sleep disruption, insomnia, or excessive daytime sleepiness, which may justify PAP treatment even at AHI levels below 15. This approach is consistent with the American Thoracic Society Research Statement, which recognizes that symptomatic patients with mild OSA may derive meaningful benefits from treatment, as well as longitudinal studies demonstrating progressively increasing cardiovascular risk across the mild-to-moderate OSA range. Therefore, an AHI ≥ 10 was considered more appropriate for the treatment-oriented screening objective of the present study than conventional OSA thresholds [,]. Furthermore, evidence from both longitudinal and cross-sectional studies suggests that cardiovascular risk may increase even at AHI levels below the conventional moderate OSA threshold (AHI < 15) [,]. Although these findings were not derived from patients with CH and therefore should not be directly generalized to this population, they provide additional rationale for exploring an AHI ≥ 10 threshold in a treatment-oriented screening strategy for patients with CH.