Obstructive Sleep Apnea in Men With Idiopathic Intracranial Hypertension: A Prospective Case-Control Study

Idiopathic intracranial hypertension (IIH) is uncommon in men. Previous studies reported on high frequency of obstructive sleep apnea (OSA) in men with IIH, but the pathophysiology of this association remains unclear. One possible culprit for increased intracranial pressure in patients with OSA is hypercapnia. The purpose of this study was to compare the rate of hypercapnia during polysomnography (PSG) study in men with and without IIH and to report on the rate and severity of OSA in men with IIH compared with control subjects of similar age and body mass index (BMI).

Prospective case-control study of male patients diagnosed with IIH underwent PSG with continuous oxygen and carbon dioxide monitoring overnight. Healthy control subjects with similar age and BMI also underwent PSG. The incidence of OSA diagnosis, rate of hypercapnia and hypoxia, and apnea hypopnea index (AHI) were compared between 2 groups.

Eleven subjects with IIH and 10 controls underwent PSG. Both groups were similar regarding age and BMI on the Mann-Whitney U test ( P = 0.072 for age, P = 0.251 for BMI). Subjects for whom carbon dioxide data were not available for more than 50% of total sleep time were excluded from hypercapnia analysis. The mean age was 41.9 years, and the mean BMI was 33.8 kg/m 2 in subjects and controls. OSA was diagnosed in 9 of 11 men with IIH and 4 of 10 controls. There was no statistically significant difference in the rate of hypercapnia and hypoxia between 2 groups for whom the data were available. All patients with BMI over 30 kg/m 2 (7 of 7) and 50% (2 of 4) controls with BMI over 30 kg/m 2 were diagnosed with OSA compared with 50% (2 of 4) of cases and 33% (2 of 6) of controls with BMI less than 30 kg/m 2 . BMI was a significant predictor of total AHI ( P = 0.042) and OSA severity ( P = 0.023), but IIH diagnosis was not ( P > 0.05).

There was no difference in hypercapnia rate between men with IIH and controls; thus, hypercapnia is an unlikely causative factor in pathophysiology of IIH. OSA on PSG was almost 2 times as prevalent in patients with IIH compared with controls; however, BMI was the strongest predictor of OSA diagnosis, and most patients (9 of 11) with BMI over 30 kg/m 2 had OSA on PSG. In men with BMI less than 30, the rate of OSA on PSG study was higher in men with IIH. Based on these data, we recommend that all men with the diagnosis of IIH should undergo PSG study.