Idiopathic intracranial hypertension is characterized by optic disc edema, elevated intracranial pressure, normal spinal fluid constituents, and absence of evidence of a mass lesion on neuroimaging (1,2). Idiopathic intracranial hypertension occurs predominantly in young, middle-aged, obese women, and case-control studies confirm that obesity and recent weight gain are more common in patients with idiopathic intracranial hypertension than in controls (3–7). Decreased cerebrospinal fluid (CSF) absorption by arachnoid villi or elevated intracranial venous pressures are mechanisms often proposed as final common pathways of multiple inciting factors (8–10).
Sleep apnea is a common sleep-related breathing disorder characterized by daytime hypersomnolence, snoring, and multiple episodes of apnea (cessation of airflow) or hypopnea (reduction in airflow) during sleep (11). A mild form of the disease is called upper airway resistance syndrome (UARS) in which repeated arousals from sleep occur because of an increased effort to breathe to overcome the narrowing of the upper airways (12).
The ocular manifestations of sleep apnea have been described in case reports or small series, and optic disc edema (13–19), glaucomatous (20), and ischemic optic neuropathy (21) have been observed. Seven case reports note the association of optic disc edema with and without increased intracranial pressure in seven sleep apnea patients (13–19). Thus, sleep apnea has been proposed to be an uncommon but recognized cause of idiopathic intracranial hypertension (18). We determined the frequency of sleep-disturbed breathing and sleep disorders in our patient population with idiopathic intracranial hypertension.
Our institution's human assurance committee approved the study protocol. We reviewed the records of patients with a diagnosis of idiopathic intracranial hypertension. To be diagnosed with idiopathic intracranial hypertension, patients were required to demonstrate bilateral disc edema, a normal neuroimaging study, and a lumbar puncture showing normal CSF contents and high pressure.
A sleep history was obtained in 53 idiopathic intracranial hypertension patients. Polysomnography was recommended in all patients with a positive sleep history for snoring or daytime somnolence. Polysomnography was performed at night and consisted of 8-hour recordings of electroencephalograms (EEG), oculograms, chin muscle and anterior tibialis muscle electromyograms, electrocardiograms, oronasal airflow, and oxygen saturation. Frequency of apnea (cessation of breathing), hypopnea (reduction in ventilation limit oxygen desaturation), and arousal (increase in EEG frequency of at least 3 seconds) was determined.
Sleep apnea was diagnosed if the frequency of apnea and hypopnea per hour of sleep (i.e., respiratory disturbance index) was five or greater. UARS was diagnosed if the number of arousals per hour of sleep (arousal index) was 20 or greater and the arousals were associated with crescendo snoring.
Thirty-seven of 53 (70%) idiopathic intracranial hypertension patients had a history of sleep disturbance. Fourteen of these 37 patients underwent polysomnography. The demographics of these 14 patients (group A) and the 23 patients who declined polysomnography (group B) are summarized in Table 1. Almost all patients in both groups were morbidly obese (body mass index, > 40). The differences between the two groups were not significant (P > 0.05).
The results of polysomnography in 14 patients are summarized in Table 2. A diagnosis of sleep-related problems was made in 13 of the 14 idiopathic intracranial hypertension patients. Sleep apnea was diagnosed in seven patients and UARS in six patients. One patient had snoring, but the number of arousals was fewer than the minimum required for the diagnosis of UARS.
Sleep-related breathing problems vary in severity from sleep apnea with respiratory failure to UARS. Patients with UARS usually do not have significant hypoxemia or hypercapnia. It is estimated that 4% of men and 2% of women in the general population have sleep apnea (11). The incidence of UARS may be higher than that of sleep apnea. The risk factors for sleep apnea include snoring, obesity, upper airway abnormalities, and alcohol intake.
The clinical features and pathophysiologic manifestations of patients with idiopathic intracranial hypertension and sleep disorders significantly overlap. Sex and age differences are the main distinguishing features between these two disorders. Sleep apnea is more common in middle-aged men, whereas idiopathic intracranial hypertension is more common in young women. Obesity is a significant risk factor for idiopathic intracranial hypertension and sleep-related breathing disorders. The prevalence of idiopathic intracranial hypertension in obese female patients more than 20% above ideal body weight is 19.3 per 100,000 compared with 1 per 100,000 in the normal, nonobese population (4). In one study, the prevalence of sleep apnea in morbidly obese patients was 77% in men and 7% in women (22). It is likely that obesity may play a central role in sleep apnea and idiopathic intracranial hypertension. Weight reduction is associated with improvement of symptoms in patients in both of these diseases (23,24).
How might sleep disorders contribute to the development of idiopathic intracranial hypertension? Several factors including hypoxia, hypercapnia, polycythemia, and increased venous pressure have been postulated as potential causes for fundus abnormalities described in sleep apnea. Hypercapnia or hypoxia, particularly during sleep, is common in patients with sleep apnea. Nocturnal hypercapnia may be responsible for increased intracranial pressure and secondary papilledema in these cases (25). Episodic elevations in intracranial pressure have been shown during apneic episodes (26). Patients with severe obstructive sleep apnea may demonstrate continuously elevated intracranial pressure (19).
Our data indicate that sleep-related breathing problems are common in patients with idiopathic intracranial hypertension. The high prevalence of sleep-related breathing disorders in our study may be somewhat inflated; patients with sleep apnea may be more likely to agree to have polysomnography than patients without. Those patients who underwent polysomnography, however, did not have substantially different demographic features compared with those patients who did not undergo polysomnography.
Our study suggests that sleep disorders may be a risk factor for idiopathic intracranial hypertension. These findings, however, do not provide evidence for a cause-and-effect relationship. Prospective studies are needed to confirm this strong association of these diseases. It is interesting to note that the only two male patients with idiopathic intracranial hypertension in our population were diagnosed as having sleep apnea. As idiopathic intracranial hypertension is uncommon in men, our findings support speculation that this association may be even more sex significant. We suggest that patients with idiopathic intracranial hypertension should be asked about the presence of symptoms of sleep apnea such as of snoring, disturbed sleep, and daytime somnolence. The presence of these symptoms should be an indication for further evaluation by polysomnography.
The authors thank Richard Rubin, MD, for contributing patients to this study.
1. Wall M. Idiopathic intracranial hypertension
. Neurol Clin 1991; 9:73–95.
2. Smith JL. Whence pseudotumor cerebri
? [editorial]. J Clin Neuroophthalmol 1985; 5:55–6.
3. Giuseffi V, Wall M, Siegel PZ, et al. Symptoms and disease associations in idiopathic intracranial hypertension
): a case-control study. Neurology 1991; 41:239–44.
4. Durcan FJ, Corbett JJ, Wall M. The incidence of pseudotumor cerebri
. Population studies in Iowa and Louisiana. Arch Neurol 1988; 45:875–7.
5. Radhakrishnan K, Ahlskog JE, Cross SA, et al. Idiopathic intracranial hypertension
). Descriptive epidemiology in Rochester, Minn, 1976 to 1990. Arch Neurol 1993; 50:78–80.
6. Radhakrishnan K, Thacker AK, Bohlaga NH, et al. Epidemiology of idiopathic intracranial hypertension
: a prospective and case-control study. J Neurol Sci 1993; 116:18–28.
7. Ireland B, Corbett JJ, Wallace RB. The search for causes of idiopathic intracranial hypertension
. A preliminary case-control study. Arch Neurol 1990; 47:315–20.
8. Gjerris F, Soelberg Sorensen P, Vorstrup S, et al. Intracranial pressure, conductance to cerebrospinal fluid outflow and cerebral blood flow in patients with benign intracranial hypertension. Ann Neurol 1985; 17:158–62.
9. Johnston I, Hawke S, Halmagyi M, et al. The pseudotumor syndrome. Disorders of cerebrospinal fluid circulation causing intracranial hypertension without ventriculomegaly. Arch Neurol 1991; 48:740–7.
10. Malm J, Kristensen B, Markgren P, et al. CSF hydrodynamics in idiopathic intracranial hypertension
: a long-term study. Neurology 1992; 42:851–8.
11. Young T, Palta M, Dempsey J, et al. The occurrence of sleep-disordered breathing among middle-aged adults. N Engl J Med 1993; 328:1230–5.
12. Guilleminault C, Stoohs R, Clerk A, et al. A cause of excessive daytime sleepiness. The upper airway resistance syndrome
. Chest 1993; 104:781–7.
13. Fincher RME, Borger HE, Chaudhary BA. Sleep apnea
and optic disc swelling. Pak J Ophthalmol 1986; 2:13–5.
14. Bucci FA, Krohel GB. Optic nerve swelling secondary to the obstructive sleep apnea
syndrome. Am J Ophthalmol 1988; 105:428–30.
15. Doyle KJ, Tami TA. Increased intracranial pressure and blindness associated with obstructive sleep apnea
. Otolaryngol Head Neck Surg 1991; 105:613–6.
16. Bloomfield RL, Felts JH, Burkart JM, et al. Optic disc edema in a pickwickian man mimicking hypertensive crisis. J Clin Hypertens 1987; 3:27–30.
17. Reeve P, Harvey G, Seaton D. Papilloedema and respiratory failure. BMJ 1985; 291:331–2.
18. Wolin MJ, Brannon WL. Disk edema in an overweight woman. Surv Ophthalmol 1995; 39:307–14.
19. Kirkpatrick PJ, Meyer T, Sarkies N, et al. Papilloedema and visual failure in a patient with nocturnal hypoventilation. J Neurol Neurosurg Psychiatry 1994; 57:1546–7.
20. Mojon DS, Hess CW, Goldblum D, et al. High prevalence of glaucoma in patients with sleep apnea
syndrome. Ophthalmology 1999; 106:1009–12.
21. Hayreh SS. Acute ischemic disorders of the optic nerve. Pathogenesis, clinical manifestations and management. Ophthalmol Clin North Am 1996; 9:407–42.
22. Rajala R, Partinen M, Sane T, et al. Obstructive sleep apnea
syndrome in morbidly obese patients. J Intern Med 1991; 230:125–9.
23. Johnson L, Krohel G, Madsen R, et al. The role of weight loss and acetazolamide in the treatment of idiopathic intracranial hypertension
). Ophthalmology 1998; 105:2313–7.
24. Browman CP, Sampson MG, Yolles SF, et al. Obstructive sleep apnea
and body weight. Chest 1984; 85:435–6.
25. Newton DAG, Bone I. Papilloedema and optic atrophy in chronic hypercapnia. Br J Dis Chest 1979; 73:399–404.
26. Sugita Y, Iijima S, Teshima Y, et al. Marked episodic elevation of cerebrospinal fluid pressure during nocturnal sleep in patients with sleep apnea
hypersomnia syndrome. Electroencephalogr Clin Neurophysiol 1985; 60:214–9.