Idiopathic intracranial hypertension.

I n the past 18 years, the Journal of Neuro-Ophthalmology has published 83 articles that directly or indirectly deal with the clinical problem of idiopathic intracranial hypertension (IIH). In addition to individual case reports, small groups of patients, and reports of psychophysical tests, there is a superb review of unresolved “vexing” issues regarding papilledema (1), a discussion of disease definition and nomenclature (2), and 2 commentaries on surgical treatment of IIH (3,4). Various causes of visual loss are described, including subretinal hemorrhage (5,6), choroidal infarction (7,8), following liposuction (9), induced hyperopia and choroidal folds (10), and as a complication of hind brain herniation after lumboperitoneal shunt with resulting cortical blindness and simultanagnosia (11). Reports of progressive visual loss after optic nerve sheath fenestration (12–14), visual loss without papilledema, (15) and IIH without papilledema (16,17) all deal with rare problems that may present to the neuroophthalmologist. The clinical issue of “normal pressure IIH” (18,19) brings up a major diagnostic problem that faces the clinician who cares for these patients; there is no noninvasive way to measure cerebrospinal fluid (CSF) pressure longitudinally. In other words, were the “normal” pressures simply sampling error? The current intraventricular (20), intraparenchymal (21) or lumbar drain CSF pressure measurements are used only briefly in dire circumstances that surround severe visual loss and urgent surgical decision making. These invasive techniques are limited to answering surgical questions and cannot be routinely used to answer questions such as how high and how continuously high are the CSF pressure. While neuroimaging abnormalities detected with magnetic resonance imaging, magnetic resonance venography, and computed tomography are highly suggestive of IIH (22–24), these changes can also be seen in patients with cerebral venous sinus thrombosis (25). Orbital ultrasonic measurement of the optic nerve sheath is a relatively insensitive noninvasive technique indicating whether the CSF pressure is elevated (sheath dilated) or not (sheath not dilated), but cannot quantitate the level of intracranial pressure (ICP). Two articles elucidated the relationship between IIH and obstructive sleep apnea (OSA) (26,27), and suggested that OSA is not a major risk factor for visual loss (27). Severity of visual loss in patients with IIH is unrelated to obesity (28) and it appears that severe obesity, by itself, does not predispose to a high incidence of papilledema (29). A series of studies on vitamin A and case reports (30–33), as well as an authoritative review of vitamin A metabolism, and its potential relationship to obesity, vitamin A storage, and carrier proteins in CSF and serum (34), all provide tantalizing clues relating IIH to vitamin A and its congeners. More work needs to be done to see whether there is a causal relationship between vitamin A metabolism and IIH. Epidemiologic and familial incidence studies (35,36) and a comparison of IIH in Israeli men and women (37) were reported. There were no clear differences between the Israeli IIH incidence study and earlier studies (36). In the male and female comparisons, women were statistically more likely to be obese than men. A report of “late-onset” IIH (patients were older than 45 years) found 5 of 14 were men (64% of the total), were obese, and a third were asymptomatic (38). Unfortunately this report was a mixture of symptomatic cases (4 of 14 patients had some identifiable cause of IIH) and idiopathic cases, which will make it difficult to compare their results with other studies of older patients. This report suggests that older patients are more likely to have an identifiable cause of increased ICP. A multitude of unusual causes of “IIH-like” conditions are reported, and such reports emphasize the need to be compulsive using the modified Dandy Criteria to make the correct diagnosis of IIH.