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STATE OF THE ART

Idiopathic Intracranial Hypertension
Deborah I. Friedman, MD and Daniel M. Jacobson, MD

Abstract: The syndrome of intracranial hypertension without structural brain or cerebrospinal fluid abnormalities and without identifiable cause, now most appropriately termed idiopathic intracranial hypertension, was described over a century ago. Although the pathogenesis of thiscondition remains unknown, diagnostic and therapeutic developments during the past two decades have substantially advanced patient management. (J Neuro-Ophthalmol 2004;24: 138–145)

NOMENCLATURE
The nomenclature for IIH remains controversial. “Benign intracranial hypertension” is no longer accepted, as significant visual morbidity may occur with this disorder (3). The term “pseudotumor cerebri,” ahistorically popular and all-encompassing term, leaves the impression that IIH is not a real disease. IIH is currently the favored term for the primary (idiopathic) disorder. For those patients with an identified cause of intracranial hypertension without structural brain imaging or CSF constituent abnormalities, the appropriate diagnostic term would be “intracranial hypertension secondary to (…).”The typical patient with IIH is an obese woman of childbearing age (4). Atypical patients include men, slim women, prepubescent children, and patients older than age 44 years.

DEFINITION
The syndrome of increased intracranial pressure (ICP) without ventriculomegaly or mass lesion, and with normal cerebrospinal fluid (CSF) composition, was first described more than a century ago, yet we stillknow little about its pathogenesis (1). Often referred to as “pseudotumor cerebri” but more appropriately called “idiopathic intracranial hypertension” (IIH), it is a surprisingly common disorder. In young overweight women, the annual incidence is as high as 20 per 100,000 persons (2). The definition of IIH has evolved with clinical experience and advances in imaging technology. Currently, IIH canbe diagnosed only if the following criteria are met (Table 1): 1) symptoms and signs attributable to increased ICP or papilledema; 2) elevated ICP recorded during lumbar puncture in the lateral decubitus position; 3) normal CSF composition; 4) no imaging evidence of ventriculomegaly or a structural cause for increased ICP, such as a brain parenchymal, ventricular, meningeal, or venous sinusabnormality; and 5) no other cause of intracranial hypertension identified, such as use of certain medications. The diagnosis and management of IIH remains based largely on anecdotal evidence. However, substantial developments during the past two decades have provided clinicians with more tools for excluding disorders that mimic IIH and for facilitating its diagnosis and management.
Departments ofOphthalmology and Neurology, University of Rochester School of Medicine and Dentistry Rochester, New York (DIF), and Departments of Neurology and Ophthalmology, Marshfield Clinic, Marshfield, Wisconsin (DMJ). Address correspondence to Deborah I. Friedman, MD, 601 Elmwood Ave, Box 569, Rochester, NY 14642; E-mail: Deborah_Friedman@ urmc.rochester.edu

NATURAL HISTORY AND VISUAL PROGNOSIS
There arefew prospective data in the era of modern imaging (computed tomography [CT], magnetic resonance imaging [MRI], and magnetic resonance venography [MRV]) to document the natural history of the disorder. Clinical experience, however, suggests that it is common for patients to have a protracted course lasting months to years, during which they may be asymptomatic but have chronic papilledema, or havesymptoms that require medical agents to lower their ICP. This suggests that intracranial hypertension, symptomatic or not, persists in many patients with IIH. Indeed, one series found that 10 (83%) of 12 patients in long-term follow-up who underwent repeated lumbar punctures showed persistently elevated ICPs ranging from 220 to 550 mm H2O (5). Recurrent symptoms and papilledema have been...