Idiopathic Intracranial Hypertension

doi:10.1016/S0025-6196(12)61045-3

Mayo Clinic Proceedings

Volume 69, Issue 2, February 1994, Pages 169-180

https://doi.org/10.1016/S0025-6196(12)61045-3 Get rights and content

Objective

This review was undertaken to summarize the significant progress that has been made in the epidemiology of idiopathic intracranial hypertension (IIH), the changing nosology, and the diagnostic criteria and therapeutic strategy.

Design

We reviewed the pertinent literature on IIH published in major English-language journals for the last 20 years.

Material and Methods

The diagnosis, epidemiology, pathophysiology, complications, and treatment of IIH are described.

Results

IIH occurs at an average annual incidence rate per 100,000 persons of 1 to 2 for the total population and 19 to 21 in obese females of the reproductive age-group. IIH is a recognized cause of reversible vision loss in adult obese women. The diagnosis of IIH requires a documented elevation of intracranial pressure, normal cerebrospinal fluid (CSF) composition, and normal findings on neuroimaging studies. At least two primary mechanisms for the development of increased CSF pressure in IIH have been postulated and supported by experimental data: vasogenic extracellular brain edema and a low conductance of CSF outflow at the arachnoid villi. This condition may be secondarily exacerbated by compression of intracranial venous sinuses by the increased intracranial pressure, resulting in a further reduction of flow across the arachnoid villi. The therapeutic strategy is determined by visual status, which needs close monitoring.

Conclusion

Although medical measures to lower the intracranial hypertension are successful in the majority of patients, surgical therapy should not be delayed in those with significant or progressive vision loss. Based on recent advances, a practical approach has been described for the diagnosis, early detection of visual impairment, and targeting therapy to preserve the vision or to reverse recent loss of vision in patients with IIH.

Section snippets

NOSOLOGY

Although the syndrome of IIH is well recognized, the terminology has varied and has been a source of confusion. Quincke¹ is attributed with the first clear description of the disease, which in 1897 he named “serous meningitis.” Before Foley introduced the term “benign intracranial hypertension,”⁷ the syndrome was variously described by a score of names such as otitic hydrocephalus, toxic hydrocephalus, sinus thrombosis causing intracranial hypertension, hypertensive meningeal hydrops,

DIAGNOSIS

The modified diagnostic criteria of Dandy for IIH3, 4, 5, 6 are illustrated in Table 1. By strictly adhering to the diagnostic criteria, the perceived benefits are twofold: (1) to facilitate epidemiologic, clinical, and experimental investigation of this syndrome in as uniform a sample as possible and (2) to allow a more rational approach to therapy through a unified concept of the pathophysiologic process.

Intracranial Hypertension Associated With Sinovenous Thrombosis.

Patients with clinical and radiologic evidence of cranial venous outflow impairment, such as raised intracranial pressure in heart failure, superior vena cava syndrome, bilateral or unilateral jugular obstruction, or lateral or superior sagittal sinus thrombosis, have often been included in the category of those with IIH.34, 37 Despite some clinical similarities, this group should be considered a distinctive diagnostic category. The pathogenesis, clinical and radiologic features, management,

DISEASES AND CONDITIONS ASSOCIATED WITH IIH

Numerous retrospective studies and reviews have emphasized the association of IIH with a vast array of other medical conditions. For example, a 1984 edition of an outstanding neurology textbook⁴⁰ listed more than 35 etiologic entities in 10 subgroups under the heading of benign intracranial hypertension, most of which are now believed to be coincidental associations.

Conditions that we would accept as probably causally linked to IIH should conform to the following criteria:⁵ (1) at least two

Descriptive Studies.

In their initial observation in Benghazi, Libya, Radhakrishnan and coworkers¹¹ reported annual incidence rates per 100,000 persons of 1.7 for the total population and 3.6 for females of all ages. Durcan and colleagues¹² surveyed all neurologists, ophthalmologists, and neurosurgeons in Iowa, eastern Nebraska, and Louisiana over a 1-year period and determined an incidence rate per 100,000 persons of 0.9 in the general population, 3.5 in females 15 to 44 years of age, and 19 in obese women aged 20

PATHOGENESIS

The pathogenesis of pseudotumor cerebri has yet to be fully understood. The ambient CSF pressure depends on the following: the venous pressure in the superior sagittal sinus, the inherent resistance of the arachnoid villi to the egress of CSF, the rate of formation of CSF, the intracranial volume of blood and brain, the elastic properties of the brain and blood vessels, and the capacity of the cranial and spinal subarachnoid space to expand.³³ Evidence in favor of and against the dysfunction of

Vision Loss.

It is not always recognized that vision loss, which is the only serious complication of IIH, may occur either early or late in the course of the disease, may be sudden or gradually progressive, and is often avoidable with appropriate therapeutic intervention. The rate of vision loss is variable, symptoms may be minimal, and, in many patients, the vision loss may be undetected until profound.

Multiple pathophysiologic mechanisms involving dysfunction of the retina, optic disc, and optic nerve

TREATMENT

Since the only permanent morbidity from IIH is loss of vision, therapy for IIH is dictated by the presence and progression of vision loss. Hence, follow-up of patients with IIH often requires the clinical skills of an ophthalmologist. In the event of vision loss, the help of an ophthalmic surgeon or neurosurgeon may be needed. Treatment of the disorder, therefore, focuses on the early detection and prevention of vision loss. However, in certain cases, treatment may have to be directed at the

Correction of the Predisposing Factors.

In the event of a presumed or overt precipitating factor (as listed in Table 2), withdrawal of the offending medication or correction of the condition, when possible, may result in the resolution of the syndrome. The role of weight reduction in the treatment of symptomatic patients with IIH is unclear; uncontrolled experience suggests this may be an effective treatment.⁸⁸ Lack of sustained patient compliance often limits this therapeutic approach. Recent weight gain was associated with visual

FUTURE RESEARCH

In the future, the following areas of research should add a great deal to a better understanding of IIH: (1) strict adherence to the diagnostic criteria to define a uniform sample of patients; (2) delineation of the natural history of the disease and risk factors for poor visual outcome through population-based studies; (3) critical examination of various reported associations through comprehensive case-control studies involving large numbers of patients; (4) exploration of the potential of

ACKNOWLEDGMENT

We thank Laura B. Long for secretarial and editorial assistance.

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