eMedicine Specialties > Ophthalmology > Neurologic Disorders

Idiopathic Intracranial Hypertension

Author: Mark S Gans, MD, Associate Professor, Director of Neuro-Ophthalmology, Department of Ophthalmology, McGill University; Clinical Director, Department of Ophthalmology, Adult Sites, McGill University Hospital Center, Interim Chairman of the Department of Ophthalmology, McGill University
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Updated: Aug 18, 2009

Introduction

Background

The presentation of a patient with symptoms of increased intracranial pressure and papilledema should be considered a clinical emergency until neuroimaging study results confirm the presence or absence of an intracranial mass. 

A significant number of patients presenting in the above fashion whose neuroimaging study results do not reveal a mass lesion are diagnosed with idiopathic intracranial hypertension. Although idiopathic intracranial hypertension, pseudotumor cerebri, and benign intracranial hypertension are synonymous with this diagnosis, the preferred term is idiopathic intracranial hypertension.

The diagnostic criteria, including those of the modified Dandy criteria as described by Dandy in 1937 and later modified by Smith in 1985, are as follows: there are symptoms and signs of increased intracranial pressure; there are no localizing neurologic signs (with the exception of a unilateral or bilateral sixth nerve paresis); cerebrospinal fluid can show increased pressure, but there are no cytologic or chemical abnormalities; and normal to small symmetric ventricles must be demonstrated. Subsequent additions to these criteria include the following: the diagnostic lumbar puncture should be in the lateral decubitus position; MRI/venography should be included to rule out intracranial venous sinus thromboses; and other causes of intracranial hypertension should be ruled out.^1,2,3

Pathophysiology

The pathophysiology of this disorder is unclear. A relative resistance to the absorption of cerebrospinal fluid across the arachnoid villi is widely presumed to be present. Other theories support an abnormality in the cerebral circulation with a resulting increase in the brain's water content. The subsequent increase in the intracranial pressure is transmitted to the structures within the intracranial cavity, including the optic nerves. Unfortunately, because of the difficulty in applying animal models of cerebrospinal fluid dynamics to humans, the underlying pathophysiology in idiopathic intracranial hypertension remains unclear.

Current hypotheses include the link between relatively obstructive segments in the distal transverse sinus and idiopathic intracranial hypertension or the presence of increased arterial inflow with an accompanying low-grade stenosis of the transverse sinus.^4,5

The disease commonly occurs in women who are overweight. The role of obesity in this disorder is unclear. In some instances, obesity and idiopathic intracranial hypertension may be familial.⁶ Obesity has been proposed to increase intra-abdominal pressure, which, in turn, raises cardiac filling pressures. This rise in pressure leads to impeded venous return from the brain (due to the valveless venous system that exists from the brain to the heart) with a subsequent elevation in intracranial venous pressure. If not treated appropriately, chronic interruption of the axoplasmic flow of the optic nerves with ensuing papilledema due to this pressure may lead to irreversible optic neuropathy.⁷

Frequency

United States

Studies of American-based populations have estimated that the incidence of idiopathic intracranial hypertension ranges from 0.9-1.0 per 100,000 in the general population. This incidence rate increases to 1.6-3.5 per 100,000 in women and to 7.9-20 per 100,000 in women who are overweight.^1,3,5

International

The incidence of idiopathic intracranial hypertension is variable from country to country. Because of the relation of the disease to body habitus, its occurrence varies according to the incidence of obesity in the respective region.

Mortality/Morbidity

• The morbidity of this disorder is mainly related to the effects of papilledema on visual function.⁸
• If left untreated, long-standing disc edema results in an irreversible optic neuropathy with accompanying constriction of the visual field and loss of color vision.^9,10
• In end-stage papilledema, central visual acuity is also involved.

Sex

A strong predilection of this disease exists for women. More than 90% of patients with idiopathic intracranial hypertension are women of childbearing age.⁵ However, men with idiopathic intracranial hypertension are twice as likely as women to lose visual function due to their papilledema. Thus, the visual function of men with idiopathic intracranial hypertension must be followed more closely to avoid irreversible damage.¹¹

Age

Although idiopathic intracranial hypertension may affect individuals of any age, most patients with this disease present in the third decade of life.⁵

Idiopathic intracranial hypertension does occur in the pediatric population¹² ; these younger patients are often not obese.

Clinical

History

• Patients usually present with symptoms related to increased intracranial pressure. These symptoms include headache, transient visual obscurations, and diplopia due to unilateral or bilateral sixth nerve palsy. Rarely, patients presenting with increased intracranial pressure with related optic nerve edema may be asymptomatic.
• Nonspecific symptoms may include dizziness, nausea, vomiting, photopsias, retrobulbar pain, and pulse-synchronous tinnitus.⁵
• Headaches¹³
  • Headaches are recorded in almost all patients with idiopathic intracranial hypertension.
  • The pain is generally described as being diffuse, which worsens in the morning and is exacerbated by the Valsalva maneuver.
• Transient visual obscurations: This visual symptom occurs in most patients. The disturbance can last up to 30 seconds and is described as a graying out of vision on a monocular or binocular basis. Orthostatic changes, such as standing up or bending over, can induce this symptom.
• Diplopia: Patients who present with double vision most frequently complain of horizontal displacement of the images. Vertical diplopia is rare, but it has been reported.

Physical

• The most significant finding in patients with this disease is bilateral disc edema secondary to the increased intracranial pressure.
• This papilledema varies from patient to patient and is indistinguishable from optic nerve swelling caused by intracranial space-occupying lesions. In more pronounced cases of disc swelling, macular involvement with subsequent edema and diminished central vision may be present. High-grade and atrophic papilledema in addition to subretinal hemorrhages are poor visual prognostic signs.
• In some instances, the disc swelling is asymmetric, or, rarely, the appearance of the optic nerve may be relatively normal.
• If left untreated, chronic disc swelling eventually leads to clinically significant visual loss. Although all patients present with enlarged blind spots during their initial perimetry, uncontrolled papilledema results in progressive peripheral visual field constriction or nerve fiber bundle defects (eg, nasal depression, nasal steps, arcuate scotomas).
• The central visual field is affected in end-stage chronic papilledema.
• Sudden loss of central vision may result from an associated anterior ischemic optic neuropathy, a vascular occlusion, or an associated subretinal neovascular membrane.
• The diplopia noted in patients with idiopathic intracranial hypertension is invariably due to unilateral or bilateral sixth nerve palsy. These cranial nerve palsies diminish with the lowering of the intracranial pressure.
• Occasionally, patients with diplopia present with oculomotor or trochlear nerve palsy.
• In rare instances, vertical diplopia is due to a skew deviation.

Causes

• Most cases of idiopathic intracranial hypertension occur in young women who are obese and, less frequently, in men who are otherwise healthy. Patients with higher body mass indexes and recent weight gain are at an increased risk for this disorder.^5,7
• If this disorder presents in an individual who is not overweight, ruling out associated risk factors is necessary. These risk factors include systemic diseases (including Lyme disease), disruption of cerebral venous flow, certain endocrine or metabolic disorders, and exposure to or withdrawal from certain exogenous substances.^3,5
• Risk factors
  • Exogenous substances
    • The list of exogenous substances associated with idiopathic intracranial hypertension is extensive. Although an association exists between these substances and this disorder, the exact causal relationship is somewhat lacking in the literature.
    • Exogenous substances associated with idiopathic intracranial hypertension include amiodarone, antibiotics (eg, nalidixic acid, penicillin, tetracycline), carbidopa, levodopa, chlordecone, corticosteroids (eg, topical, systemic), cyclosporine, danazol, growth hormone, indomethacin, ketoprofen, lead, leuprolide acetate, levonorgestrel implants, lithium, oral contraceptives, oxytocin, perhexiline, phenytoin, and vitamin A (>100,000 U/d)/retinoic acid.^3,5
    • In some instances, although a patient may present with idiopathic intracranial hypertension following exposure to a certain medication, the disorder can continue despite the cessation of the presumed offending agent.
    • Withdrawal from corticosteroids may result in idiopathic intracranial hypertension.³ If corticosteroids are used for the treatment of idiopathic intracranial hypertension, their withdrawal may lead to a rebound increase in intracranial pressure.¹
  • Systemic diseases
    • A myriad of illnesses are associated with idiopathic intracranial hypertension. Some of these disorders result in an increased viscosity of the cerebrospinal fluid. However, in most of the listed entities, the causal link with raised intracranial pressure is not clear.
    • The following diseases have been associated with idiopathic intracranial hypertension: anemia,¹⁴ chronic respiratory insufficiency, familial Mediterranean fever, hypertension, multiple sclerosis, polyangiitis overlap syndrome, psittacosis, renal disease, Reye syndrome, sarcoidosis, systemic lupus erythematosus, and thrombocytopenic purpura.³
  • Disorders of cerebral venous drainage
    • Cerebral venous compression by extravascular tumors, secondary thrombosis due to a coagulopathy, or relative stenosis due to a venous flow anomaly can result in impaired absorption of the cerebrospinal fluid and, thus, idiopathic intracranial hypertension.^4,15 Restriction of venous drainage from the head may be impaired with radical neck dissection, even if completed only on the right side (predominant drainage from the head is via the right jugular vein). Spontaneous recanalization usually occurs, but, if delayed, chronic papilledema may result.
    • The diagnosis of cerebral sinus thrombosis may be missed with the exclusive use of CT. Therefore, either in patients who present atypically or in management dilemmas, ruling out cerebral venous thrombosis with the use of MRI/venography is worthwhile.
  • Endocrine disturbances: Pregnancy is occasionally associated with idiopathic intracranial hypertension.¹ This disorder can present at any stage of pregnancy. Given the limitations of neuroimaging studies and of medically treating patients who are pregnant, both the diagnosis and the management of these patients are determined on a case-by-case basis. Any neuroimaging studies or therapeutics should be performed in conjunction with the patient's obstetrician.

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