Idiopathic Intracranial Hypertension
(Benign Intracranial Hypertension; Pseudotumor Cerebri)
(See also Approach to the Patient With Headache.)
Idiopathic intracranial hypertension causes increased intracranial pressure without a mass lesion or hydrocephalus, probably by obstructing venous drainage; CSF composition is normal.
Idiopathic intracranial hypertension typically occurs in women of childbearing age. Incidence is 1/100,000 in normal-weight women but 20/100,000 in obese women. Intracranial pressure is elevated (> 250 mm H2O); the cause is unknown but probably involves obstruction of cerebral venous outflow, possibly because venous sinuses are smaller than normal.
In children, this disorder sometimes develops after corticosteroids are stopped or after children have taken large amounts of tetracycline.
Almost all patients have a daily or near daily generalized headache of fluctuating intensity, at times with nausea. They may also have transient obscuration of vision, diplopia (due to 6th cranial nerve dysfunction), and pulsatile intracranial tinnitus. Vision loss begins peripherally and may not be noticed by patients until late in the course. Permanent vision loss is the most serious consequence. Once vision is lost, it usually does not return, even if ICP is reduced.
Bilateral papilledema is common; a few patients have unilateral or no papilledema. In some asymptomatic patients, papilledema is discovered during routine ophthalmoscopic examination. Neurologic examination may detect partial 6th cranial nerve palsy but is otherwise unremarkable.
If clinical findings suggest idiopathic intracranial hypertension, clinicians should check visual fields and optic fundi, even in patients with no visual symptoms.
Diagnosis is suspected clinically and established by brain imaging (preferably MRI with magnetic resonance venography) that has normal results (except for venous transverse), followed, if not contraindicated, by lumbar puncture with CSF testing that indicates elevated opening pressure and normal CSF composition.
Use of certain drugs and certain disorders can produce a clinical picture resembling idiopathic intracranial hypertension and should be excluded (see Table: Conditions Associated With Papilledema and Resembling Idiopathic Intracranial Hypertension).
Conditions Associated With Papilledema and Resembling Idiopathic Intracranial Hypertension
Idiopathic intracranial hypertension occasionally resolves without treatment.
Treatment of idiopathic intracranial hypertension is aimed at the following:
The carbonic anhydrase inhibitor acetazolamide (250 mg po qid) is used as a diuretic.
Obese patients are encouraged to lose weight, which may help reduce intracranial pressure.
Serial lumbar punctures are controversial but are sometimes used, particularly if, while waiting for definitive treatment, vision is threatened.
Any potential causes (disorders or drugs) are corrected or eliminated if possible.
Drugs used for migraine (particularly topiramate, which also inhibits carbonic anhydrase) may relieve headache. NSAIDs can be used as needed.
If vision deteriorates despite treatment, one of the following may be indicated:
Bariatric surgery with sustained weight loss may cure the disorder in obese patients who were otherwise unable to lose weight.
Frequent ophthalmologic assessment (including quantitative visual fields) is required to monitor response to treatment; testing visual acuity is not sensitive enough to warn of impending vision loss.
Consider idiopathic intracranial hypertension if patients, particularly overweight women, have a daily generalized headache with or without visual symptoms; check visual fields and optic fundi.
Diagnose based on results of brain imaging (preferably MRI with venography) and, if not contraindicated, lumbar puncture.
Advise weight loss if needed and treat with acetazolamide.
Do frequent ophthalmologic assessments (including quantitative visual fields) to monitor response to treatment.