Idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IIH) typically presents in an overweight young woman (although it can develop in men), often after recent weight gain. The headache has the features of raised intracranial pressure (see description of increased cerebrospinal fluid pressure headache in Classifying headaches). Drugs (eg oral contraceptive pill, tetracyclines, vitamin A analogues [eg isotretinoin]) can cause raised intracranial pressure. Refer to an expert to confirm the diagnosis, because the condition can cause permanent visual loss if it is not treated. Venous obstruction and space-occupying lesions should be excluded by magnetic resonance imaging and magnetic resonance venography (or computed tomography venography), and then raised opening pressure confirmed on lumbar puncture.

The most effective treatment for idiopathic intracranial hypertension is weight loss—consider bariatric surgery if lifestyle changes are not sufficient. To lower the intracranial pressure, acetazolamide is preferred. Use:

acetazolamide 250 mg orally, twice daily. Gradually increase the dosage to 500 mg 4 times daily as tolerated. idiopathic intracranial hypertension acetazolamide

There is little evidence for using topiramate in idiopathic intracranial hypertension. It is less effective than acetazolamide at lowering intracranial pressure, but may promote weight loss.

Monitor patients with idiopathic intracranial hypertension closely, especially their vision—test visual fields, visual acuity and colour vision (Ishihara chart). If the patient has visual symptoms but visual examination is normal, start treatment as above. If the patient's visual symptoms get worse (and especially if visual acuity, colour vision or visual fields deteriorate), refer urgently for expert advice and possible surgery (eg ventriculoperitoneal shunting, optic nerve fenestration).