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IH literally means that the pressure of the cerebrospinal fluid (CSF) that surrounds the brain is too high. Raised intracranial pressure is transmitted along the paths of the optic nerves, causing the nerves to swell (papilledema), which can lead to loss of vision and blindness.

Chances are you've encountered the terms "Pseudotumor Cerebri" or "Benign Intracranial Hypertension." While both are former names for the disorder now known as Primary or Idiopathic Intracranial Hypertension (IIH), they are inaccurate and downplay the seriousness of IH. Intracranial Hypertension (IH)--in any form--is an extremely painful and disabling disorder often resulting in loss of vision or blindness. There is nothing "benign" or "pseudo" about an IH patient's very real experience, not to mention the threat to his or her vision.

There are two categories of IH. Primary or Idiopathic Intracranial Hypertension (IIH) is IH without an identifiable causative agent. In other words, IIH occurs spontaneously, without a known cause.

Secondary Intracranial Hypertension is IH with an identifiable, causative agent, such as another underlying disease, an intracranial blood clot (dural sinus thrombosis), or certain drugs.

However, the mechanism by which IH occurs--in either case--is not known. No one knows why IH happens; only that, in some cases certain factors cause it. This is one of the vital questions that needs to be answered before a cure can be found. Currently most research favors the theory that there is resistance or obstruction to cerebrospinal fluid (CSF) outflow through the exiting pathways in the brain.