Introduction to idiopathic Intracranial Hypertension

What is IIH?

Idiopathic intracranial hypertension is a condition where the pressure inside the skull is too high without a clear cause.

• Idiopathic means no known cause.
• Intracranial means inside the skull.
• Hypertension means high pressure.

The pressure rises because the fluid that cushions the brain and spinal cord (cerebrospinal fluid or CSF) builds up. This can press on the brain and the optic nerves, which are needed for sight.

IIH was previously called pseudotumour cerebri because its symptoms can resemble those of a brain tumour, however there is no tumour.

How common is it?

IIH is uncommon. On average about 5 in 100,000 people are diagnosed each year. It is more common in young women with obesity.

Is it serious?

IIH is not usually life-threatening. However, without treatment it can cause permanent changes to your vision. Early assessment and treatment help protect your sight and reduce symptoms.

What causes it?

The exact cause is not known. Possible factors include:

• Problems with how CSF flows and is absorbed.
• Narrowing of large veins in the brain (venous sinuses), which can slow drainage and raise pressure.

Is it inherited?

There is no proven hereditary link at present.

Who is more at risk?

Anyone can develop IIH, but the risk is higher if you:

• Have a body mass index (BMI) over 30.
• Are female.
• Are aged 20 to 45.