All About IIH
What is Idiopathic Intracranial Hypertension?
Idiopathic intracranial hypertension (IIH), also known as benign intracranial hypertension or Pseudotumor cerebri, is a rare condition with an unknown cause or causes. The condition is associated with raised fluid pressure around the brain. The fluid that cushions the brain is called cerebrospinal fluid (CSF). It can cause disabling daily headaches and visual loss, which can be permanent. The raised brain pressure can press the nerves supplying the eye (also known aspapilloedema) and this can affect vision.
Who gets IIH?
IIH can happen to anyone. It is a condition found more commonly in women (90%), but some men are also affected by it. It is common in teenagers and young women, but can also affect children and adults of any age.
How common is IIH?
IIH is considered a rare disease. Recent medical reports show that IIH is happening more often. Somewhere between 1-3 people in every 100,000 get this condition in the normal population, but it becomes more common in those with obesity(BMI >30)with rates reported up to 20 per 100,000.
IIH is on the increase in women. Between 2005 and 2017 incidence has increased from 2.5 per 100,000 to 9.3 per 100,000 whilst prevalence has increased from 26:100,000 to 79:100,000.1
Incidence relates to new cases of IIH in the population in a year whereas prevalence tells us how widespread it is across the whole population.
A. Prevalence is in black. Incidence is in blue. We can see quite clearly how both has risen over the years.
B. This graph shows that IIH is most frequent in women aged 20-29.
C. This graph shows that BMI on diagnosis has an association with IIH. Incidence in women with a BMI of 18.5 is 2:100,000 per year whilst a BMI of 40 has an incidence of 28:100,000 per year.
D. The Townsend index is a measure of material deprivation within a population. 1 being better off, 5 being poorer. As you can see the incidence of IIH rises in those from poorer backgrounds.
What causes IIH?
We do not know what the cause or causes of IIH are. There is a striking association to being overweight. This is a sensitive issue. Medical studies have shown that recent weight gain can cause IIH, and found that weight loss can put IIH into remission. There is ongoing research into the cause/causes of IIH, you can read about this in the Research Section.
What is IIH without papilloedema?
IIH without papilloedema, is a rare condition where high pressure can trigger headaches but in this condition at diagnosis there is no papilloedema and these people never develop papilloedema. For further information see the IIHUK IIHWOP leaflet.
Is IIH genetic?
The cause or causes of IIH are not known. Although genes play an important role in lots of conditions, it is not yet known whether they play a role in IIH.