Intracranial hypertension (IH) means abnormally high pressure inside the skull, which may happen suddenly or build up over time.
It's an uncommon condition, with many different possible causes.
Acute IH occurs when the condition comes on rapidly – for example, as the result of a severe head injury, stroke or brain abscess. Acute IH is fatal if it's not treated promptly as a medical emergency – you will need to be admitted to hospital straight away.
This page focuses on chronic IH – a severe, lifelong condition, usually caused by an underlying disease. Emergency treatment may also be required if chronic IH is caused by a build-up of fluid in the brain or a brain tumour (see below).
However, there is sometimes no clear reason for the condition. This is often referred to as idiopathic intracranial hypertension – idiopathic means there is no known cause.
What are the causes of chronic IH?
Possible causes of chronic IH include:
abrain tumour – such as a glioma or meningioma
a brain infection – such as meningitis or encephalitis
hydrocephalus – which is a build-up of fluid in the cavities of the brain
blood vessel abnormalities – such as an arteriovenous fistula or arteriovenous malformation (an abnormal connection between an artery and a vein)
blood clotting in one of the large veins of the brain – known as a venous sinus thrombosis, usually caused by infection or severe dehydration
You can find a full list of medical conditions and medications associated with IH on the IIH UK website.
Idiopathic IH means there is no obvious cause for the IH. It is most commonly seen in overweight women in their twenties.
Experts do not fully understand the link between excess weight and IH, and losing weight can sometimes help reduce symptoms.
Idiopathic IH is also associated with:
hormone problems – such as vitamin D deficiency, Cushing's syndrome, hypoparathyroidism, underactive thyroid and overactive thyroid
certain medications – including tetracycline, steroid medication,nitrofurantoin and oral contraceptives
polycythaemia vera(having too many red blood cells)
iron deficiency anaemia
chronic kidney failure
lupus(a problem with the immune system)
Note that these conditions are only linked with idiopathic IH; they are not necessarily causes.
What are the symptoms of chronic IH?
Most people with chronic IH generally experience:
severe throbbing headaches which are often constant, worse in the morning, aggravated by straining or coughing and associated with nausea and vomiting – they are sometimes relieved by standing
changes in vision due to swollen optic nerves (known as papilloedema) – you may have blurred vision and find it difficult to watch TV or read; this can result in permanent visual impairmentand may require urgent treatment after assessment by an opthalmologist
You may also feel drowsy, confused and irritable, and have nausea and vomiting. Occasionally, you may hear a "whooshing" sound in your ears.
How is chronic IH diagnosed?
IH may be suspected if you have signs and symptoms of increased intracranial pressure, such as vision problems and headaches.
A diagnosis of IH is made by ruling out other possible causes of the symptoms. The following should apply:
a neurological examination does not show any problem with nerve, spinal cord or brain function
an opthalmology assessment may reveal eye changes
a CT scan or MRI scan may look normal
a lumbar puncture (see below) shows that you have high pressure in the cerebrospinal fluid that surrounds your brain and spinal cord
you are awake and alert
no other cause of increased intracranial pressure has been found
How is chronic IH treated?
The treatment you have depends on the underlying condition causing your IH.
If you're overweight, it's important to lose weight. This often helps to reduce eye symptoms and can sometimes relieve symptoms altogether without the need for medical treatment.
You may be given any of the following medicines to treat the underlying cause and help to relieve symptoms:
diuretic (medication to remove excess fluid from the body)
a short dose of prednisolone (a steroid medication) to relieve headaches, especially if you're at risk of losing vision
The links above will take you to more information on these drugs, including their side effects.
You may need regular lumbar punctures to remove excess cerebrospinal fluid from your spine and skull, and to help keep down intracranial pressure.
This procedure involves taking a sample of fluid from inside your lower back using a needle and syringe.
Surgery should be considered as a last resort if medication and weight loss fail to control your IH.
You may be offered shunt surgery, where a catheter (a thin, flexible tube) is inserted into the fluid-filled space in your brain or spine to divert the excess fluid to another part of the body.
The main types of shunt surgery are:
lumboperitoneal shunting (shunting fluid from the spine to the abdomen)
ventriculoperitoneal shunting (from the brain to the abdomen)
ventriculoatrial shunting (from the brain to the heart)
For many, shunt surgery provides long-term relief from symptoms. However, there is a small risk of complications, such as infection and blockage, which you should discuss with your surgeon.
Rarely, if your vision is affected, you may need to have a procedure called an optic nerve sheath fenestration (ONSF). The surgeon will slit open the sheath surrounding your optic nerve to relieve the pressure on the nerve and allow the build-up of fluid to escape.
ONSF is very effective at relieving this nerve pressure and helping to treat vision problems, but the amount of fluid removed is so small that it will not make a difference to the overall high pressure inside your skull and can lead to complications, including blindness. Your surgeon will explain all of these risks to you if you're considering this operation.
Many patients with chronic IH find that their symptoms are relieved after treatment, although attacks of symptoms can recur.
Chronic IH is a life-changing condition and your intracranial pressure will need to be continuously monitored for the rest of your life.
One cause of intracranial hypertension: a haematoma (blood) can be seen building up on the right side of the skull.