Intracranial hypertension (IH)

About intracranial hypertension (IH)

Intracranial hypertension (IH) can come on suddenly – for example, as the result of a:

• severe head injury
• stroke
• brain abscess

This is known as acute IH.

It can also be a persistent, long-lasting problem, known as chronic IH. This is rare and sometimes it's not clear why it happens.

This page focuses on chronic IH.

Symptoms of chronic IH

Symptoms of chronic IH can include:

• a constant throbbing headache – this may be worse in the morning, or when coughing or straining; it may improve when standing up
• blurred or double vision
• temporary loss of vision – your vision may become dark or "greyed out" for a few seconds at a time; this can be triggered by coughing, sneezing or bending down
• feeling and being sick
• drowsiness and irritability

Chronic IH can sometimes result in permanent vision loss, although treatment can help reduce the chances of this happening.

Causes of chronic IH

Possible causes of chronic IH include:

• a blood clot on the surface of the brain – known as a chronic subdural haematoma
• a brain tumour
• a brain infection – such as meningitis or encephalitis
• hydrocephalus– a build-up of fluid around and inside the brain
• blood vessel abnormalities – such as an arteriovenous fistula or arteriovenous malformation
• a blood clot in one of the veins of the brain – known as a venous sinus thrombosis

Rare causes include:

• a blockage in the circulation of fluid at the bottom of the skull (Chiari malformation)
• inflammation of the blood vessels in the brain (vasculitis)
• abnormal skull growth in children (craniosynostosis)

Idiopathic IH

In many cases, the cause of chronic IH is unclear. This is known as idiopathic IH, or sometimes benign IH.

It mainly affects women aged in their 20s and 30s, and has been associated with:

• being overweight or obese – most cases occur in overweight women, although it's not clear why
• hormone problems – such as Cushing's syndrome, hypoparathyroidism, an underactive thyroid or an overactive thyroid
• certain medications – including some antibiotics, steroid medication and contraceptive pills
• a lack of red blood cells (iron deficiency anaemia) or too many red blood cells polycythaemia
• chronic kidney disease
• lupus – a problem with the immune system

But these are only linked with idiopathic IH, they're not necessarily causes.

You can find a full list of conditions and medications associated with idiopathic IH  on the IIH UK website.

Tests for chronic IH

IH may be suspected if you have symptoms of increased pressure on your brain, such as vision problems and headaches.

Several tests may be carried out to diagnose it, such as:

• an examination to check functions like your muscle strength, reflexes and balance – any issues could be a sign of a problem with your brain or nerves
• an assessment of your eyes and vision
• a computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan of your brain
• a lumbar puncture – where a needle is inserted into your spine – to check for high pressure in the fluid that surrounds your brain and spinal cord

Idiopathic IH may be diagnosed if you have increased pressure on your brain and no other cause can be found.

Treatments for chronic IH

Treatment for IH depends on the underlying cause, if this is known.

The main treatments for idiopathic IH are:

• losing weight if you're overweight – this can often help reduce symptoms and may sometimes relieve them altogether
• stopping any medication that may be causing your symptoms
• medication to remove excess fluid from the body (diuretics) 
• medication to reduce the production of cerebrospinal fluid in your brain
• a short course of steroid medication to relieve headaches and reduce the risk of vision loss
• regular lumbar punctures to remove excess fluid from your spine and help reduce the pressure on your brain

Surgery

Surgery may be considered if other treatments don't help.

The main types of surgery for chronic IH are:

• shunt surgery  – a thin, flexible tube is inserted into the fluid-filled space in your skull or spine to divert excess fluid to another part of your body
• optic nerve sheath fenestration  – the protective layer surrounding your optic nerve, the nerve connecting the eye to the brain, is opened up to relieve pressure on it and allow fluid to drain away

These procedures can provide relief from your symptoms, but they also carry a risk of potentially serious complications. Talk to your surgeon about what your operation involves and what the risks are.

Outlook for chronic IH

Chronic IH can be life-threatening if it remains undiagnosed and the underlying causes are not treated. You should be referred to a specialist as soon as possible if your doctor suspects it.

Idiopathic IH isn't usually life threatening but can be a lifelong problem. While many people find their symptoms are relieved with treatment, the symptoms can recur and can have a significant impact on your life.

There's also a risk that you could lose your vision, even though treatment can help reduce this risk.

Permanent vision loss is estimated to occur in between 1 in every 5 to 20 people with idiopathic IH.

More useful links

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