Intracranial hypertension (IH) is high pressure inside the skull, which may happen suddenly or build up gradually over time.
It's a relatively common condition with many different possible causes.
This page focuses on chronic IH, where the pressure inside the head has built up gradually over time. This is usually caused by an underlying disease, but sometimes there's no clear reason. It's often a severe, lifelong disease.
Chronic IH is often referred to as idiopathic intracranial hypertension – idiopathic means there's no known cause.
What are the causes of chronic IH?
Some medical conditions, such as the following, can cause chronic IH:
- a brain 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 (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
Idiopathic IH means there's no obvious cause for IH. It's most commonly seen in overweight women in their 20s.
Experts don't fully understand the link between excess weight and IH, and losing weight only sometimes helps symptoms.
Idiopathic IH is also associated with:
- hormone problems such as vitamin D deficiency, Cushing's syndrome, hypoparathyroidism, underactive thyroid (hypothyroidism) and overactive thyroid (hyperthyroidism)
- 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're not necessarily causes.
What are the symptoms of chronic IH?
Severe cases can lead to seizures, but 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
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 doesn't show any injuries to specific brain areas
- 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're 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 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 relieve symptoms:
- acetazolamide, which may be taken along with a 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
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, although there's a small risk of complications such as an infection and blockage, which you should discuss with your surgeon.
Rarely, if your vision is affected you may need to have a procedure called 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 problems with vision, but the amount of fluid removed is so small that it won't make a difference to the overall high pressure inside your skull and can lead to complications that include blindness. Again, your surgeon will explain all of these risks to you if you're considering this operation.
Chronic IH is not usually fatal, but treatment can result in serious, sometimes life-threatening complications.
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 throughout the rest of your life.