IIH UK

Intracranial pressure, the pressure of the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord is measured in mm/H₂O or cm/H₂O. Normal intracranial pressure is considered to be 8 - 20cm (or 80 - 200mm), but can be up to 25cm (250mm) in patients who are overweight. Pressure over 25cm (250mm) is classified as intracranial hypertension. Often on diagnosis the intracranial pressure may be very high – it's not unheard of for pressure on diagnosis to be as high as 60cm (600mm)!

With treatment, for example on Diamox, it is usual for the pressure to come down, but it is not unusual for the pressure still to be 30-40cm (300-400mm), and it is said that even when the pressure is stabilised, for example by a surgically fitted shunt, that the pressure does not return to 'normal' figures, i.e. below 20cm (200mm), and will remain slightly raised.

Idiopathic Intracranial Hypertension (IIH) is often described as a condition that affects overweight women of childbearing age – it's most commonly women in their twenties and thirties who are diagnosed with IIH, and a large proportion of those diagnosed with IIH are overweight in comparison with the general population. Children and men however can also be affected, as can people who are not overweight.

It has been suggested that losing weight affects the amount of fluid that is retained by the body, including cerebrospinal fluid. Being significantly overweight can also raise the central venous pressure, which in turn can affect how "used" cerebrospinal fluid (CSF) filters back into the bloodstream. There is some evidence to suggest that losing weight can resolve the papilloedema (swelling of the optic nerves) that is associated with IIH, and there is other evidence that overweight IIH patients who lose weight are significantly less likely to still need treatment after five years.

Most doctors recommend losing weight for patients who are overweight. Some patients find that weight loss can significantly improve their symptoms and improve vision, but others find that losing weight makes no difference to their symptoms or the disease process. IIH is a complex and multi-factorial condition though, and the triggers for IIH and the mechanisms involved in causing the raised pressure in IIH are poorly understood. Even if weight loss doesn't improve your IIH symptoms though, maintain a healthy weight is important and reduces the likelihood of developing other health conditions, and can make it easier to cope with your symptoms.

CT and MRI scans are usually performed to rule out other reasons for your symptoms but in patients with IIH the scan will not normally show any abnormality, although sometimes the ventricles (fluid filled areas in the brain) are small due to swelling of the brain caused by high intracranial pressure, and areas of fluid may be seen on a scan. The only definitive proof of IIH though is a lumbar puncture or ICP monitoring showing raised CSF pressure.

Just as everyone is different, everyone's symptoms affect them differently and everyone reacts differently to medication. Usually when starting patients on acetazolomide (Diamox), the doctor will start you on a relatively low dosage of the drug. This is usually taken in divided dosage, i.e. smaller doses at intervals through the day. Many patients tolerate the side effects of the drug better when it is given in the sustained release form. Although Diamox is the most commonly prescribed medication for IIH, other diuretics may also be prescribed if Diamox is not working or you are unable to take it and other drugs may also be used to treat IIH and its symptoms.

In treating IIH the daily dosage of Diamox may be as high as 4000mg (4g). The dosage that is prescribed by your doctor depends on many factors, including your intracranial pressure, how much your vision is being affected (the severity of the papilloedema), your tolerance of the side effects of the drug and the severity of your symptoms.

The main side effects of Diamox are tingling of the hands and feet (paraesthesia) and an increased need to pass water. These are perfectly normal when taking Diamox and nothing to be concerned about.

Patients taking Diamox are usually advised to increase their consumption of potassium rich foods such as bananas, although all citrus fruits also contain relatively high amounts of potassium. If your potassium levels are very low you may also need to take a potassium supplement, although you should consult you doctor before taking any supplement. Some people have also found that increasing their vitamin C intake by taking a vitamin C supplement can help the symptoms as well.

Some doctors will only perform lumbar punctures as a diagnostic procedure. Others will perform lumbar punctures as a therapeutic procedure, i.e. to help relieve severe symptoms of IIH. When they are first diagnosed, some people need frequent lumbar punctures to lower the CSF pressure and relieve their symptoms. It is not unheard of for people to have lumbar punctures every 1–2 weeks when they are first diagnosed. Normally if severe symptoms still persist, particularly if there is any vision loss occurring, doctors will then start to consider other, i.e. surgical, options.

Often patients who have IIH will have papilloedema (swelling of the optic nerve) and enlarged blind spot (where the optic nerve enters the back of the eye). Visual problems are common with IIH and sufferers report a wide variety of vision problems including: changes in colour vision or after-images, diplopia (double vision), blurred vision, photophobia (pain and discomfort caused by bright light), reduced or fluctuating visual fields (loss of peripheral vision), and "greying out" of vision (transient visual obscurations).

Many of these visual problems are transient, they come and go, and sometimes will improve with treatment, for example Diamox. None of these symptoms means that you will lose your sight because of IIH. All of these symptoms are due to the high pressure of CSF on the optic nerve. Sometimes it may be necessary to fenestrate the optic nerve or fit a shunt to protect vision. Even once the pressure is reduced it can sometimes take a while for the papilloedema to resolve though. The most important thing to do is to make sure you attend ophthalmic appointments for checking your vision. About 5% of IIH sufferers lose some or all of their vision, but the majority of these are patients who don't attend follow-up appointments.

While most people with IIH have some degree of papilloedema, you can have IIH without papilloedema, just as some people don't have headaches. High intracranial pressure can still damage the optic nerves without papilloedema being present, which is why it is so important that you have your vision monitored regularly.

It’s most usual in IIH for visual loss to affect the peripheral vision (the area around the edges of your visual field (the visual field is the area that you can see while looking straight ahead without moving your eyes), and central vision is less likely to be affected, however many people experience blurred vision, and sometimes double vision.

Just as everyone’s symptoms are different, the visual symptoms experienced by people are different, and often vision loss isn’t permanent, improving with treatment; either medical treatments such as drugs to reduce the production of CSF, or surgical treatment such as a CSF shunt, or sometimes optic nerve sheath fenestration, though optic nerve sheath fenestration is used less often nowadays, and usually shunting is the preferred option. Often once the pressure is successfully controlled lost peripheral vision will return, though this is often a slow process.

It is important that you attend ophthalmic follow-ups regularly as the earlier vision loss is detected, the better chance of treating it.

Though severe headache is the classic symptom of IIH and may be the reason you first visit the doctor, in some people with IIH headache never occurs. Visual problems, papilloedema (swelling of the optic nerves), pulsatile tinnitus, and back and neck pain can also indicate raised intracranial pressure.

In some people symptoms of IIH resolve spontaneously, however IIH can be a chronic condition. Some people's symptoms are controlled on medication, some need regular lumbar punctures to ease their symptoms, and some need surgical intervention to protect their sight, for example by fitting a shunt. Some people find that their symptoms go into 'remission', they disappear. In some cases it is thought that this happens because your body gets used to the raised intracranial pressure, in other cases the intracranial pressure can reduce to near normal levels. In some cases symptoms do come back, in others they don't. It is important though if your symptoms improve significantly or disappear that you still have regular sight tests as abnormalities in the visual field are the first signs that intracranial pressure is rising.

Around a third of people will experience an epidural, or post lumbar puncture headache. Symptoms include nausea and vomiting, and a severe headache which is worsened by sitting or standing. A post lumbar puncture can occur within 1 to 3 days and lasts 2 to 7 days. The pain is relieved by lying flat. The treatment for a post lumbar puncture low pressure headache is to rest, lying down flat without any pillows with your feet higher than your head, and to drink plenty of fluids and take painkillers.

The amount of fluid that is drained off during a lumbar puncture varies, but over the 72 hours following a lumbar puncture, due to 'leaking' of the puncture site, additional fluid is lost and can lead to low CSF pressure which causes a severe headache that is worsened by sitting or standing. Drinking plenty of water (and some patients say also drinks high in caffiene, as caffeine raises intracranial pressure) can help as well.

If the headache continues, a procedure which can be very effective, called a blood patch, can be carried out, where a small amount of your own blood is injected into the site where the lumbar puncture was performed, so forming a clot and stopping the leaking of CSF.

It is perfectly safe to fly if you have IIH, and if you have a shunt fitted, as modern aeroplanes have pressurized cabins. Aeroplanes aren't pressurised to quite the same level as normal sea level though, and this can lead to a temporary worsening of the symptoms of any condition involving raised pressure, but these are rarely significant. When travelling you should take all the usual precautions and make sure you have sufficient medication with you. It also may be useful to carry with you a list of any medication you are taking and details of your doctor in case of emergency. You should also inform your travel insurer that you have IIH, as not doing so may invalidate your policy.

It's thought that there is a link between hormones and IIH, and many patients report a worsening of their symptoms when their menstrual period is due.

Contraceptives containing eostrogen have been implicated in the development of IIH and are associated with an increase thrombosis (blood clots), and should not be used by women with IIH. Progestogen based contraceptives though are thought to be safe, including the progestogen based 'depot injection', depot medroxyprogesterone acetate. Similarly levonorgestrel subdermal implants and levonorgestrel–releasing intrauterine systems are also considered safe.

There is no reason why you shouldn't have children if you have IIH (and a number of our forum members have had successful pregnancies after being diagnosed with IIH).

Some women do find that their symptoms worsen while they are pregnant, but many have completely normal pregnancies, though you may be considered to be 'high risk' and monitored more closely. Sometimes women with IIH are advised that they should have a cesarian birth as 'pushing' could be harmful if their intracranial pressure is raised. It is perfectly safe to have lumbar punctures while pregnant though. Diamox should not be taken if you are trying to get pregnant, and in the first trimester of pregnancy, though there are other medications that are suitable for use in pregancy. If you are planning on starting a family, you should discuss with your doctor what your options are.