About IIH
Idiopathic Intracranial hypertension (IIH) is a serious neurological condition in which high cerebrospinal fluid (CSF) pressure within the skull causes unbearable headaches, swelling of the optic nerves (papilloedema) and can result in loss of vision or blindness. IIH was formerly known as BIH (Benign Intracranial Hypertension) although this name is falling out of use now as the condition can cause permanent visual loss and therefore is certainly not harmless or benign, as sufferers who live with it's effects daily would agree. It's also sometimes known as pseudotumor cerebri (PTC) as there are some of the signs and symptoms of a brain tumour without a tumour being present(pseudo meaning false). The cause of IIH is unknown – idiopathic means "of unknown cause". IIH is a rare condition affecting about one or two in every 100,000 people, most of them women of childbearing age, but men and children can also be affected.
Diagnosis
Diagnosis of IIH is made by identifying the typical symptoms of the disease and ruling out other conditions that can cause the similar symptoms. Neurological examination is normal, except for the presence of swollen optic nerves (papilloedema), although papilloedema may not always be present, and imaging procedures such as CAT/CT scans and MRI scans are normal. Definitive diagnosis of IIH is made by performing a lumbar puncture which shows the pressure of cerebrospinal fluid (CSF) to be above 25cm/H2O.
What causes IIH?
No–one knows what causes IIH, although blood clots in the veins draining the brain can cause increased intracranial pressure. Withdrawal of steroids, large doses of vitamin A or intake of foods containing large amounts of vitamin A, use of body building–type steroids and possibly, hormonal changes and certain drugs can also cause raised intracranial pressure. Statistically, the majority of IIH sufferers are "women of childbearing age" who are overweight, which has lead some doctors think IIH is associated with being overweight. Many sufferers find though that losing weight doesn't help their symptoms, but research suggests that a 6% decrease in bodyweight can help to resolve the papillodaema (swelling of the optic nerves) that is associated with the condition.
Symptoms of IIH
The most common symptoms of IIH are: severe headache, papilloedema, temporary loss of vision, transient visual obscurations (blurred vision), double vision and decreased visual acuity, pulsatile tinnitus ("whooshing noise" in the ears in time with the pulse), and pain behind the eye and with eye movement.
Other symptoms reported by people with IIH include: nausea, vomiting, fatigue, photophobia (dislike of and pain caused by bright light), problems with balance and spatial awareness, aphasia (difficulty using or understanding words), disorientation, loss of short-term memory (sometimes also long-term memory loss), confusion, feeling 'spaced out', and lack of depth perception (for example judging the depth of stairs, steps, and curbs can be a problem). People with IIH may find unfamiliar (and even familiar) places, and traffic, confusing and overwhelming.
Treatment of IIH
If a patient is overweight, most doctors recommend losing weight, however most patients find that losing weight makes no difference to their symptoms. IIH is a complex disorder though, and a number of things have been implicated in IIH, including hormones, certain drugs, and other factors, and weight loss as a treatment is usually used in combination with other treatments, either medical or surgical.
Medical treatment
The most commonly prescribed medication is acetazolomide, which is a diuretic. It's thought that it acts by reducing the production of CSF. It's relatively safe but nearly all patients have tingling of the fingers and toes as a side effect of the medication, and patients are advised to increase their intake of potassium as acetazolomide drains the body's stores of potassium. As well as the standard acetazolomide, a sustained release form of the drug is also available, 'Diamox SR', and many patients tolerate this form of the medication better and find that the side-effects are reduced in comparison with the standard form of acetazolomide. Another diuretic commonly used is frusemide. Sometimes a short course of steroids may be given. Various analgesic drugs (painkillers) are used to treat the pain associated with IIH, with varying degrees of success, but as with all painkillers care must be taken as many drugs can be addictive and some can have severe side-effects.
Some people need repeated regular lumbar punctures (LPs) to remove excess CSF, or if symptoms don't improve on medication, surgical treatments may be considered.
Surgical treatment
Surgical treatments for IIH fall into two main types; neurosurgical ophthalmic procedures to relieve pressure on the optic nerve, and neurosurgery to drain excess CSF (cerebrospinal fluid) to reduce the intracranial pressure. Other types of surgery may be performed, but less commonly. Of the two, the reduction of the amount of CSF by surgically implanting a shunt is the most common procedure for IIH.
If vision is severely affected or threatened, optic nerve sheath fenestration (ONSF) may be considered. In this procedure, the sheath surrounding the optic nerve is slit, or a 'window' cut into the sheath to relieve the pressure on the nerve and allow the CSF to escape. While ONSF is very effective at relieving the pressure on the optic nerves, and thus helping to resolve papilloedema, the amount of CSF which is drained due to this procedure is neglible, and ONSF has little effect on the intracranial pressure overall, or on the other symptoms of IIH. Not all patients are suitable for ONSF surgery though, and in practice, due to the fact that shunting is more effective at reducing the overall intracranial pressure and alleviating symptoms, more commonly shunting is the surgery of choice for IIH.
There are two main types of shunts that are used, the lumbar–peritoneal shunt (running a tube from the spinal fluid space in the lower spine into the abdominal cavity), and ventriculo-peritoneal shunt (running a tube from the ventricles (fluid filled spaces within the brain) into the abdominal cavity). Again though, not all patients are suitable candidates for shunt surgery. CSF shunts were originally developed to treat hydrocephalus patients, which though it shares some symptoms in common with IIH, is a totally different condition. Hydrocephalus patients usually have normal or large sized ventricles in the brain, whereas in IIH, ventricles are often either small or slit-shaped, and this can make the placement of ventriculo-peritoneal shunts in IIH patients sometimes difficult. Where shunting is used though, often it is very successful in reducing symptoms and reducing the intracranial pressure for many people. Shunt infections, blockage, and over-drainage though can be a problem with shunts, and some patients require frequent revision surgery to their shunt.
Surgical intervention is usually only used as a last resort though and to protect vision because of the risks involved, i.e. the general risks of surgery and anaesthetics, infection, blockage, and over-drainage. Even when CSF pressure is successfully reduced by drugs, or by surgical intervention, though, some symptoms, including severe headaches can still occur. The reasons for this are not fully understood, and despite controlling intracranial pressure, symptoms of IIH can still be very disabling for some IIH patients.
While for some patients their symptoms may spontaneously disappear as quickly as they came on, for others a combination of medical and/or surgical treatments control their condition, and they are able to lead relatively normal lives. For others though, both medical and surgical treatments can be limited in their effectiveness, and symptoms may remain. For these patients, treatments with combinations of painkillers and other drugs are required to control the symptoms, though their effectiveness varies.
IIH isn't a life threatening condition, but for many people it can be a life changing condition.
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