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BIH (sometimes called idiopathic intracranial hypertension or pseudotumour cerebri) is a rare condition affecting about one or two in every 100,000 people, most of them women: the usual age of onset is mid-twenties. It can also occur in children, where boys and girls are equally affected, and in older adults. Onset can be sudden or insidious; it may be associated with overweight, but losing weight does not appear to arrest the disease, although American research indicates that a 6% weight loss leads to resolution of the associated papilloedema.
The causes are unclear. However, always present are:
The symptoms reported are those usually associated with raised intracranial pressure (ICP); these will commonly include headache,visual disturbances, photophobia, vomiting, problems with balance and spatial awareness, disorientation, loss of short-term memory (sometimes long-term memory loss), "pins and needles" or loss of sensation in hands. In some cases, CSF leaks down the nose. It is important to exclude cerebral tumour as a cause of the symptoms. People with raised ICP may find it difficult to cope with previously learnt everyday tasks, eg handling money or using the telephone. They may be unable to find their way around a previously familiar town: traffic is confusing, they can be unaware of kerb height (sometimes afraid to step off the kerb in case they step ҩnto spaceө; crossing the road can be a nightmare.
Diagnosis of BIH is by scan and measurement of the CSF pressure. On CT scan, the ventricles (chambers in the brain) will usually appear normal or small. The CSF pressure should always be measured despite the "normal" scan results. It will be found to be raised on lumbar puncture. On examining the eyes, papilloedema (swelling of the optic disc) may be present. This in itself is often an indication for surgical intervention.
As most people with BIH appear perfectly normal, they often do not receive the recognition they deserve. But BIH can be very disabling. Relationships suffer. Headache can be constant, thus disturbing normal sleep patterns. Depression is not uncommon.
Some 11 - 35% of people recover spontaneously; in others, management is variable. Some people do very well on a regime of diuretics and steroids but must be monitored symptomatically, and by CSF pressure measurement to protect the eyesight.
There is little evidence that drug therapy improves the long-term outcome, although a short (two week) course of steroids may be enough to re-open venous pathways so that the BIH resolves.
Where sight is affected, it may be necessary to fenestrate the optic nerve (slit the sheath surrounding the nerve): everyone should be under the care of an opthalmic surgeon.
Some people need repeated lumbar punctures to remove excess CSF, or the excess CSF may need to be diverted by means of a surgically inserted shunt. In theory, a lumbar peritoneal shunt is the shunt of choice. In practice, the patient may undergo frequent shunt revision, including changing to a ventriculo-peritoneal shunt, or insertion of a lumbar reservoir.
Once a shunt is in place, the patient is at risk of those complications sometimes associated with shunting - for whatever reason the procedure is performed. The risks include infection, blockage, and, most commonly in BIH, over-drainage.
Back pain and sciatica or arachnoiditis may occur after lumbar peritoneal shunting.
Surgery should be considered only if there is a deterioration in vision, despite drug therapy or diet; inability to tolerate medication or non-compliance with taking medicines; or severe headaches which are proved to be associated with raised CSF.
After surgery or when CSF pressure is apparently successfully reduced by drugs, headaches may still occur. These can be very debilitating and may need to be treated with combinations of various painkillers. Complementary therapies such as cranial osteopathy, Indian head massage and reflexology are often very helpful, but should only be used if the neurologist or neurosurgeon is in agreement.
For further information on BIH, please contact ASBAH's Services Department. Tel: 01733-555988.
