What is IIH?
What is Idiopathic Intracranial Hypertension (IIH)
Idiopathic Intracranial Hypertension or IIH (also called benign intracranial hypertension or pseudo tumour cerebri) is a condition of elevated brain (intracranial) pressure. “Idiopathic” means the condition is not fully understood, “intracranial” means within the brain, and “hypertension” means high pressure.
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The high pressure is also transmitted to the eye (through the optic nerves) and the spinal cord because these structures are connected to the brain. The main symptoms it causes are headache and problems with vision.
IIH is caused by too much circulating brain (cerebrospinal) fluid, placing additional pressure on the brain as well as the nerves, such as the optic nerve (vision nerve at the back of the eye).
What are the symptoms?
Elevated brain pressure can cause a number of negative impacts for patients leading to quality of life and visual impairment.
Patients commonly experience;
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Headache (most commonly) that is often worse on awakening or lying on back
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Sounds of whooshing” sounds within ears, timed to the heartbeat (referred to as pulsatile tinnitis)
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Momentarily blurred vision, resolving within a few seconds, often occurring following a change in posture (referred to as transient visual obscurations)
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Blurred vision or loss of peripheral (side) vision
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Less common symptoms:
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Double vision which can be temporary or persistent
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Back or Neck pain
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Dizziness and Nausea
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In severe cases, IIH can cause severe peripheral vision loss and blurred central vision and even lead to blindness .
What causes IIH?
The causes of IIH are unclear. However, there are several associations with IIH that exist. The strongest association is being overweight obese or experiencing a recent weight gain. However, not all overweight or obese people develop this condition. Why some people develop IIH and others do not is not well understood. Weight loss alone can achieve remission in the many cases.
Certain medications increase the chance of developing IIH. These mostly include tetracycline antibiotics (e.g., minocycline, doxycycline), high doses of vitamin A and retinoids. These medications should be discontinued and avoided in the future by people with IIH. Hormonal contraceptives (oral and implants) have not been convincingly shown to cause IIH and should not necessarily be discontinued in IIH patients. Some medical conditions are recognised to be associated with IIH, but the relationship is unclear. These include polycystic ovary disease.
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Ongoing research into the causes of IIH is needed.
How Common is IIH?
This condition affects 1 in 100,000 people in the general population, however, the rate increases up to 20 times for women between the age of 15-40 years.
It is much more common in those who are overweight, obese or who have had a recent substantial weight gain.
How is IIH Diagnosed?
There are several important steps that need to be undertaken in order to diagnose IIH:
1. Complete eye examination: This is important to identify swelling of the optic nerves which is caused by high pressure in the brain. This disc swelling is called papilloedema. Many patients are diagnosed because papilloedema is identified by their optometrists through a routine examination. A thorough eye exam is necessary to identify if there is risk of visual loss which can occur in some cases of papilloedema.
2. Brain scan: such as MRI (Magnetic Resonance Imaging) or CT (computed tomography) scan. The purpose of the brain scan is to ensure that there are no other abnormalities in the brain that may cause increased intracranial pressure such as tumours or blood clots. The brain scan can also identify features that confirm elevated intracranial pressure.
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3. Lumbar puncture: A lumbar puncture is necessary to confirm a high intracranial pressure and that the spinal fluid is normal with no abnormal features.
Diagnosis
The diagnosis of Idiopathic Intracranial Hypertension can only be met once all of the diagnostic 'Dandy' criteria are met.
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1. Optic nerve swelling by ophthalmologist (called papilloedema)*
2. Normal neurological exam performed by doctor
3. Normal brain imaging (CT or MRI scan with Venogram)
4. Normal spinal fluid sample (lumbar puncture)
5. Elevated pressure of spinal fluid sample (lumbar puncture)
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* In absence of optic nerve swelling, the diagnosis can also made if there is either;
A) 6th nerve palsy (eye cannot fully move out)
B) Specific brain imaging findings (detailed on CT / MRI radiology report)
How is IIH Treated?
Most people with IIH are treated with medications and weight loss.
Very rarely are surgical procedures required.
If you do not have significant headaches or vision loss, no medical treatment may be necessary, but weight reduction is recommended in order for the elevated pressure to normalise. The decision to treat or not treat will be made in conjunction with your doctor after reviewing your visual tests and discussing your symptoms.
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When will the IIH go away?
Can IIH come back?
IIH may resolve over months to years or it may be a lifelong medical problem.
IIH can return, and is often linked to regaining weight.
What is prognosis of IIH?
Relatively few people become blind from IIH. Most people recover if they are treated early.
Surgery is needed if medical treatment and weight loss does not stop the visual loss.
In very rare cases, blindness may occur even with correctly administered medications and surgery.