Idiopathic Intracranial Hypertension (IIH): Causes, Symptoms and Treatments

What Is Idiopathic Intracranial Hypertension (IIH)?

The brain is surrounded by a clear and colourless cerebrospinal fluid (CSF) and is an ordinary and necessary part of a normally functioning nervous system.

IIH, or idiopathic intracranial hypertension, is an uncommon medical condition with increased CSF production. The brain cannot drain this excess CSF, resulting in a rise in pressure within the skull. It is still not clear as to what causes this. One recent plausible theory is that excess adipose (fat) tissue converts female hormones (estrogen) into increased levels of male hormone (testosterone), resulting in increased CSF production.

The incidence of IIH in the general population is thought to be about 1 per 100,000, and to this day, its root cause is still unknown.

High pressure around the brain can mean putting pressure on the optic nerve; this will cause the optic nerve to swell and, over time, impact the eyes. The pressure can result in double vision or loss of sight.

IIH is also known as pseudotumor cerebri syndrome and benign intracranial hypertension.

Symptoms of Idiopathic Intracranial Hypertension (IIH)

According to one study, the following symptoms are most commonly seen:

• Headache – 94% of patients

• Visual obscurations – 68% of patients

• Pulsatile tinnitus – 58% of patients

• Eye pain – 44% of patients

Overview of the symptoms that may be experienced by people with Idiopathic Intracranial Hypertension:

• Headaches. Patients with IIH commonly complain of dull, migraine-like or throbbing pain that feels worse in the evening or upon waking up.

• Visual obscurations. Patients report that their vision appears dim, blurry, or dull. They may experience having trouble with their peripheral (side) vision or seeing double. There may be short periods where they completely lose their sight, and many patients may be unaware of their vision loss.

• Hearing problems. The increased pressure in the brain affects the cochlear nerve in the inner ear. Hence, IIH patients often have hearing issues such as pulsatile tinnitus (loud whooshing sound on one side or both), a low-pitched thumping, a blowing sound, a clicking, higher-pitched rhythmic sensation, or a swishing sound. Some may also experience hearing loss.

• Nausea and vomiting. IIH mimics migraine or brain tumour symptoms, so the patient may also experience nausea, dizziness, or vomiting.

• Seizures. Seizures are rare in IIH patients.

• Permanent vision loss. This is the most severe consequence of IIH. Health professionals, more than anything, fear the irreversible loss of vision in patients if the damage to the optic nerve is extensive.

Risk Factors for IIH

Anyone can develop IIH, but it is more commonly recognised in:

• Women in their child-bearing years (between the ages of 20 to 50) are 20x more likely to develop this condition.

• Obese people (BMI > 30), click here to calculate your BMI

• People with a thyroid condition or chronic kidney failure

• People experiencing hormonal abnormalities

• People experiencing obstructive sleep apnea

How Is IIH Diagnosed?

IIH remains a diagnosis of exclusion. Meaning, there is no definitive test to determine IIH, so doctors are only able to diagnose IIH by eliminating other causes of the symptoms. 

A patient’s eye doctor may be the first person to suspect IIH when there’s a swelling of the optic nerve, called papilloedema, during a routine eye exam or when a patient complains of headaches or vision problems.

We can typically diagnose the condition with typical symptoms as described above. The usual tests that we perform include the following:

• Optometrist review. It is common for an optometrist to see the first signs of IIH. Patients will notice visual symptoms and have these assessed.

• Ophthalmological review. An eye specialist is sometimes initially involved because the first test abnormalities for this condition are usually discovered in the eye.

• MRI brain with MR venography. This test is usually performed to ensure that patients do not have any other reasons for raised cranial pressure. Despite this, we can often see increased pressure around the eyes, and we may even see pressure changes within the large veins of the brain.

• Lumbar puncture is a safe procedure performed under local anaesthesia; a sample of fluid is withdrawn from around the spine (specifically, the subarachnoid space, which surrounds the brain and the spinal cord) to test pressure and check for any abnormalities of cerebral fluid. A discovery of increased pressure during this test usually helps with diagnosing the patient with IIH. If the pressures are high, we can remove cerebrospinal fluid to alleviate symptoms temporarily.

Treatment for Idiopathic Intracranial Hypertension (IIH)

The primary goal for treatment is to ensure that patients do not suffer long-term injury to the optic nerves and experience loss of vision as a result of chronically elevated pressure.

So as soon as the patient has been diagnosed with IIH, treatment should begin right away. 

Diet. Studies and clinical observations point to weight loss as an effective treatment. As IIH is commonly observed among the obese, doctors recommend a low-sodium weight-loss program to reduce the symptoms. Studies show that even a weight loss of 5%–10% can ease symptoms.

Medication. Common medications include acetazolamide (Diamox) or topiramate (Topamax). These medications aim to reduce cerebrospinal fluid within the brain therefore reducing the pressure. For some patients, side effects are common especially with Diamox which includes numbness and tingling in the lips and in the fingers, intolerance to carbonated beverages and occasionally dizziness. Topamax can cause wide-ranging number of side effects. Generally, however, most side effects subside once the medication has been stopped or continued for long periods.

Surgery. If weight loss and medication do not improve the patient’s condition and their eyesight deteriorates, surgery is the next best approach. The goal is to lessen the pressure around the brain or the optic nerve.

• Shunting. Shunting has historically been a standard process for patients with IIH. This involves the insertion of a small tube into the fluid spaces of the brain and the other end of the tube inserted into the abdomen. This is ineffective and low-risk procedure but unfortunately is associated with a high retreatment rate compared to other options.

• Optic nerve sheath fenestration. This procedure involves cutting a window into a membrane that surrounds the optic nerve to release excess cerebrospinal fluid. This will stabilise or improve the patient’s eyesight.

• Venous sinus stenting. This treatment has been gaining traction in the last decade as an option for patients with moderate to severe versions of this condition. In comparison to shunting, there is a low risk of retreatment and excellent long-term results. It involves an interventional neuro-radiologist inserting a stent in a large vein in the head, increasing the blood’s ability to flow. A cerebral venogram is required to assess a patient for their suitability to have a venous sinus stent. This is a low-risk day procedure that involves insertion of a wire and catheter into the body and into the large veins of the brain to assess whether there is a stenosis (narrowing) that might benefit from venous sinus stenting.
  

Should I Get a Venous Sinus Stent?

We believe sinus stenting is an effective treatment option for patients who are either:

• Unable to tolerate the medication and have ongoing papilloedema (swelling behind the eyes)

• Continue to have ongoing papilloedema despite being on large amounts of medication

We have previously considered stenting for patients who have severe headaches without papilloedema. However, given the low but important risk of significant complications (equating to 1–2%), we generally reserve this treatment for patients who risk losing their vision.

How to Prevent IIH

Currently, IIH has no known cause. Obesity and weight gain seem to play a role in a significant proportion of female patients. Keeping a healthy diet and weight is key to preventing this condition.

DISCLAIMER: The information provided is designed to support, not replace, the relationship that exists between a patient or site visitor and their existing healthcare professionals.