Idiopathic Intracranial Hypertension (IIH)

Idiopathic intracranial hypertension (IIH) is an uncommon condition involving an increase in intracranial pressure in the brain of unknown cause. It goes by a couple of other aliases, including pseudotumor cerebri, due to the signs and symptoms mimicking a brain tumor (“pseudotumor” means “false brain tumor”), and benign intracranial hypertension. It is estimated that about 100,000 Americans suffer from IIH.

 
What causes IIH?
As defined in its name, IIH happens for no particularly good reason – it’s idiopathic. IIH’s typical victims tend to be overweight or obese women between 20 and 50 years old; only about 5% of cases occur in men. IIH can also occur in children though prior to puberty there appears to be no gender bias; after puberty, women are nine times more likely to be affected than men. Because of the relationship between IIH and obesity, the incidence of IIH in Western countries was reported to have tripled over a 15-year period back in 2013, a good reminder to cut back on that burger and fries.

 
What are the symptoms of IIH?
The most commonly reported symptom of IIH is headache with almost 90% of IIH patients experiencing a vague sort of pain that may resemble a migraine or tension headache. In the majority of these cases the headache can be exacerbated by strenuous actions such as coughing and sneezing and even by more obscure activities like weightlifting or straining in the bathroom. While a headache can be ignored or explained away, the second most frequent symptom of IIH is momentary vision blackouts, which is more likely to bring a patient to their eyecare practitioner in haste. Unfortunately, in up to 24% the vision loss may be permanent. Other visual disturbances may include double vision (diplopia) or light sensitivity (photophobia – needless to say, this does not make for a fun eye exam). IIH may also present with symptoms unrelated to vision, such as tinnitus (a ringing noise in the ears), dizziness, or neck and back stiffness.

 
How is IIH diagnosed and treated?
The predominant clinical sign an eyecare practitioner may notice is the presence of papilledema, which is a swelling of the optic nerve at the back of the eye. In sudden acute cases of IIH there may also be retinal hemorrhaging associated with the swollen nerve. Papilledema is not specific to IIH, however; it simply indicates the presence of raised intracranial pressure and may be due to more sinister causes such as a brain tumour or bleeding in the brain.

A thorough retinal examination involving dilating eyedrops to widen the eye’s pupil allows a clear view of the optic nerve. In some cases, the optic nerve swelling can be quite subtle and without any hemorrhaging, which can make diagnosis of papilledema difficult to make. In other cases, IIH may occur without the presence of papilledema at all. Optical coherence tomography (OCT) scanning is useful as it measures the thickness of the retinal nerve fiber layers and may more obviously show a swelling of the retina when compared to normative data. A visual field test can map out any areas of loss out to the peripheral vision.

Ultimately, the real diagnostic clues lie in the brain and spinal cord. Neuroimaging of the brain with MRI and CT will rule out the presence of any abnormalities of the brain matter, necessary by definition of idiopathic intracranial hypertension. A lumbar puncture, also known as a spinal tap, will reveal normal cerebrospinal fluid (CSF) composition as well as demonstrate what’s known as an elevated opening pressure of CSF by inserting a needle into the spinal cavity in the back. The process of a lumbar puncture in itself may help to reduce the intracranial pressure slightly.

The mainstay of treatment for IIH lies in weight loss and dieting – it’s time to break out the salad. Moderate weight loss such as 5 to 10% of total body weight may be adequate to achieve a reduction in intracranial pressure and relief of symptoms. Unfortunately, weight loss is not easy to achieve for most people at the best of times, especially with an advertisement for delicious chicken nuggets flashing on every corner. Bariatric surgery may be offered to aid in hastening reduction of obesity and intracranial pressure.

If vision is severely threatened, an optic nerve sheath fenestration may be performed, which creates a small incision in the covering of the optic nerve to allow pressure to escape. Other treatments include the use of oral diuretics such as Diamox (acetazolamide) to reduce the production of CSF. However, there are several side effects associated with the use of Diamox, including a metallic taste in the mouth triggered by carbonated drinks – perhaps an extra incentive to lay off the Cola?

Though headaches can be due to a plethora of causes, such as dehydration, fatigue, or in-laws, it is important to get it checked out and not simply dismiss it. You may just have a false tumor.

 

 
References
Idiopathic Intracranial Hypertension. https://nei.nih.gov/health/iih/intracranial
The diagnosis and management of idiopathic intracranial hypertension and the associated headache. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4916517/
Benign intracranial hypertension (BIH; pseudotumour cerebri; PTC; idiopathic intracranial hypertension; IIH) https://www.myvmc.com/diseases/benign-intracranial-hypertension-bih-pseudotumour-cerebri-ptc-idiopathic-intracranial-hypertension-iih/

 

 


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