Causes and Treatment of Idiopathic Intracranial Hypertension (IIH)

Idiopathic intracranial hypertension (IIH) is a condition mainly affecting females that causes increased pressure around the brain and symptoms like headache and vision changes. If left untreated, permanent vision loss and blindness are possible.

Formerly known as pseudotumor cerebri, IIH is a condition of unknown origin that mostly affects females in their childbearing years. Obesity also plays a part. Certain medications can reduce the intracranial pressure, but surgery may be needed to avoid permanent vision loss.

This article describes the symptoms and causes of idiopathic intracranial hypertension, including how this rare cause of headaches is diagnosed and treated.

What Are Symptoms of Idiopathic Intracranial Hypertension?

Headache with vision changes are classic signs of IIH. On close inspection of the eye, your healthcare provider will detect papilledema, or the swelling of the optic nerve caused by increased pressure in the brain.

IIH was once called pseudotumor cerebri ("false brain tumor") because it mimics symptoms of a brain tumor. These include symptoms like:

• Headache felt mainly behind the eyes
• Ringing in the ears (tinnitus) that pulsates with your heartbeat
• Brief episodes of vision loss
• Pain with eye movement
• Poor peripheral (side) vision
• Blind spots
• Photopsia (flashing or sparkling lights)
• Diplopia (double vision)

Severe cases of IIH can place extreme pressure on an optic nerve, causing unilateral (one-sided) or bilateral (two-sided) vision loss or blindness.

What Causes Idiopathic Intracranial Hypertension?

IIH is a rare condition affecting one of every 100,000 people annually. Females are affected 20 times more often than males, most especially those between 20 and 50.

"Idiopathic" means of unknown origin. As such, IIH is a condition that occurs for no apparent reason. There are several theories as to why IIH suddenly occurs:

• The overproduction of cerebrospinal fluid (CSF)
• A sudden increase in the volume of blood or brain tissues
• The temporary obstruction of veins used to drain blood from the brain

Being overweight or having obesity also increases the risk. Studies suggest that the risk of IIH increases by 13-fold if you are 10% over your ideal body weight and by 19-fold if you are 20% over your ideal weight. Females are also affected more by weight, and scientists are unclear why.

How Idiopathic Intracranial Hypertension Is Diagnosed

In addition to a severe headache with intermittent vision loss, IIH is recognized by the development of papilloedema in one or both eyes during an ophthalmoscopic exam.

A lumbar puncture ("spinal tap") would likely be ordered to extract a sample of cerebrospinal fluid (CSF) and measure the pressure inside your skull. A pressure greater than 250 mmH2O is diagnostic for intracranial hypertension.

Thereafter, the diagnosis is exclusionary. What this means is that all other causes of your symptoms must be excluded before IIH can be confidently diagnosed. This may involve an extensive battery of tests, including blood tests, brain scans, and a lab analysis of CSF.

Among some of the conditions excluded in the differential diagnosis are:

• Cerebral venous thrombosis (blood clot in the brain)
• Brain tumor (both benign and malignant)
• Brain abscess (a pocket of pus in the brain)
• Obstructive hydrocephalus ("water on the brain")
• Subarachnoid hemorrhage (a type of brain bleed)
• Malignant hypertension (dangerously high blood pressure)

How Idiopathic Intracranial Hypertension Is Treated

The treatment of IIH typically involves a neurologist and ophthalmologist. The primary goals are to relieve symptoms and prevent vision loss. There are several treatments commonly used for this:

• Diamox (acetazolamide): This prescription drug can quickly reduce CSF production by the choroid plexus of the brain.
• Serial lumbar puncture: The diagnostic procedure can also be used to relieve intracranial pressure by removing small amounts of CSF a little at a time.
• Analgesics: These include over-the-counter drugs like Tylenol (acetaminophen) and prescription drugs like Topamax (topiramate) to ease headache pain.
• Traverse sinus stenting: This is the placement of a metal tube into a part of the skull to drain fluids and relieve pressure.
• Optic nerve sheath decompression and fenestration: With this surgery, the connective tissue surrounding the optic nerve is cut to relieve pressure.
• Cerebral shunting: This surgery creates a conduit from the brain to another part of the body, usually the abdominal cavity, to drain excess CSF.

Summary

Idiopathic intracranial hypertension is a condition of unknown origin that causes increased pressure in the brain, causing severe headaches, transient vision loss, and other symptoms. If not treated appropriately, permanent vision loss can ensue.

IIH involves a diagnosis of exclusion in which all other causes of your symptoms are excluded. Treatment involves medications and procedures (such as a spinal tap) to relieve intracranial pressure and prevent potentially irreversible damage to the optic nerve.