Idiopathic Intracranial Hypertension
Intracranial Hypertension, also known as Pseudotumor Cerebri
Idiopathic Intracranial Hypertension (IIH) means there is a high pressure around the brain. There are many causes of high pressure around the brain (for example, a brain tumor), but in this condition there is no tumor or other structural cause. One of the most striking aspects of this condition is that it occurs almost exclusively in women of childbearing age who are overweight.
What causes this condition?
IIH is considered a disorder of cerebral spinal fluid (CSF) outflow. The CSF is the fluid that surrounds the brain and spinal cord. Intracranial pressure is partly due to the balance between how much CSF is produced and how much is drained. In IIH there is likely impaired drainage of CSF, so CSF accumulates around the brain, increasing pressure. Many conditions are thought to possibly be associated with IIH, the most common by far being increased weight. Certain medications, like minocycline class antibiotics (used for acne), and vitamin A, are other associations. Why these and other conditions impair CSF drainage is debated.
What are the possible symptoms?
Intracranial hypertension causes headache, which at times can be severe, and papilledema (swelling of the optic nerve at the back of the eye) that can lead to vision loss. Other common symptoms include a pulsating sound in the ears, brief episodes of vision loss usually when standing or straining, double vision, and flashing lights in the peripheral vision.
How is IIH diagnosed?
There are defined diagnostic criteria for IIH. In general, a brain scan should not show a brain tumor or other causes of increased intracranial pressure. Also, the CSF pressure should be directly measured via a lumbar puncture and the CSF examined for abnormalities.
What are the possible treatments?
A 2014 study called the “Idiopathic Intracranial Hypertension Treatment Trial” confirmed that weight loss and a diuretic pill called acetazolamide are effective treatments for this condition. Other medications such as Topiramate (Topomax) may also be used. Treatment is generally preferred because of headaches and the risk of permanent vision loss with chronic papilledema. Weight loss may be more successful under the direction of a dietician. Weight loss by itself may cure this condition. The study showed that males, those with vision loss at presentation, and those with many transient episodes of vision loss, tend to do worse. For patients who fail medical therapy, several surgical options exist to shunt spinal fluid away from the brain, such as lumboperitoneal shunt and optic nerve sheath fenestration. Bariatric surgery is also an option, if time will allow. In general, pregnancy is not discouraged. However, acetazolamide has a “class C” safety designation, meaning it is not known to be safe or known to be harmful to the fetus. Those potential risks should be discussed with the obstetrician.
The North American Neuro-Ophthalmology Society publishes a web site with good patient information on this condition.