Eye Disorders: Pseudotumor Cerebri, also known as Idiopathic Intracranial Hypertension
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) flow. 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 possilbe treatments?
Definitive treatment is weight loss, which will cure IIH in most cases. The most common treatment is a diuretic called Acetazolamide (Diamox), which increases CSF outflow, thus restoring a more normal balance between CSF inflow and outflow. Other diuretics, and Topiramate (Topomax) may also be used. Patients need to be followed carefully for possible vision loss. If vision loss occurs, surgery to lower intracranial pressure may be offered. Sometimes repeated lumbar punctures are suggested to lower intracranial pressure. Because IIH occurs usually in women of childbearing years, possilbe pregnancy should be discussed with your doctor -- IIH may worsen with increased weight, and the medications may not be safe for the fetus (category C).
The North American Neuro-Ophthalmology Society publishes a web site with good patient information on this condition.