Idiopathic intracranial hypertension (benign intracranial hypertension, pseudotumor cerebri) is characterized by increased pressure within the skull (intracranial pressure), without any evidence of a cause.
Idiopathic intracranial hypertension occurs in only about 1 of 100,000 people, usually in women during their reproductive years. However, among young overweight women, it is 20 times more common. As more and more people are becoming overweight, the disorder is becoming more common.
Pressure in the skull may be high in some people because the large veins (venous sinuses) that carry blood from the brain are blocked. These changes cause blood to back up in the veins, including those that carry blood from the skull. The increased pressure does not result from other identifiable disorders, such as tumors, infections, or blockages that prevent the fluid that surrounds the brain (cerebrospinal fluid) from draining as it normally does.
In most people, the development of idiopathic intracranial hypertension cannot be traced to any particular event. In children, this disorder sometimes develops after corticosteroids are stopped or after children have taken large amounts of vitamin A or the antibiotic tetracycline.
Idiopathic intracranial hypertension usually begins with a daily or almost daily headache. At first, the headache may be mild, but it varies in intensity and may become severe. The headache may be accompanied by nausea, double or blurred vision, and pulsating noises within the head (tinnitus). A few people do not have any symptoms.
Increased pressure within the skull may cause the optic nerve to swell near the eyeball—a condition called papilledema. Doctors can observe the swelling by looking at the back of the eye through an ophthalmoscope.
The first sign of vision problems is loss of peripheral (side) vision. As a result, people may bump into objects for no apparent reason. Late in the disorder, vision becomes blurred. About 5% of people lose their vision, partially or completely, in one or both eyes. Once vision is lost, it may never return, even if the pressure around the brain is relieved. In some people, the disorder becomes chronic and progressively worse, increasing the risk of blindness. However, close monitoring of such people can prevent loss of vision.
The disorder recurs in about 10% of people.
Doctors suspect this disorder based on symptoms and results of a physical examination. Sometimes doctors suspect it when they detect papilledema during a routine examination with an ophthalmoscope.
Then an imaging test, usually magnetic resonance imaging (MRI), is done to check for other possible causes of increased pressure within the skull. One type of MRI (called magnetic resonance venography) can provide images of the veins that carry blood from the brain. It enables doctors to determine whether these veins are narrowed. If results are normal, a spinal tap (lumbar puncture—see Symptoms and Diagnosis of Brain, Spinal Cord, and Nerve Disorders: Spinal Tap) is done to measure the pressure of cerebrospinal fluid and to analyze the fluid. In idiopathic intracranial hypertension, the pressure of the fluid is usually increased, and the content is usually normal.
Idiopathic intracranial hypertension may resolve without treatment within 6 months. Nonetheless, overweight people should lose weight because doing so may reduce pressure within the skull. The disorder may resolve when as little as 10% of body weight is lost. However, weight reduction programs are often unsuccessful.
Drugs known to trigger the disorder, such as tetracycline, should be stopped.
Aspirin, acetaminophen, or drugs used to treat migraines may relieve the headache. Doctors may prescribe acetazolamide to help reduce the pressure. This drug can help reduce pressure in the skull in two ways:
The usefulness of doing spinal taps daily or weekly to remove cerebrospinal fluid is debated. If this treatment is used, people are closely monitored to determine whether pressure is decreasing.
Because peripheral vision is lost before people notice it, an ophthalmologist periodically checks it so that problems with vision can be identified as soon as possible.
If vision deteriorates despite these measures, surgery to reduce pressure within the skull may be needed and may be able to save vision. In one procedure (called optic nerve sheath fenestration), slits are cut in the covering of the optic nerve behind the eyeball. These slits allow cerebrospinal fluid to escape into the tissues around the eye, where the fluid passes into veins. Alternatively, a permanent drain (shunt) can be surgically placed so that excess cerebrospinal fluid can be removed. The shunt is a piece of plastic tubing placed in the spaces within the brain or in the space just below the spinal cord in the lower back. The tubing is run under the skin, usually to the abdomen, where excess fluid can drain.
If magnetic resonance venography detects a blockage in a vein, anticoagulants (blood thinners) are used. Occasionally, if anticoagulants are ineffective, a tube made of wire mesh (a stent) may be inserted through an incision into a vein in the neck and placed in the blocked vein to hold it open.
If people are obese and other measures are ineffective, surgery to help with weight reduction (bariatric surgery, such as a gastric bypass—see Obesity and the Metabolic Syndrome: Bariatric Surgery) may be done. If successful, it may cure the disorder.
Last full review/revision May 2012 by Stephen D. Silberstein, MD