Benign Intracranial Hypertension (BIH) is a rare brain injury that is associated with certain types of birth control. Without treatment, pressure inside the skull can increase dramatically and cause severe headaches and blindness.
What is BIH?
Benign Intracranial Hypertension (BIH) is a rare neurological syndrome characterized by increased pressure inside the skull due to abnormally high levels of cerebrospinal fluid.
The disease puts pressure on the brain, similar to a growing brain tumor. It can also cause damage to the optic nerve, which transmits information between the brain and eyes. The most serious complication of BIH is permanent blindness.
What Causes BIH?
The cause of BIH is unknown. However, a variety of medications are associated with increased rates of this disease. Birth control is a risk-factor, according to warnings from the National Institute of Health (NIH). Women are also three times more likely than men to develop the disease.
Levonorgestrel and BIH
A number of case reports have linked this disease with estrogen, levonorgestrel-only implants, and a progestin-only injectable contraceptive. However, experts are unable to say whether a causal association exists between birth control and BIH.
In 1995, the New England Journal of Medicine published a study linking the use of levonorgestrel birth control implants with 56 cases of intracranial hypertension or optic disc edema. In recent years, Bayer has been hit with a number of lawsuits from women who developed BIH after using Mirena, a contraceptive implant that contains levonorgestrel.
Signs & Symptoms
- Headache: Nearly all people with BIH suffer from headaches, often migraines that cause severe pain that is throbbing, pulsating, worst in the morning, typically located at the back of the head, and grows progressively more constant.
- Visual problems: About two-thirds of people with BIH develop vision problems, with one-third reporting double-vision (diplopia). Episodes of blurry vision may last 30 seconds and resolve.
- Papilledema: This complication occurs when pressure in the skull causes swelling of the optic disc located at the back of the eye (blind spot). Over time, the blind spot may grow progressively larger.
- Blindness: About 90% of people with BIH lose visual field, but only about 5% suffer blindness. Once it occurs, there is no cure.
The only way to conclusively diagnose BIH is with a painful test called a lumbar puncture (spinal tap), which involves removing a small amount of cerebrospinal fluid with a needle inserted between two vertebrae in the lower part of the spine. Lumbar punctures can also sometimes alleviate severe headaches from BIH. Papilledema may be diagnosed with an eye exam.
Medications to reduce levels of cerebrospinal fluid can often treat mild cases of BIH. For severe cases, the goal of treatment is to preserve remaining vision and prevent blindness. Surgery to implant a shunt (surgical tube) may be necessary to drain cerebrospinal fluid and reduce intracranial pressure.