Elevated Intracranial Pressure (ICP)

Understanding What Can Be Done to Decrease Pressure Under the Skull

Young woman sitting on bed with headache

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Elevated intracranial pressure (ICP), is a build-up of pressure in the skull. Whether it's caused by swelling, bleeding, a tumor, or some other problem, ICP can lead to compression of brain tissue and cause permanent damage. That's why it's considered a neurological emergency that needs to be addressed as soon as possible.

How will you know if someone has ICP? The key symptoms are blurry vision, headache, and changes in thinking that generally are worse when she's lying down. To tell if a person who's unconscious is experiencing ICP, a doctor or other medical professional usually will rely on fundoscopy, which involves lifting up an eyelid and using a bright light to illuminate the back of the eye and look for changes in the optic nerve. 

To measure the increase in pressure, a monitor can be placed beneath the skull. This has the added benefit of being able to measure ICP constantly rather than just getting a single measurement, so changes in ICP can be captured. This is especially useful when it's likely ICP will get worse, such as after brain trauma that causes swelling.

Treating ICP With Medication

One way to manage ICP is to reduce the volume of cerebrospinal fluid (CSF) in the intracranial space under the skull. This can be done by slowing down production of it within the ventricles of the brain. A medication such as Diamox (acetazolamide), which primarily is used to treat glaucoma by reducing pressure in the eye, can slow CSF production and lower ICP as a result, but usually isn't the best choice: It's only mildly effective and also can change the acidity of the blood, which is not a desirable side effect. 

Blood volume in the brain can be reduced by positioning the head to encourage the quick return of blood to the heart. If a patient is intubated (has a breathing tube in), the breathing rate can be increased to change the acidity of the patient’s blood, which will cause the arteries in the brain to narrow, reduce blood flow, and clear more room for the brain—a temporary solution at best.

Sometimes ICP is a result of edema, a leakage of fluid from blood vessels and into brain tissue. A substance such as mannitol (a naturally-occurring substance that draws fluid out of tissue) or saline can encourage fluid to return from the brain into the blood vessels. A steroid such as dexamethasone can also help reduce brain swelling.

When Surgery Is Necessary

If the brain is being squeezed by something in the skull that doesn’t belong there, like an abscess or tumor, removing it can be the answer. Another tactic is to insert a shunt in the brain through which excess CSF can drain. If there's already an ICP monitor in place, the fluid may be drained through the monitor to keep the pressure at a certain goal.

Not surprisingly, shunting has potential side effects, including an increased chance of infection and bleeding. There’s also a risk that too much CSF will be removed from the wrong places, leading to pressure shifts that lead to herniation—the movement of part of the brain to where it doesn't belong.

Another approach is to make the brain space bigger. This is done in a procedure called a craniectomy, in which a portion of the skull is removed temporarily so the brain has room to swell. It sounds scary, and it is a very risky thing to do, but when swelling is so severe that a craniectomy is necessary there really are no other options. During the period of time when the skull is removed, the tissue surrounding the brain is kept intact and clean as possible to prevent infection. 

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