The skull is a fixed volume box that holds brain tissue, blood and cerebrospinal fluid (CSF). These three components must remain in balance to maintain healthy intracranial pressure.
Increased intracranial pressure is a life-threatening medical emergency. It can lower cerebral perfusion pressure, leading to brain ischemia or compress vital structures, like the brainstem, causing herniation.
Symptoms
Many of us have had a headache that didn’t respond to an over-the-counter pain reliever and some rest. But sometimes, that headache isn’t just a normal problem and it may be a sign of something serious. That’s because some headaches are caused by a dangerous condition called increased intracranial pressure (ICP). It happens when there is excess fluid or swelling inside the skull that over-fills the limited space and puts pressure on the brain. It’s a medical emergency and needs to be treated right away.
If someone has ICP, they might also have other symptoms such as vomiting and altered mental status ranging from drowsiness to coma. They may have vision problems that range from blurred or double vision to optic disc edema, which is when the area around the eyes becomes puffy. Some people can develop ICP due to conditions that they are born with, while others experience it after trauma or neurologic disease. In severe cases, rapid treatment can lead to a better prognosis.
Increased intracranial pressure is usually the result of an injury to the skull or brain that leads to bleeding, fluid buildup or swelling. It can also be the result of a herniated brain or a tumor, which both put pressure on the spinal cord and brain tissue. When the pressure increases, it can restrict blood flow to the brain, cause a stroke or even be life-threatening.
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To diagnose ICP, doctors will take a careful history and exam. They will ask about any recent head or neck injuries and about any medications you might be taking. They will also check the pressure in your cerebrospinal fluid by performing a spinal tap or lumbar puncture. They will also use a CT scan or an MRI to make detailed X-rays and pictures of your brain and skull. The doctor might put a device in your skull to monitor the pressure and might use other tests to check for things like a tumor or a bleed in your brain.
In addition to treating the underlying cause of ICP, healthcare professionals will often try to lower the pressure by draining cerebrospinal fluid and using breathing support. If the situation is life-threatening, they might have to remove part of your skull, a procedure known as decompressive craniectomy, to allow the brain to swell without pressing on vital areas.
Diagnosis
A sudden increase in intracranial pressure is a medical emergency. If the increased pressure pushes on brain tissues and blood vessels, it can lead to permanent brain damage and even death. It can be caused by health problems like brain tumors, blood clots in the head or neck, Reye’s syndrome or infection (like meningitis and encephalitis). It can also be caused by conditions that affect your hormone levels, such as Cushing’s syndrome or hyperthyroidism. It can also be caused by certain medicines, like anti-seizure medications or corticosteroids. It can also be caused by a condition that affects your body’s ability to carry oxygen, such as obstructive sleep apnea.
The normal pressure in the skull (intracranial pressure, or ICP) is the sum of the partial pressures of your brain, cerebrospinal fluid and blood. The ICP is controlled by the cerebral autoregulation process, where blood flow to the brain varies to maintain adequate cerebral perfusion. When the ICP is high, it can damage brain cells and cause brain herniation.
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If your child has symptoms of elevated ICP, including headaches, vomiting and an altered mental status that can range from drowsiness to coma, it is important to seek immediate medical attention. The medical staff can measure your child’s ICP with a procedure called lumbar puncture (spinal tap). They may also use an X-ray, magnetic resonance imaging (MRI) or computed tomography scan of the head and brain to check for problems that can cause ICP, like brain swelling, enlarged ventricles or a brain herniation.
A funduscopic exam (an eye test) can also help diagnose ICP by revealing the amount of fluid buildup or swelling of the optic discs. A cisternal spinal tap can be done to measure the pressure of cerebrospinal fluid, and a MRI or CT scan of the brain can show any injuries, swelling or other abnormalities that could increase ICP. Your doctor may also use an ultrasound or a venography to evaluate the large veins (called venous sinuses) that carry blood from your brain. A procedure called magnetic resonance venography can help your doctor see whether these veins are narrowed, which is a sign of idiopathic intracranial hypertension.
Treatment
Unless the cause is known, elevated ICP should be treated as a medical emergency because it may lead to brain damage and other fatal complications. It is usually a complication of traumatic brain injury (TBI). Elevated ICP should be diagnosed quickly and promptly treated to prevent further damage.
A health care provider can often make the diagnosis of increased intracranial pressure by examining the patient and taking into account the history of the injury. They will also do a physical exam, including checking the blood pressure in the head and neck, and an eye exam to check for swelling around the optic nerve. They will probably also do a nervous system exam, which includes tests to test senses, balance, and mental status. They may also do a spinal tap, which involves putting a tube into a hole in the skull and measuring cerebrospinal fluid pressure. They may also do a CT scan or an MRI, which are detailed pictures of the brain and skull.
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If ICP is too high because of a brain tumor or a severe head injury, health care providers will try to decrease the size of the tumor or reduce the amount of fluid. If the increase in ICP is caused by a herniated brain, they may have to remove part of the skull — called a decompressive craniectomy. This procedure is usually performed by a neurosurgeon in the operating room, and the patient will be placed under general anesthesia. There are some risks, including a small risk of infection in the area where the bone is removed and the possibility of losing consciousness while under general anesthesia.
If the brain is not damaged, ICP will eventually return to normal and the symptoms will resolve. In the case of idiopathic intracranial hypertension, however, the symptoms do not go away and the condition is chronic. It is most common in young women who carry excess weight, which is a risk factor for this condition. People with this condition are advised to maintain a healthy weight, and they should be aware that vision changes, especially blurred or double vision, may occur as the disease progresses.
Prevention
Elevated intracranial pressure is a life-threatening medical emergency and requires immediate treatment. This is because it can lead to brain damage, as well as other serious complications such as intracranial hemorrhage and a herniated brain.
ICP is a result of forces exerted by the skull against the fluids and brain inside it. Normally, the skull is surrounded by a buffer of cerebrospinal fluid (CSF), brain blood volume and arterial blood pressure that can change cyclically with respiration or cardiac activity. This balancing force is called cerebral autoregulation. The CSF and brain blood pressures are balanced by the forces of a systemic mean arterial blood pressure in opposition to the intracranial compartmental pressures (CPP = MAP – ICP).
Injuries that cause increased ICP include traumatic brain injury, large acute ischemic stroke, intracerebral hemorrhage and brain tumors. Acute encephalitis and meningitis can also cause an increase in ICP. Idiopathic intracranial hypertension is a less common cause of increased ICP, but can lead to a herniated brain.
Any increase in pressure in the skull can lead to a decrease in blood flow to the brain and reduce its oxygen supply, leading to a severe headache and in some cases, loss of consciousness. The higher the ICP, the greater the risk of other problems, such as brain herniation and obstructive hydrocephalus, which are often fatal.
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Symptoms of elevated ICP can also be the result of an undiagnosed infection or a brain tumor, such as a medulla oblongata cyst, and should prompt immediate medical attention. Diagnosing ICP requires an invasive procedure that involves placing a pressure-sensitive probe in the skull to measure cerebrospinal fluid pressure directly.
Treatment options for a herniated brain or ICP are usually limited to medications and a controlled environment that limits movement, with a decompressive craniectomy and shunting if necessary. A reduction in metabolic rate by hyperventilation is a common strategy, but should be used only to moderate levels because hypocapnia causes vasoconstriction, decreasing blood flow and oxygen to the brain. The head should be kept in a neutral position to allow for venous drainage, and any tight neck collars or tracheostomy tubes should be removed to prevent compression of the internal jugular vein. Fever should be treated with antipyretics and hydration, as high temperatures can increase ICP.
