Definition

Intracranial pressure (ICP) refers to the pressure around the brain within the skull. This pressure is maintained by three main components: cerebrospinal fluid (CSF), blood, and the brain itself. The skull is a closed space, so an increase in ICP will cause these three components to try to adapt. However, this adaptation can be fatal and life-threatening.

Causes

The intracranial pressure (ICP) remains constant, as does the volume inside the skull. When the volume inside the skull increases, the ICP also increases. If something causes one component to increase in volume, the other components will decrease their volume to adapt. Therefore, the causes of increased ICP can be grouped based on which component's volume increases.

An increase in CSF volume can be due to increased fluid production or decreased absorption. Increased CSF can be caused by an increase in production and tumors in the structures that produce it, such as the choroid plexus. Decreased absorption of CSF can be due to blockage in the channels through which it flows and inflammation of the meninges.

An increase in blood volume in the head can result from various factors. Blood flow to the head can increase due to high levels of carbon dioxide in the blood or thinning of blood vessels, such as in aneurysms. Additionally, blockage and obstruction of venous blood flow can increase blood volume in the head. Conditions causing blood flow blockage, like heart failure, can also increase blood volume.

Brain volume can increase due to various reasons. Swelling of brain tissue can occur due to trauma, lack of oxygen, high levels of ammonia and urea, and decreased sodium levels. Additionally, volume increase can occur due to the presence of blood or other tissue in the brain, such as brain hemorrhage, tumors, abscesses, and brain tissue death.

Other causes of increased ICP include idiopathic intracranial hypertension, craniosynostosis, excessive vitamin A intake, and tetracycline antibiotic use.

Risk factor

Risk factors for increased ICP relate to the balance of components maintaining it. The most common risk factor is a history of head trauma, which can cause brain swelling and bleeding in the head. Other risk factors include stroke, epilepsy, seizures, lack of oxygen, and meningitis.

Symptoms

Signs of increased ICP are often overlooked because they are not specific. However, when several of these symptoms occur together, they may indicate increased ICP. Symptoms include worsening headaches, nausea, projectile vomiting, sudden increase in blood pressure, disorientation, double vision, shortness of breath, and seizures. Severe cases can lead to decreased consciousness or coma. These symptoms can also indicate conditions like stroke, brain tumors, or head trauma.

Diagnosis

Increased ICP is often a medical emergency. Suspicion of increased ICP arises if a patient presents with headaches, vomiting, and decreased consciousness. Visual changes can include blurriness, double vision, sensitivity to light, and optic nerve swelling, visible with an ophthalmoscope. In infants under one year, a bulging fontanelle may be observed.

Other signs include Cushing's triad: high blood pressure, decreased heart rate, and irregular breathing, indicating brain compression and downward displacement (herniation). High blood pressure triggers the body's reflex to lower the heart rate, and irregular breathing results from brainstem compression.

Consciousness assessment is crucial to determine the degree of consciousness impairment in suspected increased ICP patients. Other examinations include pupil light reflex tests, which may show unresponsiveness.

Imaging tests like CT scans are preferred in emergencies to detect the cause of increased ICP. MRI can also be used but takes longer.

Invasive monitoring of ICP can be performed under strict conditions. Candidates should not have open head injuries, should be under anesthesia if conscious but at risk of increased ICP, or have moderate head injury with potential brain swelling.

Laboratory tests, such as complete blood count, blood electrolytes, and kidney function, help identify potential causes and assess the body's response to treatment. Lumbar puncture can estimate ICP and analyze CSF, and can also relieve pressure by draining CSF.

Management

In cases of increased ICP, prioritizing airway (A), breathing (B), and circulation (C) is crucial. Treatment aims to reduce ICP and address the cause. Before medication, elevate the head 30 degrees or more and ensure the neck is centered to facilitate blood flow.

Other methods to reduce ICP include intubation and increasing respiration rate to lower brain carbon dioxide levels. Medications like mannitol and steroids can reduce ICP. Hypertonic solutions may be used if brain swelling occurs. Other drugs can reduce CSF production. Cooling the body to 32-35°C can constrict brain blood vessels.

If these measures fail, surgery, such as decompressive craniectomy, may be necessary to relieve pressure by allowing brain swelling without compressing other structures.

Complications

Severe ICP can cause vision problems due to pressure on optic nerves, leading to blurry or double vision and light sensitivity. Extremely high ICP can decrease consciousness, from drowsiness to coma. If brain compression causes brainstem pressure, it can result in irregular breathing and potentially brainstem death.

Prevention

While the ICP increase may be unpreventable, its causes can be prevented. For example, wearing helmets when biking, motorcycling, or engaging in contact or extreme sports, and using seat belts in cars. For the elderly, using canes and installing handrails can prevent falls. Keeping home floors dry, non-slippery, and uncluttered reduces fall risk for the elderly.

When to see a doctor?

Seek immediate medical attention if you or someone near you experiences severe headaches, nausea, vomiting, double vision, and decreased consciousness, especially after head trauma or with a history of high blood pressure, due to increased stroke risk. Increased ICP is life-threatening, so prompt treatment is essential.

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