How to Recognize and Treat the Most Dangerous Complication of Brain Surgery

Raised intracranial pressure is a common problem in neurosurgical and neurological practice. Elevated intracranial pressure is a dangerous condition. It is an emergency and requires immediate medical attention. Intracranial pressure has serious complications, including death.

One of the main dangers of increased intracranial pressure is that it can cause ischemia (lack of blood flow) by decreasing cerebral perfusion pressure (CPP).  The body’s response to a fall in cerebral perfusion pressure is to raise systemic blood pressure and dilate cerebral blood vessels.  This results in increased cerebral blood volume, which increases intracranial pressure, lowering CPP further and causing a vicious cycle.

Intracranial pressure is very likely to cause severe harm if it rises too high.  An increase in intracranial pressure can damage brain tissue, shift brain structures, contribute to hydrocephalus, cause brain herniation and restrict blood supply to the brain. Raised intracranial pressure results in pressure gradients between compartments and a shift in brain structures.

As the brain swells, the pressure inside the skull goes up.  If the pressure gets significantly higher than normal, it can cause damage to the brain. Since the brain is covered by the skull, there is only a small amount of room for it to swell.  

The Causes of Elevated Intracranial Pressure

Elevated intracranial pressure can be caused by the growth of a tumor or blockage of the flow of cerebrospinal fluid, or a combination of both.  Cerebrospinal fluid cycles through 4 ventricles in the brain, and its role is to bathe and cushion the brain.

Cerebral perfusion pressure (CPP) is the pressure of blood flowing to the brain, and it is normally fairly constant due to autoregulation.  Intracranial pressure is measured in millimeters of mercury and at rest, is normally 7 to 15 mmHg for a supine adult.  At 20 to 25 mmHg, the upper limit of normal, treatment to reduce intracranial pressure may be needed.

The Symptoms of Increased Intracranial Pressure

“Cushing Triad” is a group of 3 signs that increased intracranial pressure is getting higher: (1) high blood pressure with an increasing difference between the top (systolic) and bottom (diastolic) blood pressure readings; (2) slow pulse rate; and (3) abnormal breathing.

The combination of headache, papilloedema, and vomiting is considered indicative of raised intracranial pressure.  Other signs often seen in association with raised intracranial pressure, such as pupillary dilation, bilateral ptosis, impaired upgaze, and respiratory irregularity, are related to tentorial or tonsillar herniation.  Papilloedema, or swelling of the optic disc, can be a reliable sign that intracranial pressure is elevated.

The progressive deterioration in consciousness level usually accompanies rising intracranial pressure, and is a consequence of caudal displacement of the diencephalon and midbrain.

Patients with normal blood pressure retain normal alertness with intracranial pressure of 25 to 40 mmHg.  Only when intracranial pressure exceeds 40 to 50 mmHg does cerebral perfusion decrease to a level that results in loss of consciousness.  Any further elevations will lead to brain infarction and brain death.

How to Diagnose Elevated Intracranial Pressure

The most definitive way of measuring intracranial pressure is with transducers placed within the brain.  A catheter can be surgically inserted into one of the brain’s lateral ventricle and can be used to drain cerebrospinal fluid in order to decrease intracranial pressure.  This type of drain is known as an external ventricular drain (EVD).

The intracranial pressure device is attached to a monitor that gives a constant reading of the pressure within the skull. If the pressure goes up, it can be treated right away.

The Treatment for Increased Intracranial Pressure

Treatment includes relieving the brain of the increased pressure.  Medical management of increased intracranial pressure should include sedation, drainage of cerebrospinal fluid, and osmotherapy with either mannitol or hypertonic solution.

Corticosteroids can help lower or prevent swelling of the brain. Dexamethasone is the corticosteroid most commonly used to treat increased intracranial pressure. The most commonly used diuretic is mannitol, an intravascular osmotic agent that can draw fluid from both normal and abnormal brain tissue.

The head of the bed will be raised to lower the pressure.

A drastic treatment for increased intracranial pressure is a decompressive craniectomy, in which a part of the skull is removed, and the dura mater is expanded to allow the brain to swell without crushing it or causing herniation.