Raised intracranial pressure (also called intracranial hypertension) is a condition where the pressure within the skull is higher than normal, exceeding 20mmHg(1).
Normally, the total volume of the brain itself, cerebrospinal fluid (CSF) and blood within the skull should remain constant, and an increase in the volume of one of these components should lead to a decrease in the volume of one or both of the other components, maintaining a constant intracranial pressure (this is referred to as the Monro-Kellie doctrine)(2). However, if the total volume within the skull increases, this will lead to an increased pressure within the skull, which can have serious consequences. As such, intracranial hypertension is an emergency which must be treated urgently.
This article will cover the causes of raised intracranial pressure, its symptoms and complications, how it may be diagnosed, and finally, how raised intracranial pressure may be managed.
An increase in intracranial pressure may occur suddenly (acute intracranial hypertension) or over a longer period of time (chronic intracranial hypertension).
Causes of acute intracranial hypertension include(3):
- Head trauma (which may lead to a haematoma and swelling of the brain, for example)
- Infections (e.g. encephalitis, meningitis)
- Cerebral abscess (a collection of pus within the brain)
- Acute hydrocephalus (a rapid build of CSF around the brain)
Causes of chronic intracranial hypertension include(3):
- Chronic hydrocephalus
- Brain tumour
- Arteriovenous malformation (a tangle of abnormal blood vessels which forms due to direct connections between arteries and veins)
Sometimes, the cause of chronic intracranial hypertension is unknown, and this condition is referred to as idiopathic intracranial hypertension (4). This is also known as Benign Intracranial Hypertension, and often doesn’t need invasive treatment.
Symptoms and Complications
Symptoms of raised intracranial pressure include(5):
- Headache (especially those that are worse in the morning, worse when straining, or when lying down)
- Problems with vision (e.g. blurring, double vision, temporary losses of vision)
- Nausea and vomiting
- Irritability and changes in behaviour
- Dilated pupil which doesn’t react to light (although this is a very late sign)
- In children, the anterior fontanelle may be swollen, presenting as a bulge on the top of the head
In severe cases of intracranial hypertension, a patient may have a set of symptoms referred to as Cushing’s triad, which consists of bradycardia (low heart rate), hypertension (high blood pressure) and irregular breathing(6).
If left untreated, potential complications of raised intracranial pressure include(5):
- Abnormal heart rhythms and cardiac arrest
- Brain herniation, also known as ‘coning’ (where the pressure in the skull is so great, the brainstem itself is pushed through the base of the skull. This is universally fatal. A large and fixed pupil on one eye is an indication this is about to occur)
- Coma, and eventually death
Investigations and Diagnosis
If raised intracranial pressure is suspected, the following investigations may be considered(1):
- Fundoscopy – examining the retina to look for signs of intracranial hypertension, such as an enlarged optic disk (papilloedema)
- Imaging, such as a CT or MRI scan of the head, to look for a possible underlying cause of raised intracranial pressure
- Lumbar puncture – this can be used to measure the pressure of CSF within the central nervous system
- Intracranial pressure monitoring – this allows the pressure within the skull to be directly and continually measured. This may be achieved by placing a pressure monitor (or “bolt”) into the subarachnoid or epidural space, or by placing a catheter into one of the lateral ventricles (an external ventricular drain, or EVD, which can be connected to a pressure monitor). The benefit of an EVD is that it can also be used therapeutically, to drain CSF from the brain to reduce intracranial pressure.
It’s important to remember that any damage to the brain caused by the initial insult (primary brain injury) is irreversible, and the priority of all subsequent care is to reduce ‘secondary brain injury’, or ongoing brain damage, and where at all possible to reduce the chances of long term disability or death.
In an emergency situation, approaches to managing raised intracranial pressure may include(5):
- CSF drainage – as mentioned above, this may be achieved via an external ventricular drain placed into one of the lateral ventricles. A lumber puncture can also be used to drain CSF out of the central nervous system
- Raising the head-end of the bed – this may reduce intracranial pressure by increasing outflow of blood from the brain through the jugular veins in the neck
- Reduction in blood levels of carbon dioxide (which leads to a reduction in blood flow into the brain, and thus reduces intracranial pressure. This is achieved in practice by placing the patient into an induced coma and ventilating them artificially using a ventilator machine)
- Administration of osmotic agents (drugs such as mannitol or hypertonic saline) – these agents work by drawing water out of the brain down an osmotic gradient
- ‘Burr hole drainage’ – this involves the neurosurgical team making a small hole in the patient’s skull to allow drainage of (usually) blood clot
- Decompressive craniectomy – typically only used when other measures have failed, a decompressive craniectomy is a neurosurgical procedure in which a piece of the skull is removed to allow the brain to swell without increasing pressure within the skull
The definitive management of raised intracranial pressure is the treatment of the underlying cause. Patients will often spend some time in a neuro-critical care unit following an operation for raised ICP, where the goals are to essentially keep all the patient’s parameters normal, particularly blood pressure, temperature, blood glucose, carbon dioxide and sodium.
- Pinto VL, Tadi P, Adeyinka A. Increased Intracranial Pressure. StatPearls. Treasure Island (FL): StatPearls Publishing
Copyright © 2022, StatPearls Publishing LLC.; 2022.
- Mokri B. The Monro-Kellie hypothesis: applications in CSF volume depletion. Neurology. 2001;56(12):1746-8.
- Dunn LT. RAISED INTRACRANIAL PRESSURE. Journal of Neurology, Neurosurgery & Psychiatry. 2002;73(suppl 1):i23-i7.
- Boyter E. Idiopathic intracranial hypertension. Jaapa. 2019;32(5):30-5.
- Freeman WD. Management of Intracranial Pressure. Continuum (Minneap Minn). 2015;21(5 Neurocritical Care):1299-323.
- Dinallo S, Waseem M. Cushing Reflex. StatPearls. Treasure Island (FL): StatPearls Publishing
Copyright © 2022, StatPearls Publishing LLC.; 2022.