Raised intracranial pressure and brain herniation !

Raised intracranial pressure is high pressure inside the skull from swelling, bleeding, a mass or fluid. It can push the brain out of place (herniation).

Updated 2026-11-01

Structures involved

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In embryology

In the clinical exam

Why it happens

What it is

A sustained rise in the pressure inside the skull, usually above 20–22 mmHg in adults, caused by extra volume of brain tissue, blood or cerebrospinal fluid. If it keeps rising, brain tissue is pushed across the dural folds or through the foramen magnum (herniation), a life-threatening emergency.

Who gets it

A common final pathway in neurocritical care. In Colombia and Latin America, traumatic brain injury from road traffic collisions (especially motorcycles) and violence is a leading cause in young adults; stroke, intracranial haemorrhage, tumours, central nervous system infections and neurocysticercosis with hydrocephalus are other frequent causes.

Causes

Mass lesions: epidural, subdural or intracerebral haematoma, tumour, abscess
Cerebral oedema: traumatic brain injury, large ischaemic stroke, hypoxic injury, liver failure, hyponatraemia
Cerebrospinal fluid build-up: hydrocephalus, including obstruction by neurocysticercosis
Infection: meningitis and encephalitis
Increased blood volume: venous sinus thrombosis, hypercapnia, severe hypertension
Idiopathic intracranial hypertension (a chronic form, mainly in young women with obesity)

Risk factors

Severe head trauma
Large stroke or intracranial bleeding
Brain tumours
Central nervous system infections
Hypoventilation with retained carbon dioxide

Pathophysiology

The skull is a fixed box holding brain, blood and cerebrospinal fluid (Monro-Kellie doctrine). At first a new volume is offset by shifting CSF and venous blood out, but once this reserve is used up small additions cause steep rises in pressure. Cerebral perfusion pressure (mean arterial pressure minus intracranial pressure) then falls, causing ischaemia, more oedema and a vicious cycle. Pressure gradients push tissue: the cingulate gyrus under the falx (subfalcine), the medial temporal lobe (uncus) over the tentorium compressing the oculomotor nerve and midbrain (transtentorial), and the cerebellar tonsils into the foramen magnum compressing the medulla (tonsillar).

Classification

Subfalcine herniation: cingulate gyrus under the falx; can compress the anterior cerebral artery
Uncal (lateral transtentorial) herniation: ipsilateral dilated pupil from oculomotor nerve compression, then hemiparesis and coma
Central (downward transtentorial) herniation: small pupils, Cheyne-Stokes breathing, decorticate then decerebrate posturing
Tonsillar herniation: cerebellar tonsils through the foramen magnum, respiratory arrest
Upward and external (through a skull defect) herniation

Symptoms and signs

Headache, worse in the morning, on lying down or with coughing and straining
Vomiting, often without nausea
Drowsiness, confusion and a falling Glasgow Coma Scale score
Blurred or double vision; papilloedema on fundoscopy
Abducens (sixth) nerve palsy as a false localising sign
In infants: bulging fontanelle, irritability and enlarging head

Diagnosis

Clinical: Suspected from the history (trauma, stroke, tumour, infection), a falling level of consciousness, pupil changes and focal signs. Serial Glasgow Coma Scale, pupil size and reactivity, and vital signs track progression. Fundoscopy may show papilloedema, though it can be absent early.
Tests: Invasive ICP monitoring with an intraventricular catheter (which also drains CSF) or an intraparenchymal probe in severe cases; blood gases, sodium and osmolality, glucose, clotting and blood count. Lumbar puncture is avoided when a mass effect is present because it can precipitate herniation.
Imaging: Urgent non-contrast head CT shows the cause and signs of mass effect: midline shift, effaced sulci and basal cisterns, compressed ventricles or hydrocephalus. MRI and CT or MR venography are used for tumours, infection and venous thrombosis. Optic nerve sheath ultrasound is a bedside adjunct.

Differential diagnosis

Postictal state or non-convulsive status epilepticus
Metabolic or toxic encephalopathy (hypoglycaemia, uraemia, liver failure, drugs)
Brainstem stroke
Migraine with severe headache
Pseudopapilloedema (optic disc drusen)

Goal of treatment

Keep cerebral perfusion pressure adequate, lower intracranial pressure, prevent or reverse herniation and treat the cause (evacuate a haematoma, drain CSF, remove a mass, treat infection).

Treatment

Acute: First measures: secure the airway (intubation if the Glasgow Coma Scale is 8 or less), avoid hypoxia and hypotension, head of the bed raised to about 30 degrees with the head midline, and avoid tight neck ties so venous return is not blocked.
Acute: Herniation emergency: hyperosmolar therapy (mannitol or hypertonic saline) and brief controlled hyperventilation only as a bridge to definitive treatment, because prolonged hypocapnia causes cerebral ischaemia.
Medical: Supportive medical care: sedation and analgesia, normothermia, normoglycaemia and normal sodium, seizure treatment and prevention when indicated; glucocorticoids reduce oedema around tumours and abscesses but are not used in traumatic brain injury.
Procedure: External ventricular drain to remove CSF and measure pressure, especially in hydrocephalus.
Surgical: Surgery for the cause: evacuation of a haematoma, resection of a mass, or decompressive craniectomy for refractory pressure.
Follow-up: Nursing priorities: hourly neurological checks with pupils and Glasgow Coma Scale, watch for the Cushing triad, cluster care and keep the room calm, avoid coughing, straining, hip flexion and excessive suctioning, and keep the drain at the ordered level.

Complications

Brain herniation with brainstem compression and death
Global or regional cerebral ischaemia
Permanent neurological deficits and disability
Vision loss from long-standing papilloedema
Brain death

Prognosis

Depends on the cause, how high the pressure rises and how quickly it is controlled. Pressure that stays high despite treatment and signs of herniation carry a poor outlook, while early relief of a surgical cause such as an epidural haematoma can lead to a good recovery.

Prevention

Helmet use on motorcycles and bicycles and seat belts to prevent head injury
Control of blood pressure to reduce stroke and haemorrhage
Early treatment of meningitis and of neurocysticercosis

Test yourself

Think of the answer, then tap the question to see it.

What are the three signs of the Cushing triad?

Hypertension (often with a widened pulse pressure), bradycardia and irregular breathing; it signals impending herniation.

How is cerebral perfusion pressure calculated?

Mean arterial pressure minus intracranial pressure.

Which cranial nerve sign is typical of uncal herniation?

An ipsilateral fixed, dilated pupil from compression of the oculomotor nerve (III).

Why is lumbar puncture avoided when a mass lesion raises intracranial pressure?

Lowering pressure below the lesion can provoke downward herniation through the tentorium or foramen magnum.

Which two nursing measures help lower intracranial pressure?

Head of the bed at about 30 degrees with the neck midline, and avoiding activities that raise pressure such as straining, coughing, hip flexion and prolonged suctioning.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Increased intracranial pressure: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Brain herniation: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

Tentorium highlighted on the Durgical 3D model