Increased Intracranial Pressure (Raised ICP)

How pressure builds inside the skull

The skull contains three things: brain tissue, blood and cerebrospinal fluid (CSF). Normal ICP in adults is about 5 to 15 mmHg when lying down. If one component increases, the others can shift to compensate for a while, for example CSF moving into the spinal canal. Once this reserve is used up, small increases in volume cause steep rises in pressure.

High pressure:

• reduces blood flow to the brain, starving it of oxygen
• can push brain tissue from one compartment to another (herniation), compressing the brainstem, which controls breathing and consciousness

Causes

Sudden (acute)

• Traumatic brain injury: bleeding (epidural or subdural hematoma) and brain swelling.
• Bleeding in the brain: intracerebral or subarachnoid hemorrhage.
• Large stroke with swelling.
• Infections: meningitis, encephalitis and brain abscess.
• Hydrocephalus with blocked CSF flow, including blocked shunts.
• Severe low sodium, liver failure or lack of oxygen after cardiac arrest, causing brain swelling.

Gradual (chronic)

• Brain tumors: growing masses and surrounding swelling.
• Idiopathic intracranial hypertension (IIH, pseudotumor cerebri): raised pressure without a mass, mainly in women of childbearing age with obesity. Linked to recent weight gain and some medicines such as tetracyclines, high-dose vitamin A and retinoids.
• Cerebral venous sinus thrombosis: a clot in the brain's drainage veins.

Symptoms

Early

• headache, often worse in the morning, on lying down, coughing, straining or bending
• nausea and vomiting, sometimes without much nausea
• blurred vision, double vision or brief vision blackouts
• tiredness, irritability and poor concentration

Worsening

• increasing drowsiness and confusion
• seizures
• weakness on one side
• one pupil enlarging and not reacting to light

Late warning signs (Cushing's triad)

• high blood pressure with a widening pulse pressure
• slow heart rate
• irregular breathing

These signal imminent herniation and need immediate intervention.

In babies

• bulging soft spot (fontanelle)
• rapidly growing head
• vomiting and poor feeding
• irritability or a high-pitched cry
• eyes deviated downward ("sunsetting")
• unusual sleepiness

Diagnosis

• Neurological examination: level of consciousness, pupils, strength and reflexes.
• Eye exam: swelling of the optic disc (papilledema) is a key sign of raised ICP.
• CT scan: fast imaging for bleeding, swelling, tumors and hydrocephalus.
• MRI and MR venography: more detail, including tumors and venous clots.
• ICP monitoring: a pressure sensor placed in or on the brain in intensive care.
• Lumbar puncture: measures opening pressure in suspected IIH, but only after imaging shows it is safe.

Treatment

Emergency measures

• raising the head of the bed to about 30 degrees, keeping the neck straight
• supporting breathing and oxygen levels
• maintaining blood pressure to keep blood flowing to the brain
• hyperosmolar therapy: mannitol or hypertonic saline to draw fluid out of the brain
• steroids for swelling around tumors (not for head injury)
• controlling fever, seizures, pain and agitation
• sedation and, briefly, controlled faster breathing in critical situations

Procedures and surgery

• external ventricular drain: a tube to drain CSF and measure pressure
• removing a blood clot or tumor
• decompressive craniectomy: temporarily removing part of the skull so the swollen brain can expand
• shunt or endoscopic surgery for hydrocephalus

Idiopathic intracranial hypertension

• weight loss, which can put IIH into remission
• acetazolamide to reduce CSF production
• stopping triggering medicines
• headache management
• surgery (optic nerve sheath fenestration, shunting or venous sinus stenting) if vision is threatened

Outlook

Outcome depends on the cause, how high the pressure rises and how quickly it is treated. Sudden severe raised ICP can be fatal or cause lasting brain injury. Prompt recognition and treatment improve survival. IIH is not life-threatening but can cause permanent vision loss without treatment.

Frequently asked questions

What are the signs of increased intracranial pressure?

Early signs are headache that is worse in the morning or lying down, vomiting, blurred or double vision and drowsiness. Later signs include confusion, seizures, unequal pupils, slow heart rate with high blood pressure, irregular breathing and coma. Babies may have a bulging soft spot.

What causes increased intracranial pressure?

Common causes are head injury, bleeding in the brain, stroke with swelling, brain tumors, infections such as meningitis, hydrocephalus and blocked shunts. Idiopathic intracranial hypertension causes raised pressure without a mass, mainly in young women with obesity.

Is increased intracranial pressure an emergency?

Sudden raised pressure is a life-threatening emergency, because it can reduce blood flow to the brain and push brain tissue against the brainstem. Call 911 for headache with drowsiness, vomiting, seizures, weakness or unequal pupils.

How is idiopathic intracranial hypertension treated?

Treatment includes weight loss, the medicine acetazolamide to reduce spinal fluid production, stopping trigger medicines and regular eye checks. Surgery or stenting is used if vision is at risk despite treatment.