CSF Physiology, Pressure & Dynamics

Intracranial pressure (ICP)

Intracranial pressure is the pressure inside the skull, which can rise when cerebrospinal fluid builds up in hydrocephalus.

In short: Intracranial pressure (ICP)

It is the pressure within the enclosed space of the skull.
It can rise when CSF accumulates.
Normal pressure (lying down) is roughly 7 to 15 mmHg in adults.
Raised pressure causes many of the symptoms of hydrocephalus.

What it is

Intracranial pressure (ICP) is the pressure inside the skull, exerted by the brain, blood, and cerebrospinal fluid within this enclosed space. It is a key measurement in hydrocephalus and other neurological conditions.

Understanding Intracranial pressure (ICP)

Because the skull is a rigid, closed container, the volumes of brain tissue, blood, and CSF must stay in balance to keep pressure normal — a principle called the Monro-Kellie doctrine. In adults, normal ICP lying down is roughly 7 to 15 mmHg. When CSF accumulates in hydrocephalus, ICP can rise, producing symptoms such as headache, vomiting, and decreased alertness, and (in infants, whose skulls can still expand) a bulging fontanelle and increasing head size. Relieving raised ICP is a central goal of treatment. (Normal ranges vary by age and position.)

Why it matters

Understanding intracranial pressure helps families see why CSF buildup is dangerous — it can raise the pressure inside the enclosed skull — and why many hydrocephalus symptoms and treatments relate to controlling this pressure.

Common questions

What is intracranial pressure?

The pressure inside the skull.

What is normal?

Roughly 7 to 15 mmHg lying down in adults, varying by age and position.

Why does it matter in hydrocephalus?

CSF buildup can raise it, causing symptoms.

Bottom line

Intracranial pressure is the pressure inside the skull, which can rise from CSF buildup and cause many hydrocephalus symptoms.

More terms in CSF Physiology, Pressure & Dynamics

Raised intracranial pressureRaised intracranial pressure is abnormally high pressure inside the skull, a key concern in active hydrocephalus.
Opening pressureOpening pressure is the cerebrospinal fluid pressure measured at the start of a lumbar puncture, reflecting the pressure in the CSF spaces.
Monro-Kellie doctrineThe Monro-Kellie doctrine is the principle that the skull is a fixed space, so the volumes of brain, blood, and CSF must stay in balance.
Intracranial complianceIntracranial compliance is the brain's capacity to accommodate added volume, such as extra CSF, without a large rise in pressure.
Intracranial elastanceIntracranial elastance is the inverse of compliance — how much pressure rises for a given increase in volume inside the skull.

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