Raised Intracranial Pressure Quiz

See Increased Brain. Option A is correct because the skull is a rigid box once infancy has passed, so anything extra that grows inside it must take up room from something else. A brain tumour is space-occupying: it adds volume and pushes on the surrounding brain tissue, blood vessels and cerebrospinal fluid (CSF, the clear fluid that cushions the brain). This squeezing is called a mass effect. At first the brain copes by moving blood and CSF out of the skull, a principle known as the Monro-Kellie doctrine, which says that the total volume of brain, blood and CSF inside the skull is fixed, so a rise in one must be matched by a fall in another. Once these reserves run out, pressure climbs steeply. Tumours may also swell the brain around them (oedema, or excess tissue fluid) and block the flow of CSF, which adds to the effect. Typical features of raised intracranial pressure are headache that is worse in the morning or on lying down, vomiting and drowsiness. A helpful picture is a balloon being inflated inside a sealed box.

• Skull: a rigid box, so extra volume takes space from brain, blood or CSF.
• Tumour: space-occupying, causing a mass effect.
• Monro-Kellie doctrine: the total volume of brain, blood and CSF inside the skull is fixed.
• After reserves run out: intracranial pressure climbs steeply.