The pressure maintained by the brain tissue, intracellular and extracellular fluid, cerebrospinal fluid and blood. An increase in intracranial pressure may occur as a result of inflammation, injury, haemorrhage, or tumour in the brain tissue as well as of some congenital conditions. The pressure can be measured by lumbar puncture, in which a syringe attached to a manometer (pressure-measuring device) is inserted into the cerebrospinal fluid surrounding the lower part of the spinal cord. Where continuous pressure monitoring is necessary, an in-dwelling device can be implanted into a cerebral ventricle. Normal pressure is around 10 mm of mercury (Hg), with the acceptable upper limit being 25 mm Hg. Raised intracranial pressure causes lethargy, vomiting and/or headache. If severe, it can lead to death by pressure on the vital structures controlling heartbeat and breathing, localised in the hindbrain.