This is the pressure that is 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 is measured by lumbar puncture in which a syringe attached to a mamometer (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.
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