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Normal pressure hydrocephalus (NPH)

  • Definition

    Hydrocephalus refers to a build-up of fluid inside the skull, leading to brain swelling. Hydrocephalus means "water on the brain."

    Normal pressure hydrocephalus (NPH) is a rise in cerebrospinal fluid (CSF) in the brain that affects brain function. However, the pressure of the fluid is usually normal.


    Alternative Names

    Hydrocephalus - idiopathic; Hydrocephalus - adult; Hydrocephalus - communicating; Extraventricular obstructive hydrocephalus


    Causes, incidence, and risk factors

    Normal pressure hydrocephalus (NPH) is a form of hydrocephalus, which means there is too much fluid pressing on the brain.

    NPH can occur without a known cause, or it may be caused by any condition that blocks the flow of cerebrospinal fluid (CSF). The fluid-filled chambers (ventricles) of the brain enlarge to fit the increased volume of CSF. They press down on and damage or destroy brain tissue.

    Risk factors include:

    • Bleeding from a blood vessel or aneurysm in the brain (subarachnoid hemorrhage)
    • Closed head injury
    • Meningitis or similar infections
    • Surgery on the brain (craniotomy)

    CSF is produced in normal amounts in these conditions, but it is prevented from being reabsorbed normally.

    NPH is thought to account for about 5% of all dementias.