Normal pressure hydrocephalus (NPH)

Alternative names:

hydrocephalus - adult; hydrocephalus - communicating; hydrocephalus - idiopathic

Definition:

A brain disorder caused by blockage of the flow of cerebrospinal fluid, with enlargement of the ventricles within the brain and compression of the brain tissue; it may result in loss of any or all brain functions controlled by an area of the brain.

Causes, incidence, and risk factors:

Normal pressure hydrocephalus (NPH) may be a reversible or treatable disorder. It is thought to account for about 5% of all dementias. The incidence is 1 out of 100,000 people. NPH can occur at any age. The onset of symptoms is often gradual.

NPH is a form of hydrocephalus. It may occur without identifiable cause, or it may be caused by any condition where there is an obstruction to the flow of cerebrospinal fluid (CSF). The CSF is produced normally but not reabsorbed. The ventricles of the brain enlarge to accommodate the increased volume of CSF, so the pressure of CSF, when measured by lumbar puncture (spinal tap), remains normal. Brain tissue (atrophy) is damaged or destroyed because of compression by the fluid-filled ventricles. If there is an identifiable cause and the cause can be corrected, the symptoms may reverse or at least stop getting worse. If there is no identifiable cause, the disorder is often progressive.

Risk factors include disorders that may cause obstruction of the flow of CSF, such as head injury (closed), surgery on the brain (craniotomy), meningitis or similar infections, and subarachnoid hemorrhage.