What is Normal Pressure Hydrocephalus (NPH)?

Normal Pressure Hydrocephalus (NPH) is an excessive accumulation of cerebrospinal fluid (CSF), a water-like substance in the ventricles of the brain. Under normal conditions the ventricles, which are cavities within the brain, are filled with CSF. The purpose of CSF is to cushion and protect the delicate brain and spinal cord and to keep the proper balance of nutrients around these structures. CSF, which is continuously being produced in the ventricles, circulates around the brain and spinal cord and is then absorbed into the blood stream through structures called arachnoid villi. This allows for the dynamic balance between the production and removal of CSF. When too much CSF collects inside the ventricles hydrocephalus develops. This means that the amount of CSF being produced is greater than the amount being absorbed. The word hydrocephalus comes from the Greek words, “Hydros” meaning water and “Cephalus” meaning head. Hydrocephalus results when the flow of CSF is blocked in some way. With NPH it is believed that the ventricles enlarge to handle the increased volume of the CSF, and the compression of the brain from within by the fluid-filled ventricles destroys or damages brain tissue causing some of the symptoms. Unlike Hydrocephalus that typically results in increased pressure in the head when too much CSF accumulates, NPH shows little to no increased pressure, thus leading to the name “Normal Pressure Hydrocephalus”.