Normal pressure hydrocephalus (NPH) is a brain disorder in which excess cerebrospinal fluid accumulates in the brain's ventricle, causing thinking and reasoning problems, difficulty walking, and loss of bladder control.
About normal pressure hydrocephalus
Normal pressure hydrocephalus occurs when excess cerebrospinal fluid accumulates in the brain's ventricles, which are hollow fluid-filled chambers. NPH is called "normal pressure" because despite the excess fluid, cerebrospinal fluid pressure as measured during a spinal tap is often normal. As brain ventricles enlarge with the excess cerebrospinal fluid, they can disrupt and damage nearby brain tissue, causing symptoms of NPH.
NPH primarily affects people in their 60s and 70s. Scientists aren't certain how many older adults have this disorder because common symptoms of NPH are also common in other brain disorders.
Learn more: Key Types of Dementia.
The following symptoms are considered hallmarks of normal pressure hydrocephalus:
- Difficulty walking that's sometimes compared to the way a person walks "on a boat," with the body bent forward, legs held wide apart and feet moving as if they're "glued to the deck."
- Decline in thinking skills that includes overall slowing of thought processes, apathy, impaired planning and decision-making, reduced concentration, and changes in personality and behavior.
- Loss of bladder control, which tends to appear somewhat later in the disease than difficulty walking and cognitive decline.
There is no single test to determine if someone has normal pressure hydrocephalus. And even though the three hallmark symptoms listed above are considered the "classic" signs of this disorder, not everyone with NPH has all of these symptoms.
Brain imaging to detect enlargement of the ventricles, often with magnetic resonance imaging (MRI), plays a key role in diagnosing NPH. Several brain disorders, including Alzheimer's disease
, can cause overall brain tissue shrinkage that makes the ventricles look larger than normal. In NPH, although the ventricles are enlarged, brain tissue may not appear shrunken.
Because the symptoms of NPH may overlap with those of Alzheimer's and other dementias, experts recommend that a person with suspected NPH undergo examination by a neurologist with extensive experience evaluating brain disorders that affect movement, thinking skills and physical functions.
If symptoms and an MRI strongly suggest NPH, a large-volume spinal tap may be used to identify those who may benefit from a shunt. In this procedure, doctors remove a larger-than-usual amount of spinal fluid, and then observe the person for 30 to 60 minutes to note any improvements in walking or thinking and reasoning. Most people originally suspected of having NPH do not improve following a CSF removal test.
Causes and risks
In some cases, normal pressure hydrocephalus is caused by other brain disorders such as hemorrhages, infections or inflammation. But in most cases, the fluid buildup happens for unknown reasons.
Treatment and outcomes
Researchers have not found effective nonsurgical treatments for normal pressure hydrocephalus. Drugs that remove excess fluid throughout the body, such as diuretics, haven't been shown to help.
NPH can sometimes be treated with surgical insertion of a shunt, a long, thin tube that drains excess CSF from the brain to the abdomen. Difficulty walking is the symptom most likely to improve after surgery. Thinking changes and bladder control are less likely to get better. Shunting doesn't help everyone with NPH, and there's uncertainty about how best to identify those most likely to benefit.
More research is needed to:
- Understand the prevalence of NPH.
- Show how the excess CSF involved in NPH causes symptoms affecting movement, thinking and bodily functions.
- Clarify the possible benefits of shunt insertion and who is most likely to benefit.
The effectiveness of shunting in NPH has never been demonstrated in a randomized clinical trial. Most of these studies were small and followed people for a limited time. Available data suggest that difficulty walking is the symptom most likely to improve. Several studies found a significant rate of postsurgical complications. Findings also showed that short-term benefits of shunt insertion tended to decline over time.
Help is available
The Alzheimer's Association can help you learn more about Alzheimer's disease and other dementias, and help you find local support services. Call our 24/7 Helpline at 800.272.3900.
Hydrocephalus Association provides support, education and advocacy for people whose with hydrocephalus, their families and the professionals who work with them. Call the association at 888.598.3789.