What is normal pressure hydrocephalus?
Normal pressure hydrocephalus (NPH) is a progressive condition that occurs when there is too much cerebrospinal fluid (CSF) in the brain. Normally, CSF is produced inside two large cavities in the brain called ventricles. The fluid flows in and around the brain and spinal cord to cushion and protect them from injury. Veins at the top of the head absorb CSF into the bloodstream at the rate of about one ounce per hour. NPH occurs when the normal volume of CSF is not absorbed fast enough, causing the fluid to collect in the ventricles. As CSF slowly builds up in the ventricles, they enlarge and stretch the brain. This can damage nearby fibers that control the legs, bladder and memory.
What are the symptoms of NPH?
A person with NPH typically has more problems with walking than the memory and has had some symptoms for a relatively short time. Someone who has been in a nursing home for several years with severe dementia but is able to walk reasonably well probably does not have NPH.
- Walking difficulty that appears as an unstable or shuffled gain or a feeling that one’s feet are stuck to the floor and unable to step up.
- Mild dementia that can include memory loss, forgetfulness, and decreased attention span.
- Urinary problems that vary from frequency and urgency to actual incontinence
NPH is believed to account for 5% of all cases of dementia. The condition primarily affects older people, and as the population is living longer, the incidence of NPH is increasing.
What causes NPH?
NPH can develop from no known cause, or it may occur as a result of a closed head injury, brain surgery, meningitis, or a ruptured aneurysm.
How is NPH diagnosed?
NPH can be hard to diagnose because it can resemble other, more common causes of dementia or Parkinson’s. An accurate diagnosis is important because people with NPH who go untreated are likely to continue to decline. They also are likely to suffer unnecessary loss of independence and reduced quality of life.
A person who is suspected of having NPH begins consultation with a neurosurgeon or neurologist. The doctor reviews the patient’s medical history and performs a physical exam. A computed tomography (CT) or magnetic resonance imaging (MRI) scan is ordered to look for enlarged ventricles or other signs of blockage. If the scan is normal, the patient likely does not have NPH.
Gait testing also can be used to distinguish Parkinson’s from NPH. People with NPH tend to have an ataxic gait — a wide, penguin-like walk in which the legs are stiff, and the foot may drag and catch — whereas people with Parkinson’s tend to walk with small, shuffling steps. Sometimes the gait of NPH and Parkinson’s disease may not be distinguished with the naked eye. In those cases, the patient may undergo testing with a gait map, a long mat that records the timing and regularity of a person’s stride, step length, and cadence.
A neuropsychologist may test the patient’s memory and cognition. This exam may rule out another diagnosis, such as Alzheimer’s disease or non-Alzheimer’s dementia.
In NPH remains a possible diagnosis, the patient is scheduled to undergo a lumbar drain trial, a “test drive” to determine if a CSF shunt will improve the patient’s symptoms.
What are treatment options for NPH?
There is no cure for NPH, and there is no medication available. However, if diagnosed early, NPF can be treated with a shunt device that drains the excess fluid and reverses some of the symptoms. CSF shunt can provide symptom relief to some patients. Because NPH is usually a progressive disorder, the shunt extends quality of life for the patient but symptoms of NPH may return.
Sometimes a patient with NPH may be unable to have a shunt because of other health problems that would make surgery unsafe. Treatment of that condition may improve the patient's health enough so that he or she can undergo shunt surgery safely.