Normal Pressure Hydrocephalus
When excess levels of cerebrospinal fluid buildup within a person’s brain, they have a condition called normal pressure hydrocephalus. The condition can lead to gait problems, urinary incontinence (which may begin as urinary urgency), and dementia (which may begin as trouble executing complex plans). Together, these three symptoms help doctors diagnose someone with normal pressure hydrocephalus.
Normal pressure hydrocephalus is a very rare condition—it occurs in fewer than 3% of adults aged 65 and over. It affects men and women equally; because it typically affects older adults, it may sometimes be confused with other types of dementia.
When normal pressure hydrocephalus is caught early, its effects may be reversed by a procedure called ventricular shunting. However, if normal pressure hydrocephalus is diagnosed later—once dementia has set in—those symptoms cannot be reversed.
What is normal pressure hydrocephalus?
Normal pressure hydrocephalus is a condition that occurs when a person has too much fluid in the brain. This fluid, called cerebrospinal fluid (CSF), is produced in the brain and circulates in and around the brain and spinal cord. CSF helps cushion the brain and spinal cord, remove waste, and distribute important substances to the brain and spinal cord.
CSF is constantly produced in the brain. It circulates around spaces in the brain and spinal cord and eventually gets reabsorbed into the blood. If the normal circulation or absorption of CSF is disrupted, it can lead a buildup of CSF in the brain. This is a condition called hydrocephalus, a term that means “water on the brain.” Often, the accumulation of CSF increases pressure in the brain (known as intracranial pressure).
In someone with normal pressure hydrocephalus (NPH), excessive CSF builds up in the brain. Although when tested via a spinal tap, the pressure is within the normal range or only slightly elevated. It is therefore called “normal pressure” hydrocephalus. There is evidence, however, that people with NPH can have periods of increased intracranial pressure. The buildup of CSF causes cavities in the brain, called ventricles, to enlarge and can also exert pressure on brain tissue.
NPH is most common in older adults. It’s estimated that over 700,000 people in the U.S. have NPH, though under 20% of them have been diagnosed with the condition. People with NPH often have an unsteady gait, cognitive impairment, and problems with bladder control problems. In the U.S., NPH may cause up to 5% of dementia cases.
What causes normal pressure hydrocephalus?
In about half of patients, doctors don’t know what causes NPH. This form of the disease, known as idiopathic NPH, usually affects people ages 60 or older.
In other patients, the condition can be caused by a head injury, brain surgery, tumors and cysts, certain types of bleeding in the brain, and infections in the brain such as meningitis. When NPH is caused by one of these underlying causes, it is known as secondary NPH. Secondary NPH can occur in people of any age.
What are the symptoms of normal pressure hydrocephalus?
NPH is associated with three primary symptoms:
- Walking (gait) problems: People with NPH might experience anything from feeling a little “off balance” to not being able to walk. Some common problems with gait include trouble taking first steps, trouble with turns, taking short steps, shuffling, or “magnetic gait,” which feels as if there are magnets on the floor, and it is difficult to lift up the feet. Often, problems with walking are the first symptoms a person has with NPH. As problems with gait worsen, the person may need a cane or walker. They might also fall or almost fall more often.
- Cognition (thinking) or memory problems. People with NPH might lose interest in activities, have trouble remembering things that happened recently, feel “foggy,” forget things, and have trouble doing routine tasks. It’s common for someone with NPH to be disorganized when trying to do something they normally do all the time.
- Bladder control issues can include the urge to go more often and having “accidents.”
People with NPH may have only one or two of these symptoms. NPH is a progressive disease, meaning symptoms worsen over time.
How is normal pressure hydrocephalus diagnosed?
To diagnose NPH, doctors will assess the patient’s medical history, perform a physical exam, and order one or more diagnostic tests.
To obtain a medical history, the doctor will ask about symptoms, including when they began and whether they are getting worse over time. During the physical exam, the doctor will assess the patient’s gait. To do so, they may ask the patient to stand up from a seated position, walk a short distance, turn around, and return to their seat. The doctor may also ask the patient to answer some simple questions and perform some simple tasks to assess their mental status.
Imaging tests, such as a magnetic resonance imaging (MRI) scan or computed tomography (CT) scan of the brain, are needed to make the diagnosis. These scans allow doctors to check for enlarged ventricles and other changes in the brain that are characteristic of NPH.
The doctor may perform additional tests to diagnose NPH and to help determine how well surgical treatment is likely to work. These may include two tests that can show if a person’s symptoms are caused, at least in part, by increased fluid in the brain. These tests can also show if removing some of the fluid will help.
- Large-volume lumbar puncture (spinal tap): Before any testing, you will be observed and timed as you walk 10 feet. In this outpatient procedure, you will then lie on your side while a small area on your back is cleaned and numbed. A needle is then inserted into the spine and about 30 milliliters (around two tablespoons) of CSF is drained. Removing this fluid should lower intracranial pressure. After the procedure, you will perform the same 10-foot walk to see whether your walking is steadier after CSF removal. If your gait improves, it suggests that surgical implantation of a ventriculoperitoneal (VP) shunt may improve symptoms. If the test is inconclusive or if symptoms do not improve upon removal of fluid, a lumbar drain trial may be performed.
- Lumbar drain trial: Like the large-volume lumbar puncture test, in this test CSF will be removed to determine if it improves symptoms. The trial requires a 4–5-day hospital stay. Before the procedure begins, you will meet with physical and occupational therapists who will perform a series of baseline tests to evaluate your current symptoms. A catheter—a thin, flexible tube—will then be inserted in your spine under X-ray guidance. CSF will be continuously or intermittently drained via the catheter during your hospital say. Physical and occupational therapists will perform additional tests daily to see whether your symptoms improve as more and more CSF is removed. If symptoms do improve, it suggests that surgical implantation of a VP shunt will improve symptoms. During a lumbar puncture, doctors may also measure CSF pressure to check whether it is elevated. Also, CSF collected during a high-volume lumbar puncture test or a lumbar drain trail may be sent to a lab for analysis.
How is normal pressure hydrocephalus treated?
There are currently no medications to treat normal pressure hydrocephalus.
The standard treatment for normal pressure hydrocephalus is a surgical procedure to place a shunt in the ventricles of the brain and connect this drain into the abdomen. The shunt, known as a VP shunt, provides an alternative drainage pathway for the built-up fluid.
Yale is involved in a clinical trial for a new, minimally invasive procedure call the eShunt System from the device company CereVasc. With this minimally invasive approach, the eShunt is implanted between a vein high up in the neck and the base of the skull. This allows CSF to drain into the veins where it is reabsorbed by the blood. Because it is minimally invasive, there is a reduction in the risk of complications and infections compared with traditional surgery.
What is the outlook for people with normal pressure hydrocephalus?
NPH is a progressive condition and without treatment, symptoms worsen over time. Symptoms improve in about 50% to 90% of patients who have a CSF shunt surgically implanted. Outcomes tend to be best for those who receive treatment early in the course of the disease.
What makes Yale unique in its approach to normal pressure hydrocephalus?
“Yale has had a dedicated Normal Pressure Hydrocephalus Program for more than 10 years. We have dedicated team of physicians, nurse practitioners, nurses, and physical and occupational therapists who help to evaluate and treat our patients,” says Yale Medicine neurosurgeon Charles Matouk, MD. “Our team consists of experts in normal pressure hydrocephalus. We see typical and atypical NPH patients. Due to our high volume, we are involved in clinical trials and research into various aspects of this disease.”