Normal Pressure Hydrocephalus
Diagnosing NPHA diagnosis on NPH is based on:
- History, physical and neurological examination — dementia, difficulty walking and urinary incontinence
- Brain images to detect enlarged ventricles (CT or MRI scan)
As a rule, the earlier NPH is diagnosed, the better the chance for effective treatment. With early diagnosis and treatment, the symptoms of NPH can be effectively reduced. If a person with NPH is not treated, the symptoms will worsen over time, and the disorder will eventually lead to death.
Dementia caused by NPH (about 5 percent of all dementia cases) is one of the few causes of dementia that is treatable. If a patient has experienced dementia for less than two years, his or her mental abilities can improve with treatment. If a patient has had dementia for more than two years, however, the likelihood of mental improvement is very small.
The NPH Program team uses a variety of tests to help diagnose NPH, following guidelines developed by an international team of neurosurgeons. The guidelines were published in 2005 in Neurosurgery®, the official journal of the Congress of Neurological Surgeons.
Team members follow a series of steps to diagnosis — or rule out — NPH. Steps include:
- An initial examination in the NPH Clinic.
- A brain scan (if one has not been done within the last three months). Computed tomography (CT) or magnetic resonance imaging (MRI) is used to scan the brain for enlarged ventricles, an important test for patients with suspected NPH. If NPH is suspected based on a patient’s history, neurological examination, brief cognitive testing and brain imaging, the next steps include:
- Cognitive testing, conducted by a neuropsychologist, to assess the patient for signs of dementia. A neuropsychologist specializes in assessing the effect of brain injury on behavior and cognition (the ability to think, reason and perceive). Testing involves answering questions and following simple directions to determine if there is a loss of brain function related to NPH. Neuropsychological testing can help give a more accurate diagnosis of cognitive problems and help in planning treatment.
- Gait (walking) and balance assessment, conducted by a physical therapist, assesses a person’s ability to walk. Walking difficulty is one of the major symptoms of NPH. During the assessment, a patient is videotaped while he or she is observed during standing and walking. The physical therapist assesses joint range of motion, speed, the quality of gait, and how the joints move.
- A spinal tap (also called lumbar puncture), which allows an estimation of CSF pressure and an analysis of fluid. It is an outpatient test performed by a neurologist to determine if symptoms improve with removal of spinal fluid. Under local anesthetic, a thin needle is passed into the spinal fluid space of the low back. Up to 50cc (about 10 teaspoons) of CSF is removed. Gait assessment is done right after the spinal fluid is removed to see if there is gait improvement. Six to eight hours after the spinal tap, gait and cognitive assessments are repeated to check for signs of improvement in walking and cognitive abilities. If symptoms improve (a positive outcome), a diagnosis of NPH can be confirmed, and the patient may then benefit from surgical placement of a shunt to permanently drain the fluid. When the response to a spinal tap is “negative” or uncertain, further evaluation may be helpful.
- External lumbar drainage, also called continuous lumbar drainage, is a variation of the lumbar puncture where a thin, flexible tube (catheter) is left in place to drain CSF. The procedure, which requires hospitalization, is performed by a neurologist to allow removal of spinal fluid over several days. This imitates the drainage effect that a shunt would have.
- During the first 24 to 48 hours, the spinal fluid pressure is monitored by a computer. NPH has a “signature” pressure reading.
- Over the next 24 to 48 hours, the spinal fluid is drained continuously at a rate of about 10cc (about 2 teaspoons) per hour. The total amount of spinal fluid drained is about half of the amount the body produces each day.
Each day of the 72-hour period, cognition and gait are tested to look for signs of improvement. If a patient shows improvement after the three-day period, a diagnosis of NPH can be confirmed, and it’s highly likely that the patient will benefit from a shunt. If a patient does not improve after 72 hours, the likelihood that a shunt will help the patient is very low.
Because shunt placement is a lifelong treatment for NPH, team members confer to ensure a correct diagnosis is made and that a patient may truly benefit from a shunt. When a patient is correctly diagnosed with NPH, a shunt can greatly improve his or her quality of life.
Shunt PlacementWhile NPH cannot be cured, many people find relief through the surgical placement of a shunt, a thin tube that routes excess fluid from the brain to another area of the body. A shunt is the only effective treatment for NPH. The goal of shunt placement is to improve the three major symptoms of NPH: dementia, urinary incontinence and difficulty walking.
About 30 percent to 50 percent of patients with idiopathic NPH (no known cause) improve after receiving a shunt. About 50 percent to 70 percent of patients with secondary NPH (related to another brain disorder) improve with a shunt.
The shunt is implanted into one of the ventricles of the brain. The shunt consists of a small tube called a catheter and a valve device that regulates the rate of fluid drainage. The shunt is tunneled under the skin to the drainage site.
The most common type of shunt is a ventriculoperitoneal (VP) shunt, which drain excess CSF from the ventricles to the abdominal or peritoneal cavity. There are two types of shunts — non-programmable and programmable. The programmable type has valves that allow the shunt to be adjusted with a magnetic device after surgery to increase or decrease the drainage rate of the shunt. The shunt used for treating NPH usually remains in the brain permanently.
While shunts do not work for every person with NPH, many people experience symptom relief. The shunt allows the fluid to drain out of the brain, which prevents the ventricles from enlarging. This may help a patient walk better, regain bladder control and think more clearly. A successful shunt placement tends to help more with walking and bladder control than with dementia.
Regular follow-up care is important to identify any changes that could indicate problems with the shunt. Complications may include valve malfunction or catheter obstruction in the shunt system, or physical complications related to fluid drainage. These include:
- Subdural hygroma, a collection of cerebrospinal fluid beneath the outermost membrane of the brain
- Subdural hematoma, a collection of blood on the surface of the brain
- Headache associated with over-draining of cerebrospinal fluid
Other risks include those related to shunt placement, such as catheter malposition, intracerebral hematoma (bleeding within the brain) and shunt infection.
For patients with NPH who are not candidates for surgery, treatment may include measures to relieve mood and behavioral problems, cope with physical problems (incontinence and walking difficulties), and maximize physical, mental and social functioning.
Author: Marla Fraunfelder
Date: Oct. 9, 2008
|Medical Reviewer: ||Malgorzata Franczak, MD|
|Medical College of Wisconsin Neurologist||