Normal pressure hydrocephalus
The brain contains chambers called ventricles that are filled with cerebrospinal fluid (CSF). In normal pressure hydrocephalus (NPH), too much CSF gathers in the ventricles, causing them to expand and put pressure on the brain. As they enlarge over time, they can damage nearby brain tissue and cause the appearance of three classic symptoms: difficulty walking, problems with thinking and reasoning, and loss of bladder control.
Causes of normal pressure hydrocephalus
Medical professionals don’t know what causes most cases of primary NPH.
Secondary cases of NPH can develop from known causes, like a head injury, cranial surgery, subarachnoid hemorrhage, tumor or cysts, as well as subdural hematomas, bleeding during surgery, meningitis, and other brain infections.
Symptoms may appear later in life
Some people can be born with hydrocephalus, but not develop symptoms until late in life. Such persons may be completely unimpaired only to have their hydrocephalus identified on CT or MRI scans performed for unrelated reasons (for example, because of a head injury).
The percentage of asymptomatic congenital hydrocephalus patients who will eventually develop symptoms of NPH is unclear.
Symptoms of NPH
Three classic symptoms are associated with normal pressure hydrocephalus: difficulty walking, problems with thinking and reasoning, and loss of bladder control. These symptoms may not all occur simultaneously and can emerge at different stages of the disease with varying levels of severity.
Gait disturbances (difficulty walking) range in severity, from a mild imbalance to the inability to stand or walk at all.
The gait disorder is typically slow, short-stepped, often wide-based, and shuffling in character. Falls can occur with increasing frequency, and persons develop trouble descending stairs or going down sloping surfaces. Turns are often made with a series of choppy short steps and many will describe hesitancy when approaching objects in their path, trouble maintaining a uniform walking pace, or sometimes a tendency to accelerate unintentionally. A delayed or absent protective response to balance loss contributes to an increase in falls as well as the need to reach out to walls or furniture while walking to stabilize is common.
Individuals can also describe a feeling of heavy feet, as though they are magnetically attracted to the floor – “magnetic” gait, or find themselves stuck and unable to initiate a normal stride – “freezing of gait.”
For those with NPH, a gait disturbance is often the most troubling symptom and can be the first to become apparent.
Mild dementia (cognitive impairments) is described as a loss of interest in daily activities, forgetfulness, mood changes, difficulty dealing with routine tasks, difficulty making decisions or multi-tasking, and short-term memory loss. NPH is one of the few treatable forms of dementia.
In mild cases of NPH, urinary incontinence (impairment in bladder control) is typically characterized by urinary frequency and urgency. Severe cases can result in a complete loss of bladder control or urinary incontinence. However, some people with NPH never display signs of bladder problems.
Source: Hydrocephalus Association
How is NPH diagnosed?
Normal pressure hydrocephalus can sometimes be overlooked or misdiagnosed, because its symptoms are so similar to those of Alzheimer’s disease, Parkinson’s disease and Creutzfeldt-Jakob disease.
Although there are three hallmark symptoms of NPH – difficulty walking, cognitive impairment, and impaired bladder control – not everyone with normal pressure hydrocephalus experiences all three symptoms.
For that reason, your doctor will likely rely on one or more of the following tests to confirm a diagnosis of normal pressure hydrocephalus:
Clinical examination. A clinical examination performed by an experienced neurologist is crucial to properly diagnosing normal pressure hydrocephalus. Relying on their expertise in evaluating brain disorders that affect movement, thinking skills, and physical functions, this specialist will evaluate:
- An individual’s appearance, mood, anxiety level, and experience of delusions or hallucinations.
- Cognitive abilities such as memory, orientation to time and place, attention, use of language, and abilities to carry out a range of tasks and follow instructions.
- Reasoning, abstract thinking, and problem-solving.
Brain imaging. Because NPH is defined by the enlargement of the ventricles in the brain, MRIs or CT scans can play key roles in diagnosing normal pressure hydrocephalus.
Cerebrospinal fluid tests. Doctors can predict how a patient will respond to shunting (see below) by analyzing CSF. For example, when a large volume of CSF is removed from the lower back region, one or more of the NPH symptoms may lessen or reverse. This response shows that a surgical shunt would be a long-term solution.
Gait assessment. These assessments are performed by a licensed physical therapist and can help physicians determine an individual’s degree of impairment.
Treatments for normal pressure hydrocephalus
The most common and effective treatment for normal pressure hydrocephalus is the surgical insertion of a shunt. In essence, a shunt is a drainage system made up of a long, flexible tube with a valve that keeps fluid from the brain flowing in the correct direction and at the right rate.
One end of the tubing is usually placed in one of the brain’s ventricles and the rest is funneled under the skin, so the excess cerebrospinal fluid (CSF) can be absorbed in another part of the body.
Endoscopic third ventriculostomy (ETV)
In an ETV, an endoscope punctures a membrane on the floor of the third ventricle, creating a pathway for CSF to exit the ventricular system. Successful implementation of this procedure might mean that a shunt isn’t needed.
If people with NPH need a shunt, it’s typically needed for the rest of their lives, and requires regular monitoring.
Frequently asked questions (FAQs) about NPH
Yes. NPH is a cause of progressive dementia that includes three primary symptoms: difficulty walking, cognitive impairment, and impaired bladder control.
Long-term effects of NPH can vary widely and are often difficult to predict. Less severe cases, when treated appropriately, may have few, if any, serious complications. But severe long-term complications can result, including significant intellectual, developmental, and physical disabilities.
The severity of complications depends on:
- Severity of initial symptoms.
- Timeliness of diagnosis and treatment.
- Underlying medical or developmental problems.
The prognosis for NPH depends on the cause, the extent of symptoms and the timeliness of diagnosis and treatment. NPH symptoms typically worsen over time, and can even cause death, if left untreated.
However, shunt treatment helps most people recover almost completely while experiencing a good quality of life. According to the Life NPH website, if the cause of the NPH is known, the reported success rate for the shunting procedure can be as high as 80 percent. The success rate varies from 25 to 74 percent for NPH cases in which its cause is unknown.
In general, the earlier that NPH is diagnosed, the better the chance for successful treatment. The longer the symptoms have been present, the less likely it is that treatment will be successful.
No. Although we don’t have any way to cure or prevent NPH, we do know of several treatment options involving life-saving brain surgery. For more information on surgical options, see above.
National Institute of Neurological Disorders and Stroke (NINDS). Normal Pressure Hydrocephalus (https://www.ninds.nih.gov/health-information/disorders/normal-pressure-hydrocephalus)
Alzheimer’s Association. Normal Pressure Hydrocephalus (https://www.alz.org/alzheimers-dementia/what-is-dementia/types-of-dementia/normal-pressure-hydrocephalus)