What Is Normal Pressure Hydrocephalus?
Normal pressure hydrocephalus (NPH) is a neurological disorder that causes dementia. It’s characterized by walking abnormalities, dementia, and impaired bladder control.
NPH is relatively rare. According to the Hydrocephalus Association, an estimated 700,000 Americans suffer from the disorder. NHP is difficult to diagnose because its symptoms resemble other neurological diseases. Your doctor must consider your symptoms and run numerous tests to make the diagnosis. For this reason, many people go undiagnosed.
There are two types of NPH. The first type is idiopathic (iNPH). The cause of iNPH is unknown, but it most commonly occurs over the age of 60. It affects both men and women equally. The second type of NPH is known as secondary form. It’s caused by secondary disorders or symptoms that can occur at any age.
The only effective treatment for NPH is ventricular shunting. This is a surgical procedure used to relieve pressure in your brain. Most people show significant improvement after shunt placement. In fact, NPH is one of only a few causes of dementia that is potentially reversible.
Risk Factors for NPH
The risk of developing NPH increases after the age of 60. As you grow older, you may have more risk factors. Risk factors of NPH include:
Causes of NPH
The exact cause of idiopathic NPH is still unknown. However, some studies have theorized that iNPH is related to:
- weakening of veins that impairs the normal absorption of cerebral spinal fluid (CSF)
- swelling of the brain’s white matter that hinders blood flow to vital areas, like the frontal and prefrontal lobe
Secondary form NPH is precipitated by another physiologic or disease process.
Conditions that may cause this type of NPH include:
Symptoms of NPH
The three symptoms that characterize NPH are walking abnormalities, dementia, and impaired bladder control.
Minor symptoms in early NPH include:
- difficulty in walking slopes or stairs
- difficulty in rising/sitting on a chair
Over time these symptoms will become more noticeable.
Examples of walking abnormalities include:
- feeling unsteady when walking
- slowness from short steps
- walking with shuffling, halting steps
Bladder symptoms caused by NPH include:
- urinary frequency
- urinary urgency
- complete incontinence
Dementia symptoms include:
- a slowing between cognitive function and physical movement
- lack of attention and concentration
- loss of complex cognitive activities, such as conceptualizing information and carrying out multi-step actions
- loss of motor control and self-regulation
- difficulty understanding or expressing ideas
- trouble interpreting the environment
Diagnosis of NPH
It can be hard to diagnose NPH because it appears similar to other neurodegenerative diseases. Multiple tests must be used to gather sufficient evidence for a diagnosis of NPH.
Neurodegenerative diseases with symptoms similar to NPH include:
- Alzheimer’s disease
- multi-infarct dementia
- lewy body dementia
- frontotemporal dementia
To help rule out other neurological conditions, your doctor will test your mental function. This will include a mini-mental state examination, which tests your cognitive function. Your doctor may also use other assessments to test your attention and executive function, including:
- digit spat spatial span
- word fluency test
- frontal assessment battery tests
Imaging tests of the brain are helpful, though insufficient for a diagnosis. Examples of these include:
Invasive Diagnostic Tests
Invasive diagnostic tests help to confirm the diagnosis of NPH. These tests include:
- Lumbar tap test: This is an in-office procedure where a needle is inserted in your lower back to remove cerebrospinal fluid (CSF). Then, your gait is monitored to see if there are any changes before and shortly after the tap. Your doctor will look for changes in your speed and stride length, among other things. They will most likely videotape you walking before and after the procedure to get a clear comparison.
- Lumbar drainage: This procedure involves placing a temporary catheter, or small tube, in your lumbar spine. This tube drains CSF at a slow rate over a two- to seven-day period in the hospital. Your doctor will monitor any changes in your condition to assess the procedure’s success.
Treatment of NPH: Ventricular Shunting
The only successful treatment for NPH is ventricular shunting. A ventricular shunt is a medical device implanted in your brain that relieves pressure caused by fluid accumulation. Ventricular shunts are surgically implanted to drain excess CSF, which in turn relieves pressure.
Three types of shunts are used:
- ventriculoperitoneal (the most common type)
- ventriculoatrial (used rarely because of tendency to cause long-term complications)
The shunt will have valves to control the amount of CSF drainage. The options for valves include:
- adjustable-shunt valves: the valve pressure can be adjusted without another operation
- gravity-controlled valves: valve pressure is determined by the position of the body and adjusts to avoid over-drainage (recommended for mobile patients)
All surgery carries the risk of complications. Shunt surgery has serious risks that include:
- shunt malfunction
- intracranial or cerebral hemorrhage
In one study, of the patients who receive a shunt, 59 percent showed improvement. However, surgery isn’t an option for every patient with NPH. And those with severe dementia are discouraged as the risks of surgery outweigh the benefits. Also, many times people require more than one surgery to maintain improvement. Your doctor will weigh the risks and benefits of the procedure to determine the best course of action.
Long-Term Outlook for NPH
Your outlook will vary according to your age, previous health problems, and surgery. A healthy person who receives an early diagnosis has the best outlook. More than 70 percent of people who undergo modern treatment like ventriculoperitoneal shunting have clinical improvement.