Diagnosing Normal Pressure Hydrocephalus

NYU Langone neurologists are skilled experts at diagnosing normal pressure hydrocephalus, an accumulation of cerebrospinal fluid, also known simply as spinal fluid, in cavities of the brain, called ventricles.

Cerebrospinal fluid surrounds and cushions the brain and spinal cord and helps distribute important nutrients and chemicals within the central nervous system. The condition is called “normal pressure” because even though there is fluid buildup, its pressure is often measured as normal during a spinal tap.

When spinal fluid builds up in the ventricles, it causes them to enlarge and stretch the brain tissue. This can lead to problems with walking, cognitive impairment—such as memory problems and dementia—and diminished bladder control.

Normal pressure hydrocephalus typically affects adults over the age of 60. There is usually no known cause, but sometimes the condition can develop after a head injury, cranial surgery, or from meningitis or other brain infections. It can also occur as a late complication of congenital hydrocephalus.

Because its physical and cognitive symptoms are often associated with the aging process and resemble symptoms of conditions like Alzheimer’s disease or Parkinson’s disease, normal pressure hydrocephalus can be difficult to diagnose, or may be misdiagnosed.

To make a diagnosis, NYU Langone doctors first take a thorough medical history and perform a physical exam. People with the condition often have changes in urinary habits, so doctors may also ask about urgency, frequency, or issues with incontinence.

Our doctors may also perform gait evaluation, neurological evaluation, MRI or CT scans, and neuropsychological testing to diagnose normal pressure hydrocephalus.

Gait Evaluation

In a gait evaluation, the doctor asks you to take a few steps to determine if there is something unusual about the way you walk. Walking problems associated with normal pressure hydrocephalus can range from mild imbalance to the inability to stand or walk.

People with the condition often have a “magnetic gait” that is wide, slow, short-stepped, and shuffling. In some instances, people who have normal pressure hydrocephalus look like their feet are stuck to the ground. They may have trouble lifting their feet, making it difficult to climb stairs and causing falls.

The doctor may also videotape a person’s gait while he or she walks on a special computerized mat. This measures a person’s pattern of walking, called gait analysis.

Neurological Evaluation

A doctor may perform a neurological evaluation to assess if there is any cognitive impairment. He or she may ask a few questions about the person’s attention, memory, reasoning, reaction time, language ability, and emotional state. 

People who have normal pressure hydrocephalus sometimes develop mild dementia that may cause forgetfulness, short-term memory loss, and difficulty dealing with everyday tasks. Depending on symptoms, a doctor may perform more detailed neuropsychological testing as well.

CT Scan

CT scans use X-rays and computer imaging to create detailed pictures of the brain. The doctor may use this test to identify if the ventricles are enlarged, indicating cerebrospinal fluid buildup.

MRI Scan

A doctor may order an MRI scan to better view the brain, provide information about the surrounding brain tissues, look for enlarged ventricles, and evaluate the flow of cerebrospinal fluid. MRIs use a magnetic field and radio waves to create computerized two- or three-dimensional images of the inside of the head.

Lumbar Puncture

To determine how much pressure is caused by cerebrospinal fluid, a doctor may order an outpatient procedure called a lumbar puncture, also known as a spinal tap.

After applying local anesthetic to the lower back, a doctor inserts a thin needle into the spine and takes a sample of spinal fluid for analysis. If symptoms of normal pressure hydrocephalus are temporarily relieved by removing this small volume of spinal fluid, it tells a doctor that surgical treatment is likely to be effective.

Lumbar Drainage

In this procedure, a thin, flexible tube called a catheter is inserted into the lower back through a needle, similar to the lumbar puncture, and left in place to drain cerebrospinal fluid into a bag. About one half of an ounce of fluid is drained every hour.

This requires a person to stay in the hospital for about three days as the spinal fluid is continuously drained. During this time, you can get out of bed and walk around.

People whose symptoms respond well to lumbar drainage are very likely to respond to surgical treatment for normal pressure hydrocephalus.