Normal pressure hydrocephalus (NPH) is a mild, difficult-to-diagnose type of hydrocephalus, commonly referred to as "water on the brain." Symptoms of normal pressure hydrocephalus are caused by an increase of fluid in the brain known as cerebrospinal fluid (CSF). The center of your brain has cavities called ventricles that are filled with cerebrospinal fluid (CSF). This circulating CSF is constantly replenished and absorbed so that the amount of fluid inside the brain and skull remains basically constant over the course of a lifetime. For reasons that are not always understood, the amount of CSF within the brain cavities of some people increases and may increase the pressure within the brain.
Normal pressure hydrocephalus can occur at any age, but it is most common in the older population. Several factors that contribute to the development of NPH are subarachnoid hemorrhage, head trauma, infection, tumor or previous brain surgery. However, many people develop normal pressure hydrocephalus even when none of these factors are present. In these cases, although the cause of the disorder is unknown, it is believed that the re-absorption of cerebrospinal fluid into the blood stream is reduced in many of these cases.
The increase in the cerebrospinal fluid above normal levels is so mild that NPH can be hard to detect and accurately diagnose. Individuals with normal pressure hydrocephalus often have a combination of three symptoms that can help establish the diagnosis:
- Mental confusion – Mild forgetfulness, short-term memory loss, loss of interest in normal activities are often seen in people with NPH.
- Gait disturbance – Difficulty in walking can take many forms, such as taking small shuffling steps, a tendency to fall, a feeling that your feet are too heavy or difficulty climbing stairs.
- Urinary incontinence – Impaired bladder control consists of difficulty in holding back urine.
- Because NPH symptoms are similar to those of Alzheimer's, Parkinson's and other movement disorders, NPH is often misdiagnosed or unrecognized which results in patients not receiving the appropriate treatment.
Facts about Normal Pressure Hydrocephalus
- It is estimated that 375,000 people with dementia in the United States may have normal pressure hydrocephalus.
- The cause of normal pressure hydrocephalus is usually unknown.
- Without treatment, symptoms may get worse over time.
- Early diagnosis and treatment may improve the chance of a good recovery.
- After treatment, some people can recover almost completely and enjoy a good quality of life.
A Collaborative Approach to Diagnosis and Treatment
Normal pressure hydrocephalus can be difficult to diagnose, since not all of the symptoms may appear at the same time. Sometimes these same symptoms of normal pressure hydrocephalus are found in other disorders of the elderly, such as Alzheimer’s disease, Parkinson’s disease and osteoarthritis. There is no single test that establishes the diagnosis of NPH.
At the Normal Pressure Hydrocephalus Center at the Northwell Health Neuroscience Institute, we have a unique collaboration of neurologists, neurosurgeons and neuropsychologists to diagnose and treat patients with normal pressure hydrocephalus. Comprehensive diagnostics include:
- Detailed patient history and examination – is the basis of establishing the clinical diagnosis.
- CT scan (Computerized Tomography) of the head – A CT scan is often done as the first test, but may not be needed if an MRI has been obtained. The scan shows enlargement of the ventricles, or cavities, and is helpful in ruling out other specific causes for the hydrocephalus.
- MRI (Magnetic Resonance Imaging) – An MRI is more sensitive to abnormalities of the brain tissue and is a key component of the diagnostic work-up.
- Neuropsychological testing – A thorough neurologic evaluation will be done by a trained neuropsychologist and can be helpful in getting a clearer picture of the type and severity of mental impairment. It can also help in following the course of a patient’s disease.
- Gait testing – This computerized measure helps in quantifying a patient’s gait (walking) impairment and is also helpful in documenting improvement with treatment.
- Spinal tap or lumbar puncture (LP) – A very fine-gauge needle is placed into the spinal canal, and the pressure of the cerebrospinal fluid is measured. At this time, the CSF is also examined for any other abnormal findings.
- Lumbar CSF drainage – A catheter is often inserted into the spine in the lower back for continuous drainage of cerebrospinal fluid over a three-day period. This procedure is more sensitive to improvement than a lumbar puncture alone.
- Intracranial pressure monitoring – This is sometimes used in cases where the diagnosis is unclear and actual monitoring of the pressure inside the head is thought to be necessary.
We are members of the International Hydrocephalus Imaging Working Group (IHIWG), an organization that advances the study of hydrocephalus, using a wide range of imaging modalities. Our physicians have presented at IHIWG on cerebrospinal fluid physiology and modeling.