The term hydrocephalus comes from the Greek "hydro," meaning "water," and "cephalus," meaning "head."
Hydrocephalus, then, is an abnormal accumulation of water-like fluid in the head.
The fluid, called cerebrospinal fluid (CSF), is made in the spaces of the brain called ventricles.
CSF circulates around the brain and spinal cord (the central nervous system), cushioning and protecting the delicate tissues. CSF also maintains the balance of nutrients to the brain and spinal cord and removes waste products.
Every day, the body makes about 8 oz. of CSF, and about the same amount of fluid is reabsorbed into the bloodstream. Hydrocephalus occurs when there is an imbalance between the amount of CSF produced and the amount absorbed.
This imbalance can be caused by a blockage that interferes with the flow of CSF around the brain and spinal cord. This is called obstructive or non-communicating hydrocephalus. Hydrocephalus can also result from an overproduction of CSF or the under-absorption of CSF into the bloodstream. This is called communicating hydrocephalus.
Most cases of hydrocephalus are present at birth. This is called congenital hydrocephalus. Cases that develop later in life are called acquired hydrocephalus.
Many factors can contribute to acquired hydrocephalus, including head injury, stroke, brain tumor, and meningitis.
When the absorption of CSF is blocked, the CSF begins to accumulate in the ventricles of the brain, causing the ventricles to become enlarged increasing pressure inside the head.
Normal pressure hydrocephalus?
Normal pressure hydrocephalus, or NPH, is an acquired hydrocephalus that most often occurs in people over age 60. NPH is different from typical hydrocephalus in that it may not cause an obvious increase of pressure in the head, but may have fluctuations in CSF pressure from high to normal to low during the whole day.
What are the symptoms of NPH?
Primary Symptoms of NPH:
- Gait disturbance (difficulty walking)
- Dementia or forgetfulness
- Bladder control problems (as the condition progresses)
The gait in many patients with NPH is very distinctive: wide-based, short, slow and shuffling. People may have trouble picking up their feet, as if their feet are glued to the ground. They may have difficulty going up and down stairs and curbs, and as a result, they frequently falling. Gait disturbance is often the most obvious first symptom. These disturbances range in severity, from mild imbalance to the inability to stand or walk at all.
The symptoms of NPH usually get worse over time if the condition is left untreated. Patients with untreated, advanced NPH may experience seizures, which can get progressively worse. Dementia and/or bladder control problems usually appear after gait disturbances, as the condition progresses. Mild dementia can be described as a loss of interest in daily activities, forgetfulness, difficulty dealing with routine tasks and short-term memory loss. Not everyone with NPH develops an obvious mental impairment.
Bladder control problems usually involve urinary frequency and urgency in mild cases. In severe cases, however, a complete loss of bladder control (urinary incontinence) may result. Urinary frequency is the need to urinate more than usual, often as frequently as every one to two hours. Urinary urgency is a strong, immediate physical need to urinate. This urge is sometimes so strong that it cannot be controlled, resulting in incontinence. Most patients with NPH do not have headaches, which are common in patients with obstructive hydrocephalus.
What causes NPH?
Many cases of NPH have no known cause. Some cases of NPH are linked to bleeding in the brain or a blockage in CSF flow through and around the brain and spinal cord. It is believed that blockages are linked to a history of infection, stroke, or head injury.
How common is NPH?
Because the symptoms of NPH are similar to those of other diseases, people with NPH are often diagnosed with disorders such as Alzheimer's or Parkinson's disease, or the symptoms may be attributed to the aging process. For that reason, it is difficult to know how many people actually have NPH. However, it is estimated that as many as 10 percent of people with dementia attributed to other disorders may actually have NPH.
How is NPH diagnosed?
A careful review of symptoms, a medical history, and various tests are used to diagnose NPH. Tests used may include:
- Computed tomography (CT) — A CT scan is a diagnostic tool that uses X-rays and a computer to create pictures of structures inside the body. A CT scan can provide images that show the size of the ventricles.
- Lumbar puncture for NPH — Also called a spinal tap, this procedure is used to remove a sample of the CSF. For NPH, this test is used to determine if a person’s symptoms improve after removing a large amount of fluid. About 1 to 1½ oz. of fluid is removed. However, this test is not definitive.
- NPH protocol — The protocol entails a series of screening procedures, including a gait analysis, blood work, and neuropsychiatric testing. It also involves the removal of CSF through a special catheter (tube) over a 36-hour period. It is expected that following removal of CSF, there will be a dramatic, temporary relief of symptoms. The protocol also provides the surgeon with information about the potential benefit of implanting a shunt, which is a device that drains excess CSF away from the brain and spinal cord, diverting it to another part of the body, such as the abdomen or heart, where the body can absorb it.
- Magnetic resonance imaging (MRI) — An MRI scan uses a magnet and radio waves, instead of X-rays, to produce images.
- Gait analysis (walking) — This is a timed walk test. The patient is watched as he or she walks 10 meters (about 30 feet).
- Neuropsychological testing — This involves a series of questions used to see if there is a loss of brain function caused by NPH.
How is NPH treated?
NPH may be treated using an implantable shunt to drain excess CSF away from the brain and spinal cord. Shunting CSF production would control high-pressure spikes within the head and brain.
What complications are linked to NPH treatment?
Complications of NPH treatment are those associated with any surgical procedure. They include bleeding, infection, and reaction to the anesthesia used during surgery. Patients might also experience mild abdominal pain. Seizures also may occur as surgery on the brain can affect very sensitive areas of the brain. Fortunately, these complications are not common, and in most cases can be successfully treated.
What is the outlook for people with NPH?
With treatment, the symptoms of NPH can be partially or even fully reversible. On the other hand, the outlook is poor when the disorder is not treated appropriately. Without treatment, the symptoms can continue to worsen and lead, eventually, to death.