What Is Normal Pressure Hydrocephalus?
Normal pressure hydrocephalus (NPH) is a type of brain disorder, wherein excess cerebrospinal fluid builds up in the ventricles of the brain. It causes problems in reasoning, thinking, difficulty in walking, and loss of bladder control.
Brains ventricles are hollow fluid-filled chambers. Even though there is an excessive cerebrospinal fluid buildup in NPH, during a spinal tap, the measured cerebrospinal fluid remains normal; hence, the term "normal pressure". The nearby brain tissues may get damaged as the brain ventricles enlarge due to cerebrospinal fluid accumulation. To accommodate the extra CSF, the ventricles tend to press other parts of the brain, which then leads to the symptoms of NPH.
People in their 60s-70s are more prone to developing NPH. Scientists have not yet determined how many older adults have this disorder because its symptoms are also identified in other brain disorders.
Although NPH may rarely occur, this neurological disorder can also cause dementia. Since the symptoms of NPH resemble those of other neurological disorders, the condition can be difficult to diagnose. There are two types of NPH that occur. They are:
- Idiopathic or (iNPH) - This is more commonly seen in people over the age of 60. The cause of this type of NPH is unknown.
- Secondary Form - It can occur at any age and is caused by secondary disorders or symptoms.
Ventricular shunting is the only effective treatment for NPH. The pressure in the brain is relieved by this method and after shunt placement, many people tend to show improvements. As a matter of fact, NPH is one of the only few causes of dementia, which can be potentially reversed.
Pathophysiology
The disorder's pathophysiology is poorly understood. However, it may likely involve an obstruction to the reabsorption of CSF over the cerebral convexities to the venous system. As an etiology of NPH, recent studies have revealed microbleeds and cerebrovascular accidents.
An association was found between diabetes mellitus, hypertension, and white matter lesions, which was provided by clinical and radiologic evidence. In a study on patients with idiopathic NPH, a lack of adenosine or down-regulation of adenosine receptors has been discovered. In discovering the pathophysiology of the disease, the adenosine system could be the missing link since adenosine has a protective effect on the vascular system and in the modulation of inflammation. Moreover, certain pro-inflammatory cytokine markers in the CSF of patients with NPH were found to be high.
Symptoms
The following are the symptoms of NPH, which are also considered as the hallmark of NPH:
- A decline in thinking skills - It causes apathy, overall slow thought process, reduced concentration, personality and behavior changes, and impaired decision-making or planning.
- Difficulty walking - May be described as if a person is walking on a boat (legs wide apart and body bent forward). It also includes feeling unsteady, having slow short steps, halting, or shuffling steps.
- Loss of bladder control - May appear later in the disease. It also includes increased urinary frequency, urinary urgency, and complete incontinence.
The disorder also has minor symptoms, which tend to become more noticeable over time:
- Difficulty walking on stairs or slopes
- Dizziness
- Difficulty getting up from the chair or sitting on a chair
The person may also show following symptoms of dementia:
- Impaired cognitive function and physical movements
- Poor attention and concentration
- Loss of motor control and self-regulation
- Understanding and expressing ideas becomes difficult
- Loss of complete cognitive activities such as carrying out multi-step actions and conceptualizing information
- Interpreting the environment becomes difficult
Diagnosis
Normal pressure hydrocephalus cannot be determined by a single test. Although the above-mentioned symptoms are considered as classic signs, they are not all shown by individuals with NPH.
Since the treatment for NPH is quite different, it becomes important to properly distinguish the disorder from other conditions. Many tests are available to diagnose this condition. To complete the evaluation and begin treatment, your doctor may recommend you to a neurologist or neurosurgeon.
The doctor's evaluation begins by asking about your medical history, specific symptoms, the time when they started to show, previous and current medications, and family history of diseases.
To document the condition and rule out other disorders, the doctor will take a detailed physical examination. To assess your mental status, the doctor will again ask a few questions. A neurological test may be performed to document your dementia symptoms. The most accurate method of identifying and documenting cognitive problems and the strength of the person is by neuropsychological testing. For the diagnosis of NPH, evidence needs to be gathered by multiple tests. The symptoms of NPH are similar to other neurodegenerative diseases such as:
- Multi-infarct dementia
- Alzheimer’s disease
- Frontotemporal dementia
- Lewy body dementia
1. Neuropsychological Assessment
The doctor will test a patient's mental function to rule out other neurological conditions. To test for cognitive function, the doctor will do a mini-mental state examination. To test attention and executive function, the doctor may use other assessment tests such as:
- Word fluency test
- Digit span and spatial span
- Frontal assessment battery test
2. Brain Imaging
Magnetic resonance imaging (MRI) usually helps when it comes to detecting the enlargement of ventricles. This imaging scan plays a key role in the diagnosis of NPH. Overall brain shrinkage can be caused by several disorders such as Alzheimer’s disease. Thus, when compared to a normal brain, the ventricles may look larger.
Brain tissues may not appear shrunken, although the ventricles are enlarged. Thus, it is recommended by experts that to evaluate the brain disorders that affect thinking skills, movement, and physical function, the person should be extensively examined by an experienced neurologist since the symptoms of NPH, Alzheimer’s, and dementia overlap.
Although the evidence for diagnosis is insufficient, certain imaging tests such as a CT scan and PET scan can be helpful.
3. CT Scan of the Head
This imaging scan and X-ray have similarities, but a CT scan gives a three-dimensional detailed picture of the brain. However, this type of imaging scan cannot confirm the diagnosis, but rather reveal ventricular enlargement or any other changes that suggest NPH. The flow of CSF in the brain can be measured by newer techniques. However, for diagnosis, a CT scan alone will not be sufficient. This scan is painless and safe.
4. CT Cisternography
The absorption of CSF is highlighted by this method. However, this method is not widely used.
5. Invasive Diagnostic Testing
This type of testing is done to confirm the diagnosis of NPH. Procedures include:
- Spinal Tap - If NPH is strongly suggested by symptoms and MRI, and to identify those who benefit from a shunt, a large column spinal tap may be used. In this procedure, the amount of spinal fluid removed is larger than usual. For 30 to 60 minutes, the person is observed whether there are any improvements in thinking, walking, or reasoning. The doctor looks for changes in stride length and speed on gait. Most probably your gait before and after the procedure may be videotaped so that a clear comparison can be made. In the majority of people originally suspected of having NPH, no improvement was observed after the CSF removal test.
- Lumbar Drainage - In this procedure, a small tube or catheter is placed in the lumbar spine. At a slow rate, the CSF is drained over a period of 2 to 7 days. This procedure is done in the hospital. The doctor will then check if there are any changes in your condition.
Causes and Risks
Some brain diseases, which include infection, inflammation, and hemorrhage may cause NPH. However, for unknown reasons, the cerebrospinal fluid may build up. The following theories related to NPH are:
- The cause of idiopathic NPH is not yet known. The veins weaken, so the normal absorption of the cerebrospinal fluid is impaired.
- The white matter of the brain may swell and blood flow to vital areas may be hindered like the frontal and prefrontal lobes.
The physiologic or disease process may precipitate as a secondary form NPH. This type of NPH may be caused by conditions such as:
- Mass lesions
- Hemorrhage
- Traumatic brain injury
- Meningitis
- Impaired absorption of the cerebrospinal fluid
After the age of 60, the risk of developing NPH increases. The risk factors may increase as you grow older. Risk factors include:
- Hypertension
- Alzheimer’s disease
- Vascular disease
- Cerebrovascular disease
Treatment and Outcomes
Generally, NPH is a lifelong condition, which cannot be cured. However, through surgical treatment, many people can obtain substantial relief. For those who are not candidates for surgery, treatment may include:
- Measures to relieve mood changes
- Medications to relieve behavioral problems
- Coping with physical problems such as maximizing physical, mental, and social functioning, incontinence, and walking difficulties
No effective nonsurgical treatments have been found by researchers for NPH. Diuretics that are used to remove excess fluid from the body are also ineffective. However, NPH can be treated with a surgical insertion of a shunt. It consists of a long thin tube from the brain to the abdomen and drains excess CSF.
The symptom that may improve after surgery is difficulty in walking. However, improvements in bladder control and thinking are less likely. Individuals with NPH may not benefit from shunting and how best to identify those who may benefit is still uncertain.
Ventricular shunting is the only successful treatment for NPH. In the brain, a medical device is implanted and the pressure caused by fluid accumulation is relieved.
The shunts used are of three types:
- Ventriculopleural
- Ventriculoperitoneal (the most commonly used)
- Ventriculoatrial (the most rarely used since it may cause long-term complications)
To control the amount of CSF drainage, the shunt will have valves. The options are:
- Adjustable Shunt Valves - Without another operation, the valve pressure can be adjusted.
- Gravity-Controlled Valves - By the position of the body, the valve pressure is determined. To avoid shunt overdrainage, an adjustment is done.
Risks
There are risks of complications associated with surgery. The serious risks are:
- Infection
- Death
- Shunt malfunction
- Seizures
- Cerebral hemorrhage
A study was done, wherein some patients were given shunt treatment. An improvement was shown in 50 percent of the patients. However, for every person with NPH, surgery is not an option.
If the case of dementia is severe, then surgery is not recommended since the risks outweigh the benefits. Moreover, to maintain improvement, patients may require more than one surgery. To determine the best course of action, the doctor will weigh the risks and benefits of the procedure.
Long-Term Outlook
The outlook usually varies according to the patient's age, surgical history, and previous health problems. Healthy people can get the best outlook when the disease is early diagnosed. Clinical improvement has been seen in 70 percent of people who have undergone modern treatments such as ventriculoperitoneal shunting.
Self-Care
A person with this disorder should always be under the care of a medical professional. The family and caregivers should handle much of the day-to-day care. Optimizing the heath of the individual, safety, and quality of life should be the main focus of medical care.
The extent to which the patient should be cared will vary. A normal or near-normal independent life can be led by those who undergo a successful shunt surgery, while in some, the symptoms may become worse over time. Eventually, over time, close supervision and care will be needed.
It can be difficult for both you and the family members to cope with the symptoms of NPH. You may find help from support groups and share strategies to cope with the disorder.
Research
NPH research has to focus on:
- Understanding the prevalence of NPH
- Show how excess fluid can cause symptoms
- Clarify how shunt insertion is beneficial and who may likely benefit from it
In a randomized clinical trial, the effectiveness of shunting in NPH has never been demonstrated. The studies were done for a limited time and most of them were small. According to some studies, the most likely symptoms that may improve is difficulty in walking.
Postsurgical complications have been found at a significant rate by several studies. It was also shown that over time, the benefits of shunt insertion tend to reduce.
