Normal Pressure Hydrocephalus
What Is It?
Normal pressure hydrocephalus (NPH) is a form of hydrocephalus which typically occurs in older individuals. It is so named because patients tend not to have very high intracranial pressure, the pressure inside the head, for prolonged periods of time, as is typical in many other causes and forms of hydrocephalus.
Hydrocephalus generally results from some dysfunction of the normal dynamics and flow of the cerebrospinal fluid, the water-like fluid inside and surrounding the brain and spinal cord. This abnormality can lead to the clinical symptoms associated with hydrocephalus and can cause progressive dysfunction of the nervous system.
In general there is no known cause of normal pressure hydrocephalus. While some older patients with other causes of hydrocephalus, such as aqueductal stenosis, can present with similar symptoms, true idiopathic NPH has no definitive cause. It generally occurs in older adults and the elderly and because of its symptoms can sometimes be initially confused with other neurological conditions of the elderly such as Alzheimer's disease and other forms of dementia.
What Types of Symptoms Are Typical?
NPH classically presents with a triad of symptoms. This triad include a decline in cognitive function, particularly memory loss, urinary incontinence and ataxia, or unsteady gait. The gait is often described as a "magnetic gait" because of the characteristic appearance of the gait with frequent "sticking".
Because intracranial pressure does not stay very high in this form of hydrocephalus, you do not usually see many of the symptoms that are characteristic of other forms of hydrocephalus, such as headache and declining level of consciousness. However, patients with NPH can have other subtle symptoms outside of the classic triad mentioned above.
How Is The Diagnosis Typically Made?
In a patient who presents with any of the symptoms of normal pressure hydrocephalus, a full neurological assessment
is generally done. To help rule out other causes of ataxia, incontinence and memory loss, a neurological imaging study is often done, such as a CT scan
or MRI scan
. These can sometimes show enlargement of the ventricles, the fluid-filled space within the brain, consistent with hydrocephalus. Additionally, the scans help to rule out other causes such as aqueductal stenosis or a brain tumor
In a patient with symptoms and imaging consistent with NPH, further testing is often done to confirm the diagnosis and to evaluate which treatment may be most effective. For example, some physicians prefer to perform some form of cerebrospinal fluid drainage testing to see if this improves the patient's symptoms. This can involve a spinal tap (lumbar puncture) to drain a large amount of fluid or putting in a drain in the spine to continuously drain fluid over several days. If the patient's symptoms improve with drainage, some physicians feel this helps both prove the diagnosis and indicates that surgical treatment with a cerebrospinal fluid shunt may be beneficial in those patients. Some centers also place a monitor in the patient's head to record the intracranial pressure over several hours or days.
What Are Some Common Treatments?
In a patient confirmed to have symptoms consistent with normal pressure hydrocephalus, treatment is often recommended. The most common treatment is a shunt procedure
. A shunt is a small tube that is implanted into the ventricles of the brain and runs under the skin to another part of the body. It diverts the cerebrospinal fluid away from the head to somewhere else where it can be absorbed better. The most common site is the abdominal cavity, or peritoneum, so the procedure is often called a ventriculoperitoneal shunt, or VP shunt.
Shunt procedures help to relieve the symptoms of normal pressure hydrocephalus in some patients. However, not all patients will respond the same. Additionally, shunts can malfunction or become clogged, requiring replacement. A shunt is not a cure for the underlying disease, but it does improve the symptoms in many patients.
Occasionally another procedure is attempted in patients with NPH. An endoscopic third ventriculostomy is a procedure that creates an internal shunt by making a whole in one of the ventricles so that the fluid can drain to the space around the brain. No implanted catheter tube is left in place. However, while this form of treatment has been found to be very effective for many forms of hydrocephalus, its effectiveness in NPH has not been proven and many people feel it is not the most likely to improve a patient's symptoms.
Each patient is different. Therefore generalizations cannot be made about treatment for all patients with NPH or similar symptoms. Each patient should discuss their particular case and their treatment with their own treating physicians.
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This site is not intended to offer medical advice. Every patient is different, and only your personal physician can help to counsel you about what is best for your situation. What we offer is general reference information about various disorders and treatments for your education.