Hydrocephalus Association

Normal Pressure Hydrocepalus

 Hydrocephalus is a condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF).  CSF is produced within chambers in the brain called ventricles.  The fluid circulates around the brain and spinal cord to cushion and support the central nervous system.  CSF is constantly produced and resorbed at a rate of approximately one pint per day.  Spinal fluid can build up in certain circumstances and the ventricles, or chambers, become larger than normal.  This can be seen on a CAT scan or MRI of the brain.  The excessive build up of spinal fluid is called hydrocephalus, and is associated with an increased pressure inside the brain.  Hydrocephalus can occur from a blockage of the normal circulation of fluid, a blockage of resorption, or an over production of CSF.
 

Normal Pressure Hydrocephalus (NPH) is a syndrome most commonly seen in older adults.  Spinal fluid builds up in the brain, and the ventricles become enlarged, but it is not necessarily associated with increased pressure, thus the term, Normal Pressure Hydrocephalus.  The syndrome has three main symptoms:  gait disturbance, mild dementia, and impaired bladder control.  Although NPH could occur after brain trauma or infection, most cases of NPH have no known cause.

Gait imbalance, memory loss, and urinary urgency are often associated with the aging process and may be difficult to differentiate from NPH.  Alzheimer's disease, for example, is also associated with dementia, memory loss, and urinary dysfunction.  Alzheimer's oved one suffers from Normal Pressure Hydrocephalus, please involve your family physician, a neurologist, and a neurosurgeon to help with the diagnosis.

A shunt tube can be inserted which drains excess spinal fluid from the brain into the abdominal cavity.  Symptoms of gait imbalance, cognition, and urinary function may improve by draining the excess fluid.  Patients who may benefit from a shunt tube can undergo a trial before surgery to determine if they are likely to get better from the shunt. A small drainage tube is inserted into the lumbar spine to drain spinal fluid, and the patient is examined for improvements in neurologic function. 

NPH can be difficult to diagnose based on a clinic exam and brain imaging alone.  Additional tests may be needed, such as a CSF flow study, or an evaluation while undergoing temporary external drainage of CSF.  It is important to consult a team of specialists in Normal Pressure Hydrocephalus to obtain a correct diagnosis.

Normal Pressure Hydrocephalus is not Alzheimer's disease.  Alzheimer's disease, while a common cause of dementia and also associated with brain cell loss, does not respond to shunt surgery.  Specialists in Alzheimer's disease include a neurologist, and a neuron-psychologist. 

Please note that Normal Pressure Hydrocephalus differs from hydrocephalus seen in children.  The disease state and treatment are vastly different and should not be confused with one another.

Not all patients benefit from a CSF shunt.  Ultimately, the best predictor of success is the external lumbar drain test.  The external lumbar drain test involves inserting a very small tube into the low back near the spinal canal in order to drain CSF into an attached collection chamber outside the body.  Although the tube is placed into the lumbar spine, it is not near the spinal cord because the cord is higher up in the canal.  The patient stays in the hospital during this time for approximately 3-4 days.  The tube is placed under local anesthesia and usually takes just a few minutes.  Once established, the nurse drains 10 cc (2 teaspoons) of CSF every hour.  A physical therapist, and a neurologist specializing in NPH evaluate the patient for improvements in walking, bladder control, and memory function during the hospital stay.

The lumbar drain is removed on the fourth day and the patient is released home.  Close observation of the patient's function at home as noted by family members is valuable input during this time.  Patients that achieve a measurable benefit from the CSF drainage are deemed potential candidates for the CSF shunt surgery.

A shunt is a tube that redirects cerebral spinal fluid from the brain to another part of the body where the fluid is reabsorbed.  A ventriculoperitoneal (VP) shunt is most commonly used at USC.  The tube is placed into the brain ventricle (a chamber inside the brain) and travels beneath the skin to the peritoneal (abdominal) cavity.  The procedure is done under general anesthesia meaning that the patient is asleep.  Expect a 2 day hospital stay, and a post operative office visit approximately 10 days after surgery. 

As the incision heals, the patient will follow up with the neurological specialist in addition to the surgeon.  The neurologist can make adjustments to the shunt valve based upon the patient's symptoms and examination in the office.  Adjusting a shunt valve is easy and painless, taking only a few seconds with a doughnut-shaped magnet. All surgeries carry a degree of risk, even if the probability is low.  And there is no guarantee that the CSF shunt surgery will improve symptoms, although, a successful lumbar drain test is a strong indication that shunt surgery would be beneficial.  Please consult with the surgeon for a clear understanding of all risks, benefits, and treatment alternatives.