From Baptist Health South Florida
3 min. read
It may come as a surprise that there’s a type of dementia that may be reversible. The cognitive symptoms of the brain disorder, normal pressure hydrocephalus, or NPH, is linked to excess cerebrospinal fluid the accumulates in the brain’s ventricles, which are fluid-filled chambers.
As brain ventricles enlarge with the excess cerebrospinal fluid, they can disrupt and damage nearby brain tissue, leading to difficulty walking, problems with thinking and reasoning, and loss of bladder control.
The combination of the primary symptoms of moderate dementia and trouble walking is why NPH is sometimes misdiagnosed as Alzheimer’s or Parkinson’s, explains Frank Vrionis, M.D., neurosurgeon and director of Marcus Neuroscience Institute, established at Boca Raton Regional Hospital, part of Baptist Health.
NPH refers to “normal pressure” because the excess fluid as measured during a spinal tap is often of normal pressure.
“Like a filter or a drain, the spinal fluid pathways get clogged as we grow older,” said Dr. Vrionis. “The absorption does not match the production. So, slowly but steadily, you get more fluid accumulating. And then when that happens, you start getting problems in the way that the brain functions. And typically, you get issues with walking, issues with memory, and issues with control of the bladder.”
Diagnosing and Treating NPH
There’s still quite a bit that’s unknown about NPH, but early intervention and surgical placement of a shunt in the brain to drain excess fluid could reverse the symptoms, making the NPH-related dementia potentially curable. NPH usually affects people in their 60s and 70s. It is estimated that less than 20 percent of people with the disease are properly diagnosed.
Doctors may use a range of tests, including brain scans (CT and/or MRI), a spinal tap or lumbar catheter, intracranial pressure monitoring, and neuropsychological tests, to help pinpoint a diagnosis of NPH and rule out other conditions.
“The size of the fluid cavities inside the brain varies quite a bit as we grow older, depending on the degree of atrophy,” said Dr. Vrionis. “And, therefore, there’s not a single size that you can say: Ok. This is a lot of fluid. Or this is too little fluid, or normal fluid. Because of that, the best way to diagnose this disease is by a test called spinal tap, or what’s called a lumbar drain. Because every other test can be unreliable. The clinical symptoms and the lumbar drain or LP are really the way to go about it diagnosing NPH.”
Successful treatment depends on many factors, including the progress of NPH.
“The fluid now cannot get absorbed over the brain, and then it goes through the brain itself,” said Dr. Vrionis. “So, we have a lot of debris going through the brain that may be causing amyloid deposits and other kinds of entanglements – and that’s the hallmark of Alzheimer’s.”
Surgical Placement of a Shunt
NPH can sometimes be treated with surgical insertion of a shunt — a long, thin tube that drains the excess cerebrospinal fluid from the brain. Surgery is most likely to help correct difficulties walking, but can improve cognitive issues as well and loss of bladder control. Shunting may not help everyone with NPH, to reverse the symptoms of NPH but may slowdown the progression. There’s uncertainty about how best to identify those most likely to benefit.
“Shunts have their own complications, potentially, and you can get infections because they’re foreign devices,” said Dr. Vrionis. “Or you can get what’s called subdural hematomas, because of the fact that you can over-drain the brain. Because they have complications, we do not want to put shunts in everybody. We go through the process of screening to try to prognosticate and make sure that somebody really needs it before we go into that procedure.”
But there are methods of minimizing the potential complications.
“We always start with a high setting of the valve,” he explains. “In other words, we try not to over-drain right away. We try to let the brain get used to the shunt, and kind of slowly increase the amount of fluid we allow to drain.”
To help determine if a patient can benefit from shunt surgery, a high-volume spinal tap may be used. In such a procedure, a large amount of spinal fluid is removed. Physicians then observe the individual for 30 to 60 minutes, looking for any improvements in walking or thinking and reasoning.
“If NPH persists for a long time, it can cause secondary changes to the brain that may not be reversible,” said Dr. Vrionis. “We know that if you intervene early on in the process, you have better results than if you intervene late in the process.”
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