Mark D. Johnson, MD, PhD
Hydrocephalus is a disorder of cerebrospinal fluid flow. The cerebrospinal fluid bathes the entire nervous system. It's produced in the brain. It flows through a series of chambers and is then reabsorbed. Any abnormality of this process, whether it's obstruction to flow, inability to be reabsorbed or overproduction can lead to the abnormal accumulation of spinal fluid, and this is called hydrocephalus.
The most common symptoms associated with hydrocephalus include, headaches, memory problems, walking difficulties and urinary incontinence.
Hydrocephalus can develop in people of all ages, and there are many different causes of hydrocephalus. For adults, the most common form of hydrocephalus is a type of hydrocephalus called normal pressure hydrocephalus. This usually develops in patients over the age of 60. The exact cause of this is unknown.
It’s been estimated that ten to 15 percent of all patients in nursing homes have normal pressure hydrocephalus, but the vast majority of those patients don’t know it. And their physicians have not recognized these symptoms and sent them to be evaluated.
There are many types of hydrocephalus. In general, they are diagnosed by physical examination, CT scans and in some cases a lumbar puncture where the pressure of the spinal fluid is actually measured. The primary treatment for hydrocephalus is placement of a drainage tube to bypass any area of obstruction. This internal drainage system is called a shunt, ventricular peritoneal shunt or ventricular pleural shunt. There is an alternative treatment for hydrocephalus that involves using a fiber optic scope to make a small bypass within the brain that allows the spinal fluid to be diverted.
Like most diseases, the response to treatment for normal pressure hydrocephalus varies from patient to patient. In about 25 percent of patients who are treated, the results can be nearly miraculous. Patients who are confined to a wheelchair, for example, are now able to walk unassisted. Patients who have urinary incontinence may see that incontinence resolve completely.
In an additional 50 percent of patients who are treated for this disorder, the symptoms improve significantly, although they may still have some issues with their balance or with occasional episodes of incontinence. The memory and cognitive difficulties that are associated with normal pressure hydrocephalus also improve, but these are symptoms that are the most difficult to treat.
The Adult Hydrocephalus Program at Brigham and Women's Hospital has a very robust research component. We are investigating at least five different areas of research pertaining to normal pressure hydrocephalus.
The first involves trying to identify factors that are associated with the development of this disease. One of the findings that has come out of this research is the strong correlation between high blood pressure and other cardiovascular diseases and the development of normal pressure hydrocephalus. It's unclear how hydrocephalus is associated with these cardiovascular risk factors, but there is a clear association and this has been confirmed by other investigators.
We are also looking at other behavioral factors such as exercise and diet and have found some relationship between those aspects of life and the development of normal pressure hydrocephalus, as well.
Our research program also involves a careful analysis of the cerebrospinal fluid. The purpose of that study is to identify biomarkers that can be used to improve the diagnosis of normal pressure hydrocephalus. Most patients who have this disorder are either undiagnosed or misdiagnosed as other disorders, such as Parkinson's disease or Alzheimer's disease. And currently, the best way to diagnose normal pressure hydrocephalus involves an admission to the hospital for three or four days, along with daily evaluations by physical therapists. So, we would like to develop a diagnostic tool that would allow diagnosis of this disorder by any physician without a hospitalization.
We're also looking at genetic factors that might predispose to the development of normal pressure hydrocephalus. And so, we have collected DNA from patients who have this disorder and we are now analyzing that DNA looking for mutations.
And finally, we would like to understand the mechanisms that underlie this disease. Essentially, nothing is known about why patients with normal pressure hydrocephalus develop walking difficulties, urinary incontinence or dementia. So, we've developed a preclinical model of normal pressure hydrocephalus and are combining that with state-of-the-art research and genetic techniques to try understand the neural basis.
The Adult Hydrocephalus Program at Brigham and Women's Hospital was made possible by a generous donation from one of our patients who has normal pressure hydrocephalus. That donation enabled us to establish a multidisciplinary clinical program that includes a computerized gait analysis system that's only used here and nowhere else. It also established the robust research program.
In addition, to that there is a very strong public awareness component. We are making a concerted effort to educate the public about the existence of this disorder and also to talk with other physicians so that they are more likely to recognize the symptoms and send patients for evaluation.