A diagnosis of Alzheimer's or other types of dementia portends a bleak future. But for a fortunate few, there may be a reprieve.

Normal pressure hydrocephalus, a disease caused by excess water on the brain that primarily strikes older adults, has symptoms that mimic Alzheimer's, with one major difference.

"It is a very treatable and reversible condition that is in the great majority of cases unrecognized," says Dr. Norman Relkin, associate professor of neurology and neuroscience at Weill Cornell Medical College in Manhattan. "It's one of those things that even doctors don't know about, which, when discovered, can lead to a very happy ending."

Because the condition is a disease that gets progressively worse, the best outcomes occur when it is treated early. "There's kind of a window of opportunity for intervening," Relkin says.

Normal pressure hydrocephalus, often referred to as NPH, can be definitively identified only by a brain scan or an MRI. There is no cure, but it can be effectively treated by surgically implanting a shunt that regulates brain fluid. The surgery's costs are covered by Medicare.

Because the condition has been discovered relatively recently, research on its prevalence and the number of patients with the disease who have been misdiagnosed with Alzheimer's is not definitive. The Hydrocephalus Association estimates as many as 375,000 older Americans have the condition. Relkin, while not citing a figure, says, "Numbers could well rise into the hundreds of thousands if all cases were found and treated."

There are some tantalizing clues how the symptoms differ from Alzheimer's. People who have the condition tend to exhibit a shuffling, "glue-footed" gait where it looks as if their feet are stuck to the ground. "They don't bend at the ankles and lift their legs," Relkin says. "Their steps become very short."

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Also, memory problems are subtly different. In Alzheimer's, memory loss is characterized by rapid forgetting. While there's forgetfulness with normal pressure hydrocephalus sufferers, they respond better to reminders. "It's more that the information is still in their brain, but they're having trouble accessing it," Relkin says.

What is most amazing is the rapid recovery once someone with the condition is successfully treated. Often, these patients were believed to be suffering with Alzheimer's, and some were even institutionalized. After surgery, many resume normal lives, a gratifying outcome for patients, their families and Relkin himself.

"For someone like myself, who has worked in the Alzheimer's field for quite some time, it's a breath of fresh air when we can take people who are severely impaired and give them back their lives," he says.

For more information about normal pressure hydrocephalus, go to nwsdy.li/nph.