WASHINGTON, Feb. 21 (Xinhua) -- German researchers have identified a simple walking test that may be able to accurately diagnose dementia.

The study, published on Wednesday in the journal Neurology, showed that seeing how fast a person can walk while doing something else at the same time can help differentiate whether someone has idiopathic normal pressure hydrocephalus (iNPH) or progressive supranuclear palsy (PSP), two different causes for dementia.

The iNPH, caused by excess fluid in the brain, can often be reversed but it is usually not diagnosed because it shares symptoms like walking, balance and thinking problems with other neurologic conditions, primarily the PSP. There is no cure for PSP, but treatment may help ease symptoms.

"It is important that people with idiopathic normal pressure hydrocephalus are accurately diagnosed so they can be treated, and their health can improve," said study author Charlotte Selge of the Ludwig Maximilian University of Munich in Germany.

"A simple walking test may help determine if a person has iNPH or PSP relatively early in the course of the disease. Our study found that adding another task while someone walks, and evaluating how it affects their walking ability, improves accuracy of the diagnosis."

The study involved 27 people with iNPH, 38 people with PSP, and 38 healthy people of similar sex and age. All were able to walk at least 30 feet without a walker or cane.

The researchers assessed participants' manner of walking, or gait, by having all participants walk on a pressure-sensitive carpet that was 22 feet long.

People were first asked to walk at three different speeds: slow, their preferred speed and as fast as possible. They were then asked to walk and count backwards at the same time and after that, to walk while carrying a tray.

The researchers found that walking while counting backwards resulted in a greater reduction of walking speed in those with PSP than in those with iNPH. Walking speed was reduced by 34 percent in those with PSP and by 17 percent in those with iNPH.

When walking while carrying a tray, gait worsened for those with PSP but actually improved for those with iNPH, which may mean the dual-task test wasn't challenging enough for those with iNPH, Selge said.

By just assessing walking, the researchers were able to accurately diagnose who had PSP and who had iNPH 82 percent of the time. But when adding both dual-task tests to the assessment, diagnostic accuracy increased to 97 percent.

"Our findings suggest that adding these dual-task tests would be an inexpensive and effective way to improve diagnosis of iNPH," said Selge.