Better diagnosis and treatment over the last 30 years have considerably reduced the risk of dying from a highly fatal type of aneurysm, Dutch scientists reported on Thursday.

Techniques such as CT and MRI scans are now widely used in the developing world to detect aneurysms but it was not known how big an impact these tests and other improvements such as dedicated stroke units have had.

To find out, the team reviewed data on nearly 9,000 patients worldwide and found better treatment and diagnosis appear to have cut the risk of dying from a so-called subarachnoid hemorrhage from 51 percent in 1973 to just 35 percent in 2002.

"In future, (deaths) after (aneurysms) might decrease even more owing to new diagnostic and therapeutic methods," Dennis Nieuwkamp and colleagues from the University Medical Center in Utrecht in the Netherlands wrote in the journal Lancet Neurology.

Subarachnoid hemorrhages, which are a bursting of a blood vessel on the surface of the brain, affect only about eight in 100,000 people every year in wealthy countries.

But the aneurysms place a big burden on society because they kill many patients, while survivors are often disabled and dependent on somebody to care for them.

Nieuwkamp and his team reviewed 33 studies from 19 countries between 1973 and 2002 and adjusted for factors such as age and sex while also looking at regional differences.

They said the new technology had paid off. Aside from Japan where 12 percent fewer people died, there were no regional differences.

The researchers suggested that the difference in Japan might be due to how quickly people were admitted to the hospital for early treatment of an aneurysm.