A study from the University of Hong Kong (HKU) on Tuesday showed that more than a third of stroke patients who were treated beyond the traditional six-hour golden period had recovered well, offering hope to those once thought untreatable.

The researchers studied more than 50 stroke patients who were treated beyond six hours, with the most notable case being a patient who was treated 22 hours after his stroke.

One of the HKU researchers, Associate Professor of Surgery Kevin Cheng, explained that the key to this medical breakthrough lies in advances in imaging technology, which now allows doctors to assess the proportion of brain cells that can be saved, enabling more targeted interventions.

"In the past, if we just base on a plain CT scan, we cannot estimate the area of the brain having damage. We can just see if there is any blood," he said

"But with the advancement in the CT perfusion, we can differentiate...which part of the brain is still salvageable and the total volume and the mismatch ratio. So these factors are very accurate and can help us to accurately differentiate those patients who can benefit."

Acute ischaemic stroke is caused by a blockage in an artery that supplies blood to the brain. Brain cells can quickly die while the flow of oxygen and nutrients is restricted, leading to loss of brain function, paralysis, speech problems and even death.