Stroke patients usually receive thrombolysis, an injection that dissolves a blood clot. But medication must be given within 4 hours of symptoms appearing. If it is, 32 percent of patients can regain mobility and leave the hospital within three months.
But it cannot be used for patients who have been on blood-thinning drugs, are suffering from hypertension, have a history of brain hemorrhage or undergone major surgery in three months previously.
Also, about 30 percent of people hit by an ischemic stroke have a large vessel clogged, and the mortality rate in this group is as high as 19 percent if they are treated with the injection alone.
But a minimally invasive neurosurgical procedure - an intra- arterial thrombectomy - can help patients unfit for the injection, says consultant Mona Tse Man-yu.
Queen Mary Hospital introduced the technique in 2005 to be in a time window of six hours after the onset of symptoms.
A microcatheter is inserted into a thigh artery and navigates to the cerebral vessel, Tse said.
"The microcatheter is like a straw," she explained, "and this straw is linked to a suction catheter. Like a vacuum cleaner, it sucks the blood clot and pulls it down the tube then out of the body."
Experience in other countries found it boosts recovery by 20 percent compared to traditional treatment.
Tse said Queen Mary once used the procedure on a patient awaiting a heart transplant. Such patients usually have heart functions supported by an external machine, and blood-thinning drugs are prescribed to lower the chances of clotting. But one patient still suffered from a stroke, so the procedure was used to remove the clot.
A week later the patient received a new heart. Tse said it would not have been possible without the earlier surgery.
A study of about 1,300 patients in countries including Germany, Australia, the United States and Canada shows a significant recovery rate when patients are treated with the injection and the thrombectomy.
Forty-six percent of them walked out of hospital whereas of 50 percent given the injection alone 26 percent did so.
Tse said QMH does 10 thrombectomies among about 600 to 700 stroke patients a year as exacting screening is vital.
Five or six other public hospitals in Hong Kong offer the surgery.
The complication rate is about 10 percent, Tse said, with serious consequences including hemorrhage or stroke at a new location.
She urged people to seek medical help immediately if they suspect they are suffering a stroke. Symptoms include slurred speech, a crooked smile and weak limbs.