Though many studies have looked at the risk of a major stroke after a minor stroke, or a transient ischaemic attack (TIA), the results have been conflicting, with the seven-day stroke risk ranging from nil to 12.8 percent.
But an article to be published in the December issue of The Lancet Neurology confirms the risk as substantial, adding that the lowest risk of a follow-on stroke was among patients treated as emergency cases in specialist stroke units.
The article is based on a study by Matthew Giles and Peter Rothwell of Oxford University, who reviewed various studies on the risk of stroke within a week of a TIA to estimate overall stroke risk.
The duo combined results from 18 studies to show that the risk of stroke after a TIA is substantial at 5.2 percent - that is, one in 20 TIA patients will have a stroke within a week.
They also found that the lowest risks of stroke were seen in patients treated in specialist stroke units (0-9 percent) and the highest in those who did not receive urgent treatment (11 percent).
"Our study almost fully explains why the results of previous studies have been conflicting, and illustrates the importance of the methods used by a medical study when interpreting its results," the article says.
"These results support the argument that a TIA is a medical emergency and that urgent treatment in specialist units may reduce the risk of subsequent stroke."