A patient who suffered a minor stroke or TIA (transient ischemic attack) has a significant risk of experiencing a major stroke within a week, says an article in The Lancet Neurology, December issue. Minor stroke patients who are treated as emergency cases in specialist stroke units run the lowest risk of a major stroke soon afterwards.
The authors explain that although previous studies had investigated a possible link of major stroke after minor one or TIA, results have shown the risk to range from 12.8% to 0%, leading to problems in their interpretation. If reliable risk estimation were available the benefits of early treatment could be maximized, allowing effective planning of the provision of service, as well as justifying the investment in public education.
Dr Matthew Giles and Professor Peter Rothwell, Stroke Prevention Research Unit, University of Oxford, UK, examined all studies of major stroke risk within one week after TIA to estimate the overall stroke risk. They also examined study methods, settings, populations, treatments, and case mix.
Their research included 18 cohorts involving 10,112 patients. They worked out that the risk of major stroke within 7 days of a TIA is 5.2%, considered substantial – one in twenty patients who has a TIA will have a major stroke within a week. The authors explained that the variations in calculated risks were mainly due to study method, setting and treatment. They also found that the lowest risk of major stroke within seven days on a TIA were in studies of emergency treatment in specialist stroke units – here the risks were estimated to be 0.9%. The highest risks were among population-based studies without urgent treatment, 11%.
“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 risk of stroke reported amongst patients treated urgently in specialist units was substantially lower than risks reported among other patients treated in alternative settings. 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. This is particularly relevant in the UK, where TIA services are patchy and there are substantial delays to TIA patients receiving appropriate treatments,” the authors wrote.
*Quotes are from the author directly and cannot be found in the text of the article.
The results are consistent with (and include) the EXPRESS Study (Lancet 2007; 370: 1432-42) and SOS-TIA study (Lancet Neurology 2007; 6: 953-60). The results are also consistent with (but do not include, for methodological reasons) the FASTER study (Lancet Neurology 2007; 6: 961-69). By taking these four studies together, our understanding of the prognosis and effective treatment of TIA is advanced.
Written by׃ Christian Nordqvist