Prognosis of vertebrobasilar transient ischaemic attack and minor stroke

Vertebrobasilar (VB) territory transient ischaemic attacks (TIAs) and minor strokes are perceived to have a better prognosis than carotid territory events, and are sometimes managed less aggressively. However, this notion stems mainly from a few small studies in the 1960s and 1970s, and has not been systematically tested. We therefore identified all published studies of prognosis after TIA or minor stroke using MEDLINE and EMBASE, and hand-searching reference lists and relevant journals. In addition, we attempted to include all available individual patient data (IPD) from studies that had not published outcome data by territory of presenting event. Odds of recurrent events were calculated within studies and combined by fixed-effects meta-analysis. Heterogeneity between studies was calculated using the chi2 method. We stratified the analysis by time interval between presenting event and inclusion in study, and by study setting (population-based, published hospital-based and unpublished hospital-based). Publication bias was tested for by linear regression of the standard normal deviate against precision. Eight hundred and twenty abstracts were reviewed, and 304 papers were considered in detail. Of these, 43 studies representing 36 independent cohorts (12,196 patients) reported outcomes by territory of presenting event. IPD from five studies (4643 patients) were also included. The following results compare relative risks of VB with carotid events. Studies including the acute phase (up to 7 days) after the presenting event found a higher relative risk of subsequent stroke in patients with VB events odds ratio (OR) 1.47, 95% confidence interval (CI) 1.1-2.0, P = 0.014. Conversely, studies mainly recruiting after the acute phase found a lower relative risk (OR 0.74, 95% CI 0.7-0.8, P = 0.00001). In published hospital-based studies, the risk of recurrent stroke was lower for patients presenting with VB events (OR 0.68, 95% CI 0.6-0.8, P < 0.00001). However, there was no difference in hospital-based IPD (OR 1.02, 95% CI 0.8-1.3, P = 0.91). Moreover, in population-based studies, patients with VB events had a higher risk of stroke (OR 1.48, 95% CI 1.1-2.0, P = 0.025). There was no within-stratum heterogeneity. There was no difference in the risk of fatal stroke (OR 1.04, 95% CI 0.8-1.4, P = 0.90). Therefore, we found no evidence that patients presenting with VB events have a lower risk of subsequent stroke or death compared with patients presenting with carotid TIA or minor stroke. Indeed, their risk of stroke is probably higher in the acute phase. Patients with VB events require active preventive treatment.