Does microbleed predict haemorrhagic transformation after acute atherothrombotic or cardioembolic stroke?

OBJECTIVES Cerebral microbleeds (MBs) are known to be indicative of bleeding-prone microangiopathy and may predict incident intracerebral haemorrhage. However, there is controversy concerning the causal relationship between the presence of MBs and haemorrhagic transformation (HTf) after ischaemic stroke. METHODS Of the 1034 patients with acute ischaemic stroke who were consecutively admitted to our hospital, 377 patients with stroke due to large-artery atherothrombosis or cardioembolism were selected for participation in this study. We examined the MBs using T2*-weighted gradient-echo MRI performed within 24 hours after admission, and the incidence of HTf was assessed using follow-up brain MRI during the hospitalisation period. RESULTS Of the 377 patients with stroke, 234 were male (62.1%) and the mean age was 66.2 +/-11.7 years. MBs were initially found in 109 patients (28.9%), and newly incident HTf was noted during the hospitalisation period in 74 patients (19.6%). The presence of MBs was not increased in the patients with HTf (24.3% vs. 30.0% in the patients without HTf; p = 0.331). In addition, the number of MBs was not higher in the patients with HTf (0.7+/-1.5 vs. 1.8+/-8.1; p = 0.234). This lack of significance between MBs and HTf persisted after stratification by stroke mechanism. CONCLUSIONS This study suggests that underlying MBs do not predict incident HTf after acute ischaemic stroke. The clinical significance of MBs should be differentially evaluated according to the type of disease (intracerebral haemorrhage vs. HTf).