Microbleeding on MRI as a Marker for Hemorrhage After Stroke Thrombolysis
To the Editor:
We noted with interest the article by Dr Kidwell et al,1 who describe an MRI application that detects microbleeds. Kidwell et al propose that this technique can identify patients who might be at high risk for hemorrhagic complications, if intravenous or intra-arterial thrombolysis is given. We agree that this application merits further study and have recently seen an example of asymptomatic hemorrhage after thrombolysis, in an intravenous tissue plasminogen activator (IV tPA)–treated patient. This 76-year-old female had no evidence of hemorrhage on pretreatment noncontrast CT. IV tPA was initiated 149 minutes after onset of symptoms, because of persisting right hemiplegia and global aphasia. MRI was performed 25 minutes after tPA infusion was initiated. Six microbleeds were seen on T2*-(susceptibility) weighted image using a 3-Tesla MRI scanner (Signa Medical Systems) as illustrated in Figure 1. The following day, CT brain scan was repeated, identifying an asymptomatic post-tPA hemorrhage. This was in the general area where a microbleed was visualized initially (Figure 2). This case example supports the claim by Kidwell et al of an association between microbleeding and tPA-related hemorrhage. Imaging at 3 Tesla has greater sensitivity to magnetic susceptibility and, therefore, may increase the sensitivity in identifying these lesions. We would also note that the identification of microbleeds could predict long-term complications of anticoagulation. Our patient with multiple microbleeds received long-term anticoagulation for chronic atrial fibrillation, which was presumed to be the cause of her stroke. This decision is a problematic one, especially when considering that warfarin-related intracerebral hemorrhage occurs in approximately 0.2% to 0.6% of treated patients.2 If an elderly population has a rate of microbleeding in the range of 5%,3 as previous studies have suggested, this MRI finding could also represent an important predictor of this serious long-term complication.
Larger-scale studies are needed to evaluate if the presence of microbleeds is useful in predicting patients who are at a higher risk for intracerebral hemorrhage from thrombolysis or long-term anticoagulation therapy.
- ↵Kidwell CS, Saver JL, Villablanca JP, Duckwiler G, Fredieu A, Gough K, Leary MC, Starkman S, Gobin YP, Jahan R, Vespa P, Liebeskind DS, Alger JR, and Vinuela F. Magnetic resonance imaging detection of microbleeds before thrombolysis: an emerging application. Stroke. 2002; 33: 95–98.
- ↵Rosand J, Hylek EM, O’Donnell H, Greenberg SM. Warfarin-associated hemorrhage and cerebral amyloid angiopathy: a genetic and pathologic study. Neurology. 2000; 55: 947–951.
- ↵Roob G, Schmidt R, Kapeller P, Lechner A, Hartung HP, Fazekas F. MRI evidence of past cerebral microbleeds in a healthy elderly population. Neurology. 1999; 52: 991–994.