Susceptibility-weighted imaging for cerebral microbleed detection in super-acute ischemic stroke patients treated with intravenous thrombolysis

Abstract

Objective: Fast magnetic resonance imaging (MRI) and susceptibility-weighted imaging (SWI) methods may provide more accurate detection of the highly variant time window for successful intravenous (IV) thrombolytic drug treatment (averaging 3 hours) for cerebral microbleeds (CMBs) in acute stroke patients.

Methods: This prospective study applies fast MRI and SWI for examination of 279 prescreened ischemic stroke patients within 12 hours of stroke onset. One hundred and sixty-two (58·1%) of 279 patients were diagnosed with super-acute ischemic stroke with restricted diffusion, hyperintense diffusion-weighted imaging signals, and no ischemic change in T2-weighted imaging, fluid-attenuated inversion recovery, or T1-weighted imaging signals. Recombinant tissue plasminogen activator IV thrombolysis was administered to 113 (69·75%) patients (thrombolysis group). All patients underwent regular sequence MRI and SWI follow-up.

Results: Computed tomography and MRI sequence scans revealed hemorrhagic transformations in 13 (11·50%) thrombolysis and four (8·16%) non-thrombolysis group patients. MRI-guided thrombolysis treatment produced no significant differences between the two groups. SWI revealed new CMBs in 46 (40·70%) and nine (18·37%) thrombolysis and non-thrombolysis group patients, respectively. Significantly better National Institutes of Health stroke scale (24 hours) (P<0·05), modified Rankin scale (90 days) (P<0·01), and life quality Barthal index scores were observed in CMB patients (P<0·01).

Conclusions: SWI revealed higher CMB incidence and clinical improvement in recombinant tissue plasminogen activator IV thrombolysis-treated super-acute ischemic stroke patients, suggesting that CMBs may indicate vascular re-canalization/reperfusion. Thus, SWI can be applied to extend individual patient windows for thrombolytic treatment beyond general recommendations of treatment within 3 hours, allowing treatment up to 12 hours from stroke onset.

Keywords:

• Magnetic resonance imaging
• Susceptibility-weighted imaging
• Cerebral microbleeds
• Thrombolysis
• Ischemic stroke

We are thankful for the support and funding provided by the Key Discipline Construction Project of the Pudong Health Bureau of Shanghai (grant no. PWZXK2010-03), Outstanding Leader Training Program of the Pudong Health Bureau of Shanghai (grant no. PWR12010-02), Research Grant for Health Science and Technology of the Pudong Health Bureau of Shanghai (grant no. PKJ2010-Y28, PW2009A-12), and the National Eleven-Fifth Scientific and Technological Brainstorm project (grant nos. 2006BA101A11 and 2007BA105B07).