Silent Brain MRI Infarcts and Subsequent Stroke Type In the Cardiovascular health Study
Objective: Silent infarcts seen on cranial MRI scans are a risk factor for subsequent clinical stroke in the elderly. This study examines the type of clinical strokes seen in those with silent infarcts. Methods: Cranial MRI examination was completed on 3324 Cardiovascular Health Study (CHS) participants aged 65+ who were without a prior history of clinical stroke. Incident strokes were identified over an average follow-up of 4 years and classified as hemorrhagic or ischemic. Ischemic strokes were further subdivided into lacunar, cardioembolic, atherosclerotic or other/unknown. Results: Silent MRI infarcts >3mm were found in approximately 28% (n=923). Of these, 7% (n=67) subsequently had a clinically evident stroke. The characteristics of the silent MRI infarcts in those who sustained an incident stroke were as folows: 56 had only subcortical infarcts, of which 55 were <20mm; 4 had only cortical infarcts; and 7 had both cortical and subcortical infarcts. Of those with only subcortical silent MRI infarcts, 16% (n=9) went on to a hemorrhagic stroke and 84% (n=47) sustained an ischemic stroke. The ischemic strokes were subtyped as 12 cardioembolic, 3 lacunar, 2 atherosclerotic and 30 unknown/other. Considering only those with cortical silent infarcts, either alone or in combination with subcortical infarcts, there was 1 hemorrhagic stroke and 10 ischemic strokes. Half of the ischemic strokes were cardioembolic and half were unknown type. Conclusion: Elderly individuals with silent subcortical infarcts who go onto subsequent stroke may be at risk not only for lacunar infarcts but also cardioembolic or hemorrhagic strokes.