1. From a cohort study, stroke risk was increased eight-fold when lesions both small and large were observed using MRI.
2. The presence of small cerebrovascular lesions was associated with a three-fold higher risk for subsequent stroke compared with no lesions.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Brain lesions identified on MRI that are larger than 3 mm are commonly referred to as subclinical brain infarctions (SBI). These SBIs, along with white matter hyperintensities (WMH), are associated with an increased risk for stroke. On the other hand, brain lesions less than 3 mm have an unknown effect on the patient’s stroke risk. This study evaluated the effect of lesion size on stroke incidence, stroke-related mortality and all-cause mortality in a middle-aged patient cohort. The resulting analysis showed that, compared with an absence of lesions, the presence of lesions <3 mm was associated with a three-fold higher risk, the presence of lesions ≥3 mm was associated with a two-fold higher risk, and the presence of lesions of both sizes was associated with an eight-fold higher risk for stroke. The primary risk factor associated with the occurrence of brain lesions <3 mm only was hypertension. The study was limited in that it did not have a large number of stroke events or stroke-related deaths. Although results from larger studies are still needed, this study showed that brain lesions <3 mm are associated with stroke and mortality and could help identify patients with increased stroke risk earlier.
In-Depth [prospective cohort]: This study examined participants in the Atherosclerosis Risk in Communities (ARIC) study cohort who were aged 55 years or older, either Caucasian or African American, and had no previous history of stroke. Participants in the study underwent a brain MRI during the period covering 1993 to 1995 and were then followed for an average of 14.5 years. The number of clinical strokes and deaths were obtained via surveillance methods through the year 2010. The presence of brain lesions <3 mm was associated with a hazard ratio (HR) of 3.47 for stroke (95% CI, 1.86 to 6.49) compared to no lesions, the presence of brain lesions ≥3 mm had a HR of 1.94 (CI, 1.22 to 3.07), and the presence of lesions of both sizes had a HR of 8.59 (CI, 4.69 to 15.73). Hypertension was the primary risk factor associated with presence of lesions <3 mm only (RRR, 2.17 [CI, 1.14 to 4.13]).
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