Silent infarction in acute stroke patients. Prevalence, localization, risk factors, and clinical significance: the Copenhagen Stroke Study.

BACKGROUND AND PURPOSE: Our objective was to study age-specific prevalence, computed tomographic (CT) characteristics, risk factors, and the prognostic influence on stroke outcome of silent infarction in acute stroke patients. METHODS: The study was prospective and community-based and included 801 acute stroke patients, of whom 587 had first-ever stroke. A CT scan was performed in 500 (85%) of the 587 patients with first-ever stroke. CT was reviewed blindly, and infarcts were classified according to patient history as silent or symptomatic. Patients were evaluated initially with the Mini-Mental State Examination (MMSE) and weekly with both the Scandinavian Stroke Scale (SSS) and the Barthel Index (BI) from the onset of stroke to completion of rehabilitation. CT characteristics, risk factors, and stroke outcome were compared in stroke patients with and without silent infarction. RESULTS: The prevalence of silent infarction in patients with first-ever stroke and recurrent strokes was similar, at 29% (group aged 0 to 54 years, 16%; 55 to 64 years, 22%; 65 to 74 years, 30%; 75 years or older, 33%). Silent infarcts were small and subcortical. Independent risk factors were increasing age (odds ratio OR, 1.95 per 25 years; confidence interval CI, 1.19 to 3.15), hypertension (OR, 1.75; CI, 1.13 to 2.70), claudication (OR, 1.74; CI, 1.01 to 3.00), and male sex (OR, 1.72; CI, 1.12 to 2.64); other stroke risk factors such as atrial fibrillation and former transient ischemic attack were not independent risk factors. Patients with and without silent infarction did not differ in frequency of prestroke home care (P = .2). MMSE (P = .56), initial BI (P = .62) and SSS score (P = .08), BI (P = .85) and SSS score (P = .75) after completion of rehabilitation, or in the speed of recovery (P = .85). Length of hospital stay, mortality rate, and discharge rate to nursing home also did not differ between the two groups. CONCLUSIONS: This community-based study shows that silent infarction in stroke patients is more related to certain stroke risk factors than others and that silent infarction does not seem to influence the prognosis of stroke.