BASE-LINE SILENT CEREBRAL INFARCTION IN THE ASYMPTOMATIC CAROTID ATHEROSCLEROSIS STUDY

Background and Purpose In a group of patients with high-grade asymptomatic carotid artery stenosis, we prospectively determined the prevalence and radiological characteristics of clinically asymptomatic brain infarction evident on computed tomography. Risk factors and extent of carotid disease were also determined. Methods Patients randomized into the Asymptomatic Carotid Atherosclerosis Study (ACAS) underwent a neurological history, a detailed stroke/transient ischemic attack question naire, and a detailed neurological examination. Computed tomography scans were examined by standardized criteria developed as part of a quality-control program supervised by a neuroradiologist. The presence, location, and size of all cerebral infarctions evident by computed tomography were determined. Results Among 1132 patients, 848 had no history of stroke or transient ischemic attack. One hundred twenty-six patients (15%) had a silent infarct; 95 (11%) had one, 24 (3%) had two, and 7 (1%) had three or more infarcts. The infarct size was small and deep for 117 patients (72%), less than one-half lobe for 45 (28%), and one-half to less than one lobe for 1 (0.5%). The silent infarcts were evenly distributed ipsilaterally and contralaterally to the study artery but were significantly more frequent in the right hemisphere (P<.05). Factors associated with silent infarction were abnormal gait (P<.001), abnormal deep tendon reflexes or plantar responses (P=.038), but not degree of carotid stenosis. Silent infarction was less frequent among this totally asymptomatic cohort (15%) compared with those with transient ischemic attacks (34/139, 25%; P<.001). Conclusions Silent infarction in the setting of asymptomatic carotid stenosis is not uncommon, but silent infarctions are rarely sizable. The clinical significance of silent cerebral infarction in patients with asymptomatic carotid artery stenosis has yet to be established.