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

Background and Purpose In a group of patients with high-grade asymptom atic carotid artery stenosis, we prospectively determined the prevalen ce and radiological characteristics of clinically asymptomatic brain i nfarction evident on computed tomography. Risk factors and extent of c arotid disease were also determined. Methods Patients randomized into the Asymptomatic Carotid Atherosclerosis Study (ACAS) underwent a neur ological history, a detailed stroke/transient ischemic attack question naire, and a detailed neurological examination. Computed tomography s cans were examined by standardized criteria developed as part of a qua lity-control program supervised by a neuroradiologist. The presence, l ocation, and size of all cerebral infarctions evident by computed tomo graphy were determined. Results Among 1132 patients, 848 had no histor y of stroke or transient ischemic attack. One hundred twenty-six patie nts (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 dee p for 117 patients (72%), less than one-half lobe for 45 (28%), and on e-half to less than one lobe for 1 (0.5%). The silent infarcts were ev enly 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 trans ient ischemic attacks (34/139, 25%; P<.001). Conclusions Silent infarc tion in the setting of asymptomatic carotid stenosis is not uncommon, but silent infarctions are rarely sizable. The clinical significance o f silent cerebral infarction in patients with asymptomatic carotid art ery stenosis has yet to be established.