Abstract
Evidence of old cerebral infarction on magnetic resonance imaging (MRI) is common in acute stroke patients without a prior history of stroke. This experience led us to investigate the incidence of silent cerebral infarction (SCI) in the patients with essential hypertension, a well-known major predisposing factor for stroke. The incidence, number, size and localization of SCI on MRI (MARK-J, 0.1T) and the prevalence of risk factors for stroke were investigated both in 66 hypertensive patients (WHO stage I or II; 63±9 (mean±S.D.) years old) and in 42 age-matched normotensive patients (61±9 years old). Risk factors selected were as follows: diabetes mellitus, hypercholesterolemia, daily alcohol intake, cigarette smoking, obesity, cardiac disease (arrhythmia and ischemic heart disease), hyperuricemia and high hematocrit. In hypertensive patients, the relationships between the incidence of SCI and hypertensive damages in major organs were also investigated. SCI was found in 45 out of the 108 subjects studied and a total of 216 SCI lesions were detected. All of the SCI lesions were localized in the subcortical white matter or in the basal ganglia. All SCI lesions were smaller than 3cm in diameter and 201 lesions (93%) were smaller than 1cm. The incidence of SCI tended to be higher in hypertensive patients (47%) than that in normotensives (33%) and increased significantly with advancing age in hypertensives from 26.9% in the 50s to 86.7% in the 70s, while no significant increase was noted in normotensives. In the hypertensives, significantly higher incidence of SCI was noted in patients with hypertensive changes in major target organs (72-73% in patients with organ involvement vs. 33-39% in those without). With respect to the characteristics of SCI lesions in the normo- and hypertensive patients with SCI, the average number of SCI lesions was significantly higher in the hypertensives than that in normotensives (6.0 vs. 2.1) and SCI lesions in the hypertensives were more frequently detected in the brain areas supplied by perforating arteries than in normotensives (47% vs. 24%). As for the incidence of stroke risk factors, patients with SCI showed a significantly higher incidence of cardiac disease than those without SCI (22% vs. 4%), while no significant differences were noted in the incidence of the remaining risk factors between patients with and without SCI. These results clearly demonstrated that SCI was frequently seen in older hypertensive patients free of stroke symptoms especially when moderate hypertensive changes were revealed in the target organs. Furthermore, the higher incidence of SCI of the hypertensives in the brain areas supplied by the perforating arteries strongly suggested that hypertensive arterial changes might play a crucial role for the occurence of SCI, because characteristic hypertensive angionecrotic and/or arteriosclerotic changes are known to be frequently observed in the perforating arteries of the brain.
