P atchy subcortical lesions are frequently identified on magnetic resonance imaging (MRI) of the brain in the elderly. 1 -4 On computed tomography (CT) these lesions appear as periventricular zones of lucency and have been termed "leuko-araiosis" by Hachinski and colleagues.
5Despite limited knowledge of the pathological correlates of the lesions, there has been speculation about their nature, pathophysiology, and clinical significance.Epidemiology Subcortical MRI lesions are most commonly seen in the elderly, occurring in 30-92% of patients older than 60 years of age 1 -2 and also in 22% of persons under the age of 40.2 The lesions are found scattered throughout the deep cerebral white matter, notably in the frontal and parieto-occipital periventricular regions, and basal ganglia, especially the globus pallidus and putamen. On T 2 -weighted MRI, the lesions are hyperintense and may appear as thick rims surrounding the lateral ventricles, as caps around the poles of the lateral ventricles, as unifocal patches, or as multifocal subcortical patches that at times are confluent ( Figure I).
6Risk factors associated with these lesions include old age, a history of ischemic cerebrovascular disease, and hypertension.2 -7 -9 With one exception, 10 studies have shown no significant association between these lesions and diabetes, cardiac disease, and carotid disease. However, these studies lack statistical power. There is a high incidence of subcortical MRI lesions in patients with clinically suspected Alzheimer's disease (AD) and senile dementia of the Alzheimer type (SDAT) regardless of their vascular risk factors.