Periventricular lesions on MRI. Facts and theories.

Abstract

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.

Endothelial Function and White Matter Hyperintensities in Older Adults With Cardiovascular Disease

“…10 Furthermore, neuropathological studies have documented that chronic vascular injury in the blood vessels of the brain leads to atrophic changes immediately surrounding these damaged vessels. 36,37 These atrophic spaces become filled with extracellular fluid that then appears as WMH on MRI. Thus, it is possible that chronic impairment of the vasodilatory response may contribute, in part, to the development of WMH over time.…”

Neuropsychological Impairment Correlates With Hypoperfusion and Hypometabolism but Not With Severity of White Matter Lesions on MRI in Patients With Cerebral Microangiopathy

“…DWML are even present in a number of elderly persons without any neurological signs. 37 Fein et al 38 examined patients with extensive DWML on MRI and found no major cognitive or focal neurological deficits. On the other hand, van Swieten et al 39 observed that hypertensive patients with confluent DWML on T2-weighted MRI showed a more pronounced cognitive impairment than hypertensive patients with only "patchy or punctate" hyperin- tensities or than normointense patients.…”

Cranial computed tomographic observations in multi-infarct dementia. A controlled study.

“…Although some studies have shown a relation between these lesions and dementia, others have shown no such association. 31 The underlying pathophysiology of this white matter disease is thought to be vascular in origin. In select patients with motor and cognitive deficits, pathological study may show diffuse demyelination of the deep white matter, gliosis, necrosis, small subcortical infarcts, arteriolar sclerosis, and dilation of the ventricular system.…”