Abstract
The term “lacunar infarction” referred to small infarctions in the basal ganglia, internal capsule, thalamus, and brainstem, due to hypertensive small vessel disease. However, it has become common to refer to all small infarctions as lacunar. It is important to understand that true lacunes occur in a phylogenetically ancient part of the brain, the “vascular centrencephalon”, where short straight arteries with few branches transmit high blood pressure straight through to end-arterioles. The cortex is supplied by long arteries with many branches, so there is a very large blood pressure gradient in the brain. When blood pressure in the brachial artery is 117/75 mmHg, the pressure in the lenticulostriate artery would be 113/73, and the pressure in small parietal arterioles would be only 59/38 mmHg. Recent studies have reported that patients with a pulse pressure >60 mmHg and diastolic pressure <60 mmHg have a doubling of coronary risk and a 5.85-fold increase in stroke risk. This means that new low systolic targets being proposed will probably decrease the incidence of true lacunes, but increase small subcortical infarctions in the hemispheres. The pathogenesis of small vessel disease should be interpreted in the light of these blood pressure gradients.
Highlights
There is a widespread tendency to assume that small vessel disease in the brain is one single condition, but it is apparent that there are several different kinds of small vessel diseases
The purpose of this review is to focus on an aspect of small vessel disease that is seldom considered: Blood pressure gradients in the brain
The association goes in both directions: Strokes aggravate dementia, and amyloid aggravates strokes
Summary
There is a widespread tendency to assume that small vessel disease in the brain (ischemia due to arteriolar disease, as opposed to atherosclerosis or emboli) is one single condition, but it is apparent that there are several different kinds of small vessel diseases. Subcortical Infarcts and Leukoencephalopathy (CADASIL), it appears likely that there are at least three different kinds of small vessel disease, found in different regions of the brain: Deep/hypertensive, lobar/hypotensive, and periventricular/venous. It is clear that a stroke is a major contributor to dementia This is the case for the kinds of strokes associated with small vessel disease. Whitehead et al studied infarct size and cognitive dysfunction, comparing ischemia alone, with ischemia and injection of Beta amyloid. They found that infarct volumes were higher in the presence of amyloid compared with the ischemia alone. Infarct volume was significantly smaller 28 days after surgery, compared with 7 days after surgery. The mechanisms underlying the interactions of stroke, dementia, amyloid, and inflammation were reviewed in 2014 [3]
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