The pathophysiology of Lacunar infarcts are:

The term lacunar infarction refers to infarction following atherothrombotic or lipohyalinotic occlusion of a small aery (30-300 m) in the brain. The aeries comprising the circle of Willis, the basilar and veebral aeries all give rise to 30- to 300-m branches that penetrate the deep gray and white matter of the cerebrum or brainstem. Each of these small branches can occlude either by atherothrombotic disease at its origin or by the development of lipohyalinotic thickening. Thrombosis of these vessels causes small infarcts that are referred to as lacunes. These infarcts range in size from 3 mm to 2 cm in diameter. Hypeension and age are the principal risk factors. Ref: Harrison's Internal Medicine, 18th Edition, Page 3271, 3276