Lipohyalinosis is a small-vessel

Blood vessel

The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

 disease in the brain. Originally defined by Fischer as 'segmental arteriolar wall disorganisation', it is characterised by vessel wall thickening and a resultant reduction in luminal

Lumen (anatomy)

A lumen in biology is the inside space of a tubular structure, such as an artery or intestine...

 diameter. Fischer considered this small-vessel disease to be the result of hypertension

Hypertension

Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

, induced in the acute stage by fibrinoid necrosis

Fibrinoid necrosis

Fibrinoid necrosis is a form of necrosis, or tissue death, in which there is accumulation of amorphous, basic, proteinaceous material in the tissue matrix with a staining pattern reminiscent of fibrin. It is associated with conditions such as immune vasculitis Fibrinoid necrosis is a form of...

 that would lead to occlusion

Vascular occlusion

Vascular occlusion is a sudden blockage of a blood vessel, usually with a clot. It differs from thrombosis in that it can be used to describe any form of blockage, not just one formed by a clot. When it occurs in a major vein, it can, in some cases, cause deep vein thrombosis. The condition is...

 and hence lacunar stroke. However, recent evidence suggests that endothelial dysfunction as a result of inflammation is a more likely cause for it. This may occur subsequent to blood-brain barrier

Blood-brain barrier

The blood–brain barrier is a separation of circulating blood and the brain extracellular fluid in the central nervous system . It occurs along all capillaries and consists of tight junctions around the capillaries that do not exist in normal circulation. Endothelial cells restrict the diffusion...

 failure, and lead to extravasation

Leukocyte extravasation

Leukocyte extravasation is the movement of leukocytes out of the circulatory system, towards the site of tissue damage or infection. This process forms part of the innate immune response, involving the recruitment of non-specific leukocytes...

 of serum components into the brain that are potentially toxic. Lacunar infarction could thus occur in this way, and the narrowing – the hallmark feature of lipohyalinosis – may merely be a feature of the swelling occurring around it that squeezes on the structure.

Hypertension is a strong causative factor. So-called deep-perforating arteries – relatively small arteries branching off of relatively large arteries (most commonly the lenticulostriate arteries from the middle cerebral artery) – are especially prone. Uncontrolled hypertension and diabetes are risk factors for this condition. Lacunar infarcts are a result of atherosclerosis

Atherosclerosis

Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...

(microthrombi) and lipohyalinosis. These affect the deep structures of the brain and may leave small (~5mm) cavity lesions.

Chronic familial lipohyalinosis is a rare inherited variant.