Lacunar strokes, like all strokes, are damaged areas in the brain. Like most strokes, they are caused when the flow of blood to an area of the brain is interrupted. Lacunar strokes are special because they involve small arteries near the center of the brain. These small arteries feed deep brain structures such as your basal ganglia, thalamus or pons.

Imagine a branching tree. A large branch from the tree trunk may gently divide into two smaller branches, which divide into even smaller twigs. This gradual size change is the way most blood vessels “branch” to reach the outer areas of your brain. But near to the base of the tree, a few very small branches may poke outwards sideways, directly from the bark on the trunk.

The arteries involved in a lacunar stroke branch sideways from large brain blood vessels just like this — like a small branch on a large tree trunk. Because of their direct connection to large arteries, these vulnerable vessels are not shielded from peaks of high blood pressure.

High blood pressure is the main cause of lacunar strokes. It can cause direct damage to small arteries. Or it can dislodge debris (small clumps or clots) into the circulation, which can block flow downstream in these small vessels.

“Lacuna” is a Latin word meaning “pool” or “cavity.” Lacunar strokes were named because autopsies revealed soft or liquefied areas in the brain where this type of stroke had happened.

Lacunar strokes can cause dramatic symptom. But they have a better recovery rate than other strokes.