A small stroke deep within the brain (e.g., in the internal capsule, basal ganglia, thalamus, or pons) caused by damage to or a blockage of a tiny penetrating artery. Lacunar infarctions are associated with a kind of vascular damage caused by chronic high blood pressure called lipohyalinosis. They may be asymptomatic, showing up only on brain imaging, or may produce pure motor, pure sensory, ataxic, or mixed motor and sensory symptoms.