Overview of Lacunes
The lacunar hypothesis proposes that (1) symptomatic lacunes present with distinctive lacunar syndromes and (2) a lacune is due to occlusion of a single, deep penetrating artery generated by a specific vascular pathology.
The above concept is controversial because different definitions of lacunes have been used. Lacunes may be confused with other empty spaces, such as enlarged perivascular (Virchow-Robbins) spaces, in which the specific small-vessel pathology is occasionally absent. Originally, lacunes were defined pathologically, but lacunes are now diagnosed on clinical and radiologic grounds.
This problem is compounded by the present inability to image a single penetrating artery.
Much of our current knowledge of lacunar strokes is due to Fisher’s prior cadaveric dissection of postmortem stroke patients. He found that most symptomatic lacunar strokes are due to the occlusion of penetrating arteries of 200-800 μm in diameter, whereas those with smaller-diameter penetrating artery infarcts tended to be asymptomatic.
Another study suggests that by using a gene expression profile, small deep infarct (SDI) differences between lacunar and nonlacunar strokes can be distinguished. SDIs of unclear cause are typically of nonlacunar etiology. This knowledge leads researchers to believe that complete workups of SDIs are critical to identifying potential cardioembolic and arterial causes of strokes.
Definition of lacunes
Lacunes may be defined as small subcortical infarcts (< 15 mm in diameter) in the territory of the deep penetrating arteries; these lesions may present with specific lacunar syndromes or they may be asymptomatic. Unfortunately, the 5 classic lacunar syndromes established by Fisher and their radiologic appearances are not specific for lacunes. Lacunes occur most frequently in the basal ganglia and in the internal capsule, thalamus, corona radiata, and pons.
Incidence of lacunar strokes
In the United States and other Western nations, lacunes account for 15-25% of all ischemic strokes.
However, differences in the reported incidence rates of lacunar strokes between US and European studies may be due in part to different definitions used in the studies. In two community-based studies in the United States, the annual incidence rates of lacunar strokes were 13.4 and 19.5 cases per 100,000 population. However, two European community-based studies found higher annual incidence rates (31.7 and 53 cases per 100,000 population).
A study by Rukn et al indicated that among ischemic strokes in Middle Eastern and North African countries, lacunar strokes are the second most common type (24.1%).
The incidence of lacunar strokes increases with age (mean age of first lacunar stroke, 65 y), and men may be affected more than women. Some studies have also found higher frequencies of lacunar strokes in black persons, Mexican Americans, and Hong Kong Chinese.