Lacunar infarcts are small (0.2 to 15 mm in diameter) noncortical infarcts caused by occlusion of a single penetrating branch of a large cerebral artery . These branches arise at acute angles from the large arteries of the circle of Willis, stem of the middle cerebral artery (MCA), or the basilar artery. Although this definition implies that pathological confirmation is necessary, diagnosis in vivo may be made in the setting of appropriate clinical syndromes and radiological tests.
Dechambre first used the term "lacune" in 1838 to describe softenings in subcortical regions of the brain found on autopsy . At the time, there was dispute regarding whether these lacunes were caused by encephalitis, a late phase of a small hemorrhage, or ischemic necrosis. Marie in 1901 first described a clinical syndrome associated with multiple lacunes, characterized by sudden hemiplegia with good recovery, a characteristic gait with small steps ("marche a petits pas de Dejerine"), pseudobulbar palsy, and dementia .
In the 1960s, careful clinicopathological correlations by Fisher generated the so-called "lacunar hypothesis," which suggested that lacunes are due to a chronic vasculopathy related to systemic hypertension, cause a variety of defined clinical syndromes, and imply a generally good prognosis .
The introduction of CT and MRI has generated data that both supports and opposes the lacunar theory [5,6]. Some authors have suggested abandoning the concept altogether [7,8]. Detractors of the lacunar hypothesis note the lack of animal data or an animal model of lacunar infarction and the demonstration of embolic sources from the heart, aorta, or large arteries in a substantial percentage of lacunar strokes [9,10]. Proponents concede that some small number of lacunes may result from emboli, but they point out that the proportion of embolic sources found in association with lacunar syndromes is far lower than for other ischemic stroke types and that there are clear clinical and epidemiologic reasons to separate lacunes from other ischemic stroke subtypes [10,11].
One of the major difficulties in interpreting these data stems from the inability of imaging techniques to show that an infarct was due to occlusion of a single penetrating artery. Furthermore, various studies have used different sets of criteria to define "lacunar infarcts" and the many lacunar syndromes [12,13]. However, continuing publications on the subject have demonstrated that the term "lacune" is clinically useful and has gained wide acceptance in the literature.