From the Guidelines
The size cutoff for a lacunar infarct is typically less than 1.5 cm in diameter, as defined by the American Heart Association/American Stroke Association guideline from 2021 1. This specific size criterion helps differentiate lacunar infarcts from larger territorial infarcts, which involve occlusion of major cerebral arteries. Lacunar infarcts result from occlusion of a single penetrating artery that supplies the deep brain regions, most commonly due to lipohyalinosis or microatheroma of these small vessels. The small size of lacunar infarcts corresponds to their clinical presentation as lacunar syndromes, which include pure motor hemiparesis, pure sensory stroke, sensorimotor stroke, ataxic hemiparesis, and dysarthria-clumsy hand syndrome. When evaluating brain imaging, particularly MRI, this size cutoff is an important diagnostic feature, though the clinical presentation and location are equally important in making the diagnosis of lacunar stroke. Some studies have suggested smaller size cutoffs, such as less than 1 cm in size 1, but the most recent and highest quality evidence supports the 1.5 cm cutoff. Key points to consider when diagnosing lacunar infarcts include:
- Location in deep brain structures such as the basal ganglia, internal capsule, thalamus, or brainstem
- Size less than 1.5 cm in diameter on CT or MRI
- Clinical presentation as a lacunar syndrome
- Absence of evidence of a concomitant cortical infarct.
From the Research
Size Cutoff for Lacunar Infarct
- The size cutoff for lacunar infarct is a topic of debate, with some studies suggesting that the traditional cutoff of 15 mm may not be valid 2, 3.
- A study published in 2007 found that the infarct diameter in patients with small vessel disease (SVD) was not significantly different from those with middle cerebral artery disease (MCAD), suggesting that the 15 mm size criterion may not be a reliable indicator of lacunar infarction 2.
- Another study published in 2016 found that the size of lacunar infarction may be dependent on the branching order of the lenticulostriate arteries, and that the median length of lesions was 11.1 mm on DWI images 4.
- A study published in 2007 suggested that a grading system, rather than a dichotomizing system, may be more effective in predicting lacunar stroke, taking into account factors such as infarct size, stroke syndrome, and unilateral multiple deep infarcts 3.
- The evidence suggests that the size cutoff for lacunar infarct is not a clear-cut value, and that other factors such as clinical presentation, imaging findings, and underlying vascular disease should be considered in the diagnosis and management of lacunar infarction 5, 4, 2, 3.