From the Guidelines
A lacunar infarct is typically defined as a small subcortical infarct with a maximum diameter of less than 1.5 cm. This definition is based on the most recent guideline from the American Heart Association/American Stroke Association, published in 2021 1. The size cutoff of less than 1.5 cm is crucial for distinguishing lacunar infarcts from larger territorial infarcts and has implications for clinical classification, treatment decisions, and prognosis assessment. Some key points to consider about lacunar infarcts include:
- They occur in the deep regions of the brain, specifically in the territory of penetrating arteries that branch from larger cerebral vessels.
- They result from occlusion of small penetrating arteries, often due to lipohyalinosis or microatheroma formation related to chronic hypertension or diabetes.
- Despite their small size, lacunar infarcts can cause significant neurological deficits depending on their location, including pure motor hemiparesis, pure sensory syndrome, sensorimotor stroke, ataxic hemiparesis, or dysarthria-clumsy hand syndrome.
- Modern neuroimaging techniques like MRI with diffusion-weighted imaging are particularly useful for detecting these small infarcts, as stated in the guideline 1. The guideline provides a conceptual representation of ischemic stroke subtypes, including lacunar stroke, and emphasizes the importance of accurate diagnosis and classification for effective management and prevention of stroke 1.
From the Research
Size Cutoff of Lacunar Infarct
- The size cutoff of lacunar infarct is a topic of debate, with some studies suggesting that the traditional 15 mm diameter criterion may not be valid 2, 3.
- A study published in 2007 found that there were no clinical and lesion-size differences between middle cerebral artery disease (MCAD) and small vessel disease (SVD), suggesting that the 15 mm size criterion may not be a reliable indicator of lacunar infarction 2.
- Another study published in 2007 proposed a grading system rather than a dichotomizing system to predict lacunar stroke, taking into account the size of the infarct and the stroke syndrome 3.
- A study published in 2017 found that the diameter of acute lacunar lesions on initial diffusion-weighted MRI was markedly reduced on follow-up, with a mean percentage of final diameter over initial diameter of 53.57% ± 26.45% 4.
- The same study found that all of the lesions were less than 15 mm on follow-up, with 51.6% of the patients having cavitated lesions, 21.9% having white matter lesions, and 26.6% having disappeared lesions 4.
Infarct Size and Lacunar Infarction
- Infarct size may be used as a method to distinguish between small vessel disease (SVD) and branch atheromatous disease (BAD) in lacunar infarction patients with normal middle cerebral artery (MCA) 5.
- A study published in 2016 found that patients with SVD had smaller infarct lesions compared to those with BAD, with a mean length of lesions of 11.1 mm on diffusion-weighted images (DWI) and a mean height of 12.26 mm on fluid-attenuated inversion recovery (FLAIR) images 5.
- The lacunar infarction diameter on DWI and FLAIR images was negatively correlated with the level of lowest layer of infarction lesions, suggesting that infarct size may be related to the underlying pathogenesis of lacunar infarction 5.