Tolga Daniel Dittrich, MD
Lacunar stroke syndromes represent a significant proportion of the patient population that stroke neurologists encounter in their everyday practice. Diffusion-weighted (DWI) magnetic resonance (MR) imaging remains the gold standard for detecting lacunar ischemia, with higher sensitivity than computed tomography (CT). Nevertheless, multimodal CT with perfusion (CT-P) imaging has become the imaging modality of choice in the context of acute stroke in many institutions, given its wider availability and rapid image acquisition. However, in the automated post-processed core-penumbra CT maps, the often small, circumscribed perfusion delays are not necessarily represented.
In their retrospective study, Garcia-Esperon et al. investigate the accuracy and predictive value of different CT-P maps in the identification of acute lacunar stroke syndromes with anatomic reference (i.e., anterior or posterior fossa, if anterior fossa subcortical or cortical). All included patients (N=106) underwent CT-P and MR imaging; patients with corresponding vascular occlusions were excluded. Two independent neurologists specializing in stroke assessed the results of acute CT imaging (native and perfusion series) in patients with MR-graphically confirmed ischemic stroke.
Among the 106 patients who presented with the clinical picture of a lacunar syndrome, 59 had lacunar, 33 cortical, and 14 patients had proven posterior fossa ischemia on MR imaging. Automated core-penumbra maps were found to be good only for identifying cortical lesions (AUC 0.82; AUC [subcortical] 0.55, AUC [posterior] 0.66). The additional inclusion of the delay time (DT) and mean transient time (MTT) perfusion maps substantially improved the detection of subcortical ischemia (AUC 0.80) and only slightly improved that of cortical and posterior ischemia (AUC [cortical] 0.87, AUC [posterior] 0.69). Figure 1 shows an illustrative correlation of the intermodal comparison between CT-P deficits (i.e., prolonged MTT and DT) and DWI-MR lesions.
The finding that CT-P maps have better sensitivity in predicting lacunar infarcts than native CT may be unsurprising — especially when radiologically experienced neurologists perform the evaluation, as in this case. However, in the interest of maximizing the diagnostic yield of routine multimodal CT imaging, it is relevant to everyday clinical practice, that the combined analysis of MTT, DT, and core-penumbra maps improves the identification of lacunar strokes.
