Detectability, Prevalence, and Significance of Early CT Signs of Hemispheric Infarction

Abstract

The view that CT is negative within the first 24–48 h after stroke has been handed down over the past 20 years. However, even with the first generation of CT scanners the prevalence of CT findings was not low during this time period. Using the 80 × 80 or 160 × 160 matrix of the early EMI scanner, Yock and Marshall observed five infarctions with “patchy low-density areas with irregular margins” less than 1 day old [45]. Aulich et al. described positive signs of cerebral infarctions in 54% of 41 patients examined within 48 h of symptom onset. In two patients they observed an area of low density within 3–4 h after the onset of symptoms [2]. Inoue et al. observed hypodense areas in three of 14 patients within the first 6 h and in eight of nine patients between 6 and 24 h [16]. Wall et al. found 79% CT scans positive within 24 h after onset of symptoms, and 65% of the positive scans were obtained at or less than 12 h after stroke [42]. More recent work has shown higher incidences of positive CT scans during the first 6 h after stroke: Tomura et al. studied 25 patients with embolic cerebral infarction between 40 and 340 min after the onset of symptoms. Twenty-three CT scans (92%) were positive, with obscuration of the lentiform nucleus [35]. Bozzao et al. observed parenchymal hypodensity in 25 of 36 patients (69%) [5]. Truwit et al. reported 23 of 27 patients (85%) with hypodensity on CT scan after stroke, the insular cortex being involved in all instances [37]. Horowitz et al. reported on hypodensity and mass effect in 56% of 50 scans [14]. When MR versus CT imaging were compared for identical patients within 3 h of acute hemispheric stroke, CT was found positive for 19 (53%) and MRI for 18 (50%) patients [21]. Von Kummer et al. reported 17 positive CT scans (68%) performed in a series of 25 patients with MCA trunk occlusion during the first 2 h. The incidence of positive CT findings increased to 89% in the third hour after symptom onset and to 100% thereafter [40]. In another series of patients with hemispheric stroke the incidence of early CT signs of infarction was 82% [41]. The initial CT of the ECASS population (620 patients) showed hypodense areas in 46%, less than or equal to 33% of the MCA territory in 35%, and areas exceeding 33% (exclusion criterion) in 8%.