The difference in diffusion-weighted imaging with apparent diffusion coefficient between spontaneous and postoperative intracranial infection

Abstract

Background. Although the roles of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) have been accepted as the initial or confirmatory diagnostic tool for spontaneous intracranial infections, the usefulness of these has rarely been investigated in intracranial infections after a craniotomy procedure. Through an analysis of the clinico-radiological characteristics of spontaneous and postoperative intracranial infections, the authors revealed the specific factors that affect the accuracy of DWI and ADC in diagnosing intracranial infections. Methods. The authors retrospectively analyzed 67 intracranial infections confirmed using preoperative MR imaging, including the DWI, ADC and gadolium-enhanced (Gd) images, and by peroperative pus drainage. Results. In 67 enrolled patients, no or uncertain diffusion restriction on DWI and ADC was found in 9 cases (13%). All the cases showed typical peripheral enhancement on Gd images. Among nine cases without diffusion restriction, postoperative infection was seen in five cases (62.5% [5/8 postoperative infection group] vs. 6.8% [4/59 spontaneous infection group], p = 0.001). On multivariate analysis, postoperative infection was the predictive factor for false-negative restriction on DWI and ADC (hazard ratio: 41.2, 95% confidential index: 2.39–710.25, p = 0.01). Conclusion. Despite the excellent availability of DWI and ADC for diagnosing spontaneous intracranial infections, negative restriction results of those images are not sufficient to exclude postoperative intracranial infection.