Cerebral thromboembolism: value of susceptibility-weighted imaging in the initial diagnosis of acute infarction.

Susceptibility-weighted imaging (SWI) is commonly used to diagnose cerebral hemorrhage, calcification, and other T2* lesions. Its role in the detection of cerebral thromboemboli has been suggested for emboli of the anterior division of the middle cerebral artery (MCA). The purpose of our study was to determine SWI's accuracy and sensitivity in detection of all sites of cerebral thromboemboli, not just MCA emboli. Two neuroradiologists retrospectively reviewed consecutive MRI brain examinations with SWI for cerebral thromboemboli in 100 patients with clinical suspicion for stroke determined by the NIH Stroke Scale (NIHSS) score. FLAIR, MRA, CT, and catheter angiography were reviewed for thromboemboli in the same patients. Thromboembolic sites included: the internal carotid artery (ICA) terminus, anterior MCA, posterior MCA, any other cerebral artery, or if not present. The exclusion criteria included: no magnetic resonance angiogram (MRA) or catheter angiogram for comparison, lack of restricted diffusion, lacunar infarcts, and the presence of massive hemorrhage. The accuracy, sensitivity, and specificity of each imaging modality were determined. Twenty-four patients were excluded based on the aforementioned criteria. Cerebral thromboemboli were identified in 35 of the remaining 76 patients. Of the 35 patients with thromboemboli, 30 were identified on SWI. FLAIR detected 22/35 emboli, MRA 30/33, CT 18/35, and catheter angiography 12/12. The accuracies for SWI, FLAIR, and CT were 97%, 84%, and 74%, respectively. The sensitivities for SWI, FLAIR, and CT were 85%, 61%, and 52%, respectively. The specificities for SWI, FLAIR, and CT were 100%, 98%, and 93%, respectively. There is an adjunctive role of SWI to identify cerebral thromboemboli in patients with acute infarction. SWI is superior to FLAIR and CT, and complementary to MRA and catheter angiography in emboli detection. This study supports SWI detection of MCA emboli, but also emphasizes its utility in emboli detection of other arteries based on a high accuracy and sensitivity.

Chemistry of metapleural gland secretions of three attine ants,Atta sexdens rubropilosa, Atta cephalotes, andAcromyrmex octospinosus (Hymenoptera: Formicidae).

The chemical composition of the secretions of the metapleural glands of workers and soldiers of twoAtta species,Atta sexdens rubropilosa andA. cephalotes, and workers ofAcromyrmex octospinosus, has been studied. As indicated by infrared spectrometry and confirmed by the ninhydrin test, the secretions contain chiefly proteins. Of the volatile acidic portion, which is present as ionized salts, phenylacetic acid is the major component in workers and soldiers ofA. s. rubropilosa andA. cephalotes. BothAtta species also contain 3-hydroxydecanoic acid and its homolog as minor components together with indoleacetic acid. While there are qualitative similarities in the acidic composition in the secretions ofA. s. rubropilosa andA. cephalotes, they differ quantitatively. The secretion ofAcromyrmex octospinosus contains 3-hydroxydecanoic and indoleacetic acids, but lacks phenylacetic acid. The bactericidal and fungicidal actions of the three major substances have been confirmed.