Angiographic warning of hemorrhagic transformation after stent retriever thrombectomy procedure.

This study reports cerebral angiographic findings observed after stent retriever thrombectomy that is suggestive of a higher risk of hemorrhagic transformation (HT). A woman aged 65-75 presented with a right middle cerebral artery syndrome confirmed by non-contrast CT brain scan. Endovascular revascularization using the Solitaire device was placed across the thromboembolic occlusion and thromboembolectomy was performed. Angiography showed complete recanalization of the left internal carotid artery, anterior and middle cerebral artery branches. Twelve hours following the procedure the patient had a hemorrhagic conversion of the ischemic infarct with significant mass effect causing herniation. Despite surgical intervention (hemicraniectomy) the patient died. The angiographic features following revascularization of the vessels distal to the occlusion showed subtle dilations which were visualized at the branch points of the vessels. This may be a warning sign of increased risk of HT.

Review of three magnetic resonance arthrography related infections.

We report three cases of intra-articular infection which followed injection for magnetic resonance arthrography. In an effort to reduce the risk of arthrogram related infection, representatives from radiology, infectious disease medicine, and microbiology departments convened to analyze the contributing factors. The proposed source was oral contamination from barium swallow studies which preceded the arthrogram injections in the same room. We propose safety measures to reduce incidence of arthrogram related infections.

Angiographic warning of hemorrhagic transformation after stent retriever thrombectomy procedure.

This study reports cerebral angiographic findings observed after stent retriever thrombectomy that is suggestive of a higher risk of hemorrhagic transformation (HT). A woman aged 65-75 presented with a right middle cerebral artery syndrome confirmed by non-contrast CT brain scan. Endovascular revascularization using the Solitaire device was placed across the thromboembolic occlusion and thromboembolectomy was performed. Angiography showed complete recanalization of the left internal carotid artery, anterior and middle cerebral artery branches. Twelve hours following the procedure the patient had a hemorrhagic conversion of the ischemic infarct with significant mass effect causing herniation. Despite surgical intervention (hemicraniectomy) the patient died. The angiographic features following revascularization of the vessels distal to the occlusion showed subtle dilations which were visualized at the branch points of the vessels. This may be a warning sign of increased risk of HT.

Chemistry of 4-alkylaryloxenium ion "precursors": sound and fury signifying something?

Quinol esters 2b, 2c, and 3b and sulfonamide 4c were investigated as possible precursors to 4-alkylaryloxenium ions, reactive intermediates that have not been previously detected. These compounds exhibit a variety of interesting reactions, but with one possible exception, they do not generate oxenium ions. The 4-isopropyl ester 2b predominantly undergoes ordinary acid- and base-catalyzed ester hydrolysis. The 4-tert-butyl ester 2c decomposes under both acidic and neutral conditions to generate tert-butanol and 1-acetyl-1,4-hydroquinone, 8, apparently by an SN1 mechanism. This is also a minor decomposition pathway for 2b, but the mechanism in that case is not likely to be SN1. Decomposition of 2c in the presence of N3- leads to formation of the explosive 2,3,5,6-tetraazido-1,4-benzoquinone, 14, produced by N3--induced hydrolysis of 8, followed by a series of oxidations and nucleophilic additions by N3-. No products suggestive of N3--trapping of an oxenium ion were detected. The 4-isopropyl dichloroacetic acid ester 3b reacts with N3- to generate the two adducts 2-azido-4-isopropylphenol, 5b, and 3-azido-4-isopropylphenol, 11b. Although 5b is the expected product of N3- trapping of the oxenium ion, kinetic analysis shows that it is produced by a kinetically bimolecular reaction of N3- with 3b. No oxenium ion is involved. The sulfonamide 4c predominantly undergoes a rearrangement reaction under acidic and neutral conditions, but a minor component of the reaction yields 4-tert-butylcresol, 17, and 2-azido-4-tert-butylphenol, 5c, in the presence of N3-. These products may indicate that 4c generates the oxenium ion 1c, but they are generated in very low yields (ca. 10%) so it is not possible to definitively conclude that 1c has been produced. If 1c has been generated, the N3--trapping data indicate that it is a very short-lived and reactive species in H2O. Comparisons with similarly reactive nitrenium ions indicate that the lifetime of 1c is ca. 20-200 ps if it is generated, so it must react by a preassociation process. Density functional theory calculations at the B3LYP/6-31G*//HF/6-31G* level coupled with kinetic correlations also indicate that the aqueous solution lifetimes of 1a-c are in the picosecond range.