Circumferential segmental vessel-wall enhancement on black blood MRI in patients referred for the evaluation of vasculopathy.

BACKGROUND: High resolution intracranial vessel wall magnetic resonance imaging, or black blood MRI, has recently gained traction as an adjunct to computed tomography angiography, magnetic resonance angiography, and digital subtraction angiography in the characterization of atherosclerosis, vasculitides, and inflammatory changes in the aneurysm wall. However, the occurrence of uniform circumferential segmental arterial vessel wall enhancement (CSWE) in patients without these diagnoses has not previously been studied. The purpose of this study is twofold: 1) to evaluate the prevalence of CSWE in the major intracranial arteries in patients without vasculitides, symptomatic atherosclerosis, or aneurysmal subarachnoid hemorrhage and 2) to determine the association, if any, between such enhancement and risk factors for cerebrovascular atherosclerotic disease. MATERIALS & METHODS: A retrospective study of vessel wall magnetic resonance imaging examinations was performed to evaluate for CSWE in 26 patients without known vessel wall pathology such as aneurysms or vasculitides and intracranial hemorrhage. Further evaluation of CSWE association with major intracranial atherosclerotic disease risk factors including hypertension, hyperlipidemia, diabetes mellitus and cigarette smoking was performed. RESULTS AND CONCLUSION: 46% of the cohort of patients demonstrated CSWE. Among the patients with CSWE, there was increased prevalence of CSWE in the posterior circulation vasculature with particular predilection to the V4 vertebral artery segments (92%), although there was greater association of anterior circulation CSWE with risk factors for atherosclerosis. Patients with anterior circulation CSWE also demonstrated the most number of segments with CSWE. We therefore propose that CSWE, particularly in the anterior circulation, may portend early atherosclerosis.

Early aortic repair worsens concurrent traumatic brain injury.

BACKGROUND: Blunt thoracic aortic injury (BTAI) and traumatic brain injury (TBI) are the leading causes of death after blunt trauma, and TBI is common among patients with BTAI. Although aspects of aortic management, such as repair timing and procedural anticoagulation therapy, may complicate TBI, the optimal management of these patients is undefined. METHODS: Adults with BTAI and moderate to severe TBI admitted to a level I trauma center over 12 years were retrospectively analyzed; patients presenting in extremis were excluded. The primary outcome was neurologic progression within 48 hours of aortic repair. Patients undergoing nonoperative aortic management served as controls for baseline TBI progression. Secondary outcomes were aortic morbidity and mortality and overall inpatient survival. RESULTS: Of 309 patients with BTAI, 138 had concurrent TBI, and 75 were included for analysis. Twenty-two (29%) were treated nonoperatively, 29 (39%) had early aortic repair (17 open, 12 endovascular), and 24 (32%) had delayed repair (3 open, 21 endovascular). The severity of TBI was similar between groups. Early aortic repair within 24 hours of admission was independently associated with worsening TBI, regardless of repair modality or anticoagulation use. In contrast, patients undergoing delayed repair had no perioperative neurologic progression despite procedural anticoagulation therapy. Early aortic repair was also associated with increased aortic morbidity and mortality. CONCLUSIONS: For patients with BTAI and TBI, early aortic intervention is associated with progressive TBI regardless of repair modality, as well as increased aortic morbidity and mortality. Patients not requiring emergent intervention can undergo delayed repair with full anticoagulation therapy.

Effect of helix stability on the formation of loop-loop complexes.

Kissing loop complexes are loop-loop complexes where two RNA hairpins interact through their complementary loops. In this work, we have investigated the role of the helical stems on the ability of hairpins derived from the ColE1 plasmid to associate as kissing loop complexes in the presence and absence of divalent cations. Our results show that although kissing loop complexes form more readily in the presence of Mg(2+), they are able to form in the presence of 850 mM NaCl, as long as their stems contain at least six base-pairs. Formation of the Na(+) loop-loop complexes is facilitated by changing the sequence at the stem-loop interface to include less stable AU base pairs. We suggest that the conformation at the stem-loop interface is critical in the formation of kissing loop complexes and that in the absence of Mg(2+) the conformation at the stem-loop interface is packed more loosely than with Mg(2+), to allow for a lower charge density. Consistent with this hypothesis, shortening the stems to five base pairs results in unfolding of the hairpins and formation of an extended duplex rather than a kissing loop complex because the short stems are not stable enough to tolerate the necessary conformation at the stem-loop interface to allow the formation of a kissing loop complex.