Distance to thrombus in acute middle cerebral artery occlusion: a predictor of outcome after intravenous thrombolysis for acute ischemic stroke.

BACKGROUND AND PURPOSE: In patients with acute middle cerebral artery (MCA) stroke, therapeutic decisions are influenced by the location of the occlusion. This study aimed to analyze clinical outcomes in patients with acute ischemic MCA stroke treated with systemic intravenous thrombolysis (IVT) using recombinant tissue plasminogen activator, according to the location of the occlusion. METHODS: Of 621 patients screened, 136 with acute stroke and MCA occlusion confirmed by CT angiography were retrospectively included in this study. The distance from the carotid T to the thrombus (DT) on coronal maximum intensity projection images and the thrombus length were measured. The correlation between DT and the modified Rankin Scale score at 90 days was analyzed. RESULTS: DT was an independent predictor of clinical outcome in stroke patients treated with IVT. A long DT was significantly correlated with a good clinical outcome (modified Rankin Scale score at 90 days ≤2). A poor clinical outcome was exponentially more likely than a good outcome when the DT was <16 mm (P<0.001). The thrombus length was not correlated with the modified Rankin Scale score at 90 days. A long thrombus (>8 mm) occurred significantly more often in the proximal MCA than the distal MCA (P<0.001). CONCLUSION: DT is an independent predictor of clinical outcome in patients with acute MCA occlusion treated with IVT. In acute stroke with MCA occlusion confirmed by CT angiography and DT <16 mm, the likelihood of a good clinical outcome after treatment with IVT was exponentially <50%. This might warrant the evaluation of other therapy forms than IVT in patients with proximal MCA occlusion.

Long-term functional and neurological outcome after simultaneous treatment with tissue-plasminogen activator and hyperbaric oxygen in early phase of embolic stroke in rats.

The combination of hyperbaric oxygen therapy (HBO) and recombinant tissue-plasminogen activator (tPA) is of interest in the treatment of acute ischemic stroke with a view to combine positive effects of both strategies. We investigated neurological and functional outcome after early treatment with HBO additional to tPA in ischemic stroke. Focal cerebral ischemia was induced using an embolic stroke model in 87 male Wistar rats. Animals were randomized to therapy with tPA+HBO, tPA alone, or control. Menzies score, Beam walk, and the Corner test were assessed for a period of 4 weeks following ischemia. Within the first 24 h neurological deficits improved in all groups but most pronounced in animals treated with tPA+HBO. Thereafter, a deterioration of neurological deficits occurred in the tPA+HBO group with significant differences at day 7, 8, 18, and 24 (P<0.05). Surprisingly, Beam walk and Corner test results did not differ significantly between all groups. This first report of early simultaneous treatment with tPA and HBO in experimental embolic stroke with 4-week follow-up confirms previous studies reporting positive effects of HBO shortly after the ischemia. Following the acute phase, combined tPA and HBO resulted in deterioration of neurological deficits without affecting functional recovery. Future studies should focus on interactions of tPA and HBO on molecular level leading to delayed damage to brain tissue at risk.

Characteristics, distribution and diagenetic stages of chert in the La Silla Formation (Lower Ordovician), Argentine Precordillera

The late Cambrian - late Tremadocian La Silla Formation is a carbonate unit of the eastern Precordillera in Argentina whose facies indicate a shallow platform environment. Until this moment, there were no studies that referred to the diagenetic evolution of these rocks. The present study involves the characteristics and distribution of the silicification that affects this unit and determines its different diagenetic stages through petrographic (with cathodoluminescence support) and stratigraphic analyses. An early diagenetic chert, in a stage previous to the compactation, was observed. This chert is related to silica-rich seawater in contact with permeable and porous sediments. A later pulse of chert, associated with fracturing, also occurs. The knowledge provided by the characteristics and distribution of chert in these carbonates is significant, especially when considering that the La Silla Formation in San Juan province is the most quarried unit for the elaboration of lime.

A Formação La Silla (Neo Cambriano-Neo Tremadociano) é formada por depósitos carbonáticos da região da Pré-Cordilheira leste, Argentina. As faciologias encontradas em tais depósitos indicam um ambiente de deposição caracterizado por uma plataforma rasa. Até o momento, nenhum estudo tratou especificamente da evolução diagenética dessas rochas. O presente estudo envolve as características e distribuição da silicificação que afeta esta formação e apresenta os diferentes estágios diagenéticos ocorridos, através de análises petrográficas (auxiliadas por catodoluminescência) e estratigráficas. Foi identificado um pulso precoce de silicificação, anterior ao processo de compactação das rochas afetadas. Esta silicificação foi favorecida pela presença de água do mar rica em sílica em contato com sedimentos porosos e permeáveis. Também foi identificado um pulso de silicificação tardia, associado a eventos de fraturamento das rochas. O conhecimento adquirido sobre as características e a distribuição da silicificação nestes depósitos carbonáticos é importante, especialmente quando se considera que a Formação La Silla, na Província de San Juan, é a formação mais minerada para a produção de calcário.