Diabetic muscle infarction in a patient with acute embolic stroke

Diabetic mellitus (DM) has many well-known complications. However, there is one rare complication, diabetic muscle infarction (DMI), which is usually under diagnosed. Hereby, we present a 53-year-old Chinese man with a history of DM, hypertension and atrial fibrillation. He had acute onset of severe left lower leg pain and swelling with difficulty in walking 4 days before admission. Physical examination revealed non-pitting and non-erythematous swelling with cold sensation of the left medial calf muscles. Magnetic resonance image (MRI) showed homogenous high signal changes in the calf muscles on T2 images, which indicated DMI. After anticoagulation treatment, the patient had a fair recovery within 4 weeks and he could walk by himself thereafter. DMI is a rare complication of poorly controlled DM. It does have a characteristic clinical presentation and MRI findings. Increased clinical awareness is important for early recognition and correct treatment.     

An improved photochemical model of embolic cerebral infarction in rats.

To provide further evidence that the multiple cerebral infarcts found in rats following photochemical damage to the carotid artery are caused by emboli and to eliminate the systemic hypotension and heating of the blood reported with the previous photochemical embolic stroke model (rose bengal and a green laser), I have modified the photochemical technique. Brain pathology was studied in 18 Wistar rats following carotid artery irradiation with a red laser (632 nm) at powers ranging from 100 to 800 mW/cm2 for 10 or 20 minutes following the injection of the photosensitizing dye Photofrin II. Multiple cerebral arterioles were occluded by platelet aggregates containing frequent erythrocytes and leukocytes, identical to the thrombotic material in the carotid artery but different from the platelet aggregates seen in the carotid artery and the brain in the rose bengal model. Eighty infarcts were distributed randomly throughout the brain ipsilateral to the nonocclusive carotid thrombus. Significant heating (0.5 degree C or more) of the blood occurred only with laser powers higher (1,600 mW/cm2) or laser irradiations longer (25 minutes) than those used in the improved model of embolic stroke. This model mimics one mechanism of stroke in humans and provides a means to study systematically the morphological evolution of small cerebral infarcts.     

Delayed matrix metalloproteinase inhibition reduces intracerebral hemorrhage after embolic stroke in rats

Hemorrhagic transformation (HT) and brain edema are life-threatening complications of recombinant tissue plasminogen activator (rt-PA)-induced reperfusion after ischemic stroke. The risk of HT limits the therapeutic window for reperfusion to 3 h after stroke onset. Pre-treatment with matrix metalloproteinase (MMP) inhibitors reduces HT and cerebral edema in experimental stroke. However, whether a delayed therapeutic intervention would be beneficial is unknown. In this study, 215 male Sprague–Dawley rats were subjected to embolic stroke and 75 rats were included in the final analysis. The animals were treated with the MMP inhibitor p-aminobenzoyl-gly-pro-d-leu-d-ala-hydroxamate before or after 3 or 6 h of ischemia. Animals were monitored for reperfusion and received rt-PA 6 h after ischemia onset. The results at 24 h showed that MMP inhibition 3 h after ischemia significantly decreased the degree of brain edema (17% of hemispheric enlargement in the treated group versus 24% in controls, P = 0.018), reduced the risk (OR = 0.163; 95% CI: 0.029 to 0.953) and gravity (0.09 versus 0.19 mg of parenchymal hemoglobin, P = 0.02) of intracerebral hemorrhage, and improved neurological outcome (20% of the treated animals had a slight deficit; all of the controls had a bad outcome, P < 0.05). Delaying MMP inhibition to 6 h after ischemia restricted the beneficial role of the treatment to a reduction in the risk of parenchymal hemorrhage (OR = 0.242; 95% CI: 0.060 to 0.989). Our results confirm the involvement of MMPs in HT and support the possibility of extending the therapeutic window for thrombolysis in stroke by administering a broad-spectrum MMP inhibitor after the onset of ischemia.     

Brain hemorrhages after rt-PA treatment of embolic stroke in spontaneously hypertensive rats.

Intracerebral hemorrhage is a major complicating factor of thrombolytic therapy of stroke. To investigate the incidence of bleeding in animals with a diseased vascular system, thrombolysis was carried out in spontaneously hypertensive rats (SHR) after clot embolism of the right middle cerebral artery (MCA). Three hours after embolism SHR were treated with either recombinant tissue-plasminogen activator (rt-PA) or saline, and neurological deficits and intracerebral hemorrhages were evaluated after 3 days survival. Rt-PA-treated SHR exhibited a significantly higher incidence of hemorrhages than untreated rats but neurological deficits and survival rates showed a non-significant trend for improvement. This model offers the possibility of investigating the pathophysiology of post-thrombolytic complications in a clinically relevant small animal model.     

Acute methylphenidate treatments reduce sucrose intake in restricted-fed bingeing rats

Recent evidence suggests that methylphenidate HCl may be effective at limiting the frequency and the amount of binge eating. The present study investigated if daily treatments with methylphenidate reduced the bingeing-like behavior observed in restricted-fed adult male rats. Three groups (n = 6) received peripheral injections of methylphenidate in doses of 1.5 or 0.75 mg/kg/day, or saline, 3 days prior and 7 days during a previously characterized intermittent feeding regimen that results in a gradual increase of sucrose and food intake. The higher, but not the lower, dose of methylphenidate reduced sucrose intake to an asymptotic level starting after 3 days of the feeding protocol and concurrently led to an increase in the intake of chow. The high dose methylphenidate group also had two-fold lower plasma insulin levels compared with the saline-treated animals at the time of sacrifice on the last day of the feeding regimen. Further histological assays revealed that the methylphenidate treatments, irrespective of the dose used, resulted in selectively higher dopamine transporter and D2-like receptor labeled bindings in the shell region of the nucleus accumbens. These results suggest that relatively low-dose methylphenidate treatments may be effective for the management of binge eating by reducing the intake of palatable foods and may not interfere with short-term regulation of energy balance. These findings further support the notion that the mesoaccumbens dopamine system plays an important role in restricted access-induced sucrose bingeing in this rat model.     

Treatment of embolic stroke in rats with bortezomib and recombinant human tissue plasminogen activator

Stroke elicits a progressive vascular dysfunction, which contributes to the evolution of brain injury. Thrombolysis with tissue plasminogen activator (tPA) promotes adverse vascular events that limit the therapeutic window of stroke to three hours. Proteasome inhibitors reduce vascular thrombotic and inflammatory events, and consequently protect vascular function. The present study evaluated the neuroprotective effect of bortezomib, a potent and selective inhibitor of the proteasome, alone and in combination with delayed thrombolytic therapy on a rat model of embolic focal cerebral ischemia. Treatment with bortezomib reduces adverse cerebrovascular events including secondary thrombosis, inflammatory responses, and blood brain barrier (BBB) disruption, and hence reduces infarct volume and neurological functional deficit when administrated within 4 h after stroke onset. Combination of bortezomib and tPA extends the thrombolytic window for stroke to 6 h, which is associated with the improvement of vascular patency and integrity. Real time RT-PCR of endothelial cells isolated by laser-capture microdissection from brain tissue and Western blot analysis showed that bortezomib upregulates endothelial nitric oxide synthase (eNOS) expression and blocks NF-kappaB activation. These results demonstrate that bortezomib promotes eNOS dependent vascular protection, and reduces NF-kappaB dependent vascular disruption, all of which may contribute to neuroprotection after stroke.     

Neuroprotective effect of hyperbaric oxygen therapy monitored by MR-imaging after embolic stroke in rats

The potential neuroprotective effects of hyperbaric oxygen (HBO) were tested in an embolic model of focal cerebral ischemia with partially spontaneous reperfusion. Rats (n = 10) were subjected to embolic middle cerebral artery occlusion (MCAO) and diffusion weighted MRI (DWI) was performed at baseline, 1, 3, and 6 h after MCAO to determine the ADC viability threshold yielding the lesion volumes that best approximated the 2,3,5-triphenyltetrazolium chloride (TTC) infarct volumes at 24 h (experiment 1). For assessment of neuroprotective effects, rats were treated with 100% oxygen at 2.5 atmospheres absolute (ATA, n = 15) or normobaric room air (n = 15) for 60 min beginning 180 min after MCAO (experiment 2). DWI-, perfusion (PWI)- and T2-weighted MRI (T2WI) started within 0.5 h after MCAO and was continued 5 h, 24 h (PWI and T2WI only), and 168 h (T2WI only). Infarct volume was calculated based on TTC-staining at 24 h (experiment 1) or 168 h (experiment 2) post-MCAO. ADC-lesion evolution was maximal between 3 and 6 h. In experiment 2, the relative regional cerebral blood volume (rCBV) of both groups showed similar incomplete spontaneous reperfusion in the ischemic core. HBO reduced infarct volume to 145.3 +/- 39.6 mm3 vs. 202.5 +/- 58.3 mm3 (control, P = 0.029). As shown by MRI and TTC, HBO treatment demonstrated significant neuroprotection at 5 h after embolic focal cerebral ischemia that lasted for 168 h.     

Identification of embolic stroke in patients with large vessel occlusion: The Chinese embolic stroke score,CHESS

AimsThe aim of the study was to develop a simple and objective score using clinical variables and quantified perfusion measures to identify embolic stroke with large vessel occlusions.MethodsEligible patients from five centers participating in the International Stroke Perfusion Imaging Registry were included in this study. Patients were split into a derivation cohort (n = 213) and a validation cohort (n = 116). A score was developed according to the coefficients of independent predictors of embolic stroke from stepwise logistic regression model in the derivation cohort. The performance of the score was validated by assessing its discrimination and calibration.ResultsThe independent predictors of embolic stroke made up the Chinese Embolic Stroke Score (CHESS). There were: history of atrial fibrillation (3 points), non‐hypertension history (2 points), and delay time>6 s volume/delay time>3 s volume on perfusion imaging ≥0.23 (2 points). The AUC of CHESS in the derivation cohort and validation cohort were 0.87 and 0.79, respectively. Patients with a CHESS of 0 could be identified as low‐risk of embolic stroke, with a CHESS of 2–4 could be identified as medium‐risk and with a CHESS of 5–7 could be regarded as high‐risk. The observed rate of embolic stroke of each risk group was well‐calibrated with the predicted rate.ConclusionCHESS could reliably and independently identify embolic stroke as the cause of large vessel occlusion.     

Hydroxyethyl starch 200/0.5 reduces infarct volume after embolic stroke in rats.

BACKGROUND AND PURPOSE: We evaluated isovolumic hemodilution with hydroxyethyl starch 200/0.5 in a rat model of focal cerebral ischemia. This compound avoids the unfavorable viscosity and erythrocyte aggregation abnormalities of low molecular weight dextran during administration over a period of several days. METHODS: Sprague-Dawley rats, anesthetized with 0.5-1% halothane and 70% N2O, were subjected to silicon cylinder (treated and control groups) or sham (sham group) embolization of the cerebral circulation. Thirty minutes after embolization, the treated group (n = 5) was infused with 11 ml/kg of 10% hydroxyethyl starch 200/0.5, and the control (n = 5) and sham (n = 4) groups were infused with saline for 1 hour. In the treated group, 7.1 ml/kg of blood was withdrawn. After 24 hours, the animals were reanesthetized, and cerebral blood flow was determined with [14C]iodoantipyrine. Alternative brain slices were either incubated with 2,3,5-triphenyltetrazolium chloride for infarct volume determination or frozen for ischemic volume and cerebral blood flow determination using autoradiography. RESULTS: The hematocrit in the treated group was reduced from (mean +/- SEM) 46 +/- 1% to 35 +/- 2% at 1.5 hours (p < 0.01). Cortical blood flow was within the normal range of 115-185 ml/min/100 g, except for the ischemic cortex in the embolized groups, treated and control. The ischemic and infarct volume of the treated group was reduced by 74% (p < 0.05) and 89% (p < 0.05), respectively, from the control group. The treated and sham ischemic and infarct volumes were not statistically different. CONCLUSIONS: These data suggest that hydroxyethyl starch 200/0.5 could be an effective treatment for ischemic stroke when administered early, because it reduces infarct and ischemic volumes from control values to levels indistinguishable from those of the sham group.     

Recurrence of embolic stroke during intravenous thrombolysis

An 81-year-old man with atrial fibrillation presented with embolic stroke in the right middle cerebral artery. During intravenous thrombolysis, he became comatose and developed a recurrent embolism in the top of the basilar artery. Intra-arterial mechanical disruption of the embolus failed to recanalize. Laboratory studies on admission demonstrated thrombocytosis, but echocardiography performed after thrombolysis did not identify an embolic source, including mural thrombi.     

A novel embolic stroke model resembling lacunar infarction following proximal middle cerebral artery occlusion in beagle dogs

It is estimated that lacunar infarcts account for 25% of all ischemic strokes, but its exact etiology is still on debating. The existing controversies include whether the embolisms can indeed cause lacunar stroke in humans or animal models. We hypothesized that lacunar infarction can be induced by the proximal middle cerebral artery (MCA) segmental occlusion involving the orifices of lenticulostriate arteries in animal models, which have abundant distal cerebral collateral anastomosis. Our work here establishes a proximal MCA occlusion model using thrombi (autologous blood clots about 1.7 mm in diameter and 5 mm in length) in 8 beagle dogs, evaluates the progression of ischemic lesions at 30 min interval within 6 h after embolization using the diffusion weighted imaging (DWI), and discusses the potential mechanisms of lacunar infarction. Our results indicate that the left proximal MCAs can be successfully occluded in all dogs using interventional single-thrombus method. The small solitary or multiple ischemic lesions shown in DWI were observed in the deep brain area, with the mean detecting time of 1.21 ± 0.45 h using DWI and diameter of 6.62 ± 0.60mm in 6h-DWI after procedure. In conclusion, our method established an ischemic model which can recapitulate the radiologic and histologic changes in lacunar infarcts, suggesting that emboli can cause lacunar infarcts in animal model.     

Regression of intracardiac thrombus after embolic stroke

Using two-dimensional echocardiography, we studied the pathophysiology of intracardiac thrombus regression accompanied by anticoagulant therapy in 82 consecutive patients with acute cardiogenic cerebral embolism. We noted intracardiac thrombus in 15 patients; nine of the 15 were started on anticoagulant therapy with warfarin potassium to maintain the prothrombin time between 2.5 and 3.5 (international normalized ratio). Serial two-dimensional echocardiograms were obtained for these nine patients before and after anticoagulation, with the plasma levels of fibrinopeptide A, fibrinopeptide B beta 15-42, and D-dimer measured at the same time. In eight of the nine patients the intracardiac thrombi gradually decreased in size while the plasma level of fibrinopeptide A fell to within the normal range and the plasma levels of fibrinopeptide B beta 15-42 and D-dimer remained above the normal ranges. In the other patient the thrombus disappeared, with embolization to the right arm immediately after starting anticoagulant therapy. Mobile or small thrombi regressed earlier than nonmobile or large ones. We conclude that regression of intracardiac thrombi after anticoagulation may be based on the relative predominance of plasma fibrinolytic activity over anticoagulation-inhibited thrombin activity.     

抑制基质金属蛋白酶-9可延长大鼠脑栓塞后尿激酶溶栓时间窗

目的研究基质金属蛋白酶抑制剂强力霉素和三七皂甙对大鼠脑栓塞后不同时间尿激酶静脉溶栓效果及并发症的干预作用,评价基质金属蛋白酶抑制剂对尿激酶溶栓治疗时间窗的干预效果。方法采用大鼠自体血栓塞大脑中动脉闭塞(MCAO)模型,分别用免疫组织化学法、TTC染色、伊文氏蓝法和分光光度计法对基质金属蛋白酶-9(MMP-9)、脑梗死体积、血脑屏障通透性和脑出血量进行检测。结果相应时间段尿激酶(UK)溶栓组与缺血对照组比较MMP-9表达显著增高,血脑屏障通透性和脑出血量均有增加趋势,以12h UK组明显;6h UK组较缺血对照组脑梗死体积明显降低。强力霉素和三七皂甙联合尿激酶治疗的各组与相应时间点单用尿激酶组比较MMP-9表达显著降低,脑梗死体积明显下降,血脑屏障通透性和脑出血量均有改善。结论基质金属蛋白酶抑制剂联合溶栓治疗,提高溶栓疗效,减轻溶栓后血脑屏障破坏和出血性转化,可能有延长溶栓治疗时间窗的作用。     

Lesion development and reperfusion benefit in relation to vascular occlusion patterns after embolic stroke in rats

Vascular occlusion sites largely determine the pattern of cerebral tissue damage and likelihood of subsequent reperfusion after acute ischemic stroke. We aimed to elucidate relationships between flow obstruction in segments of the internal carotid artery (ICA) and middle cerebral artery (MCA), and (1) profiles of acute ischemic lesions and (2) probability of subsequent beneficial reperfusion. Embolic stroke was induced by unilateral intracarotid blood clot injection in normotensive (n=53) or spontaneously hypertensive (n=20) rats, followed within 2 hours by magnetic resonance (MR) angiography (MRA), diffusion- (DWI) and perfusion-weighted magnetic resonance imaging (MRI) (PWI). In a subset of animals (n=9), MRI was repeated after 24 and 168 hours to determine the predictive value of the occlusion pattern on benefit of reperfusion. The extent of cerebral perfusion and diffusion abnormality was related to the pattern of flow obstruction in ICA and MCA segments. Hypertensive animals displayed significantly larger cortical perfusion lesions. Acute perfusion-diffusion lesion mismatches were detected in all animals that subsequently benefitted from reperfusion. Yet, the presence of an angiography-diffusion mismatch was more specific in predicting reperfusion benefit. Combination of DWI, PWI, and MRA exclusively informs on the impact of arterial occlusion profiles after acute ischemic stroke, which may improve prognostication and subsequent treatment decisions.     

Combination treatment with dipyridamole, aspirin, and tPA in an embolic model of stroke in rats

Antithrombotic therapy has been shown to be effective in preventing secondary strokes. Inhibition of platelet function may reduce formation of thrombi thereby reducing the incidence of stroke. However, stronger inhibition of platelets is correlated with increased risk of bleeding events. The purpose of this study was to test the protective effects of combination therapy with dipyridamole and acetylsalicylic acid (ASA) in comparison to ASA alone, and whether such combination treatment may produce any added benefits when tissue plasminogen activator (tPA) treatment is also used. The study was divided into three parts. In part A, effect of antiplatelets on infarct volume was assessed. In part B, perfusion deficits were measured. In part C, efficacy of antiplatelet therapy in combination with tPA was assessed. In part A, dipyridamole and aspirin treatment significantly reduced infarct volume (P<0.05). In part B, treatment with dipyridamole significantly reduced the perfusion deficits as compared to control (P<0.05). In part C, dipyridamole plus tPA or dipyridamole and aspirin plus tPA significantly decreased infarct volume as compared to tPA alone (P<0.05). The present study suggests that there is significant protection with dipyridamole as both infarct volume and perfusion deficits are significantly reduced. Dipyridamole with tPA also significantly reduced infarct volume as compared to tPA alone. Our data suggests that higher doses of antithrombotic therapy with dipyridamole offer best neuroprotection.