应用MR弥散和灌注技术分析大脑中动脉狭窄供血区血流状况的比较

目的:探讨磁共振的动态磁敏感对比增强(DSC-MRI)技术和动脉自旋标记(ASL)方法的差异,并明确ASL方法在缺血性脑血管病患者脑血流灌注中的应用价值.方法:回顾性分析48例经磁共振血管造影(MRA)证实的一侧大脑中动脉(MCA)狭窄或闭塞的短暂性脑缺血发作(TIA)患者的影像学资料,并选择35例健康志愿者作为对照,通过ASL和DSC两种灌注加权成像(PWI)技术扫描,得到平均脑血流量(CBF)图和灌注参数图,与弥散加权成像(DWI)所得参数图比较,观察两种方法判定MCA狭窄侧脑组织血流灌注的差异.结果:ASL方法显示,患侧脑组织局部脑血流量(rCBF)为(30.4±8.2) mL·100 g-1·min-1,对侧脑组织的rCBF为(58.3±11.4)mL·100 g-1·min-1,患侧脑组织rCBF低于正常侧脑组织(P<0.05);DSC方法显示,患侧rCBF为(28.7±12.8)mL·100 g-1·min-1,对侧脑组织的rCBF为(54.2±9.5) mL·100 g-1·min-1,患侧rCBF低于正常侧脑组织(P<0.05);ASL和DSC方法检测同一血管狭窄侧脑组织的rCBF,两组rCBF的差异无统计学意义(P>0.05).ASL和DSC方法显示,健康志愿者的rCBF分别为(56.8±10.7) mL·100 g-1·min-1和(55.2±9.8) mL·100 g-1·min-1,与血管狭窄对侧的正常脑组织的rCBF两两比较差异无统计学意义(P>0.05);DWI显示狭窄动脉供血区域异常的病灶表观弥散系数(ADC)平均值为(522.3±57.2)×10-6 mm2·s-1,对侧正常脑组织的ADC平均值为(756.8±67.6)×10-6 mm2·s-1,狭窄动脉供血区域ADC平均值低于对侧正常脑组织ADC平均值(P<0.05).结论:ASL方法可以判定MCA狭窄患者的低灌注状态,弥散结合灌注扫描可以判定侧脑组织狭窄患者的缺血半暗带.     

Reduction of ischemic brain injury by topical application of glial cell line-derived neurotrophic factor after permanent middle cerebral artery occlusion in rats

BACKGROUND AND PURPOSE: Glial cell line-derived neurotrophic factor (GDNF) plays important roles in the survival and recovery of some mature neurons under pathological conditions. However, the effect of GDNF in ameliorating ischemic brain injury has not been well documented. Therefore, we investigated a possible effect of GDNF on the changes of infarct size, brain edema, DNA fragmentation, and immunoreactivities for caspases after permanent middle cerebral artery occlusion (MCAO) in rats. METHODS: For the estimation of ischemic brain injury, we calculated the infarct size of MCA region and also measured the brain water content as edema formation at 24 hours after the MCAO. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick labeling (TUNEL) staining was performed for the detection of DNA fragmentation. Immunoreactivities for caspase-1 (ICE), caspase-2 (Nedd-2), and caspase-3 (CPP32) were stained. RESULTS: Both infarct size and brain edema after permanent MCAO were significantly reduced by topical application of GDNF (48% and 30% decreases, P=0.01). TUNEL staining and immunoreactivities for caspases were markedly induced at 12 hours after permanent MCAO in the vehicle-treated animals. However, the spatial distribution of those immunohistochemically positive cells was dissociative in each caspase. Induction of TUNEL staining and immunoreactivities for caspases-1 and -3 was greatly reduced with GDNF treatment, whereas the reduction of caspase-2 staining was only minimum. CONCLUSIONS: These data suggest that the reduction of infarct size and brain edema by GDNF was greatly associated with the reduction of DNA fragmentation and apoptotic signals predominantly through caspases-1 and -3 cascades.     

Diagnosis of middle cerebral artery stenosis by transcranial color-coded real-time sonography

BACKGROUND & PURPOSE: This study was performed to determine the usefulness of transcranial color-coded real-time sonography (TCCS) in detecting stenosis in the horizontal portion of the middle cerebral artery (MCA). METHODS: Using TCCS and the incident angle correction technique, we measured the peak-systolic flow velocity in bilateral MCAs in 45 consecutive patients in whom cerebral angiography was carried out within 1 week before or after TCCS. Three patients had a stenosis of 75% or greater and four had a unilateral occlusion of the extracranial internal carotid artery (ICA) (the ICS and ICO groups, respectively). Eight patients had a stenosis of 50% or greater (one bilateral and seven unilateral) (the M1S group). Four patients had unilateral distal occlusion of the horizontal portion of the MCA (the M1O group). Twenty-six patients had no significant extra- or intracranial stenosis on the ipsilateral or contralateral side (the control group). RESULTS: Mean peak-systolic flow velocity on the affected side was 83.0 +/- 20.8 cm/s in the ICS group, 59.8 +/- 23.2 cm/s in the ICO group, and 62.3 +/- 33.7 cm/s in the M1O group. In the control group, the mean peak-systolic flow velocity was 116.0 +/- 31.5 cm/s. In the M1S group, however, the mean peak-systolic flow velocity (334.2 +/- 35.7 cm/s) on the affected side always exceeded 180 cm/s (mean value +/- 2 SD in the control group), and was significantly higher than that in the other groups. The mean peak-systolic flow velocity in the M1S group increased with the grade of stenosis. CONCLUSION: The M1S group members could easily be distinguished from the other group members by their peak-systolic flow velocity in excess of 180 cm/s. Measurement of the peak-systolic flow velocity of the MCA by TCCS may help to identify a significant stenosis in the horizontal portion of the MCA.     

Induction of spreading depression in the ischemic hemisphere following experimental middle cerebral artery occlusion: effect on infarct morphology

This study was undertaken to test whether transient depolarizations occurring in periinfarct regions are important in contributing to infarct spread and maturation. Following middle cerebral artery (MCA) occlusion we stimulated the ischemic penumbra with recurrent waves of spreading depression (SD) and correlated the histopathological changes with the electrophysiological recordings. Halothane-anesthetized, artificially ventilated Sprague-Dawley rats underwent repetitive stimulation of SD in intact brain (Group 1; n = 8) or photothrombotic MCA occlusion coupled with ipsilateral common carotid artery occlusion (Groups 2 and 3, n = 9 each). The electroencephalogram and direct current (DC) potential were recorded for 3 h in the parietal cortex, which represented the periinffarct border zone in ischemic rats. In Group 2, only spontaneously occurring negative DC shifts occurred; in Group 3, the (nonischemic) frontal pole of the ischemic hemisphere was electrically stimulated to increase the frequency of periinfarct DC shifts. Animals underwent perfusion-fixation 24 h later, and volumes of complete infarction and scattered neuronal injury ("incomplete infarction") were assessed on stained coronal sections by quantitative planimetry. Electrical induction of SD in Group 1 did not cause morphological injury. During the initial 3 h following MCA occlusion, the number of spontaneous periinfarct depolarization in Group 2 (7.0 +/- 1.5 DC shifts) was doubled in Group 3 by frontal current application (13.4 +/- 2.7 DC shifts; p < 0.001). The duration as well as the integrated negative amplitude of DC shifts over time were significantly greater in Group 3 than in Group 2 rats (duration, 5.7 +/- 3.8 vs. 4.1 +/- 2.5 min; p < 0.05). Histopathological examination disclosed well-defined areas of pannecrosis surrounded by a cortical rim exhibiting selectively damaged acidophilic neurons and astrocytic swelling in otherwise normal-appearing brain. Induction of SD in the ischemic hemisphere led to a significant increase in the volume of incomplete infarction (19.0 +/- 6.1 mm3 in Group 3 vs. 10.3 +/- 5.1 mm3 in Group 2; p < 0.01) and of total ischemic injury (100.7 +/- 41.0 mm3 in Group 3 vs. 66.5 +/- 24.7 mm3 in Group 2; p < 0.05). The integrated magnitude of DC negativity per experiment correlated significantly with the volume of total ischemic injury (r = 0.780, p < 0.0001). Thus, induction of SD in the ischemic hemisphere accentuated the development of scattered neuronal injury and increased the volume of total ischemic injury. This observation may be explained by the fact that with limited perfusion reserve, periinfarct depolarization are associated with episodic energy failure in the acute ischemic penumbra.     

Contribution of transcranial color-coded real-time sonography to the etiopathogenetic classification of middle cerebral artery stenosis

Transcranial color-coded real-time sonography (TCCS) and cranial computed tomography were applied to patients with middle cerebral artery (MCA) stenosis to evaluate whether these techniques may disclose additional aspects of the pathophysiology of the stenotic lesion. In 15 patients with MCA stenosis identified by transcranial Doppler sonography, the echogenicity of the stenotic segment was estimated subjectively by TCCS. The density of the stenotic segment, prior to being detected by TCCS, was quantified by computed tomography. In 5 of the 15 patients, transcranial image-directed Doppler sonography identified a hyperechogenic lesion in association with the stenotic vascular segment; computed tomography demonstrated a "dense" artery (Hounsfield units [HU] > 120) in the corresponding vascular segment. In 10 patients the echogenicity of the stenotic segment was found to be normal, with a computed tomography density of < 100 HU in the corresponding segment. Hyperechogenic and hyperdense stenotic vascular segments in TCCS and computed tomography, respectively, may indicate an arteriosclerotic vascular lesion with calcium deposits. Normal echogenicity and normal to slightly elevated computed tomography-density of a stenotic vascular segment may suggest the presence of a thrombotic/embolic lesion.     

Giant aneurysm of the middle cerebral artery

A case of a giant aneurysm of the middle cerebral artery, (4.5 X 4.5 X 9.5 CM) presenting as a mass lesion, which was successfully excised is described. This case is compared to the few previous accounts of giant aneurysms of the middle cerebral artery larger than 3 cm in diameter.     

Long-term functional outcome following transient middle cerebral artery occlusion in the rat: Correlation between brain damage and behavioral impairment.

The assessment of both histological and functional long-term outcomes after cerebral ischemia is increasingly recommended for preclinical studies. Whereas correlations between behavioral impairments and primary ischemic lesion are documented, little is known about their relationships with remote nonischemic regions that undergo secondary degeneration, such as the thalamus. Anesthetized rats were subjected to mild (30 min) or severe (60 min) occlusion of the middle cerebral artery. Two months after ischemia, sensorimotor behavior was assessed according to the neurological score, limb-placing, adhesive-removal, and staircase tests; the final histological lesion was measured after this assessment. Cortical damage was correlated to all transient and long-lasting sensorimotor deficits, whereas striatal lesion was more consistently reflected by the forelimb-placing reflexes and adhesive-removal motor deficits. By contrast, the thalamic atrophy was not correlated to early neurological impairment, but rather to the late sensory deficit at the adhesive-removal test and to the skilled forepaw reaching alteration at the staircase test. This suggests that thalamus contributes, albeit moderately, to the ischemia-induced long-lasting sensorimotor deficits, some of which represent relevant targets for therapeutic interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Expression of glucose transporters in rat brain following transient focal ischemic injury

To better understand genetic diversity of mammalian reoviruses, we studied sequence variability in the S3 gene segment of 17 field-isolate reovirus strains and prototype strains of the three reovirus serotypes. Strains studied were isolated over a 37-year period from different mammalian hosts and geographic locations. A high degree of variability was observed in the nucleotide sequences of the S3 gene, whereas the deduced amino acid sequences of the S3 gene product, sigma NS, were highly conserved. When variability among the S3 nucleotide sequences was analyzed using pairwise comparisons, we found that 5' and 3' noncoding regions were significantly more conserved than the remainder of the gene. This high degree of sequence conservation was also observed within the first 15 nucleotides of the 5' coding region. Phylogenetic analyses showed that multiple alleles of the S3 gene cocirculate and that genetic diversity in the S3 gene does not correlate with host species, geographic locale, or date of isolation. Phylogenetic trees constructed from variation in the S3 sequences are distinct from those previously generated from sequences that encode attachment protein sigma 1, core protein sigma 2, and outer capsid protein sigma 3, which supports the hypothesis that reovirus gene segments reassort in nature. These findings suggest that reovirus gene segments are well-adapted to mammalian hosts and that reovirus evolution has reached an equilibrium.     

Changes in reactivity of the middle cerebral artery caused by cerebral circulation disturbances of ischemic and hemorrhagic types in rats

Reactivity of the middle cerebral artery (MCA) to serotonin was attenuated in vitro in vessels taken from rats following an audiogenic stress. The MCA reactivity to endothelin remained unchanged. Chronic cerebral ischemia diminished the 5-HT-induced contraction and the contractile responses to endothelin were enhanced. Preliminary hypoxic adaptation decreased the artery sensitivity to endothelin in ischemic animals. The findings suggest that a progressing ischemia may involve changes in reactivity of cerebral vessels whereupon hypoxic adaptation may prove to be protecting the brain from ischemia development.     

Gd-enhanced 3D phase-contrast MR angiography and dynamic perfusion imaging in the diagnosis of renal artery stenosis

The objective of this study was to investigate the role of contrast enhancement using a three-dimensional (3D) phase-contrast (PC) magnetic resonance (MR) sequence (3D PC-MRA) and to assess the value of a dynamic MR perfusion study of the kidneys to determine the hemodynamic relevance of unilateral renal artery stenosis (RAS). Seventeen patients with unilateral RAS were examined on a standard 1.0 T imaging system using a phase shift and magnitude sensitive 3D PC sequence (TR=160 ms, TE=9 ms, venc. 30 cm/s). Following the initial pre-contrast 3D PC-MRA a dynamic first pass perfusion study was performed using a Turbo-FLASH 2D sequence (TR=4.5 ms, TE=2.2 ms, TI=400 ms) after bolus injection of 0.15 mmol gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA)/kg body weight. The 3D PC-MRA was then repeated during infusion of 0.15 mmol Gd-DTPA/kg body weight. Evaluation by three independent readers was based on maximum intensity projection images. Source images were rendered on request. Signal intensity (SI) over time curves of the renal cortex were obtained from the dynamic perfusion study and analyzed for maximum signal enhancement as well as temporal relationship to the aortic SI curve. Results from 3D PC-MRA revealed a sensitivity (pre-/post-contrast) of 100%/89%, specificity of 76%/63%, positive predictive value of 80%/69 %, negative predictive value of 90%/78%, and accuracy of 85%/75% (p=0.07). Interobserver agreement was kappa=0.61/kappa=0.47 (pre/post Gd-DTPA), respectively. Increased signal-to-noise was present in all segments of the renal arteries post contrast (p=0.0003). This came along with image degradation due to aliasing and elevated SI of venous flow that partially obscured the renal arteries. Dynamic SI curves showed a significantly decreased maximum SI in RAS (p=0.01-0.001). A temporal delay of cortical signal intensity enhancement could not be confirmed in this setting. Gd-enhanced 3D PC-MRA did not yield a superior diagnostic value in the diagnosis of RAS compared to pre-contrast measurements. Dynamic perfusion imaging of the kidneys, in combination with 3D PC-MRA, can contribute additional information in suspected unilateral RAS.     

Behavioral management of chronic hallucinations and delusions following right middle cerebral artery stroke.

Describes the application of a brief psychotherapeutic intervention with potential utility in the management of hallucinations and delusions following brain damage. The procedure is illustrated with a case study of a 52-yr-old man who developed auditory hallucinations with delusional interpretation after a stroke that damaged the right temporo-parietal region. The intervention was developed based on substantial evidence of the efficacy of cognitive behavioral treatment of medication-resistant hallucinations in schizophrenic patients. Treatment involved cognitive restructuring via education of the patient and family members about the nature of the symptomatology and training in a number of simple behavioral compensatory strategies designed to minimize the impact of the symptoms on daily activities. Follow-up evaluations over a 20-month interval indicated that the intervention may be an efficacious supplement to pharmacological treatment of hallucinations and delusions following stroke. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhanced protein synthesis in the ipsilateral substantia nigra following middle cerebral artery occlusion in the rat

The purpose of this randomised single blinded study was to determine the optimal size of laryngeal mask airway in the normal adult population, to test the validity of the current selection criteria and to determine if any externally measured anatomical variable correlated with optimal size. In each of 30 apnoeic anaesthetised adults weighting less than 100 kg, size 3, 4 and 5 laryngeal mask airways were inserted in random order by a skilled user and the cuff inflated to a standard pressure (60 cm H2O). Optimal size was based on four criteria in order of priority: number of attempts at placement, oropharyngeal leak pressure, fiberoptic score and percentage of vocal cords seen. The size 5 laryngeal mask airway was optimal in 19/30 and the size 4 in 11/30. In no patient was the size 3 the optimal fit. Oropharyngeal leak pressure was significantly higher for each progressively large size and the fiberoptic view was significantly better for the size 4 and size 5. There was no significant predictive value in any externally measured anatomical variable, but height was the most useful. The best current selection strategy was to choose a size 5 for males and size 4 for females. Potentially useful new strategies may be to use the size 5 in all adults, or a size 5 > or = 165 cm in height and size 4 for < 165 cm. We conclude that predicting the optimal size of laryngeal mask airway for individual adult patients is complex. The best size selection strategies involve use of the size 4 and 5 laryngeal mask airways in adults.     

Diffusion-weighted MR imaging of acute cerebral ischemia

Diffusion-weighted MR imaging has been used in studies on experimental animal models and on patients with acute cerebral ischemia. Compared with CT and conventional MR techniques, diffusion-weighted imaging can provide earlier and more precise detection of the location and the extent of an ischemic lesion during the critical first few hours after the onset of stroke. Quantitative apparent diffusion coefficient (ADC) mapping of the brain water can also be carried out by recording a series of diffusion-weighted images with different amplitudes of the displacement encoding gradients. ADC maps can provide important information about the extra- and intracellular water homeostasis. ADC reduction of the tissue water is one of the early signals of the pathophysiological cascade resulting from ischemic tissue injury. Diffusion MR imaging has become a valuable tool in stroke research. It may also prove a valuable tool in monitoring the efficiency of therapeutic effects in stroke patients. It is our intention to provide an overview of the recent development in this area with emphasis on the diffusion-weighted MR techniques, and to discuss the possible underlying biophysical mechanisms responsible for the contrast of diffusion-weighted imaging.     

Diffusion tensor MR imaging of the human brain

PURPOSE: To assess intrinsic properties of water diffusion in normal human brain by using quantitative parameters derived from the diffusion tensor, D, which are insensitive to patient orientation. MATERIALS AND METHODS: Maps of the principal diffusivities of D, of Trace(D), and of diffusion anisotropy indices were calculated in eight healthy adults from 31 multisection, interleaved echo-planar diffusion-weighted images acquired in about 25 minutes. RESULTS: No statistically significant differences in Trace(D) (approximately 2,100 x 10(-6) mm2/sec) were found within normal brain parenchyma, except in the cortex, where Trace(D) was higher. Diffusion anisotropy varied widely among different white matter regions, reflecting differences in fiber-tract architecture. In the corpus callosum and pyramidal tracts, the ratio of parallel to perpendicular diffusivities was approximately threefold higher than previously reported, and diffusion appeared cylindrically symmetric. However, in other white matter regions, particularly in the centrum semiovale, diffusion anisotropy was low, and cylindrical symmetry was not observed. Maps of parameters derived from D were also used to segment tissues based on their diffusion properties. CONCLUSION: A quantitative characterization of water diffusion in anisotropic, heterogeneously oriented tissues is clinically feasible. This should improve the neuroradiologic assessment of a variety of gray and white matter disorders.     

Monofilament intraluminal middle cerebral artery occlusion in the mouse

The rat middle cerebral artery (MCA) occlusion model with an intraluminal filament is well characterized with a two hour period of occlusion in widespread use. The recent availability of transgenic animals has led to an interest in adapting the MCA model in the mouse. To date the model has not been well characterized in the mouse. We performed the present study to compare different durations of MCA occlusion and to validate new functional assessments in this model. The MCA occlusion model (5-0 filament) was used. Swiss-Webster mice, 24-44 g, were randomly assigned to four groups: one hour of occlusion; two hours of occlusion; three hours of occlusion; or permanent occlusion. At 48 hours post-ischemia, the animals were rated on three neurologic function scales, and then the brains were removed for lesion size determination. Overall, there was a significant difference in lesion volume (p < 0.001) between the groups. In the permanent group of mice, the average lesion volume was 78.41 +/- 17.47 mm (n = 12); two and three hours of ischemia produced 51.29 +/- 29.82 mm3 (n = 11) and 54.85 mm3 (n = 13), respectively, significantly different than the one hour group 14.84 +/- 31.34 mm3 (n = 11). All three functional scoring systems found significant overall differences between the four groups with our detailed General and Focal scores producing more robust between group treatment differences and showing correlation coefficients of r = 0.766 and r = 0.788, respectively to infarct volume. The MCA filament occlusion model can be successfully adapted in the mouse with either two or three hour occlusions producing reliable infarcts. New functional scoring systems unique to the mouse appear to add additional information.