Weijian Chen

Metabolite changes in the ipsilateral and contralateral cerebral hemispheres in rats with middle cerebral artery occlusion

Cerebral ischemia not only causes pathological changes in the ischemic areas but also induces a series of secondary changes in more distal brain regions (such as the contralateral cerebral hemisphere). The impact of supratentorial lesions, which are the most common type of lesion, on the contralateral cerebellum has been studied in patients by positron emission tomography, single photon emission computed tomography, magnetic resonance imaging and diffusion tensor imaging. In the present study, we investigated metabolite changes in the contralateral cerebral hemisphere after supratentorial unilateral ischemia using nuclear magnetic resonance spectroscopy-based metabonomics. The permanent middle cerebral artery occlusion model of ischemic stroke was established in rats. Rats were randomly divided into the middle cerebral artery occlusion 1-, 3-, 9- and 24-hour groups and the sham group. 1H nuclear magnetic resonance spectroscopy was used to detect metabolites in the left and right cerebral hemispheres. Compared with the sham group, the concentrations of lactate, alanine, γ-aminobutyric acid, choline and glycine in the ischemic cerebral hemisphere were increased in the acute stage, while the concentrations of N-acetyl aspartate, creatinine, glutamate and aspartate were decreased. This demonstrates that there is an upregulation of anaerobic glycolysis (shown by the increase in lactate), a perturbation of choline metabolism (suggested by the increase in choline), neuronal cell damage (shown by the decrease in N-acetyl aspartate) and neurotransmitter imbalance (evidenced by the increase in γ-aminobutyric acid and glycine and by the decrease in glutamate and aspartate) in the acute stage of cerebral ischemia. In the contralateral hemisphere, the concentrations of lactate, alanine, glycine, choline and aspartate were increased, while the concentrations of γ-aminobutyric acid, glutamate and creatinine were decreased. This suggests that there is a difference in the metabolite changes induced by ischemic injury in the contralateral and ipsilateral cerebral hemispheres. Our findings demonstrate the presence of characteristic changes in metabolites in the contralateral hemisphere and suggest that they are most likely caused by metabolic changes in the ischemic hemisphere.

Larger size ratio associated with the rupture of very small (≤3 mm) anterior communicating artery aneurysms

Background Anterior communicating artery (AcoA) aneurysms have a high rupture risk, and ruptured AcoA aneurysms tend to be smaller than other intracranial aneurysms. We aimed to determine the incidence and morphologic predictors of aneurysm rupture of very small AcoA aneurysms. Methods We conducted a retrospective analysis of 519 consecutive patients with single AcoA aneurysms between December 2007 and February 2015 in our hospital. Aneurysm morphologies were re-measured using CT angiography images. Very small aneurysms were defined as those with a maximum size ≤3 mm, and small aneurysms were defined as those with a maximum size ≤5 mm. Multivariate regression analyses were used to determine the association between aneurysm morphology and aneurysm rupture status. Results Of the 474 ruptured AcoA aneurysms, 134 (28.3%) aneurysms were very small and 278 (58.6%) aneurysms were small. In the univariate analysis for very small aneurysms, larger aneurysm size (p=0.037), larger size ratio (p=0.002), higher aneurysm height (p=0.038), smaller vessel size (p=0.012), and dominant A1 segment configuration (p=0.011) were associated with aneurysm rupture. Multivariate analysis revealed that a larger size ratio was independently associated with the rupture status of the very small aneurysms (OR 3.69, 95% CI 1.5 to 9.0; p=0.004), and larger aneurysm size, larger size ratio, and dominant A1 segment configuration were associated with the rupture of small aneurysms. Conclusions About one-third of ruptured AcoA aneurysms were very small. A larger size ratio, rather than other aneurysm morphologies, was independently associated with the rupture of very small AcoA aneurysms.

Computed Tomography Perfusion Deficits during the Baseline Period in Aneurysmal Subarachnoid Hemorrhage Are Predictive of Delayed Cerebral Ischemia

BACKGROUND AND PURPOSE Delayed cerebral ischemia (DCI) is a frequent and fearful complication following aneurysmal subarachnoid hemorrhage (aSAH). The aim of this study is to assess the diagnostic accuracy of computed tomography perfusion (CTP) during an admission baseline period for the prediction of DCI. METHODS Fifty-four aSAH cases were screened by baseline CTP within 3 days after aSAH and were reexamined with CTP 7-17 days after aSAH. Relative cerebral blood volume, relative cerebral blood flow (CBF), and relative mean transit time were measured. DCI was confirmed by a combination of noncontrast CT, CTP reexamination, and clinical assessment of neurologic deficits. Quantitative baseline and reexamination CTP data for all patients were compared between DCI and without DCI groups using Students t-tests. The quantitative baseline and reexamination CTP data of DCI patients were compared using paired Students t-tests. The χ2 test was used to evaluate incidences of DCI between different baseline relative CBF levels. The optimal cutoff value for each parameter was established by receiver operating characteristic curve analysis. RESULTS Of the patients included in this study, 33.3% (18 of 54) developed DCI. There was a significant difference in the incidence of DCI among different baseline relative CBF subsets (χ2 = 38.00, P < .05). A relative CBF of .84 had the highest specificity and sensitivity of predicting DCI. CONCLUSION CTP parameters during the baseline period can be helpful for the early identification of aSAH patients who are at high risk for DCI.

Control study of low tube voltage computed tomography angiography (CTA) and digital subtraction angiography (DSA) in diagnosing intracranial micro-aneurysm

The aim of this study was to investigate the diagnostic values of low tube voltage cerebral computed tomography (CT) angiography (L‐CTA, 100 kV) of intracranial micro‐aneurysms (IMA, maximum diameter ≤3 mm). The clinical and imaging data of a total of 59 IMA patients confirmed by 3D rotational angiography (3DRA) or surgery were retrospectively analyzed; their L‐CTA data were compared with those of IMA and 3DRA so as to investigate the diagnostic sensitivity, specificity, and accuracy of IMA, as well as to objectively evaluate the related radiation dose. Based on the results of 3DRA, 65 cases of IMA and a total of 70 aneurysms, including 65 micro‐aneurysms, were found in the 59 cases. L‐CTA detected a total of 64 IMA, including six multiple cases of IMA, as well as three false positive cases and four missed cases. Compared with the 3DRA (gold standard), the diagnostic sensitivity, specificity, and accuracy of L‐CTA toward IMA were 93.85%, 99.56%, and 99.08%, respectively, and the associations of aneurysm size measured by L‐CTA and 3DRA were good. Compared with conventional CTA, the effective dose of L‐CTA was reduced by 36.23%. L‐CTA has high diagnostic sensitivity toward IMA, and can effectively reduce the radiation dose, so it is worth implementing.

Whole‑brain CT perfusion imaging using increased sampling intervals: A pilot study

The aim of the present study was to investigate the feasibility of whole-brain perfusion imaging using the increased sampling interval protocol for 320-detector row dynamic-volume computed tomography (CT). A total of 12 volunteers were recruited. The novel protocols with 11 volumes (defined as protocol P11) and 15 volumes (defined as protocol P15) were performed on the volunteers to evaluate whether P11 and P15 are able to acquire comparable results to the standard protocol with 19 volumes (defined as protocol P19) according to the as-low-as-reasonably-achievable principle. All data were acquired using a dynamic-volume CT scanner with a 16 cm-wide detector with 320 rows. The scanned transverse images from volunteers were analyzed using the Volume-Engineered System workstation. The MedCalc software package was used for Bland-Altman analysis of all variables. The data inconsistency of mean transit time (MTT), cerebral blood volume (CBV), cerebral blood flow (CBF), and time to peak (TTP) between P11/P15 and P19 were all <5%, and the data were trustworthy. The mean differences of MTT, CBV, CBF and TTP between P15 and P19 were less than those between P11 and P19. The consistencies of perfusion parameters acquired with protocols P15 and P19 were higher compared with those acquired with P11. In whole-brain perfusion, the new protocol P15 has higher consistency with P19 than P11, and the radiation dose may be reduced by ~16% without degradation of perfusion parameters. Therefore, P15 should be recommended as a routine procedure in whole-brain perfusion imaging.

Apparent diffusion coefficient evaluation for secondary changes in the cerebellum of rats after middle cerebral artery occlusion

Supratentorial cerebral infarction can cause functional inhibition of remote regions such as the cerebellum, which may be relevant to diaschisis. This phenomenon is often analyzed using positron emission tomography and single photon emission CT. However, these methods are expensive and radioactive. Thus, the present study quantified the changes of infarction core and remote regions after unilateral middle cerebral artery occlusion using apparent diffusion coefficient values. Diffusion-weighted imaging showed that the area of infarction core gradually increased to involve the cerebral cortex with increasing infarction time. Diffusion weighted imaging signals were initially increased and then stabilized by 24 hours. With increasing infarction time, the apparent diffusion coefficient value in the infarction core and remote bilateral cerebellum both gradually decreased, and then slightly increased 3-24 hours after infarction. Apparent diffusion coefficient values at remote regions (cerebellum) varied along with the change of supratentorial infarction core, suggesting that the phenomenon of diaschisis existed at the remote regions. Thus, apparent diffusion coefficient values and diffusion weighted imaging can be used to detect early diaschisis.