Young Il Chun

Optimization of MR Parameters of 3D TOF-MRA for Various Intracranial Stents at 3.0T MRI

Purpose The in-stent signal reduction of the stented artery caused by susceptibility artifact or radiofrequency shielding artifact limited the use of time-of-flight MR angiography (TOF-MRA) as a follow-up tool after intracranial stenting. We showed the degree of an artifact according to different stent types, and optimized MR parameters for TOF-MRA in patients with intracranial stent on 3.0 T MRI. Materials and Methods Four stents (Neuroform, Wingspan, Solitaire, and Enterprise) were placed in a vascular flow phantom and imaged by changing flip angle (FA; 20°,30°,40°,50° and 60°) and bandwidth (BW; 31, 42 and 62.5 KHz) using TOF-MRA. Source data of each image set with different FA and BW were reconstructed with the maximal intensity projection (MIP) technique, and MIP images were used to evaluate the in-stent signal reduction of each stent according to the change of MR parameters. The in-stent signal reduction was assessed by calculating the relative in-stent signal (RIS) inside the stent as compared with background and signal intensity of the tube outside the stent. The optimal FA and BW of each stent were determined by comparing the RIS in each stent by one-sample t test. Finally, one neuroradiologist chose one image set with the best image quality. Results The mean RIS for Neuroform, Wingspan, Solitaire and Enterprise stent was 66.3 ± 6.0, 44.2 ± 5.8, 22.8 ± 3.3 and 8.2 ± 2.9, respectively. The significantly high RIS of each stent was obtained with FA/BW value of 20°/31 KHz (Neuroform), 20°/31 KHz and 30°/42 KHz (Wingspan), 40°/42 KHz and 50°/31 KHz (Solitaire) and 40°/31 KHz and 50°/31 KHz (Enterprise). Among these MIP images with significantly high RIS, images with FA/BW value of 20°/31 KHz (Neuroform and Wingspan) and 50°/31 KHz (Solitaire and Enterprise) had the best image quality. Conclusion The degree of artifact was variable according to the design of each intracranial stent. The luminal visualization of closed-cell design stents such as Solitaire and Enterprise can be improved by higher FA. Thus, MR parameter should be adjusted according to the type of intracranial stents.

Time-Resolved 3D Contrast-Enhanced MRA on 3.0T: a Non-Invasive Follow-Up Technique after Stent-Assisted Coil Embolization of the Intracranial Aneurysm

Objective To evaluate the usefulness of time-resolved contrast enhanced magnetic resonance angiography (4D MRA) after stent-assisted coil embolization by comparing it with time of flight (TOF)-MRA. Materials and Methods TOF-MRA and 4D MRA were obtained by 3T MRI in 26 patients treated with stent-assisted coil embolization (Enterprise:Neuroform = 7:19). The qualities of the MRA were rated on a graded scale of 0 to 4. We classified completeness of endovascular treatment into three categories. The degree of quality of visualization of the stented artery was compared between TOF and 4D MRA by the Wilcoxon signed rank test. We used the Mann-Whitney U test for comparing the quality of the visualization of the stented artery according to the stent type in each MRA method. Results The quality in terms of the visualization of the stented arteries in 4D MRA was significantly superior to that in 3D TOF-MRA, regardless of type of the stent (p < 0.001). The quality of the arteries which were stented with Neuroform was superior to that of the arteries stented with Enterprise in 3D TOF (p < 0.001) and 4D MRA (p = 0.008), respectively. Conclusion 4D MRA provides a higher quality view of the stented parent arteries when compared with TOF.

Retrograde stent placement for coil embolization of a wide-necked posterior inferior cerebellar artery aneurysm

Wide-necked aneurysms of the posterior inferior cerebellar artery (PICA) are infrequently encountered in cerebrovascular practice, and endovascular treatment is difficult or impossible even with the use of several neck remodeling techniques. We present the case of a patient with a wide-necked aneurysm of the PICA, which was treated by the retrograde stenting through the contralateral vertebral artery and vertebrobasilar junction with antegrade coil embolization.

Serial Expression of Hypoxia Inducible Factor-1α and Neuronal Apoptosis in Hippocampus of Rats with Chronic Ischemic Brain

OBJECTIVE The purpose of this study is to investigate serial changes of hypoxia-inducible factor 1α (HIF-1α), as a key regulator of hypoxic ischemia, and apoptosis of hippocampus induced by bilateral carotid arteries occlusion (BCAO) in rats. METHODS Adult male Wistar rats were subjected to the permanent BCAO. The time points studied were 1, 2, 4, 8, and 12 weeks after occlusions, with n=6 animals subjected to BCAO, and n=2 to sham operation at each time point, and brains were fixed by intracardiac perfusion fixation with 4% neutral-buffered praraformaldehyde for brain section preparation. Immunohistochemistry (IHC), western blot and terminal uridine deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay were performed to evaluate HIF-1α expression and apoptosis. RESULTS In IHC and western blot, HIF-1α levels were found to reach the peak at the 2nd week in the hippocampus, while apoptotic neurons, in TUNEL assay, were maximal at the 4th week in the hippocampus, especially in the cornu ammonis 1 (CA1) region. HIF-1α levels and apoptosis were found to fluctuate during the time course. CONCLUSION This study showed that BCAO induces acute ischemic responses for about 4 weeks then chronic ischemia in the hippocampus. These in vivo data are the first to show the temporal sequence of apoptosis and HIF-1α expression.

Clinical characteristics of cerebral venous thrombosis in a single center in Korea.

Objective The purpose of this study is to investigate the clinical characteristics of cerebral venous thrombosis (CVT) in a single center in Korea. Methods A total of 36 patients were diagnosed with CVT from August 2005 to May 2013. The patient data regarding age, sex, disease stage, pathogenesis, location, laboratory findings, radiological findings, and treatment modalities were retrospectively collected. The results were compared with those of previous studies in other countries. Results The patient group comprised 21 men and 15 women with a mean age of 46.9 years (ranging from three months to 77 years). The most common cause was a prothrombotic condition (8 patients, 22.2%). Within the patient group, 13 patients (36.1%) had a hemorrhagic infarction, whereas 23 (63.9%) had a venous infarction without hemorrhage. By location, the incidence of hemorrhagic infarction was the highest in the group with a transverse and/or sigmoid sinus thrombosis (n=9); however, the proportion of hemorrhagic infarction was higher in the cortical venous thrombosis group (75%) and the deep venous thrombosis group (100%). By pathogenesis, the incidence of hemorrhagic infarction was the highest in the prothrombotic group (n=6), which was statistically significant (p=0.016). Conclusion According to this study, CVT was more prevalent in men, and the peak age group comprised patients in the sixth decade. The most common cause was a prothrombotic condition. This finding was comparable with reports from Europe or America, in which CVT was more common in younger women. Hemorrhagic infarction was more common in the prothrombotic group (p=0.016) than in the non-prothrombotic group in this study.

Enhanced Efficacy of Human Brain-Derived Neural Stem Cells by Transplantation of Cell Aggregates in a Rat Model of Parkinson's Disease

Objective Neural tissue transplantation has been a promising strategy for the treatment of Parkinsons disease (PD). However, transplantation has the disadvantages of low-cell survival and/or development of dyskinesia. Transplantation of cell aggregates has the potential to overcome these problems, because the cells can extend their axons into the host brain and establish synaptic connections with host neurons. In this present study, aggregates of human brain-derived neural stem cells (HB-NSC) were transplanted into a PD animal model and compared to previous report on transplantation of single-cell suspensions. Methods Rats received an injection of 6-OHDA into the right medial forebrain bundle to generate the PD model and followed by injections of PBS only, or HB-NSC aggregates in PBS into the ipsilateral striatum. Behavioral tests, multitracer (2-deoxy-2-[18F]-fluoro-D-glucose ([18F]-FDG) and [18F]-N-(3-fluoropropyl)-2-carbomethoxy-3-(4-iodophenyl)nortropane ([18F]-FP-CIT) microPET scans, as well as immunohistochemical (IHC) and immunofluorescent (IF) staining were conducted to evaluate the results. Results The stepping test showed significant improvement of contralateral forelimb control in the HB-NSC group from 6-10 weeks compared to the control group (p<0.05). [18F]-FP-CIT microPET at 10 weeks posttransplantation demonstrated a significant increase in uptake in the HB-NSC group compared to pretransplantation (p<0.05). In IHC and IF staining, tyrosine hydroxylase and human β2 microglobulin (a human cell marker) positive cells were visualized at the transplant site. Conclusion These results suggest that the HB-NSC aggregates can survive in the striatum and exert therapeutic effects in a PD model by secreting dopamine.

Multimodal CT: Favorable Outcome Factors in Acute Middle Cerebral Artery Stroke with Large Artery Occlusion

Background: We investigated which parameters of multimodal computed tomography (CT) or their combinations might be useful as additional imaging predictors for favorable outcomes in acute stroke patients with large artery occlusion. Methods: The parameters of multimodal CT, including non-enhanced CT, CT angiography, perfusion CT parameters, CT angiography source image (CTA-SI), and collateral flow, were analyzed in 66 consecutive patients with acute middle cerebral artery stroke with large artery occlusion. For favorable outcomes at the 3-month follow-up, odds ratios of multimodal CT parameters with an optimum predictive cut-off Alberta Stroke Program Early CT Score (ASPECTS) were assessed. Results: Cerebral blood volume (CBV) ASPECTS ≥6, CTA-SI ASPECTS ≥7, and good collateral flow were associated with a favorable outcome. The combination of those parameters had better predictive validity compared to a single parameter only: CBV (p = 0.039), CTA-SI (p = 0.038), and collateral flow (p < 0.001). Conclusion: Among the various parameters of multimodal CT, CBV ASPECTS ≥6, CTA-SI ASPECTS ≥7, and good collateral flow might be the most reliable predictors for favorable outcomes in acute stroke patients with large artery occlusion. Moreover, considering these parameters simultaneously might improve the predictive validity of multimodal CT for functional outcome.

Atherosclerotic arterial wall change of non-stenotic intracracranial arteries on high-resolution MRI at 3.0T: Correlation with cerebrovascular risk factors and white matter hyperintensity.

OBJECTIVE Prior to detecting intracranial arterial stenosis, atherosclerotic wall change or plaque with positive remodeling can be evaluated with high-resolution MRI (HRMRI). We prospectively evaluate atherosclerotic arterial wall change in patients without intracranial stenosis using HRMRI at 3.0T and correlate the atherosclerotic change, cerebrovascular risk factors, and white matter hyperintensity (WMH). METHODS Patients were prospectively recruited for one year and underwent brain MRI, TOF-MRA and HRMRI using axial 3D T1 FSE of the intracranial arteries. After excluding patients with intracranial stenosis, two neuroradiologists graded the atherosclerotic change of the intracranial arterial wall on HRMRI and WMH using a 4-point scale. The relationship between atherosclerotic changes on HRMRI, cerebrovascular risk factors, and WMH were statistically evaluated. RESULTS Eighty-three patients without intracranial arterial stenosis were finally included. Older age (p=0.000), hypertension (p=0.002), and hyperlipidemia (p=0.007) were associated with severe atherosclerotic change on HRMRI. On multivariate analysis, older age (OR: 0.114; 95% CI: 0.033-0.397; p=0.001) and hypertension (OR: 0.178; 95% CI: 0.049-0.651; p=0.009) were significantly associated with severe atherosclerotic change on HRMRI. The presence of moderate and severe WMH was associated with older age, hypertension, and severe atherosclerotic change on HRMRI. On multivariate analysis, atherosclerotic change on HRMRI remained the only variable significantly associated with WMH (OR: 0.086; 95% CI: 0.016-0461; p=0.004). CONCLUSION Older age and hypertension are significantly associated with intracranial atherosclerotic change on HRMRI. Atherosclerotic change detected on HRMRI may be the strongest risk factor for WMH than any other cerebrovascular risk factor in patients without intracranial stenosis.

Grading of intracerebral hemorrhage in ruptured middle cerebral artery aneurysms.

Objective To propose grading of intracerebral hemorrhage (ICH) in ruptured middle cerebral artery (MCA) aneurysms, which helps to predict the prognosis more accurately. Methods From August 2005 to December 2010, 27 cases of emergent hematoma evacuation and aneurysm clipping for MCA aneurysms were done in the authors clinic. Three variables were considered in grading the ICH, which were 1) hematoma volume, 2) diffuse subarachnoid hemorrhage (SAH) that extends to the contralateral sylvian cistern, and 3) the presence of midline shifting from computed tomography findings. For hematoma volume of greater than 25 mL, we assigned 2 points whereas 1 point for less than 25 cc. We also assigned 1 point for the presence of diffuse SAH whereas 0 point for the absence of it. Then, 1 point was assigned for midline shifting of greater than 5 mm whereas 0 point for less than 5 mm. Results According to the grading system, the numbers of patients from grade 1 to 4 were 4, 6, 8 and 9 respectively and 5, 7, 8, 4 and 3 patients belonged to Glasgow Outcome Scale (GOS) 5 to 1 respectively. It was found that the patients with higher GOS had lower ICH grade which were confirmed to be statistically significant (p<0.01). Preoperative Hunt and Hess grade and absence of midline shifting were the factors to predict favorable outcome. Conclusion The ICH grading system composed of above three variables was helpful in predicting the patients outcome more accurately.

Eosinophilic Myelitis in the Cervical Cord Mimicking Intramedullary Cord Tumor

Eosinophilic myelitis (EM) or atopic myelitis is a rare disease characterized by a myelitic condition in the spinal cord combined with allergic process. This disease has specific features of elevated serum IgE level, active reaction to mite specific antigen and stepwise progression of mostly the sensory symptoms. Toxocariasis can be related with a form of EM. This report describes two cases of cervical eosinophilic myelitis initially considered as intramedullary tumors. When a differential diagnosis of the intramedullary spinal cord lesion is in doubt, evaluation for eosinophilic myelitis and toxocariasis would be beneficial.