Kouichi Misaki

Identification of the Inflow Zone of Unruptured Cerebral Aneurysms: Comparison of 4D Flow MRI and 3D TOF MRA Data

BACKGROUND AND PURPOSE: The hemodynamics of the inflow zone of cerebral aneurysms may be a key factor in coil compaction and recanalization after endovascular coil embolization. We performed 4D flow MR imaging in conjunction with 3D TOF MRA and compared their ability to identify the inflow zone of unruptured cerebral aneurysms. MATERIALS AND METHODS: This series comprised 50 unruptured saccular cerebral aneurysms in 44 patients. Transluminal color-coded 3D MRA images were created by selecting the signal-intensity ranges on 3D TOF MRA images that corresponded with both the luminal margin and the putative inflow. RESULTS: 4D flow MR imaging demonstrated the inflow zone and yielded inflow velocity profiles for all 50 aneurysms. In 18 of 24 lateral-projection aneurysms (75%), the inflow zone was located distally on the aneurysmal neck. The maximum inflow velocity ranged from 285 to 922 mm/s. On 4D flow MR imaging and transluminal color-coded 3D MRA studies, the inflow zone of 32 aneurysms (64%) was at a similar location. In 91% of aneurysms whose neck section plane angle was <30° with respect to the imaging section direction on 3D TOF MRA, depiction of the inflow zone was similar on transluminal color-coded 3D MRA and 4D flow MR images. CONCLUSIONS: 4D flow MR imaging can demonstrate the inflow zone and provide inflow velocity profiles. In aneurysms whose angle of the neck-section plane is obtuse vis-a-vis the imaging section on 3D TOF MRA scans, transluminal color-coded 3D MRA may depict the inflow zone reliably.

Contrast-enhanced fluid-attenuated inversion recovery MRI is useful to detect the CSF dissemination of glioblastoma.

We present three cases of glioblastoma with CSF dissemination that contrast-enhanced fluid-attenuated inversion recovery MRI was sensitive enough to detect compared with contrast-enhanced T1-weighted MRI. An autopsy was performed on one patient, and its histologic findings proved the existence of CSF dissemination.

Prediction of carotid artery in-stent restenosis by quantitative assessment of vulnerable plaque using computed tomography

BACKGROUND AND PURPOSE To assess the relationship between plaque volume evaluated by multidetector computed tomographic angiography (MDCT) and in-stent restenosis (ISR) after carotid artery stenting (CAS). MATERIALS AND METHODS From a retrospectively maintained database, data were collected for 52patients with carotid artery stenosis treated with CAS between 2007 and 2012. We defined ISR of≥50% as a peak systolic velocity≥200cm/s on echo-duplex scan. Carotid plaques were subdivided into four components according to radiodensity in Hounsfield units (HU) as follows: <0, 0-60, 60-130, and>600HU. Risk factors that influenced ISR were compared using univariate and multivariate Cox regression analyses. RESULTS During a median follow-up period of 36months, ISR of≥50% was detected in five patients (9.6%). In the univariate Cox proportional hazard regression analysis, renal insufficiency, coronary artery disease, total plaque volume, and plaque volumes with radiodensities<0 and≥600HU increased the risk for ISR (P<0.10). When the significant risk factors determined from the univariate analysis were subjected to a multivariate analysis, only the volumes of the plaque components with radiodensities<0 HU independently predicted the development of ISR (hazard ratio: 1.041; 95% confidence interval: 1.006-1.078; P=0.021). CONCLUSION Our data suggest that the high volume of the plaque components with radiodensities<0HU was independently associated with the increased risk of ISR after CAS. Quantitative and qualitative tissue characterizations of carotid plaques using MDCT might be a useful predictive tool of the development of ISR.

MGMT promoter methylation and temozolomide response in choroid plexus carcinoma

Choroid plexus carcinoma (CPC) is a malignant tumor with a strong tendency to spread along the cerebrospinal fluid pathway. There is no standardized chemotherapy protocol for this rare tumor. We report a 38-year-old man with CPC in the lateral ventricle with obstructive hydrocephalus. Because of the poor demarcation between thalamus and fornix, subtotal tumor resection was performed. Postoperative spine magnetic resonance (MR) image revealed whole spinal axis dissemination. After diagnosis of CPC, the patient was treated with whole ventricular and spine radiation concomitant with temozolomide chemotherapy, although the O6-methylguanine-DNA methyltransferase (MGMT) promoter was found to be unmethylated. Although MR images revealed transient stable disease during adjuvant therapy, tumor progression was depicted after four cycles of temozolomide therapy. We discuss the ineffectiveness of adjuvant temozolomide therapy for CPC in connection with O6-methylguanine-DNA methyltransferase promoter methylation.

Delayed asymptomatic coil migrations toward different arteries after aneurysmal embolization: case report.

Delayed coil migration after endovascular treatment with detachable coils, particularly several months after treatment, is extremely rare. In this report, the authors describe a 77-year-old female in whom delayed coil migration to the anterior cerebral artery and posterior communicating artery (PCoA) developed 3 months after an uncomplicated aneurysm embolization. The patient was successfully retreated with a closed-cell stent. Computational fluid dynamics (CFD) revealed high wall shear stress (WSS) and multiple vortices in the residual cavity of the initially treated aneurysm. CFD could be useful to detect and predict this complication, and a stent-assisted technique could be an important treatment option.

Pseudoaneurysm formation caused by the withdrawal of a Trevo ProVue stent at a tortuous cerebral vessel: a case report.

This is the first report on the mechanism of pseudoaneurysm formation after withdrawal of a stent retriever. A 79-year-old woman developed cardiogenic embolization of the distal middle cerebral artery (M2). The deployed stent retriever bent because of vessel tortuosity. After withdrawal of the stent with strong resistance, complete revascularization was achieved, but an extravasation was detected at the site. Eight hours after disappearance of the extravasation, re-bleeding occurred with aneurysm-like pooling of contrast media. Direct surgical observation confirmed a pseudoaneurysm formation. The pseudoaneurysm was likely formed by avulsion of a fine vessel during withdrawal of the stent retriever at a tortuous vessel.

Inflow hemodynamics evaluated by using four-dimensional flow magnetic resonance imaging and the size ratio of unruptured cerebral aneurysms

PurposePrediction of the rupture risk is critical for the identification of unruptured cerebral aneurysms (UCAs) eligible for invasive treatments. The size ratio (SR) is a strong morphological predictor for rupture. We investigated the relationship between the inflow hemodynamics evaluated on four-dimensional (4D) flow magnetic resonance (MR) imaging and the SR to identify specific characteristics related to UCA rupture.MethodsWe evaluated the inflow jet patterns and inflow hemodynamic parameters of 70 UCAs on 4D flow MR imaging and compared them among 23 aneurysms with an SR ≧2.1 and 47 aneurysms with an SR ≦2.0. Based on the shape of inflow streamline bundles with a velocity ≧75% of the maximum flow velocity in the parent artery, the inflow jet patterns were classified as concentrated (C), diffuse (D), neck-limited (N), and unvisualized (U).ResultsThe incidence of patterns C and N was significantly higher in aneurysms with an SR ≧2.1. The rate of pattern U was significantly higher in aneurysms with an SR ≦2.0. The maximum inflow rate and the inflow rate ratio were significantly higher in aneurysms with an SR ≧2.1.ConclusionsThe SR affected the inflow jet pattern, the maximum inflow rate, and the inflow rate ratio of UCAs. In conjunction with the SR, inflow hemodynamic analysis using 4D flow MR imaging may contribute to the risk stratification for aneurysmal rupture.

Treatment Result in the Initial Stage of Kanazawa Mobile Embolectomy Team for Acute Ischemic Stroke

Five recent multicenter randomized controlled trials (RCTs) have clearly shown the superiority of mechanical thrombectomy in large vessel occlusion acute ischemic stroke compared to systemic thrombolysis. Although 14 hospitals in Ishikawa prefecture have uninterrupted availability of systemic thrombolysis, mechanical thrombectomy is not available at all of these hospitals. Therefore, we established a Kanazawa mobile embolectomy team (KMET), which could travel to these hospitals and perform the acute reperfusion therapy. In this article, we report early treatment outcomes and validate the effectiveness of a network between affiliated hospitals and KMET. Between January 2014 and December 2015, 48 patients, aged 45–92 years (mean: 73.0 years), underwent acute reperfusion therapy provided by KMET in 10 affiliated hospitals of Kanazawa University Hospital. The pre-treatment NIHSS scores ranged from 5 to 39 (mean: 19.1). ASPECTS+W ranged from 1 to 11 (mean: 7.3). Successful revascularization, defined as thrombolysis in cerebral infarction (TICI) 2b or 3, was achieved in 38/48 cases (80%), and a good outcome, defined as modified Rankin Scale (mRS) score from 0 to 2 at 90 days after the treatment, was achieved in 24/48 cases (50%). There were two cases of intracranial bleeding (4%). Mean time from onset to recanalization was 297 min. These results, which are similar to those of five previous RCTs, suggest that a collaborative network between affiliated hospitals and KMET is effective for acute reperfusion therapy in local areas wherein experienced neuroendovascular specialists are insufficient.

Cerebral Infarction Related to Carmustine Wafers in Glioblastoma: A Case Report

Implantation of carmustine-impregnated wafers (Gliadel®) into the tumor resection cavity has demonstrated a survival benefit for patients with malignant glioma. However, some precautions should be taken regarding Gliadel implantation. We report a case of a 63-year-old man with glioblastoma who was implanted with Gliadel after a left temporal lobe tumor had been removed, and who later developed vasospasm of the lenticulostriate artery close to the implanted Gliadel, leading to serious cerebral infarction. Therefore, the implantation of Gliadel in cases where important vessels run close to the resection cavity should be considered with great caution.

Parent Artery Curvature Influences Inflow Zone Location of Unruptured Sidewall Internal Carotid Artery Aneurysms

BACKGROUND AND PURPOSE: Future aneurysmal behaviors or treatment outcomes of cerebral aneurysms may be related to the hemodynamics around the inflow zone. Here we investigated the influence of parent artery curvature on the inflow zone location of unruptured sidewall internal carotid artery aneurysms. MATERIALS AND METHODS: In 32 aneurysms, the inflow zone location was decided by 4D flow MR imaging, and the radius of the parent artery curvature was measured in 2D on an en face image of the section plane corresponding to the aneurysm orifice. RESULTS: The inflow zone was on the distal neck in 10 (group 1, 31.3%), on the lateral side in 19 (group 2, 59.4%), and on the proximal neck in 3 (group 3, 9.4%) aneurysms. The radius in group 1 was significantly larger than that in group 2 (8.3 mm [4.5 mm] versus 4.5 mm [1.9 mm]; median [interquartile range]; P < .0001). All 7 aneurysms with a radius of >8.0 mm were in group 1. All 18 aneurysms with a radius of <6.0 mm were in group 2 or 3. In two group 3 aneurysms, the inflow zone was located in a part of the neck extending beyond the central axis of the parent artery. CONCLUSIONS: The inflow zone locations of sidewall aneurysms can be influenced by the parent artery curvature evaluated in 2D on an en face image of the section plane corresponding to the aneurysm orifice.