Kouhei Nii

Fukuoka University, Hukuoka, Fukuoka, Japan

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Publications (43)52.54 Total impact

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    ABSTRACT: Background: Stent-assisted coil embolization (SACE) is used to address wide-necked or complex aneurysms. However, as they may recanalize after SACE, predictors of recanalization are needed. We investigated the relationship between follow-up angiographic results and the morphology of sidewall (SW) aneurysms in patients treated by SACE. Methods: Between September 2010 and September 2014, we performed 80 SACE procedures for SW intracranial aneurysms. Angiographic findings, obtained immediately after the procedure, 3-6 months thereafter, and when aneurysmal recanalization was suspected on MR angiogram scan, were recorded. Morphologically, the SW aneurysms were classified as "outside" (OS) and "partially inside" (PI) based on the curve of the axes of the proximal or distal parent artery with respect to the aneurysmal neck. Follow-up angiographic studies on OS- and PI SW aneurysms were compared. Results: On the initial angiograms, we classified 42 aneurysms as OS and 38 as PI. Immediately after SACE, there was no significant difference in the angiographic findings on OS and PI aneurysms. However, on follow-up angiograms, there was a significant difference in the rate of spontaneous improvement (4 of 42 [OS] versus 21 of 38 [PI], P = .001). We performed additional coil embolization to treat 3 recanalized OS aneurysms. Conclusions: SW aneurysms classified morphologically as PI tended to occlude progressively even after incomplete occlusion by SACE. In contrast, aneurysms classified as OS must be observed carefully after SACE.
    No preview · Article · Dec 2015 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    ABSTRACT: Stent-assisted coil embolization is effective for intracranial aneurysms, especially for wide-necked aneurysms; however, the optimal antiplatelet regimens for postoperative ischemic events have not yet been established. We aimed at determining the efficacy and safety of a triple antiplatelet therapy regimen after intracranial stent-assisted coil embolization. We retrospectively evaluated patients who underwent stent-assisted coil embolization for unruptured intracranial aneurysms or during the chronic phase of a ruptured intracranial aneurysm (≥4 weeks after subarachnoid hemorrhage onset). We recorded the incidence of ischemic and bleeding events 140 days postoperatively. We assessed 79 cases in patients who received either dual (n = 51) or triple (n = 28) antiplatelet therapy. The duration of triple antiplatelet therapy was 49 ± 29 days. Seven patients in the dual group experienced postoperative ischemic events. Compared to the dual group, the triple group had a similar incidence of postoperative bleeding events but a significantly lower incidence of postoperative ischemic events (P < .05). Triple antiplatelet therapy had a significantly lower incidence of postoperative ischemic events and a similar incidence of postoperative bleeding events 140 days postoperatively. Copyright © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.
    No preview · Article · Apr 2015 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    ABSTRACT: Recent sporadic reports have described successful endovascular treatment of cerebral aneurysms associated with fenestration. We experienced an unruptured cerebral aneurysm case, with fenestration of the horizontal portion of the anterior cerebral artery that was successfully treated with coil embolization using an intracranial stent. An 80-year-old man presented with a chief complaint of gait disorder. Magnetic resonance imaging showed an incidental unruptured aneurysm. Three-dimensional digital subtraction angiography revealed a cerebral aneurysm associated with fenestration of the horizontal portion of the anterior cerebral artery. Endovascular surgery was performed at the patient's request. Conservation of the fenestrated vessels and perforators is important in the treatment of cerebral aneurysm associated with fenestration. Intracranial stents are reportedly useful for conserving not only parent vessels but also their perforators. In the present case, no postoperative perforator damage occurred. An endovascular approach is a potential treatment option with full evaluation of the relationship between the aneurysm and fenestrated vessels.
    No preview · Article · Jan 2015 · No shinkei geka. Neurological surgery
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    ABSTRACT: Objective: We report a case of acute internal carotid artery (ICA) severe stenosis completely recanalized using a stent placement and a Solitaire FR.Case presentation: A 72-year-old man presented with sudden onset of left hemiplegia and dysarthria. MRI showed early ischemic changes in the right insular cortex and frontal cortex along with right severe ICA stenosis. Cerebral angiography demonstrated severe stenosis at the origin of the right ICA and middle cerebral artery (MCA) occlusion. The ICA stenosis was improved by stent placement at the origin of ICA, and MCA occlusion was done by thrombectomy using the Solitaire FR resulting in neurological improvement.Conclusion: IV-tPA therapy was not particularly useful in patients with ICA severe stenosis. However, if standard medical management is ineffective in patients with acute cerebral infarction due to tandem arterial lesions, combined percutaneous revascularization of each lesions can prevent catastrophic events.
    Preview · Article · Jan 2015
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    ABSTRACT: We investigated the incidence of embolic protection device retrieval difficulties at carotid artery stenting (CAS) with a closed-cell stent and demonstrated the usefulness of a manual carotid compression assist technique. Between July 2010 and October 2013, we performed 156 CAS procedures using self-expandable closed-cell stents. All procedures were performed with the aid of a filter design embolic protection device. We used FilterWire EZ in 118 procedures and SpiderFX in 38 procedures. The embolic protection device was usually retrieved by the accessory retrieval sheath after CAS. We applied a manual carotid compression technique when it was difficult to navigate the retrieval sheath through the deployed stent. We compared clinical outcomes in patients where simple retrieval was possible with patients where the manual carotid compression assisted technique was used for retrieval. Among the 156 CAS procedures, we encountered 12 (7.7%) where embolic protection device retrieval was hampered at the proximal stent terminus. Our manual carotid compression technique overcame this difficulty without eliciting neurologic events, artery dissection, or stent deformity. In patients undergoing closed-cell stent placement, embolic protection device retrieval difficulties may be encountered at the proximal stent terminus. Manual carotid compression assisted retrieval is an easy, readily available solution to overcome these difficulties. Copyright © 2014 National Stroke Association. Published by Elsevier Inc. All rights reserved.
    No preview · Article · Nov 2014 · Journal of Stroke and Cerebrovascular Diseases
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    ABSTRACT: Background: No predictor of postoperative ischemic events has been identified in patients undergoing carotid artery stenting (CAS). We aimed to determine whether N(ε)-(carboxymethyl)lysine (CML) in debris trapped by an embolic protection filter device is a predictor of postoperative ischemic events. Methods: We enrolled 27 patients (73.4 ± 7.2 years; 22 male, 5 female) who underwent CAS for carotid artery stenosis. Diffusion-weighted magnetic resonance imaging was performed before and after the procedure. Protein samples were extracted from the debris. CML and myeloperoxidase were examined by solid phase enzyme-linked immunosorbent assay and Western blot analysis. Results: Seventeen patients had 0 or 1 new lesion (nonmultiple lesions) postoperatively, whereas 10 patients had 2 or more new lesions postoperatively (multiple lesions). The CML concentration of the protein sample was significantly higher in patients with multiple lesions than in those with nonmultiple lesions (6.26 ± 2.77 ng/mg protein and 3.36 ± 1.57 ng/mg protein, respectively; P = .010). Statin therapy for dyslipidemia was associated with a lower incidence of multiple lesions and a lower concentration of CML in the protein sample (P = .004 and P = .02, respectively). Receiver operating characteristic analysis showed that the area under the curve for CML was significantly greater than .5 (.877; 95% confidence interval, .742-1.00). Conclusions: CML derived from debris may distinguish between patients with postoperative multiple ischemic lesions and those with postoperative nonmultiple lesions who undergo CAS.
    No preview · Article · Oct 2014 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    ABSTRACT: Objective: Coil embolization for wide-necked and bilobulated aneurysms remains a technical challenge even with stent assistance. Stent assistance prevents coil protrusion to the parent vessel, but restricts microcatheter movement. The restriction of microcatheter movement makes the role of the coil’s shape memory important on the coil distribution within the aneurysm. We aimed to determine which coils are appropriate for wide-necked and bilobulated aneurysms with stent assistance by investigating the distribution of coils with differing shape memory.Methods: A silicone bilobulated aneurysm model was used to compare three types of coils (ED coil Infini, Axium Helix, and Axium 3D). Coil performance was assessed using three parameters: (1) the effect of stent assistance on coil distribution, (2) the difference in first coil distribution caused by a difference in shape memory, and (3) the influence of first coil distribution on second coil distribution.Results: Without stent assistance, coil protrusion into the parent vessel was detected immediately after beginning coil insertion for ED coil Infini; however, this coil protrusion was prevented using stent assistance. With stent assistance, the lowest shape memory coil resulted in the most homogenous distribution. The distribution of second coil was influenced by first coil.Conclusion: Without stent assistance, low shape memory coil was more likely to prolapse into the parent vessel compared to higher shape memory coil. When combined with a stent, the low shape memory coil demonstrated more homogenous distribution of the aneurysm compared to the higher shape memory coil, and allowed denser packing.
    No preview · Article · Jan 2014

  • No preview · Article · Jan 2014 · Surgery for Cerebral Stroke
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    ABSTRACT: Carotid in-stent thrombosis can cause thromboembolic events although it is a rare complication of carotid artery stenting(CAS). We present a successful case of percutaneous mechanical thrombectomy for symptomatic subacute in-stent thrombosis. A 64-year-old man was hospitalized for the treatment of a cerebral infarction presenting with dysarthria and left upper extremity weakness. Following sufficient medical management including dual anti-platelet therapy, CAS was performed because cerebral angiograms showed severe and long-segment right internal carotid artery(ICA)stenosis. Although the stenosis was resolved, right cerebral infarction presented with progressive left hemiparesis 12 days after CAS. Emergency cerebral angiograms revealed right ICA occlusion due to in-stent thrombosis. Rapid revascularization with percutaneous mechanical thrombectomy of the in-stent occlusion was performed using the Penumbra Aspiration System because a microguidewire could not pass through the occlusion. Post-procedural angiogram revealed recanalization of the right ICA, and the patient was free from neurological events after the last procedure. The evaluation and treatment of peri-procedural in-stent thrombosis following CAS must be prompt and aggressive for prevention of catastrophic events. Percutaneous mechanical thrombectomy is a useful tool for rapid treatment of acute or subacute in-stent thrombosis after CAS.
    No preview · Article · Sep 2013 · No shinkei geka. Neurological surgery
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    ABSTRACT: Stent-assisted coil embolization is effective for intracranial aneurysms, especially wide-necked aneurysms; however, the optimal antiplatelet regimens for ischemic events that develop after coil embolization have not yet been established. We aimed to determine the onset time of such postoperative ischemic events and the relationship between these events and antiplatelet therapy. We performed coil embolization using a vascular reconstruction stent for 43 cases of intracranial aneurysms and evaluated the incidence of postoperative ischemic events in these cases. Nine patients showed postoperative ischemic events during the follow-up period (13 ± 7 months). Two patients developed cerebral infarction within 24 hours. Five patients developed transient ischemic attack within 40 days while they were receiving dual antiplatelet therapy. In addition, 1 patient showed cerebral infarction 143 days postoperatively during single antiplatelet therapy, and a case of transient visual disturbance was reported 191 days postoperatively (49 days after antiplatelet therapy had been discontinued). We increased the number of antiplatelet agents in 4 of these patients. The other 5 patients were under strict observation with dual antiplatelet therapy. All these patients were shifted to single antiplatelet therapy 3-13 months postoperatively. No recurrence of ischemic events was noted. Postoperative ischemic events are most likely to occur within 40 days postoperatively. For patients with postoperative ischemic events, additional ischemic events can be prevented by increasing the number of antiplatelet agents; subsequently, they can be shifted to single antiplatelet therapy after the risk of recurrence has decreased.
    No preview · Article · Aug 2013 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    ABSTRACT: An 87-year-old man presented with extracranial vertebral artery (VA) occlusion and progressive vertebrobasilar ischemia despite maximal medical management. Cerebral angiography showed left proximal VA occlusion, termination of the right VA at the ipsilateral posterior inferior cerebellar artery, and hypoplastic bilateral posterior communicating arteries. Although the stump of the left VA ostium was not visualized, the distal patent artery was reconstituted via muscular branches from the left subclavian artery (SCA). Endovascular angioplasty with a stent for left VA occlusion was performed. The non-visualized VA ostium was extrapolated from the computed tomography angiography findings of the distal patent VA and the partial calcification of the SCA. The occluded VA was penetrated by the guide wire and revascularized by balloon angioplasty with the stent using the support of a snare wire inserted via the left brachial artery for stabilization of the guide catheter. This treatment resulted in resolution of the severe neurological findings.
    No preview · Article · Jun 2013 · Neurologia medico-chirurgica
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    ABSTRACT: The pull-through angioplasty technique allows stable wire tension and stabilization of the device during the procedure. In this technique, a guide wire is passed from one sheath to another, usually with the aid of a snare device. We describe the treatment of occlusive subclavian artery disease and lesion at the origin of the vertebral artery employing a brachiofemoral pull-through technique without using a snare device. In this technique, the guide wire is advanced from the femoral artery to the brachial artery. The guide wire is directly inserted into the sheath placed at the brachial artery. The brachial artery is compressed proximal to the point of sheath insertion to prevent bleeding. The sheath is extracted temporally and the guide wire is caught outside of the body. The sheath is then introduced again through the guide wire. We used the pull-through technique without a snare device in seven cases, and we were able to build the pull-through system in six of these cases without a snare device. This pull-through technique without a snare device is not difficult to use, and may reduce the time and cost of angioplasty procedures.
    No preview · Article · Jun 2013 · Interventional Neuroradiology
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    ABSTRACT: The clinical effects of two different types of antiplatelet drugs, cilostazol and thienopyridine drugs, were compared in patients treated by carotid artery stenting (CAS). Two hundred patients scheduled for CAS were randomized to either cilostazol or a thienopyridine drug (ticlopidine or clopidogrel). The study was conducted in open-label design. Aspirin was also given to all patients. All episodes of periprocedural hemodynamic instability (bradycardia, hypotension) were recorded together with all instances of stroke, cardiac morbidity, and death within 30 days of the procedure. Angiographic follow-up studies were conducted about 6 months after CAS. Finally, 197 patients were enrolled in this study; 97 were treated with cilostazol (cilostazol group) and 100 with a thienopyridine drug (thienopyridine group). In the 30-day follow-up period, the incidence of stroke, cardiac adverse effects, and death was not significantly different between the 2 groups (cilostazol group 7.2%, thienopyridine group 11.0%; p = 0.85). The incidence of intra- and postprocedural bradycardia was significantly lower in the cilostazol group (cilostazol group 18.6% and 2.1%, thienopyridine group 40.0% and 18.0%, respectively; p < 0.01). Although the incidence of intraprocedural hypotension did not significantly differ between the 2 groups, postprocedural hypotension was significantly lower in the cilostazol group (16.5% vs. 34.0%, p < 0.01). In-stent restenosis on follow-up angiograms was lower in the cilostazol group but not significantly (0% vs. 4.4%, p = 0.12). This small open-label study shows that cilostazol may reduce periprocedural bradycardia and hypotension compared with thienopyridine drugs in patients treated by CAS.
    No preview · Article · Mar 2013 · Neurologia medico-chirurgica
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    ABSTRACT: Objective: During balloon-assisted coil embolization of intracranial aneurysms with the HyperForm balloon microcatheter (HyperForm; eV3 Neurovascular, Irvine, CA, USA) we encountered an instance where the balloon was inflated unexpectedly when a guidewire was fixed by the thumbwheel of the Y-connector provided with the one-touch slide-type valve. We report this phenomenon with a description of procedural precautions.Method: Between April 2011 and December 2012, balloon-assisted coil embolization with HyperForm was performed in 24 patients with intracranial aneurysms at our facility. The Y-connectors that were used to connect the HyperForm were provided with either a one-touch slide-type valve (13 patients) or a conventional throttle valve (11 patients).Result: The balloon inflated in all 13 patients when the guidewire was fixed by turning the thumbwheel of the Y-connector provided with the one-touch slide-type valve during the setup of HyperForm. In Y-connectors with the conventional throttle valve, balloon inflation was not observed after performing the same procedure.Conclusion: The Y-connector provided with the one-touch slide-type valve is beneficial for reducing blood loss from cases requiring the frequent insertion and removal of devices. However, if the Y-connector is used with a single-lumen balloon catheter, which is inflated after the tip opening is closed with a guidewire, turning the thumbwheel will increase the internal pressure of the catheter and consequently pose a risk of unexpected balloon inflation.
    No preview · Article · Jan 2013
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    ABSTRACT: Purpose: This retrospective study aimed to compare the effectiveness of the embolization prevention mechanism of two types of embolic protection device (EPD)-a distal protection balloon (DPB) and a distal protection filter (DPF). Methods: Subjects were 164 patients scheduled to undergo carotid artery stenting: a DPB was used in 82 cases (DPB group) from April 2007 until June 2010, and a DPF was used in 82 cases (DPF group) from July 2010 to July 2011. Rates of positive findings on postoperative diffusion-weighted imaging (DWI) and stroke incidence were compared. Results: Positive postoperative DWI results were found in 34 cases in the DPB group (41.4 %), but in only 22 cases in the DPF group (26.8 %), and there was only a small significant difference within the DPF group. In the DPB group, there was one case of transient ischemic attack (TIA) (1.2 %) and four cases of brain infarction (2 minor strokes, 2 major strokes; 4.9 %), compared to the DFP group with one case of TIA (1.2 %) and no cases of minor or major strokes. Conclusions: In this study, significantly lower rates of occurrence of DWI ischemic lesions and intraoperative embolization were associated with use of the DPF compared to the DPB.
    No preview · Article · Nov 2012 · Japanese journal of radiology
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    ABSTRACT: Hyperperfusion syndrome (HPS) is a rare but severe complication after carotid artery stenting (CAS). Reliable methods for predicting HPS remain to be developed. We aimed to establish a predictive value of hemorrhagic HPS after CAS. Our retrospective study included 136 consecutive patients who had undergone CAS. We determined the cerebral circulation time (CCT) by measuring the interval between the point of maximal opacification of the terminal portion of the internal carotid artery and the cortical vein. We calculated intraprocedural CCT changes (ΔCCT) by subtracting postprocedural CCT values from preprocedural CCT values. The mean ΔCCT was 0.9 ± 0.9 seconds; 3 patients (2.2%) with prolonged ΔCCT (2.7, 5.4, and 5.8 seconds) developed HPS. The cutoff time of 2.7 seconds predicted hemorrhagic HPS retrospectively with 100% sensitivity and 99% specificity. Our findings suggest that post-CAS HPS can be predicted by using the ΔCCT value obtained by intraprocedural digital subtraction angiography. Patients with a ΔCCT >2.7 seconds require careful intensive hemodynamic and neurologic monitoring after CAS.
    No preview · Article · Dec 2011 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    ABSTRACT: The rates of hemodynamic depression (HD) and thromboembolism were compared in 95 carotid artery stenting (CAS) procedures performed in 87 patients with severe carotid artery stenosis using self-expandable braided Elgiloy stents (Wallstent) in 52 and slotted-tube Nitinol stents (Precise) in 43 procedures. The blood pressure, pulse rate, and neurological signs were recorded at short intervals during and after CAS. All patients underwent diffusion-weighted magnetic resonance imaging within 5 days after the procedure. The incidences of hypotension, bradycardia, and both were 17.9%, 3.2%, and 11.6%, respectively. The rate of postprocedural HD was 23.1% with Wallstent and 44.2% with Precise; the difference was significant (p = 0.025). No patient manifested major cardiovascular disease after CAS. Diffusion-weighted magnetic resonance imaging revealed thromboembolism after 26.9% and 34.9% of Wallstent and Precise stent placement procedures, respectively; the difference was not significant. The type of self-expandable stent placed may affect the risk of procedural HD in patients undergoing CAS. Postprocedural HD was resolved successfully by the administration of vasopressors and by withholding antihypertensive agents.
    No preview · Article · Aug 2011 · Neurologia medico-chirurgica
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    ABSTRACT: Selection of the appropriate diameter of stent is difficult in patients with the size mismatch between the internal carotid artery (ICA) and the common carotid artery (CCA). Although stent overexpansion (SOE) in the ICA after carotid artery stenting (CAS) is suspected of producing restenosis, SOE has not been well established. We discuss its incidence, predictors, and outcomes. We retrospectively reviewed follow-up angiographs of 206 CAS-treated arteries in 201 patients who had undergone CAS. SOE was defined as angiographic evidence of an intimal gap between the non-stented normal and the dilated stented ICA at the distal stent edge. We also collected data on the patients' clinical status, comorbidities, and radiological and procedural data. Patients with SOE were further followed up closely by duplex ultrasound scans. SOE was detected in nine of 206 CAS-treated ICAs (4.4%). Univariate analysis revealed a significant association between SOE and open-cell stents, the stent diameter (p < 0.01), pre-procedural stenosis, the ICA diameter, ICA/CCA ratio, and the ICA/stent ratio (p < 0.05). Entering these variables into a logistic regression model, open-cell stents were the only variable that significantly increased the risk for SOE (OR 2.36; 95% CI 0.99-4.60; p < 0.05). During a mean clinical follow-up of 31.1 months (range 24-39 months), none of the patients with SOE developed new neurologic ischemic symptoms, stent-edge stenosis, or in-stent restenosis. SOE after CAS was not associated with clinical adverse effects. This study suggests that the diameter of stent should be determined by reference to the CCA diameter without respect to the ICA diameter.
    No preview · Article · Jul 2011 · Neuroradiology
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    ABSTRACT: The difference between coil-embolized ruptured and unruptured aneurysms with respect to intra-aneurysmal thrombus formation remains to be determined. We examined whether there was a difference between ruptured and unruptured coil-embolized aneurysms in the rate and timing of thrombus formation in the aneurysmal sac and discuss the effect of thrombus on the treatment outcome. We evaluated 209 aneurysms with an aneurysmal dome smaller than 10 mm and a neck size less than 4 mm. Of these, 91 (43.5%) were ruptured. We assessed intra-aneurysmal thrombus formation by the coil-packing ratio (CPR): the percentage of coil volume occupying the aneurysmal sac. The initial CPR was defined as the CPR at which contrast influx into the sac ceased and the final CPR as that at the end of the procedure. ΔCPR was calculated as the difference between initial and final CPRs. Embolized aneurysms were evaluated on follow-up angiograms. The initial CPR was significantly lower in ruptured aneurysms (P < .01), and there was not a significant difference in the final CPR between ruptured and unruptured aneurysms (P = .05). ΔCPR was significantly higher in ruptured aneurysms (P < .01). The rate of aneurysmal recanalization was significantly higher in ruptured aneurysms (P < .05). The incidence of recanalization was high in ruptured aneurysms with low initial CPR and ΔCPR values. In ruptured aneurysms, intra-aneurysmal thrombus formation tends to occur in the earlier stages of coil embolization. In some cases, thrombus formation may inhibit dense coil packing and result in recanalization.
    No preview · Article · Apr 2011 · Neurosurgery
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    ABSTRACT: Three women older than 75 years presented with spontaneous superficial temporal artery (STA) pseudoaneurysms manifesting as a pulsatile mass in the preauricular region. None of the patients had a history of trauma. Histological examination of the surgically removed masses identified pseudoaneurysms based on the presence of connective tissue and adventitia. Spontaneous STA pseudoaneurysms are extremely rare. We suggest that all 3 aneurysms were associated with latent dissection and external force exerted by the frames of glasses.
    No preview · Article · Jan 2011 · Neurologia medico-chirurgica