A Review of Robotic Interventional Neuroradiology.

Robotic interventional neuroradiology is an emerging field with the potential to enhance patient safety, reduce occupational hazards, and expand systems of care. Endovascular robots allow the operator to precisely control guidewires and catheters from a lead-shielded cockpit located several feet (or potentially hundreds of miles) from the patient. This has opened up the possibility of expanding telestroke networks to patients without access to life-saving procedures such as stroke thrombectomy and cerebral aneurysm occlusion by highly-experienced physicians. The prototype machines, first developed in the early 2000s, have evolved into machines capable of a broad range of techniques, while incorporating newly automated maneuvers and safety algorithms. In recent years, preliminary clinical research has been published demonstrating the safety and feasibility of the technology in cerebral angiography and intracranial intervention. The next step is to conduct larger, multisite, prospective studies to assess generalizability and, ultimately, improve patient outcomes in neurovascular disease.

An Update on the Adjunctive Neurovascular Support of Wide-Neck Aneurysm Embolization and Reconstruction Trial: 1-Year Safety and Angiographic Results.

BACKGROUND AND PURPOSE: The safety and efficacy of the PulseRider for the treatment of wide-neck, bifurcation aneurysms at the basilar and carotid terminus locations were studied in a prospective trial, the Adjunctive Neurovascular Support of Wide-Neck Aneurysm Embolization and Reconstruction (ANSWER) trial, reporting on initial 6-month angiographic and clinical results. This report provides insight into the longer term durability and safety with 12-month data. MATERIALS AND METHODS: Aneurysms treated with the PulseRider among enrolled sites were prospectively studied. Updated 12-month data on clinical and imaging end points are included. RESULTS: Thirty-four patients were enrolled (29 women, 5 men) with a mean age of 60.9 years. The mean aneurysm height ranged from 2.4 to 15.9 mm with a mean neck size of 5.2 mm (range, 2.3-11.6 mm). At 1 year, there were no device migrations or symptomatic in-stent stenoses. Raymond-Roy I occlusion was achieved in 53% of cases at the time of treatment and progressed to 61% and 67% at 6 and 12 months, respectively. Adequate occlusion (Raymond-Roy I/II) progressed from 88% at 6 months to 90% at 12 months. No recanalizations were observed. There was 1 delayed ischemic event. Good outcome (mRS 0-2) was achieved in 90% of patients. CONCLUSIONS: The updated 1-year results from the ANSWER trial demonstrate aneurysm stability and an acceptable safety profile for aneurysms treated at the basilar apex and carotid terminus. Prospective data from a larger set of aneurysms treated at other locations are required to assess how treatment with PulseRider compares with alternatives for treating wide-neck bifurcation aneurysms.

Cerebral vasospasm patterns following aneurysmal subarachnoid hemorrhage: an angiographic study comparing coils with clips.

BACKGROUND AND PURPOSE: Cerebral vasospasm following aneurysmal subarachnoid hemorrhage (aSAH) results in significant morbidity due to ischemia. Subarachnoid hematoma evacuation during aneurysm clipping reduces the incidence of vasospasm. However, studies comparing endovascular coiling with open clipping have reported similar rates of spasm. We addressed the question of how coiling produces similar (if not less) vasospasm without the benefit of clot evacuation by evaluating vasospasm patterns among patients with aSAH. We hypothesize that cerebrospinal fluid (CSF) circulation plays a major role in clearing blood breakdown products, and that coiling may preserve CSF flow in the subarachnoid space. METHODS: A retrospective chart review identified 36 (18 coiled/18 clipped) patients with aSAH who developed angiographic vasospasm. The degree of spasm was quantified using an ordinal scale from 0 (none) to 5 (severe) for 26 anatomic vessel segments evaluated on 164 successive angiograms. Statistical analysis was performed using the Fisher exact test for proportions and the Wilcoxon and Student t tests on ordinal/continuous measures. Quadratic regression was also used as a model for spasm activity versus post-bleed days. RESULTS: In both the coiling and clipping groups the most severely spastic vessels were located adjacent to aneurysm rupture. Perianeurysmal spasm affected all subjects. However, whereas spasm remained largely confined in patients treated by clipping, those who underwent coiling developed stepwise progression distally over time. The distal vasospasm severity scores were higher among subjects treated by coiling, particularly in the most dependent regions of the subarachnoid space. CONCLUSIONS: Patients with aSAH treated by endovascular coiling and surgical clipping demonstrate distinct vasospasm patterns. While both initially exhibit perianeurysmal spasm, patients treated by coiling go on to develop stepwise progression distally over time. This finding may reflect dispersion of blood breakdown products along preserved CSF egress pathways in patients treated by endovascular coiling.

Temporal correlation between wall shear stress and in-stent stenosis after Wingspan stent in swine model.

BACKGROUND AND PURPOSE: A recent randomized clinical trial on intracranial atherosclerosis was discontinued because of the higher frequency of stroke and death in the angioplasty and stent placement group than in the medical treatment group. An in-depth understanding of the relationship between biologic responses and flow dynamics is still required to identify the current limitations of intracranial stent placement. MATERIALS AND METHODS: Five Wingspan stents were deployed in tapered swine ascending pharyngeal arteries. Temporal wall shear stress distributions and in-stent stenosis were evaluated at days 0, 7, 14, and 28 after stent placement. The physiologic role of wall shear stress was analyzed regarding its correlation with in-stent stenosis. RESULTS: In-stent stenosis reached a peak of nearly 40% at day 14 and decreased mainly at the distal stent segment until day 28. The wall shear stress demonstrated a characteristic pattern with time on the basis of the in-stent stenosis change. The wall shear stress gradient increased from the proximal to distal segment until day 14. At day 28, the trend was reversed dramatically, decreasing from the proximal to the distal segment. A significant correlation between the in-stent stenosis growth until day 14 and low wall shear stress values just after stent placement was detected. In-stent stenosis regression between days 14 and 28 was also associated with the high wall shear stress values at day 14. CONCLUSIONS: These data suggest that the physiologic wall shear stress can control the biphasic in-stent stenosis change in tapered arteries.

Middle cranial fossa sphenoidal region dural arteriovenous fistulas: anatomic and treatment considerations.

BACKGROUND AND PURPOSE: DAVFs rarely involve the sphenoid wings and middle cranial fossa. We characterize the angiographic findings, treatment, and outcome of DAVFs within the sphenoid wings. MATERIALS AND METHODS: We reviewed the clinical and radiologic data of 11 patients with DAVFs within the sphenoid wing that were treated with an endovascular or with a combined endovascular and surgical approach. RESULTS: Nine patients presented with ocular symptoms and 1 patient had a temporal parenchymal hematoma. Angiograms showed that 5 DAVFs were located on the lesser wing of sphenoid bone, whereas the other 6 were on the greater wing of the sphenoid bone. Multiple branches of the ICA and ECA supplied the lesions in 7 patients. Four patients had cortical venous reflux and 7 patients had varices. Eight patients were treated with transarterial embolization using liquid embolic agents, while 3 patients were treated with transvenous embolization with coils or in combination with Onyx. Surgical disconnection of the cortical veins was performed in 2 patients with incompletely occluded DAVFs. Anatomic cure was achieved in all patients. Eight patients had angiographic and clinical follow-up and none had recurrence of their lesions. CONCLUSIONS: DAVFs may occur within the dura of the sphenoid wings and may often have a presentation similar to cavernous sinus DAVFs, but because of potential associations with the cerebral venous system, may pose a risk for intracranial hemorrhage. Curative embolization through a transarterial or transvenous approach is the primary therapeutic strategy for these lesions. In incompletely embolized patients, exclusion of any refluxing cortical veins is necessary.

Effects of perianeurysmal environment during the growth of cerebral aneurysms: a case study.

BACKGROUND AND PURPOSE: The natural history of cerebral aneurysms is thought to be governed by multifactorial processes involving hemodynamics, biomechanics, mechanobiology, and perianeurysmal environment. The purpose of this study was to highlight the importance of considering the influence of contacts with perianeurysmal environment structures on the hemodynamics and geometric evolution of intracranial aneurysms. MATERIALS AND METHODS: A large aneurysm of the basilar artery in contact with bone and observed to grow during a 4-year follow-up period was selected for study. Anatomic models were constructed from longitudinal CTA images acquired at 1-year intervals during the observation period. Computational fluid dynamics simulations were carried out under pulsatile flow conditions to analyze the blood flow pattern and WSS distribution in the aneurysm during its evolution. RESULTS: The aneurysm was observed to grow against the bone, resulting in a geometric change of the proximal parent artery, which, in turn, induced substantial changes in the aneurysm hemodynamics. In particular, a region of elevated WSS created by the inflow streams was observed to shift locations around the place where the aneurysm enlarged in contact with the bone as the aneurysm progressed. In addition, a "notch" near the distal end of the aneurysm, away from the bone and subject to relatively high WSS, was observed to grow and, later, completely disappear. CONCLUSIONS: Contacts with perianeurysmal structures need to be considered and analyzed to assess whether they could exert a significant influence on the geometric evolution of each individual intracranial aneurysm and its hemodynamics.

Wall shear stress distribution inside growing cerebral aneurysm.

BACKGROUND AND PURPOSE: Hemodynamic stimulation has been suggested to affect the growth of cerebral aneurysms. The present study examined the effects of intra-aneurysmal hemodynamics on aneurysm growth. MATERIALS AND METHODS: Velocity profiles were measured for 2 cases of AcomA aneurysms. Realistically shaped models of these aneurysms were constructed, based on CT angiograms. Flow fields and WSS in the models were measured by using particle image velocimetry and LDV. In 1 case, hemodynamic changes were observed in 4 stages of growth over a 27-month period, whereas no development was observed in the other case. RESULTS: The growing model had a smaller and more stagnant recirculation area than that in the nongrowth model. The WSS was markedly reduced in the enlarging region in the growing models, whereas extremely low WSS was not found in the nongrowth model. In addition, a higher WSSG was consistently observed adjacent to the enlarging region during aneurysm growth. CONCLUSIONS: The results indicated that the flow structure of recirculation itself does not necessarily lead to high likelihood of cerebral aneurysm. However, WSSG and WSS were distinctly different between the 2 cases. Higher WSSG was found surrounding the growing region, and extremely low WSS was found at the growing region of the growing cerebral aneurysm.

Partial recanalization of concomitant internal carotid-middle cerebral arterial occlusions promotes distal recanalization of residual thrombus within 24 h.

OBJECTIVES: Acute, simultaneous, concomitant internal carotid artery (ICA) and middle cerebral arteries (MCA) occlusions almost invariably lead to significant neurological disability if left untreated. Endovascular therapy is frequently the method of treatment in such situations but there remains a chance of incomplete recanalization. Successful recanalization of the proximal aspect of the occlusion may allow for endogenous thrombolysis and facilitate further endogenous recanalization of any residual MCA occlusion. METHODS: Consecutive patients with acute ischemic stroke undergoing endovascular therapy for tandem extracranial ICA-MCA or contiguous intracranial ICA-MCA occlusions were retrospectively analyzed. Rates of facilitated endogenous recanalization at 24 h (FER(24)) were compared by imaging within the immediate post-intervention 5-24 h period in those with proximal recanalization and in those without. RESULTS: 17 patients were included in the analysis. 12 patients had good initial proximal recanalization but a residual partial or total occlusion of the MCA while five patients failed any recanalization. Seven patients (58.3%) in the first group and none in the second had FER(24) on interval imaging after intervention (p=0.04). The probability of death and disability at discharge was less in patients with FER(24) than those without (p=0.05). CONCLUSIONS: More than half of all patients who present with both ICA and MCA occlusions who are only partially recanalized will undergo facilitated endogenous recanalization within the subsequent 24 h following intervention.

The risk of acute radiocontrast-mediated kidney injury following endovascular therapy for acute ischemic stroke is low.

BACKGROUND AND PURPOSE: Endovascular therapy is an alternative for the treatment of AIS resulting from large intracranial arterial occlusions that depends on the use of iodinated RCM. The risk of RCM-mediated AKI following endovascular therapy for AIS may be different from that following coronary interventions because patients may not have identical risk factors. MATERIALS AND METHODS: All consecutive patients with large-vessel AIS undergoing endovascular therapy were prospectively recorded. We recorded the baseline kidney function, and RCM-AKI was assessed according to the AKIN criteria at 48 hours after RCM administration. We compared the rate of RCM-AKI 48 hours after the procedure and sought to determine whether any preexisting factors increased the risk of RCM-AKI. RESULTS: We identified 99 patients meeting inclusion criteria. The average volume of contrast was 189 ± 71 mL, and the average creatinine change was -4.6% at 48 hours postangiography. There were 3 patients with RCM-AKI. Although all 3 patients died as a result of their strokes, return to baseline creatinine levels occurred before death. There was a trend toward higher rates of premorbid diabetes mellitus, chronic renal insufficiency, preadmission statin and NSAID use, and a higher serum creatinine level on admission for the RCM-AKI group. The volume of procedural contrast was similar between groups (those with and those without RCM-AKI) (P = .5). CONCLUSIONS: In this small study, the rate of RCM-AKI following endovascular intervention for AIS was very low. A much larger study is required to determine its true incidence.

Higher rates of mortality but not morbidity follow intracranial mechanical thrombectomy in the elderly.

BACKGROUND AND PURPOSE: Mechanical thrombectomy is a promising means of recanalizing acute cerebrovascular occlusions in certain situations. We sought to determine if increasing age adversely affects prognosis. MATERIALS AND METHODS: We reviewed all Merci thrombectomy cases and compared patients younger than 80 years of age with older individuals. We compared these 2 age groups with respect to recanalization rates, hospital LOS, hemorrhagic transformation, and death and disability on discharge. RESULTS: Elderly patients were more likely to die from their stroke than those younger than 80 years of age, regardless of recanalization success (48% versus 15%; OR, 5.5; 95% CI, 2.1-14.1). Among survivors, there was no difference in the probability of having a good functional outcome (mRS,

Recanalization rates decrease with increasing thrombectomy attempts.

BACKGROUND AND PURPOSE: Use of the Merci retriever is increasing as a means to reopen large intracranial arterial occlusions. We sought to determine whether there is an optimum number of retrieval attempts that yields the highest recanalization rates and after which the probability of success decreases. MATERIALS AND METHODS: All consecutive patients undergoing Merci retrieval for large cerebral artery occlusions were prospectively tracked at a comprehensive stroke center. We analyzed ICA, M1 segment of the MCA, and vertebrobasilar occlusions. We compared the revascularization of the primary AOL with the number of documented retrieval attempts used to achieve that AOL score. For tandem lesions, each target lesion was compared separately on the basis of where the device was deployed. RESULTS: We identified a total of 97 patients with 115 arterial occlusions. The median number of attempts per target vessel was 3, while the median final AOL score was 2. Up to 3 retrieval attempts correlated with good revascularization (AOL 2 or 3). When >or=4 attempts were performed, the end result was more often failed revascularization (AOL 0 or 1) and procedural complications (P = .006). CONCLUSIONS: In our experience, 3 may be the optimum number of Merci retrieval attempts per target vessel occlusion. Four or more attempts may not improve the chances of recanalization, while increasing the risk of complications.

Quantitative hemodynamic analysis of brain aneurysms at different locations.

BACKGROUND AND PURPOSE: Studies have shown that the occurrence of brain aneurysms and risk of rupture vary between locations. However, the reason that aneurysms at different branches of the cerebral arteries have different clinical presentations is not clear. Because research has indicated that aneurysm hemodynamics may be one of the important factors related to aneurysm growth and rupture, our aim was to analyze and compare the flow parameters in aneurysms at different locations. MATERIALS AND METHODS: A total of 24 patient-specific aneurysm models were constructed by using 3D rotational angiographic data for the hemodynamic simulation. Previously developed computational fluid dynamics software was applied to each aneurysm to simulate the blood-flow properties. Hemodynamic data at peak pulsatile flow were recorded, and wall shear stress (WSS) and flow rate in the aneurysms and parent arteries were quantitatively compared. To validate our method, a comparison with a previously reported technique was also performed. RESULTS: WSS and flow rate in the aneurysms at the peak of the cardiac cycle were found to differ in magnitude between different locations. Multiple comparisons among locations showed higher WSS and flow rate in middle cerebral artery aneurysms and lower WSS and flow rate in basilar artery and anterior communicating artery aneurysms. CONCLUSIONS: We observed changes in hemodynamic values that may be related to aneurysm location. Further study of aneurysm locations with a large number of cases is needed to test this hypothesis.

Intra-aneurysmal hemodynamics during the growth of an unruptured aneurysm: in vitro study using longitudinal CT angiogram database.

BACKGROUND AND PURPOSE: The role of blood-flow biomechanics on the size, morphology, and growth of cerebral aneurysms is poorly known. The purpose of this study was to evaluate intra-aneurysmal hemodynamics before and after aneurysm growth. MATERIALS AND METHODS: A flow-simulation study was performed in a middle cerebral artery (MCA) aneurysm with a bleb that grew after 1-year follow-up. Geometrically realistic in vitro models before and after aneurysm growth were constructed on the basis of CT angiograms. Blood-flow velocity, vorticity, and wall shear stress were obtained by using particle imaging velocimetry and laser Doppler velocimetry. RESULTS: No significant quantitative differences were noted among the overall flow structures before and after aneurysm growth, with the exception of less vorticity in the bleb after aneurysm growth. A circulating flow pattern was seen within the aneurysm domes. A blood-flow separation was observed at the margins of the bleb. No impingement of inward flow into the enlarging bleb was noted. Before the aneurysm growth, the wall shear stress was high at the aneurysm neck and also at the margin of the bleb. The value of wall shear stress decreased in the deeper part of the bleb. This value decreased even more after the aneurysm growth. CONCLUSIONS: Intra-aneurysmal hemodynamic structures before and after the growth of an MCA aneurysm were compared. Further investigation with a similar approach is mandatory to obtain a firm conclusion.

Bioabsorbable polymeric material coils for embolization of intracranial aneurysms: a preliminary experimental study.

OBJECT: A new embolic agent, bioabsorbable polymeric material (BPM), was incorporated into Guglielmi detachable coils (GDCs) to improve long-term anatomical results in the endovascular treatment of intracranial aneurysms. The authors investigated whether BPM-mounted GDCs (BPM/GDCs) accelerated the histopathological transformation of unorganized blood clot into fibrous connective tissue in experimental aneurysms created in swine. METHODS: Twenty-four experimental aneurysms were created in 12 swine. In each animal, one aneurysm was embolized using BPM/GDCs and the other aneurysm was embolized using standard GDCs. Comparative angiographic and histopathological data were analyzed at 2 weeks and 3 months postembolization. At 14 days postembolization, angiograms revealed evidence of neck neointima in six of eight aneurysms treated with BPM/GDCs compared with zero of eight aneurysms treated with standard GDCs (p < 0.05). At 3 months postembolization, angiograms demonstrated that four of four aneurysms treated with BPM/GDC were smaller and had neck neointima compared with zero of four aneurysms treated with standard GDCs (p = 0.05). At 14 days, histological analysis of aneurysm healing favored BPM/GDC treatment (all p < 0.05): the grade of cellular reaction around the coils was 3 +/- 0.9 (mean +/- standard deviation) for aneurysms treated using BPM/GDCs compared with 1.6 +/- 0.7 for aneurysms treated using GDCs alone; the percentage of unorganized thrombus was 16 +/- 12% compared with 37 +/- 15%, and the neck neointima thickness was 0.65 +/- 0.26 mm compared with 0.24 +/- 0.21 mm, respectively. At 3 months postembolization, only neck neointima thickness was significantly different (p < 0.05): 0.73 +/- 0.37 mm in aneurysms filled with BPM/GDCs compared with 0.16 +/- 0.14 mm in aneurysms filled with standard GDCs. CONCLUSIONS: In experimental aneurysms in swine, BPM/GDCs accelerated aneurysm fibrosis and intensified neck neointima formation without causing parent artery stenosis or thrombosis. The use of BPM/GDCs may improve long-term anatomical outcomes by decreasing aneurysm recanalization due to stronger in situ anchoring of coils by organized fibrous tissue. The retraction of this scar tissue may also decrease the size of aneurysms and clinical manifestations of mass effect observed in large or giant aneurysms.

Intraaneurysmal flow dynamics study featuring an acrylic aneurysm model manufactured using a computerized tomography angiogram as a mold.

OBJECT: To obtain precise flow profiles in patients' aneurysms, the authors developed a new in vitro study method featuring an aneurysm model manufactured using three-dimensional computerized tomography (3D CT) angiography. METHODS: A clear acrylic basilar artery (BA) tip aneurysm model manufactured from a patient's 3D CT angiogram was used to analyze flow modifications during one cardiac cycle. Stereolithography was utilized to create the aneurysm model. Three-dimensional flow profiles within the aneurysm model were obtained from velocity measurements by using laser Doppler velocimetry. The aneurysm inflow/outflow zones changed dynamically in their location, size of their cross-sectional area, and also in their shapes over one cardiac cycle. The flow velocity at the inflow zone was 16.8 to 81.9% of the highest axial velocity in the BA with a pulsatility index (PI) of 1.1. The flow velocity at the outflow zone was 16.8 to 34.3% of the highest axial velocity of the BA, with a PI of 0.68. The shear stress along the walls of the aneurysm was calculated from the fluid velocity measured at a distance of 0.5 mm from the wall. The highest value of shear stress was observed at the bleb of the aneurysm. CONCLUSIONS: This clear acrylic model of a BA tip aneurysm manufactured using a CT angiogram allowed qualitative and quantitative analysis of its flow during a cardiac cycle. Accumulated knowledge from this type of study may reveal pertinent information about aneurysmal flow dynamics that will help practitioners understand the relationship among anatomy, flow dynamics, and the natural history of aneurysms.

Endovascular treatment of basilar tip aneurysms using Guglielmi detachable coils: anatomic and clinical outcomes in 73 patients from a single institution.

OBJECTIVE: Seventy-three consecutive patients with 75 basilar tip aneurysms were treated with Guglielmi detachable coil (GDC) technology. Their anatomic and clinical outcomes are discussed. METHODS: Seventy-five basilar tip aneurysms were treated with the GDC system at the University of California, Los Angeles Medical Center from 1990 to 1999. The average age of the population was 48.3 years (range, 28-82 yr). Forty-two patients (57.5%) presented with acute subarachnoid hemorrhage, 8 patients (10.9%) had unruptured aneurysms with mass effect, and 23 patients (31.5%) had incidental aneurysms. Thirty-one aneurysms (41.3%) were small with a small neck, 18 (24%) were small with a wide neck, 16 (21.3%) were large, and 10 (13.3%) were giant aneurysms. RESULTS: Immediate anatomic outcomes demonstrated complete or near-complete occlusion in 64 aneurysms (85.3%) and incomplete occlusion in 7 aneurysms (9.3%). Four aneurysms (5.3%) could not be embolized because of anatomic difficulties. Of the 69 patients treated with GDCs, 63 patients (91.3%) remained neurologically intact or unchanged from their initial clinical status. Procedure-related morbidity and mortality were 4.1% and 1.4%, respectively. Long-term follow-up angiograms were obtained in 41 patients with 42 aneurysms. Thirty aneurysms (71.4%) demonstrated complete or near-complete occlusion. One incompletely embolized giant aneurysm ruptured during the follow-up period. CONCLUSION: In contrast to surgical clipping of basilar tip aneurysms, the main technical challenge of the Guglielmi detachable coiling procedure depends on the shape of the aneurysm, not its location. The results of this study indicate that endovascular GDC technology is an appropriate therapeutic alternative in ruptured or unruptured basilar tip aneurysms regardless of patient age, clinical presentation, clinical status, or timing of treatment.

Endovascular treatment of experimental aneurysms by use of a combination of liquid embolic agents and protective devices.

BACKGROUND AND PURPOSE: The use of liquid embolic agents for embolization of cerebral aneurysms has been reported in the neurosurgical literature. The most important limitation of this technique is the relatively poor control of migration of the liquid embolic agent into the parent artery. We performed an experimental aneurysm study using a liquid embolic agent and different protective devices to evaluate the safety and technical feasibility of this endovascular technique. METHODS: Forty lateral aneurysms were surgically constructed on 20 common carotid arteries of swine. Onyx alone was used to obliterate eight aneurysms. Onyx was also used in combination with microcoils (n = 11), microstents (n = 6), balloons inflated proximally to the neck of the aneurysm (n = 6), and across the neck of the aneurysm (n = 7). One control aneurysm was embolized with Guglielmi detachable coils (GDCs) alone. RESULTS: The use of a microballoon across the neck of the aneurysm, a microstent deployed across the neck of the aneurysm, or the deposit of GDCs into the aneurysm allowed faster and more complete filling of the aneurysm with Onyx. However, these protection devices did not totally preclude intractable migration of Onyx into the parent artery (migration rate, 9-33%). CONCLUSION: Although complete occlusion of experimental aneurysms with Onyx is feasible using protective devices, migration of the liquid embolic agent into the parent artery or intracranially remains a difficult challenge. Further experimental studies need to be performed to master this technique and to select those aneurysms that can be safely treated in clinical practice.

Rapidly enlarging dermoid cyst over the anterior fontanel: a case report and review of the literature.

A case report of a rapidly enlarging dermoid cyst over the anterior fontanel is presented. Our presentation demonstrates the course of rapid enlargement of the tumor with radiological images, which were examined at birth and during the process of the tumor enlargement. The literature is reviewed with respect to the nature of this tumor, especially to the relationship of tumor enlargement.

[Detection and genotype analysis of GB virus C/hepatitis G virus (GBV-C/HGV) in the sera of Japanese patients with hemophilia A].

The recently discovered GB virus C/hepatitis G virus (GBV-C/HGV) has been shown to be scarcely associated with hepatitis, though its possible pathogenesis remains unknown. In previous report, we designed primers for semi-nested reverse transcription-polymerase chain reaction (RT-PCR) to detect 5'-noncoding region of GBV-C/HGV, and screened the sera from 45 patients with liver diseases or on hemodialysis. In this study, we studied the prevalence of GBV-C/HGV infection in the sera from 35 patients with hemophilia A by this RT-PCR method, and also performed sequence analysis for all isolates including those from the non-hemophilic patients previously reported. GBV-C/HGV was detected in 8.57% (3/35) of the hemophilic patients. The isolates from hemophilic patients had several common mutations, and these mutations were also common in the "West African" genotype isolates represented by the prototype GBV-C. However, sequences in the isolates from other positive patients with liver diseases or on hemodialysis were quite different from those in the isolates from hemophilic patients, and those in the "European/American" genotype isolates represented by the prototype HGV. These sequences were consistent with "Asian" genotype. Simple restriction fragment length polymorphism (RFLP) analysis using the restriction enzyme HhaI successfully discriminated these genotypes. In the hemophilic patients, GBV-C/HGV might have been transmitted by transfusions of the imported plasma-derived clotting factor concentrates. Thus the difference in GBV-C/HGV genotype between the hemophilic patients and the others is suggested to be related to transmission route.