Occlusion of Extracranial-Intracranial Bypass Anastomosis-Associated Aneurysms Following Contralateral High-Flow Extracranial-Intracranial Bypass in a Patient with Impaired Cerebrovascular Reserve.

BACKGROUND AND IMPORTANCE: Extracranial-intracranial (EC-IC) bypass anastomosis-associated aneurysms are rare sequelae of cerebral revascularization surgery. Although treatment paradigms are not well defined, clipping, trapping with revision bypass, and donor vessel ligation represent the most common microsurgical approaches. CLINICAL PRESENTATION: A 53-yr-old male presented with cognitive decline, left extremity weakness, and left visual field blurriness. Computed tomographic angiography of head/neck demonstrated bilateral cervical internal carotid artery occlusion and magnetic resonance imaging of brain showed a small right parieto-occipital lobe infarct. The patient's symptoms worsened despite aggressive medical management. Therefore, a right superficial temporal artery to middle cerebral artery (STA-MCA) bypass was performed for flow augmentation. Follow-up digital subtraction angiography (DSA) approximately 1 yr after surgery noted 2 new aneurysms adjacent to the patent STA-MCA anastomosis. Perfusion imaging at that time showed persistently reduced blood flow in the left cerebral hemisphere. A left STA-MCA bypass was performed, and intraoperative blood flow measurements showed this to be a high-flow bypass. Follow-up DSA 4 mo later demonstrated involution of the right STA-MCA bypass and occlusion of the anastomosis-associated aneurysms with increased perfusion of the right cerebral hemisphere via collateral blood flow from the patent high-flow left STA-MCA bypass. At 7 mo following left STA-MCA bypass, the patient's neurological examination remained stable and perfusion imaging showed improved blood flow in the left cerebral hemisphere. CONCLUSION: We present a unique case in which a high-flow left EC-IC bypass with robust contralateral collateral blood flow was associated with subsequent occlusion of a right EC-IC bypass and 2 anastomosis-associated aneurysms in a patient with bilateral impaired cerebrovascular reserve.

Microsurgical Management of Intracranial Aneurysms After Failed Flow Diversion.

BACKGROUND: Flow diversion has become increasingly popular for treatment of cerebral aneurysms in the past few years. In an increasing number of patients with aneurysms, flow diversion (FD) has failed, with a paucity of reported data regarding salvage treatment for these challenging cases. METHODS: We present a multicenter series of 13 aneurysms for which FD failed and that were subsequently treated with open surgery. We also present a review of the reported data regarding operative management of aneurysms after unsuccessful FD. RESULTS: Twelve patients with 13 aneurysms were included in the present study. All 12 patients had undergone surgery after FD because of persistent aneurysm filling, mass effect, or aneurysm rupture. The patients underwent aneurysm clipping and parent vessel reconstruction, decompression of the aneurysm mass, occlusion of proximal flow to the aneurysm, or aneurysm trapping with or without extracranial-intracranial artery bypass. CONCLUSIONS: Aneurysms for which FD fails present a variety of unique and challenging management situations that will likely be encountered with increased frequency, given the popularity of FD. Microsurgical salvage options require individualized care tailored to the underlying pathological features, patient characteristics, and surgical expertise.

Glue Embolization with Guide Catheter Dextrose Push of Recurrent Dural Arteriovenous Fistula Previously Embolized with Onyx: Neuroendovascular Surgical Video.

Onyx (ethylene vinyl alcohol, ev3, Irvine, California, USA) is commonly used to treat dural arteriovenous fistulas (DAVFs) and presents several advantages over n-butyl cyanoacrylate glue (Codman Neurovascular Inc, Raynham, Massachusetts, USA) including slower, more controlled injections and better penetration via radial casting. However, Onyx is nonthrombogenic and may result in incomplete casting, recanalization, and DAVF recurrence. Here, we demonstrate glue embolization with guide catheter dextrose push of a recurrent DAVF previously embolized with Onyx. A 79-year-old female diagnosed with a Cognard IIA+B DAVF was successfully treated with transarterial Onyx injection. A 6-month follow-up angiogram, however, revealed recurrence of the DAVF with recanalization of the previously embolized draining vein. She subsequently underwent retreatment using glue embolization with a guide catheter dextrose push. Informed written consent was obtained. A Magic microcatheter (Balt Extrusion, Irvine, California, USA) was passed via a 6-French Envoy guide catheter (Codman Neurovascular) in the external carotid artery and was used to select the superficial temporal artery and then navigated distally through a transosseous connection into the dura. A dilute 12.5% concentration of glue was injected slowly and continuously and was seen to fill in spaces within the old Onyx material. Dextrose 5% in water was concomitantly injected through the guide catheter to ensure distal migration of the glue and occlusion of the draining vein. Glue embolization with dextrose push is a valuable treatment option for DAVF, especially in smaller recurrent feeders that can fill in the Onyx recanalized cast. The 6-month follow-up angiogram showed persistent occlusion of the dural fistula (Video 1).

Transarterial Glue Embolization and Covered Stenting of Large Carotid Body Tumor in Same Setting: Neuroendovascular Surgical Video.

Surgical resection is considered to be the treatment of choice for carotid body tumors. However, surgery can be complicated by intraoperative bleeding, injury to the internal carotid artery, and cerebral ischemia. Consequently, preoperative endovascular strategies including transarterial or percutaneous embolization or covered carotid stenting may be used. These neuroendovascular techniques have been described infrequently in the literature. Here, we showcase transarterial glue embolization followed by covered carotid stenting of a large carotid body tumor in the same setting (Video 1). A 53-year-old male presented with a 6-cm pulsatile and enlarging neck mass, as well as swallowing difficulty. Craniofacial computed tomography scan and digital subtraction angiography were consistent with a carotid body tumor. It was decided to perform preoperative embolization. Using roadmap guidance, a Prowler microcatheter (Codman Neurovascular, Inc., Raynham, Massachusetts, USA) was navigated into a tumor feeder vessel and a dilute 12% concentration (mix of 1 mL glue, 7 mL ethiodized oil) of the liquid embolic agent N-BCA (N-butyl cyanoacrylate; Codman Neurovascular, Inc.) was injected and seen to cast the tumor. During embolization, dextrose 5% water was injected through the guide catheter to enhance glue penetration into the tumor bed. Then, 2 covered stents (iCAST, Atrium Medical Corporation, Hudson, New Hampshire, USA) were deployed within the cervical internal carotid artery extending from levels C1-C6, spanning the carotid bifurcation, and excluding the external carotid artery. The patient underwent surgical resection 8 weeks later. The patient recovered from the procedures without any complications. Informed consent for the procedure and publication was obtained.

Pipeline Embolization of Giant Cavernous Internal Carotid Artery Aneurysm with Direct Carotid Puncture and Arteriotomy Closure Device: Neuroendovascular Surgical Video.

Flow diversion technology has revolutionized the treatment of complex anterior circulation cerebral aneurysms. However, vessel tortuosity and atherosclerotic disease may hamper the standard transfemoral access used in these procedures. Percutaneous direct carotid puncture is a viable alternative, but adequate carotid closure must be achieved. Here, we present the first case of a giant partially thrombosed aneurysm of the cavernous internal carotid artery treated with a Pipeline embolization device (PED; ev3 Neurovascular, Irvine, California, USA) via direct carotid puncture. A 79-year-old female presented with bilateral giant cavernous internal carotid artery aneurysms. She was successfully treated with PED on the right side and failed treatment with PED on the left side using a transfemoral approach due to common carotid artery tortuosity. She was lost to follow-up but presented 3 years later with worsening left eye pain and ophthalmoplegia. Percutaneous direct carotid puncture was performed under ultrasound guidance, and a 6-French sheath was inserted. Using roadmap guidance, a Marksman microcatheter (ev3 Neurovascular) with the support of a Navien intermediate catheter (ev3 Neurovascular) was advanced into the left middle cerebral artery, and 4 PEDs were deployed within the paraclinoid and cavernous segments of the internal carotid artery to completely cover the neck of the aneurysm. Carotid closure was performed for the first time with a Mynx collagen plug device (AccessClosure, Inc., Mountain View, California, USA). The patient recovered from the procedure without any complications, and her ophthalmoplegia partially improved. Informed patient consent for the procedure and for publication was obtained (Video 1).

Hemodynamic characteristics associated with cerebral aneurysm formation in patients with carotid occlusion.

OBJECTIVE: The pathogenesis of cerebral aneurysms in patients with internal carotid artery (ICA) occlusion is hypothesized to be hemodynamic. For the first time, the authors quantify the hemodynamic characteristics associated with aneurysm formation in patients with ICA occlusion. METHODS: Records of patients with unilateral ICA stenosis or occlusion ≥ 90% who underwent hemodynamic assessment before treatment using quantitative MR angiography were retrospectively reviewed. The patients were classified into 2 groups based on the presence or absence of aneurysms. The hemodynamic parameters of flow volume rate, flow velocity, and wall shear stress (WSS) were measured in each vessel supplying collateral flow-bilateral A1 segments and bilateral posterior communicating arteries-and then compared between the groups. RESULTS: A total of 36 patients were included (8 with and 28 without aneurysms). The mean flow (72.3 vs 48.9 ml/min, p = 0.10), flow velocity (21.1 vs 12.7 cm/sec, p = 0.006), and WSS (22.0 vs 12.3 dynes/cm2, p = 0.003) were higher in the A1 segment contralateral to the side of the patent ICA in patients with versus without aneurysms. All de novo or growing aneurysms in our cohort were located on the anterior communicating artery (ACoA) or P1 segment. CONCLUSIONS: Flow velocity and WSS are significantly higher across the ACoA in patients who harbor an aneurysm, and de novo or growing aneurysms are often located on collateral vessels. Thus, robust primary collaterals after ICA occlusion may be a contributing factor in cerebral aneurysm formation.

Ruptured posterior cerebral artery aneurysm presenting with a contralateral cranial nerve III palsy: A case report.

BACKGROUND: Posterior cerebral artery aneurysms can frequently present with an ipsilateral cranial nerve III palsy. CASE DESCRIPTION: We report the first case of a posterior cerebral artery aneurysm associated with a contralateral cranial nerve III palsy. A 64-year-old male presented with acute subarachnoid hemorrhage, Hunt and Hess grade 3, and a left-sided fixed and dilated pupil. Computed tomography scan showed hemorrhage, mainly within the left basal cisterns. Digital subtraction angiography revealed a right-sided P1-P2 junction aneurysm. CONCLUSIONS: This case demonstrates that, although the neurological exam can help pinpoint the location of a lesion, false localizing signs should be recognized.

Effect of Age on Cerebral Arteriovenous Malformation Draining Vein Stenosis.

OBJECTIVE: The pathogenesis of venous intimal hyperplasia and venous outflow stenosis associated with cerebral arteriovenous malformation (AVM) draining veins is poorly understood. We sought to determine the relationship between venous stenosis and age. METHODS: All patients with an AVM seen at our institution between 1990 and 2016 who underwent a diagnostic cerebral angiogram were retrospectively reviewed. Draining vein stenosis was measured from angiograms before any treatment. The relationship between venous stenosis and age was assessed. RESULTS: We included 281 patients (mean age 39 years, age range 3-83 years, 55% male). Venous stenosis measuring ≥50% was present in 59 patients (21% of cohort). Peak age at presentation was 25-29 years, whereas peak frequency of venous stenosis ≥50% was 50-54 years. Venous stenosis was present in a significantly higher proportion of patients ≥50 years versus <50 years (P = 0.03). Mean percentage stenosis was significantly higher in patients ≥50 years versus <50 years (32% vs. 22%, P = 0.001). CONCLUSIONS: Clinically significant cerebral AVM draining vein stenosis appears to be associated with older age, suggesting that venous stenosis is a progressive disease that occurs by the same process that leads to intimal hyperplasia. These results should be confirmed with a population-based longitudinal study.

Middle cerebral artery pressure changes following Pipeline flow diversion.

Objective Pipeline embolization devices (PED) are commonly used for endovascular treatment of cerebral aneurysms but changes in intracranial hemodynamics after PED deployment are poorly understood. Here, we assess middle cerebral artery (MCA) and systemic blood pressure before and after PED treatment. Methods Records of patients with cerebral aneurysms proximal to the internal carotid artery terminus treated with PED at our institution between 2015 and 2017 were retrospectively reviewed. Patients were included if ipsilateral MCA pressure measurements were available. Ipsilateral MCA pressure was transduced via the microcatheter before and after PED deployment. Systemic arterial blood pressure was also simultaneously recorded. MCA, systemic blood pressure, and ratios of MCA to systemic blood pressure values were compared before and after treatment among the study cohort using the two-sample paired Student t test. Results Fourteen patients were included. Mean age was 54 years. Among the entire cohort, the ratio of MCA to systemic systolic and mean blood pressure were significantly higher after treatment (respectively 0.76 vs. 0.69, p = 0.01, and 0.94 vs. 0.89, p = 0.03), and the ratio of MCA to systemic diastolic pressures showed an increasing trend (1.08 vs. 1.03, p = 0.09). The percentage of ratio increase was independent of aneurysm size ( r = -0.24, p = 0.42 for systolic ratio; r = -0.09, p = 0.74 for diastolic ratio; r = -0.09; p = 0.76 for mean ratio, respectively). Conclusions Following PED deployment, the ratio of ipsilateral MCA to systemic systolic and mean blood pressure increased. These pressure changes should be further evaluated in a larger sample size.

Cerebral Aneurysm Size and Distal Intracranial Hemodynamics: An Assessment of Flow and Pulsatility Index Using Quantitative Magnetic Resonance Angiography.

BACKGROUND: The relationship between cerebral aneurysm size and risk of rupture is well documented, but the impact of aneurysms on distal intracranial hemodynamics is unknown. OBJECTIVE: To examine the relationship between aneurysm size and distal intracranial hemodynamics prior to treatment. METHODS: Patients seen at our institution between 2006 and 2015 with cerebral aneurysms within the internal carotid artery (ICA) segments (proximal to ICA terminus) were retrospectively reviewed. Patients were included if the aneurysm was unruptured, and were excluded if a contralateral aneurysm was present. Flows within bilateral ICAs and middle cerebral arteries (MCA) were measured prior to any treatment using quantitative magnetic resonance angiography. Pulsatility index (PI = [systolic - diastolic flow velocity]/mean flow velocity) within each vessel was then calculated. Hemodynamic parameters were analyzed with respect to aneurysm size. RESULTS: Forty-two patients were included. Mean aneurysm size was 13.5 mm (range 2-40 mm). There was a significant correlation between aneurysm size and ipsilateral MCA PI (P = .006; r = 0.441), MCAipsilateral/ICAipsilateral PI ratio (P = .003; r = 0.57), and MCAipsilateral/MCAcontralateral PI ratio (P = .008; r = 0.43). Mean PI in the ipsilateral ICA was 0.38 (range 0.17-0.77) and ipsilateral MCA was 0.31 (range 0.08-0.83), and mean PI in contralateral ICA was 0.35 (range 0.19-0.57) and MCA was 0.30 (range 0.07-0.89). CONCLUSION: Larger aneurysm size correlates with higher ipsilateral MCA PI, demonstrating that aneurysms affect distal intracranial hemodynamics.

Accuracy in Identifying the Source of Subarachnoid Hemorrhage in the Setting of Multiple Intracranial Aneurysms.

BACKGROUND: Subarachnoid hemorrhage cases with multiple cerebral aneurysms frequently demonstrate a hemorrhage pattern that does not definitively delineate the source aneurysm. In these cases, rupture site is ascertained from angiographic features of the aneurysm such as size, morphology, and location. OBJECTIVE: To examine the frequency with which such features lead to misidentification of the ruptured aneurysm. METHODS : Records of patients who underwent surgical clipping of a ruptured aneurysm at our institution between 2004 and 2014 and had multiple aneurysms were retrospectively reviewed. A blinded neuroendovascular surgeon provided the rupture source based on the initial head computed tomography scans and digital subtraction angiography images. Operative reports were then assessed to confirm or refute the imaging-based determination of the rupture source. RESULTS: One hundred fifty-one patients had multiple aneurysms. Seventy-one patients had definitive hemorrhage patterns on initial computed tomography scans and 80 patients had nondefinitive hemorrhage patterns. Thirteen (16.2%) of the cases with nondefinitive hemorrhage patterns had discordance between the imaging-based determination of the rupture source and intraoperative findings of the true ruptured aneurysm, yielding an imperfect positive predictive value of 83.8%. Of all multiple aneurysm cases with subarachnoid hemorrhage treated by surgical or endovascular means at our institution, 4.3% (13 of 303) were misidentified. CONCLUSION: Morphological features cannot reliably be used to determine rupture site in cases with nondefinitive subarachnoid hemorrhage patterns. Microsurgical clipping, confirming obliteration of the ruptured lesion, may be preferentially indicated in these patients unless, alternatively, all lesions can be contemporaneously and safely treated with endovascular embolization.

Middle cerebral artery flow velocity increases more in patients with delayed intraparenchymal hemorrhage after Pipeline.

OBJECTIVE: Pipeline Embolization Devices (PED) are commonly used for endovascular treatment of cerebral aneurysms but can be associated with delayed ipsilateral intraparenchymal hemorrhage (DIPH). The role that altered intracranial hemodynamics may play in the pathophysiology of DIPH is poorly understood. We assess middle cerebral artery (MCA) flow velocity changes after PED deployment. MATERIALS AND METHODS: Patients with aneurysms located proximal to the internal carotid artery terminus treated with PED at our institution between 2015 and 2016 were retrospectively reviewed. Patients were included if MCA flow velocities were measured using transcranial Doppler. Bilateral MCA flow velocities, ratio of ipsilateral to contralateral MCA flow velocity, and bilateral MCA pulsatility index before and after PED deployment were assessed. RESULTS: 10 patients of mean age 52 years were included. Two patients had DIPH within 48 hours after PED deployment. We observed that these two patients had a higher increase in ipsilateral MCA mean flow velocity after treatment compared with patients without DIPH (39.5% vs 5.5%). Additionally, before PED deployment, patients with DIPH had a higher ipsilateral MCA pulsatility index (1.55 vs 0.98) and a higher ratio of ipsilateral to contralateral MCA mean flow velocity (1.35 vs 1.04). CONCLUSIONS: After PED, ipsilateral MCA mean flow velocity increases more in patients with DIPH. These flow velocity changes suggest the possible role of altered distal intracranial hemodynamics in DIPH after PED treatment of cerebral aneurysms. Further data are required to confirm this observation.

Validation of cerebral arteriovenous malformation hemodynamics assessed by DSA using quantitative magnetic resonance angiography: preliminary study.

BACKGROUND: The hemodynamic evaluation of cerebral arteriovenous malformations (AVMs) using DSA has not been validated against true flow measurements. OBJECTIVE: To validate AVM hemodynamics assessed by DSA using quantitative magnetic resonance angiography (QMRA). MATERIALS AND METHODS: Patients seen at our institution between 2007 and 2016 with a supratentorial AVM and DSA and QMRA obtained before any treatment were retrospectively reviewed. DSA assessment of AVM flow comprised AVM arterial-to-venous time (A-Vt) and iFlow transit time. A-Vt was defined as the difference between peak contrast intensity in the cavernous internal carotid artery and peak contrast intensity in the draining vein. iFlow transit times were determined using syngo iFlow software. A-Vt and iFlow transit times were correlated with total AVM flow measured using QMRA and AVM angioarchitectural and clinical features. RESULTS: 33 patients (mean age 33 years) were included. Nine patients presented with hemorrhage. Mean AVM volume was 9.8 mL (range 0.3-57.7 mL). Both A-Vt (r=-0.47, p=0.01) and iFlow (r=-0.44, p=0.01) correlated significantly with total AVM flow. iFlow transit time was significantly shorter in patients who presented with seizure but A-Vt and iFlow did not vary with other AVM angioarchitectural features such as venous stenosis or hemorrhagic presentation. CONCLUSIONS: A-Vt and iFlow transit times on DSA correlate with cerebral AVM flow measured using QMRA. Thus, these parameters may be used to indirectly estimate AVM flow before and after embolization during angiography in real time.

Contrast Time-Density Time on Digital Subtraction Angiography Correlates With Cerebral Arteriovenous Malformation Flow Measured by Quantitative Magnetic Resonance Angiography, Angioarchitecture, and Hemorrhage.

BACKGROUND: Digital subtraction angiography (DSA) currently provides angioarchitectural features of cerebral arteriovenous malformations (AVMs) but its role in the hemodynamic evaluation of AVMs is poorly understood. OBJECTIVE: To assess contrast time-density time (TT) on DSA relative to AVM flow measured using quantitative magnetic resonance angiography (QMRA). METHODS: Patients seen at our institution between 2007 and 2014 with a supratentorial AVM and DSA and QMRA obtained prior to any treatment were retrospectively reviewed. Regions of interest were selected on the draining veins at the point closest to the nidus. TT on DSA was defined as time needed for contrast to change image intensity from 10% to 100%, 100% to 10%, and 25% to 25%. TT was correlated to AVM total flow, angioarchitectural features, and hemorrhage. RESULTS: Twenty-eight patients (mean age 35.6 yr) were included. Six patients presented with hemorrhage. Mean AVM volume was 11.42 mL (range 0.3-57.7 mL). Higher total AVM flow significantly correlated with shorter TT100%-10% and TT25%-25% (P = .02, .02, respectively). Presence of venous stenosis correlated significantly with shorter TT100%-10% (P = .04) and TT25%-25% (P = .04). AVMs with a single draining vein exhibited longer TT25%-25% compared to those with multiple draining veins (P = .04). Ruptured AVMs had significantly shorter TT10%-100% compared to unruptured AVMs (P = .05). CONCLUSION: TT on DSA correlates with cerebral AVM flow measured using QMRA and with AVM angioarchitecture and hemorrhagic presentation. Thus, TT may be used to indirectly estimate AVM flow during angiography in real-time and may also be an indicator of important AVM characteristics associated with outflow resistance and increased rupture risk, such as venous stenosis.

Intracranial contrast transit times on digital subtraction angiography decrease more in patients with delayed intraparenchymal hemorrhage after Pipeline.

Background Pipeline embolization devices (PEDs) are used for endovascular treatment of cerebral aneurysms but can be associated with delayed ipsilateral intraparenchymal hemorrhage (DIPH). Changes in intracranial hemodynamics after PED are poorly understood. Objective Here, we assess hemodynamic changes after PED in patients and compare these changes in patients with and without DIPH (DIPH+ and DIPH-). Methods Records of patients with distal internal carotid artery (ICA) aneurysms treated with PED at our institution between 2012 and 2017 were retrospectively reviewed. Regions of interest were selected proximally to PED over the cavernous ICA and distally over the middle cerebral artery (MCA), and then transit times were determined using syngo iFlow software (Siemens). Ratio of MCA to ICA transit time was compared before, after treatment, and at follow-up. Ratios were also compared between DIPH+ and DIPH- subgroups. Correlations between aneurysm size, age, and ratios were investigated. Results Fifty-three patients were included. The ratio of MCA to ICA transit time decreased significantly after PED deployment (1.13 vs. 1.22, p < 0.01). The ratio in the DIPH + subgroup ( n = 4) was significantly lower (1.00 vs. 1.14, p = 0.01) and decreased significantly more (21% vs. 4.4%, p = 0.02) compared to the DIPH- subgroup ( n = 49). The ratio tended to be higher in larger aneurysms at baseline ( r = 0.25, p = 0.07) but not after PED treatment ( r = 0.11, p = 0.15). Age did not correlate with ratio. Conclusion The ratio of MCA to ICA transit time decreases following PED treatment and decreases more in patients with DIPH. These contrast transit time changes can be detected in real time immediately after PED deployment.

Cerebral arteriovenous malformation draining vein stenosis is associated with atherosclerotic risk factors.

OBJECTIVE: The pathogenesis of venous outflow stenosis associated with cerebral arteriovenous malformation (AVM) draining veins is poorly understood. We sought to determine the relationship between venous stenosis and atherosclerotic risk factors. MATERIALS AND METHODS: All patients with an AVM seen at our institution between 1990 and 2016 were retrospectively reviewed. Patients <18 years of age were excluded. Patients were classified into two groups based on the presence or absence of venous stenosis. Patient charts were reviewed for the following atherosclerotic risk factors: age >50 years, sex, race, hypertension, type 2 diabetes mellitus, hyperlipidemia, coronary artery disease, chronic kidney disease stage III, and cigarette smoking. The relationship between venous stenosis and atherosclerotic risk factors was assessed using univariate and multivariate analyses. RESULTS: 278 patients were included (mean age 41 years, 55% men). Venous stenosis was present in 87 patients (31% of the cohort). The presence of venous stenosis was significantly associated with age >50 years (P=0.05), hypertension (P=0.05), diabetes (P=0.02), and hyperlipidemia (P=0.001). Multivariate analysis showed that hyperlipidemia (P=0.05) was predictive of draining vein stenosis. CONCLUSIONS: Venous stenosis is associated with several atherosclerotic risk factors, suggesting that cerebral AVM venous outflow stenosis occurs by a degenerative process. Additional studies can show whether these modifiable risk factors may be targeted to prevent draining vein stenosis and AVM rupture.

Correlation Between Contrast Time-Density Time on Digital Subtraction Angiography and Flow: An in Vitro Study.

BACKGROUND AND PURPOSE: Digital subtraction angiography (DSA) provides an excellent anatomic characterization of cerebral vasculature, but hemodynamic assessment is often qualitative and subjective. Various clinical algorithms have been produced to semiquantify flow from the data obtained from DSA, but few have tested them against reliable flow values. METHODS: An arched flow model was created and injected with contrast material. Seventeen injections were acquired in anterior-posterior and lateral DSA projections, and 4 injections were acquired in oblique projection. Image intensity change over the angiogram cycle of each DSA run was analyzed through a custom MATLAB code. Time-density plots obtained were divided into 3 components (time-density times, TDTs): TDT10%-100% (time needed for contrast material to change image intensity from 10% to 100%), TDT100%-10% (time needed for contrast material to change image intensity from 100% to 10%), and TDT25%-25% (time needed for contrast material to change from 25% image intensity to 25%). Time-density index (TDI) was defined as model cross-sectional area to TDT ratio, and it was measured against different flow rates. RESULTS: TDI10%-100%, TDI100%-10%, and TDI25%-25% all correlated significantly with flow (P < 0.001). TDI10%-100%, TDI100%-10%, and TDI25%-25% showed, respectively, a correlation coefficient of 0.91, 0.91, and 0.97 in the anterior-posterior DSA projections (P < 0.001). In the lateral DSA projection, TDI100%-10% showed a weaker correlation (r = 0.57; P = 0.03). Also in the oblique DSA projection, TDIs correlated significantly with flow. CONCLUSIONS: TDI on DSA correlates significantly with flow. Although in vitro studies might overlook conditions that occur in patients, this method appears to correlate with the flow and could offer a semiquantitative method to evaluate the cerebral blood flow.

Rupture After Bypass and Distal Occlusion of Giant Anterior Circulation Aneurysms.

BACKGROUND: Giant aneurysms are very high-risk lesions both in terms of natural history and treatment. Bypass with distal occlusion is thought to be a safe treatment option for these aneurysms. Here, we report 2 cases of aneurysm rupture after bypass and distal occlusion, review the literature, and discuss the possible underlying mechanisms, in the hopes of influencing treatment planning and averting such complications in the future. CASE DESCRIPTION: Two patients successfully underwent surgical treatment of a giant anterior circulation aneurysm via bypass and distal vessel occlusion. In each case, there was sudden thrombosis of the aneurysm without any sign of rupture at the time of surgery. Both patients then experienced delayed postoperative rupture with devastating consequences. CONCLUSIONS: Aneurysm rupture can occur after bypass and distal occlusion, despite initial appearances of intraoperative stability. We suggest that the mechanisms are not a simple pressure within the dome and may be due to rapid thrombosis with subsequent aneurysm wall destabilization or stretching and capacitance causing persistent filling. When possible, it seems that complete trapping or proximal occlusion may be preferable to distal occlusion for these giant aneurysms. The optimal management of these highly morbid lesions remains to be determined.