Ryan P. Morton

Pipeline Embolization Device as primary treatment for blister aneurysms and iatrogenic pseudoaneurysms of the internal carotid artery

Background Blood blister type aneurysms (BBAs) and pseudoaneurysms create a unique treatment challenge. Despite many advances in open surgical and endovascular techniques, this subset of patients retains relatively high rates of morbidity and mortality. Recently, BBAs have been treated with flow-diverting stents such as the Pipeline Embolization Device (PED) with overall positive results. Methods Four patients presented with dissecting internal carotid artery (ICA) aneurysms treated with the PED (two BBAs presenting with subarachnoid hemorrhage (SAH), two pseudoaneurysms after injury during endoscopic trans-sphenoidal tumor surgery). Results Three patients had a successful angiographic and neurological outcome. One patient with a BBA re-ruptured during initial PED placement, again in the postoperative period, and later died. Primary PED treatment involved telescoping stents in two patients and coil embolization supplementation in one patient. Conclusions The PED should be used selectively in the setting of acute SAH. Dual antiplatelet therapy can complicate hydrocephalus management, and the lack of immediate aneurysm occlusion creates the risk of short-term re-rupture. PED treatment for iatrogenic ICA pseudoaneurysms can provide a good angiographic and neurological outcome.

Basilar tip aneurysms: a microsurgical and endovascular contemporary series of 100 patients.

BACKGROUND Endovascular therapy has largely replaced microsurgical clipping for the treatment of basilar tip aneurysms. OBJECTIVE We describe the variables our center evaluates when choosing to clip or coil basilar tip aneurysms and our outcomes. Four case illustrations are presented. METHODS All patients with ruptured or unruptured basilar tip aneurysms from 2005 to April 2012 were examined. The patients were treated by 2 interventional neuroradiologists and 2 dually trained neurosurgeons. RESULTS There were 63 ruptured (clipped 38%, coiled 62%) and 37 unruptured (clipped 35%, coiled 65%) aneurysms in this 100-patient study. Seventy percent of the patients with ruptured aneurysms and 92% of the patients with unruptured aneurysms had a good outcome (modified Rankin scale 0-2) at 3 months. For ruptured aneurysms, there was a statistically significant difference in clipping and coiling with respect to age and treatment modality (clip 48.8 years, coil 57.6 years). Patients in the coiled group had higher dome-to-neck (1.3 vs 1.1) (P = .01) and aspect ratios (1.6 vs 1.2) (P = .007). In the ruptured coiling group, 69.5% achieved a Raymond 1 radiographic outcome, 28% Raymond 2, and 2.5% Raymond 3. Eleven (17.4%) patients required re-treatment, and 3 (4.4%) patients were re-treated more than twice. Coiling of unruptured aneurysms resulted in 75% Raymond 1. There were no residual lesions for unruptured clipped aneurysms. There were no differences in outcome between clipping and coiling in the ruptured and unruptured group. CONCLUSION In our current management of basilar tip aneurysms, the majority can be treated via endovascular means, albeit with the expectation of a higher percentage of residual lesions and recurrences. Microsurgery is still appropriate for aneurysms with complex neck morphologies and in young patients desiring a more durable treatment.

Cerebral Aneurysms Treated with Flow-Diverting Stents: Computational Models with Intravascular Blood Flow Measurements

BACKGROUND AND PURPOSE: Computational fluid dynamics modeling is useful in the study of the hemodynamic environment of cerebral aneurysms, but patient-specific measurements of boundary conditions, such as blood flow velocity and pressure, have not been previously applied to the study of flow-diverting stents. We integrated patient-specific intravascular blood flow velocity and pressure measurements into computational models of aneurysms before and after treatment with flow-diverting stents to determine stent effects on aneurysm hemodynamics. MATERIALS AND METHODS: Blood flow velocity and pressure were measured in peri-aneurysmal locations by use of an intravascular dual-sensor pressure and Doppler velocity guidewire before and after flow-diverting stent treatment of 4 unruptured cerebral aneurysms. These measurements defined inflow and outflow boundary conditions for computational models. Intra-aneurysmal flow rates, wall shear stress, and wall shear stress gradient were calculated. RESULTS: Measurements of inflow velocity and outflow pressure were successful in all 4 patients. Computational models incorporating these measurements demonstrated significant reductions in intra-aneurysmal wall shear stress and wall shear stress gradient and a trend in reduced intra-aneurysmal blood flow. CONCLUSIONS: Integration of intravascular dual-sensor guidewire measurements of blood flow velocity and blood pressure provided patient-specific computational models of cerebral aneurysms. Aneurysm treatment with flow-diverting stents reduces blood flow and hemodynamic shear stress in the aneurysm dome.

Accuracy of Computational Cerebral Aneurysm Hemodynamics Using Patient-Specific Endovascular Measurements

Computational hemodynamic simulations of cerebral aneurysms have traditionally relied on stereotypical boundary conditions (such as blood flow velocity and blood pressure) derived from published values as patient-specific measurements are unavailable or difficult to collect. However, controversy persists over the necessity of incorporating such patient-specific conditions into computational analyses. We perform simulations using both endovascularly-derived patient-specific and typical literature-derived inflow and outflow boundary conditions. Detailed three-dimensional anatomical models of the cerebral vasculature are developed from rotational angiography data, and blood flow velocity and pressure are measured in situ by a dual-sensor pressure and velocity endovascular guidewire at multiple peri-aneurysmal locations in 10 unruptured cerebral aneurysms. These measurements are used to define inflow and outflow boundary conditions for computational hemodynamic models of the aneurysms. The additional in situ measurements which are not prescribed in the simulation are then used to assess the accuracy of the simulated flow velocity and pressure drop. Simulated velocities using patient-specific boundary conditions show good agreement with the guidewire measurements at measurement locations inside the domain, with no bias in the agreement and a random scatter of ≈25%. Simulated velocities using the simplified, literature-derived values show a systematic bias and over-predicted velocity by ≈30% with a random scatter of ≈40%. Computational hemodynamics using endovascularly measured patient-specific boundary conditions have the potential to improve treatment predictions as they provide more accurate and precise results of the aneurysmal hemodynamics than those based on commonly accepted reference values for boundary conditions.

Angiographic perfusion imaging: real-time assessment of endovascular treatment for cerebral vasospasm.

Cerebral perfusion analysis is useful in the diagnosis and treatment of cerebral vasospasm. A new modality of real‐time cerebral perfusion imaging and analysis has been developed using standard 2‐dimensional angiography. We report our initial experience with this technique to assess response to therapy during endovascular vasospasm procedures.

Low-dose head computed tomography in children: a single institutional experience in pediatric radiation risk reduction

OBJECT In this study, the authors describe their experience with a low-dose head CT protocol for a preselected neurosurgical population at a dedicated pediatric hospital (Seattle Childrens Hospital), the largest number of patients with this protocol reported to date. METHODS All low-dose head CT scans between October 2011 and November 2012 were reviewed. Two different low-dose radiation dosages were used, at one-half or one-quarter the dose of a standard head CT scan, based on patient characteristics agreed upon by the neurosurgery and radiology departments. Patient information was also recorded, including diagnosis and indication for CT scan. RESULTS Six hundred twenty-four low-dose head CT procedures were performed within the 12-month study period. Although indications for the CT scans varied, the most common reason was to evaluate the ventricles and catheter placement in hydrocephalic patients with shunts (70%), followed by postoperative craniosynostosis imaging (12%). These scans provided adequate diagnostic imaging, and no patient required a follow-up full-dose CT scan as a result of poor image quality on a low-dose CT scan. Overall physician comfort and satisfaction with interpretation of the images was high. An additional 2150 full-dose head CT scans were performed during the same 12-month time period, making the total number of CT scans 2774. This value compares to 3730 full-dose head CT scans obtained during the year prior to the study when low-dose CT and rapid-sequence MRI was not a reliable option at Seattle Childrens Hospital. Thus, over a 1-year period, 22% of the total CT scans were able to be converted to low-dose scans, and full-dose CT scans were able to be reduced by 42%. CONCLUSIONS The implementation of a low-dose head CT protocol substantially reduced the amount of ionizing radiation exposure in a preselected population of pediatric neurosurgical patients. Image quality and diagnostic utility were not significantly compromised.

Endovascular treatment of intracranial aneurysms in Loeys–Dietz syndrome

Background Loeys–Dietz syndrome (LDS) is an autosomal dominant connective tissue disorder characterized by extensive arterial aneurysms. The successful clipping of intracranial aneurysms in patients with LDS has been reported in a limited number of patients but endovascular treatment of intracranial aneurysms in LDS has never before been described. The first successful cases of endovascular management of five intracranial aneurysms in two patients with LDS are reported. Clinical presentation The first patient was an asymptomatic 45-year-old woman with LDS and two incidentally discovered, unruptured wide necked aneurysms (6×5 mm and 4×2 mm) arising from the ophthalmic segment of the left internal carotid artery. Both aneurysms were successfully embolized via Neuroform stent assisted coiling. The second patient was an asymptomatic middle 40s woman with LDS found to have an unruptured anterior communicating artery aneurysm (7×4 mm) as well as two ophthalmic segment aneurysms (2.5×3.7 mm and 2.9×3.5 mm). All three aneurysms were successfully embolized via Neuroform stent assisted coiling in two staged procedures. There were no periprocedural complications in either patient. Long term follow-up imaging demonstrated durable embolization in all aneurysms in both patients. Conclusion This is the first reported case series of endovascular management of intracranial aneurysms in the setting of LDS. The endovascular approach was safe, effective and durable in all aneurysms in both patients, and should be considered when treating patients with LDS and intracranial aneurysms.

Monitoring flow in extracranial-intracranial bypass grafts using duplex ultrasonography: a single-center experience in 80 grafts over 8 years.

BACKGROUND High-flow extracranial-intracranial (EC-IC) bypass is performed by using radial artery graphs (RAGs) or saphenous vein grafts (SVGs) for various pathologies such as aneurysms, ischemia, and skull-base tumors. Quantifying the acceptable amount of blood flow to maintain proper cerebral perfusion has not been well established, nor have the variables that influence flow been determined. OBJECTIVE To identify the normative range of blood flow through extracranial-intracranial RAGs and SVGs as measured by duplex ultrasonography. Multiple variables were evaluated to better understand their influence of graft flow. METHODS All EC-IC grafts performed at Harborview Medical Center from 2005 to 2012 were retrospectively reviewed for this cohort study. Daily extracranial graft duplex ultrasonography with flow volumes and transcranial graft Doppler were examined, as were short- and long-term outcomes. Both ischemic and hyperemic events were evaluated in further detail. RESULTS Eighty monitorable high-flow EC-IC bypasses were performed over the 8-year period. Sixty-five bypasses were performed by using RAGs and 15 were performed with SVGs. The average flow was 133 mL/min for RAGs and 160 mL/min for SVGs (P = .25). For both RAG and SVG groups, the donor and recipient vessel selected significantly impacted flow. For the RAG group only, preoperative graft diameter, postoperative hematocrit, and postoperative date significantly influenced flow. A 1-week average of >200 mL/min was 100% sensitive to cerebral hyperemia syndrome. CONCLUSION This study establishes the normative range of duplex ultrasonographic flow after high-flow EC-IC bypass, as well the usefulness and practicality of such monitoring as a surrogate to flow in the postoperative period.

Low-dose head computed tomography in children: a single institutional experience in pediatric radiation risk reduction: clinical article.

OBJECT In this study, the authors describe their experience with a low-dose head CT protocol for a preselected neurosurgical population at a dedicated pediatric hospital (Seattle Childrens Hospital), the largest number of patients with this protocol reported to date. METHODS All low-dose head CT scans between October 2011 and November 2012 were reviewed. Two different low-dose radiation dosages were used, at one-half or one-quarter the dose of a standard head CT scan, based on patient characteristics agreed upon by the neurosurgery and radiology departments. Patient information was also recorded, including diagnosis and indication for CT scan. RESULTS Six hundred twenty-four low-dose head CT procedures were performed within the 12-month study period. Although indications for the CT scans varied, the most common reason was to evaluate the ventricles and catheter placement in hydrocephalic patients with shunts (70%), followed by postoperative craniosynostosis imaging (12%). These scans provided adequate diagnostic imaging, and no patient required a follow-up full-dose CT scan as a result of poor image quality on a low-dose CT scan. Overall physician comfort and satisfaction with interpretation of the images was high. An additional 2150 full-dose head CT scans were performed during the same 12-month time period, making the total number of CT scans 2774. This value compares to 3730 full-dose head CT scans obtained during the year prior to the study when low-dose CT and rapid-sequence MRI was not a reliable option at Seattle Childrens Hospital. Thus, over a 1-year period, 22% of the total CT scans were able to be converted to low-dose scans, and full-dose CT scans were able to be reduced by 42%. CONCLUSIONS The implementation of a low-dose head CT protocol substantially reduced the amount of ionizing radiation exposure in a preselected population of pediatric neurosurgical patients. Image quality and diagnostic utility were not significantly compromised.

Computational fluid dynamics of cerebral aneurysm coiling using high-resolution and high-energy synchrotron X-ray microtomography: comparison with the homogeneous porous medium approach

Background Computational modeling of intracranial aneurysms provides insights into the influence of hemodynamics on aneurysm growth, rupture, and treatment outcome. Standard modeling of coiled aneurysms simplifies the complex geometry of the coil mass into a homogeneous porous medium that fills the aneurysmal sac. We compare hemodynamics of coiled aneurysms modeled from high-resolution imaging with those from the same aneurysms modeled following the standard technique, in an effort to characterize sources of error from the simplified model. Materials Physical models of two unruptured aneurysms were created using three-dimensional printing. The models were treated with coil embolization using the same coils as those used in actual patient treatment and then scanned by synchrotron X-ray microtomography to obtain high-resolution imaging of the coil mass. Computational modeling of each aneurysm was performed using patient-specific boundary conditions. The coils were modeled using the simplified porous medium or by incorporating the X-ray imaged coil surface, and the differences in hemodynamic variables were assessed. Results X-ray microtomographic imaging of coils and incorporation into computational models were successful for both aneurysms. Porous medium calculations of coiled aneurysm hemodynamics overestimated intra-aneurysmal flow, underestimated oscillatory shear index and viscous dissipation, and over- or underpredicted wall shear stress (WSS) and WSS gradient compared with X-ray-based coiled computational fluid dynamics models. Conclusions Computational modeling of coiled intracranial aneurysms using the porous medium approach may inaccurately estimate key hemodynamic variables compared with models incorporating high-resolution synchrotron X-ray microtomographic imaging of complex aneurysm coil geometry.