Sleep-Disordered Breathing and Idiopathic Normal-Pressure Hydrocephalus: Recent Pathophysiological Advances.

PURPOSE OF REVIEW: Idiopathic normal-pressure hydrocephalus (iNPH) is characterized clinically by ventriculomegaly, abnormal gait, falls, incontinence, and cognitive decline. This article reviews recent advances in the pathophysiology of iNPH concerning sleep-disordered breathing (SDB) and glymphatic circulation during deep sleep. RECENT FINDINGS: The authors found iNPH frequently associated with obstructive sleep apnea (OSA). A critical factor in iNPH is intracranial venous hypertension delaying drainage of cerebrospinal fluid (CSF) into the cerebral venous sinuses. CSF-venous blood circulates in the jugular veins and finally drains into the heart. During SDB, repeated reflex attempts to breathe induce strong respiratory efforts against a closed glottis thereby increasing the negative intrathoracic pressure. This causes atrial distortion and decreases venous return to the heart resulting in retrograde intracranial venous hypertension. Additionally, repeated awakenings from OSA impede sleep-associated circulation of interstitial CSF into the glymphatic circulation contributing to hydrocephalus. Sleep has become a critical element in the cognitive changes of aging including iNPH.

Idiopathic normal-pressure hydrocephalus and obstructive sleep apnea are frequently associated: A prospective cohort study.

BACKGROUND: Idiopathic normal-pressure hydrocephalus (iNPH) is defined by ventriculomegaly, cognitive decline, urinary incontinence and gait problems. Vascular risk factors (VRF) are associated with iNPH but obstructive sleep apnea (OSA) -a well-known independent VRF- is seldom mentioned. METHODS: We investigated the presence of sleep-disordered breathing in a prospective cohort of 31 consecutive unselected patients with iNPH using sleep questionnaires and nocturnal polysomnography (PSG). RESULTS: We found OSA in 90·3% (28/31) patients with iNPH; all had undiagnosed sleep abnormalities (snoring, awakenings, nocturia) and excessive daytime sleepiness (Epworth scale = 11·4 ±â€¯6·4; normal <8). Nocturnal PSG showed moderate-to-severe OSA in 25 patients (80·6%) with mean apnea-hypopnea index (AHI) 31·6 ±â€¯23·6/h; mean respiratory distress index (RDI) 34·5/h; and, mean SaO2 desaturation at nadir, 82·2 ±â€¯7·5%. The observed OSA prevalence is statistically significant: 90·3%, 95%CI 74·3-97·5; p = 0·000007. Other VRF included overweight body-mass index (BMI >25- < 30 kg/m2) in 59%, hyperhomocysteinemia 57%, hypertension 43%, hyperlipidemia 39%, diabetes 32%, smoking 21%, coronary disease 18%, and previous stroke 10%. CONCLUSION: Abnormal sleep breathing is frequently associated with iNPH. Validation in larger series is required but we suggest including sleep evaluation in patients suspected of iNPH.

Quantification of velocity reduction after flow diverter placement in intracranial aneurysm: An ex vivo study with 3D printed replicas.

Phase contrast MRI (pcMRI) was used to measure flow before and after placement of a flow diverter (n = 3). Decreases from 18% to 31% in flow velocity were seen in the inflow jet of the aneurysms. Flow patterns were also compared. It was observed that the gross aneurysmal flow patterns were maintained after flow diverter placement despite decreased fluid velocities. All measurements were carried out in 3D printed aneurysm replicas.

Mid- and long-term outcomes of carotid-cavernous fistula endovascular management with Onyx and n-BCA: experience of a single tertiary center.

INTRODUCTION: Endovascular therapy is the preferred treatment for most carotid-cavernous fistulas (CCFs). Early reports have documented excellent initial clinical and radiographic outcomes after embolization of CCFs with Onyx or n-butyl cyanoacrylate (n-BCA), but little evidence is available about the long-term durability of this technique. OBJECTIVE: To characterize the long-term durability of CCF liquid embolization. METHODS: The authors retrospectively reviewed a database of 24 CCFs in 21 consecutive patients who underwent Onyx or n-BCA embolization of a CCF from 2006 to 2013 at our institution. RESULTS: A total of 25 Onyx or n-BCA embolization procedures were attempted and 24 successfully completed during the study, resulting in complete or near-complete occlusion by the end of the study in all 24 CCFs (obliteration success, 100%). Attempted embolization in a single CCF failed initially, but was performed successfully at a later date by a different approach. None of the 24 CCFs recanalized, regrew, or required any further treatment subsequent to Onyx or n-BCA embolization throughout a mean 12.4 months of angiographic follow-up (range 1-36 months). Clinically significant complications were seen in three embolization procedures, including cranial nerve palsies (n=1), embolic infarct (n=1), and intraperitoneal hemorrhage (n=1). CONCLUSIONS: Early evidence has indicated that endovascular embolization with Onyx is relatively safe and effective at achieving an initial angiographic cure for CCFs. Results of our series suggest that angiographic and clinical outcomes of Onyx and n-BCA embolization remain stable at mid- and long-term follow-up.

Modern interventional management of stroke.

Acute ischemic stroke continues to be one of the leading causes of disability and death and is a financial burden to an already taxed health care system. Much research and investigation has been carried out over the past decade on various recanalization devices aimed at restoring cerebral blood flow. Despite the rapidly improving technical abilities of these devices, it has been difficult to demonstrate corresponding improved clinical outcomes. This article will describe the application of the most recent generation of these devices and briefly discuss the ongoing discrepancy between these technical achievements and stroke outcomes.

Magnetic resonance imaging as a tool to assess reliability in simulating hemodynamics in cerebral aneurysms with a dedicated computational fluid dynamics prototype: preliminary results.

PURPOSE: As an example of enhancing information in clinical image data by computational methods, simulating hemodynamics in cerebral aneurysms by means of computational fluid dynamics (CFD) is currently a topic of active research. Challenges consist in translating this engineering technology into clinical research, validating the simulations and addressing a potential clinical value of the results. In this preliminary study, we demonstrate the use of phase contrast magnetic resonance imaging (pcMRI) for assessing the reliability of CFD results. MATERIALS AND METHODS: For six cerebral aneurysms where intra-aneurysmal velocity information was available by 2D pcMRI, steady CFD simulations with constant inflow were performed using a dedicated CFD prototype system. Major features of the velocity patterns derived from pcMRI were compared to those obtained with the CFD. RESULTS: Good qualitative agreement between measured (2D pcMRI) and simulated (CFD) features of the intra-aneurysmal velocity patterns were obtained. These findings are discussed in the broader framework of the expectations towards CFD simulations in a clinical research setting. CONCLUSIONS: Computational simulations reproduce major features of measured velocity patterns in cerebral aneurysms. Looking forward, these simulations need to be refined towards specific applications in clinical research.

Validation of computational fluid dynamics methods with anatomically exact, 3D printed MRI phantoms and 4D pcMRI.

A new concept of rapid 3D prototyping was implemented using cost-effective 3D printing for creating anatomically correct replica of cerebral aneurysms. With a dedicated flow loop set-up in a full body human MRI scanner, flow measurements were performed using 4D phase contrast magnetic resonance imaging to visualize and quantify intra-aneurysmal flow patterns. Ultrashort TE sequences were employed to obtain high-resolution 3D image data to visualize the lumen inside the plastic replica. In-vitro results were compared with retrospectively obtained in-vivo data and results from computational fluid dynamics simulations (CFD). Rapid prototyping of anatomically realistic 3D models may have future impact in treatment planning, design of image acquisition methods for MRI and angiographic systems and for the design and testing of advanced image post-processing technologies.

Delayed Hydrocephalus and Perianeurysmal Cyst Formation After Stent-Assisted Coil Embolization of a Large, Unruptured Basilar Apex Aneurysm: A Case Report and Literature Review.

PURPOSE: Endovascular aneurysm embolization possesses a unique set of infrequently seen complications distinct from those associated with microsurgical clipping, which may arise after an otherwise uncomplicated coil embolization procedure, including postembolization, hydrocephalus, and perianeurysmal cyst formation. DESIGN: The authors report an illustrative case of 2 rarely seen complications of aneurysm embolization with literature review. METHODS: We present a case of a basilar apex aneurysm that was treated with endovascular coil embolization with multiple Cerecyte (Micrus Endovascular, San Jose, Calif) coils and 2 Enterprise (Codman & Shurtleff, Inc, Raynham, Mass) stents. RESULTS: Postembolization angiography demonstrated complete aneurysm obliteration without distal branch occlusion or other complication. Twenty-two months after the embolization, however, the patient presented with progressively worsening headaches. Repeat magnetic resonance imaging revealed hydrocephalus and a perianeurysmal cyst measuring 1 × 2 cm adjacent to the previously coiled basilar apex aneurysm. After endoscopic third ventriculostomy, the patient experienced significant relief of her headaches and was discharged to rehabilitation. CONCLUSIONS: Clinicians should be aware that worsening or new neuro-ophthalmic findings may be the presenting sign of postembolization hydrocephalus or perianeurysmal cyst formation.

Hemodynamics at the ostium of cerebral aneurysms with relation to post-treatment changes by a virtual flow diverter: a computational fluid dynamics study.

Computational fluid dynamics (CFD) techniques have been refined for modeling the hemodynamics in cerebral aneurysms. Recent interest has focused on understanding hemodynamic changes by treatment with a flow diverter (FD), i.e. a stent with a dense metal mesh which is placed across the ostium to divert the majority of flow away from the aneurysm. Potential complications include remnant inflow jets but, more seriously, aneurysm hemorrhage. For optimization of treatment outcome, a better understanding of the effects caused by the FD would be beneficial. In particular, pressure and velocity distributions at the aneurysm ostium are of interest, as they will be directly affected by the FD which in turn will influence post-treatment hemodynamics inside the aneurysm. Here, we report the results of a CFD study investigating the relationship between pre-treatment and post-treatment velocities, pressures and wall shear stresses (WSS) in the aneurysm with corresponding hemodynamic conditions at the aneurysm ostium prior to treatment. The study was carried out using a dedicated CFD prototype which allows modeling the effects of a virtual FD integrated into patient-specific geometries utilizing Darcy's law. Velocities and WSS were reduced in all cases post FD treatment, pressure increased in one case. Heterogeneous distributions of the velocity magnitude were found at the ostium with focal maxima indicating potential risk zones for remnant inflow jets into the aneurysms. Pressures at the ostium correlated with pressure changes inside the aneurysm which could become a pre-treatment indicator for the evaluation of the suitability of a particular aneurysm for FD treatment.

Tetrahedral vs. polyhedral mesh size evaluation on flow velocity and wall shear stress for cerebral hemodynamic simulation.

Haemodynamic factors, in particular wall shear stresses (WSSs) may have significant impact on growth and rupture of cerebral aneurysms. Without a means to measure WSS reliably in vivo, computational fluid dynamic (CFD) simulations are frequently employed to visualise and quantify blood flow from patient-specific computational models. With increasing interest in integrating these CFD simulations into pretreatment planning, a better understanding of the validity of the calculations in respect to computation parameters such as volume element type, mesh size and mesh composition is needed. In this study, CFD results for the two most common aneurysm types (saccular and terminal) are compared for polyhedral- vs. tetrahedral-based meshes and discussed regarding future clinical applications. For this purpose, a set of models were constructed for each aneurysm with spatially varying surface and volume mesh configurations (mesh size range: 5119-258, 481 volume elements). WSS distribution on the model wall and point-based velocity measurements were compared for each configuration model. Our results indicate a benefit of polyhedral meshes in respect to convergence speed and more homogeneous WSS patterns. Computational variations of WSS values and blood velocities are between 0.84 and 6.3% from the most simple mesh (tetrahedral elements only) and the most advanced mesh design investigated (polyhedral mesh with boundary layer).

Clinical differences between angiographically negative, diffuse subarachnoid hemorrhage and perimesencephalic subarachnoid hemorrhage.

OBJECTIVE: To identify prognostic factors for vasospasm, hydrocephalus, and clinical outcomes in patients with angiographically negative, non-traumatic, diffuse subarachnoid hemorrhage (d-SAH). METHODS: Retrospective review of patients who experienced angiographically negative SAH at our institution over the past 6 years was undertaken. The patients were stratified based on grade at presentation, severity, and pattern of SAH on initial non-enhanced, computed tomography (CT) of the head into perimesencephalic and diffuse subtypes. The patients were further differentiated based on the development of vasospasm, hydrocephalus and required treatments, and clinical outcomes. Patients were excluded if a causative lesion was discovered subsequently. RESULTS: Ninety-four patients with angiographically negative SAH were identified. A total of 31 patients were considered to have the perimesencephalic (p-SAH) subtype, while 63 patients fit criteria for the diffuse (d-SAH) subtype. Compared to the p-SAH subtype, those patients with d-SAH subtype had significantly higher risk for complications related to SAH with an increased incidence of hydrocephalus (50.8% vs. 9.6%), requirement for external ventricular drainage (41% vs. 9.6%), and for the hydrocephalus requiring eventual permanent cerebrospinal fluid diversion (20.6% vs. 0%). Patients with d-SAH were also at an increased risk for symptomatic vasospasm (28.6% vs. 9.6%). Ultimately, only 76% of d-SAH patients achieved complete recovery and independent living, compared to 96.7% of p-SAH patients. CONCLUSION: The angiographically negative d-SAH pattern is associated with worse presentations and outcome. These patients are at increased risk for vasospasm and hydrocephalus requiring aggressive treatment and should therefore be cared for with a higher level of surveillance.

Intracranial hemorrhage associated with stent-assisted coil embolization of cerebral aneurysms: a cautionary report.

OBJECT: The introduction of the Neuroform microstent has facilitated the embolization of complex cerebral aneurysms, which were previously not amenable to endovascular therapy. Typically, the use of this stent necessitates the administration of dual antiplatelet therapy to minimize thromboembolic complications. Such therapy may increase the risk of hemorrhage in patients who require concurrent external ventricular drainage and/or subsequent permanent cerebrospinal fluid diversion. METHODS: The authors' neurosurgical database was queried for all patients who underwent stent-assisted coil embolization for cerebral aneurysms and who required an external ventricular drain (EVD) or ventriculoperitoneal (VP) shunt placement for management of hydrocephalus. RESULTS: Thirty-seven patients underwent stent-assisted coil embolization for intracranial aneurysms at the authors' institution over a recent 2-year period. Seven of these patients required placement of an EVD and/or a VP shunt. Three of the 7 patients suffered an immediate intraventricular hemorrhage (IVH) associated with placement or manipulation of an EVD; 1 experienced a delayed intraparenchymal hemorrhage and an IVH; 1 suffered an aneurysmal rehemorrhage; and the last patient had a subdural hematoma (SDH) that resulted from placement of a VP shunt. This patient required drainage of the SDH and exchange of the valve. CONCLUSIONS: The necessity of dual antiplatelet therapy in the use of stent-assisted coil embolization increases the risk of intracranial hemorrhage and possibly rebleeding from a ruptured aneurysm. This heightened risk must be recognized when contemplating the appropriate therapy for a cerebral aneurysm and when considering the placement or manipulation of a ventricular catheter in a patient receiving dual antiplatelet therapy. Further study of intracranial procedures in patients receiving dual antiplatelet therapy is indicated.

Neurosurgical management of intracranial aneurysms previously treated with endovascular therapy.

OBJECTIVE: With the increased use of endovascular therapy, an increasing number of patients with incompletely treated intracranial aneurysms are presenting for further surgical management. This study reviews our experiences with such patients. METHODS: During a 7-year period, 38 patients with 40 intracranial aneurysms who were initially treated with endovascular therapy underwent surgical obliteration of refractory or recurrent lesions. All patients were recorded in a prospective registry, and their clinical data and imaging studies were analyzed retrospectively. RESULTS: Twenty-six anterior and 14 posterior circulation aneurysms were treated. Four aneurysms were on the cavernous internal carotid artery, 13 were on the distal internal carotid artery, 6 were on the anterior communicating artery complex, 2 were on the middle cerebral artery, 3 were on the posteroinferior cerebellar artery, 1 was at the vertebrobasilar junction, 3 were on the superior cerebellar artery, 4 were at the basilar apex, 2 were on the posterior cerebral artery, and 1 was on the distal vertebral artery. Two pseudoaneurysms-one on the petrocavernous segment of the internal carotid artery and one on the distal VA-also were treated. The median time until recurrence was 6 months. Thirty-one aneurysms were clip-ligated, and six were treated with trapping. Three extracranial-intracranial bypasses were performed. One aneurysm was treated with muslin wrapping. Two aneurysms required the use of surgical approaches that involved hypothermic circulatory arrest. Nine aneurysms required coil mass extraction and/or complex vascular reconstruction to complete lesion obliteration. All aneurysms except the single wrapped aneurysm were successfully excluded from the intracranial circulation. Two deaths occurred as a result of the operative procedures, and another patient died as a result of subarachnoid hemorrhage-induced massive myocardial infarction. Ultimately, 86.8% of patients achieved an excellent or good recovery. CONCLUSION: With endovascular therapy assuming an increasing role in the treatment of patients with intracranial aneurysms, more lesions that are refractory to initial treatment will require surgical management. Our experience indicates that good results are attainable, although technical challenges are frequently encountered.

Extracranial-intracranial vein graft bypass for giant intracranial aneurysm surgery for pediatric patients: two technical case reports.

OBJECTIVE AND IMPORTANCE: Herein we describe two cases of extracranial-intracranial vein graft bypasses for the treatment of giant intracranial aneurysms in prepubertal pediatric patients. One patient is, we think, the youngest patient reported in the literature to have been successfully treated in such a manner, with a good long-term outcome. Such grafts seem to enlarge longitudinally during the growth spurt, making such techniques reasonable long-term therapeutic options for the management of complex intracranial aneurysms in pediatric patients. CLINICAL PRESENTATION: Patient 1, a 13-year-old boy, presented with headaches and rapidly progressive right cavernous sinus syndrome. Computed tomography and cerebral angiography revealed a giant, fusiform, right intracavernous internal carotid artery aneurysm. Patient 2, a 23-month-old girl, was discovered to harbor an asymptomatic, recurrent, giant, fusiform, left M1 middle cerebral artery aneurysm 1 year after presenting with seizures related to subarachnoid hemorrhage from the aneurysm, for which she had been treated with clipping and an M2-M2 anastomosis. INTERVENTION: Both patients underwent craniotomies, with sacrifice of the proximal parent vessel (the distal cervical internal carotid artery and the proximal middle cerebral artery, respectively), combined with cerebral revascularization through extracranial-intracranial saphenous vein bypass grafts. Both patients experienced excellent long-term clinical outcomes, have undergone significant growth, and exhibit excellent long-term graft patency and aneurysm obliteration. CONCLUSION: These two cases highlight the safety and efficacy of extracranial-intracranial vein graft bypasses among prepubertal pediatric patients. The indications for bypass procedures to treat giant intracranial aneurysms are discussed, and the technical aspects of maximizing vein bypass graft patency are reviewed.