Immunohistochemical Analysis of Debris Captured by Filter-Type Distal Embolic Protection Devices for Carotid Artery Stenting.

BACKGROUND: Little is known about the micro-debris captured in filter-type distal embolic protection devices (EPD) used for carotid stenting (CAS). This study aimed to determine the histological and immunohistochemical characteristics of such debris by using a new liquid-based cytology (LBC) technique. METHODS: Fifteen patients who underwent CAS using a filter-type distal EPD (FilterWire EZ; Boston Scientific, Marlborough, MA, USA) were included in the study. After gross inspection of each recovered filter device, micro-debris were collected using a new LBC technique (SurePath; TriPath Imaging, Inc., Burlington, NC). Histological and immunohistochemical analysis of the recovered debris was performed. The pre- and postoperative brain magnetic resonance imaging and neurological status of each patient were also reviewed. RESULTS: No patient developed ipsilateral symptomatic stroke due to a thromboembolic event. All 15 patients (100%) had microscopically identifiable debris in the filters, whereas gross inspection detected visible debris only in 5 patients (33.3%). Histological analysis revealed various types of structural components in an advanced atheromatous plaque, including fragments of fibrous cap, calcified plaque, smooth muscle cells, and necrotic tissue fragment infiltrated with monocytes and macrophages. CONCLUSIONS: Filter-type EPDs may contribute to reducing the risk of CAS-related embolic events by capturing micro-debris even when gross inspection of the recovered filter shows no visible debris in the device.

Computational fluid dynamics analysis of tandem carotid artery stenoses: Investigation of neurological complications after carotid artery stenting.

BACKGROUND: Combined extra- and intracranial carotid artery stenoses, particularly involving multiple lesions, show complex hemodynamic properties and represent a therapeutic dilemma. We used computational fluid dynamics (CFD) to investigate whether insufficient cerebral blood flow (CBF) in a 70-year-old man with tandem stenoses was the cause of aphasia and right hemiparesis after carotid artery stenting (CAS) of the extracranial stenosis. METHOD: Three-dimensional digital subtraction angiography (3D-DSA) was performed before and after balloon angioplasty and CAS in the patient. The geometrical and rheological conditions of the carotid arteries were determined, and computational meshes were generated from the patient-specific 3D-DSA datasets. CFD analysis was performed, and hemodynamic parameters such as mass flow, pressure, fractional flow reserve, and streamlines were calculated. RESULTS: Post-CAS simulations showed that the percentage of internal carotid artery mass flow from common carotid artery mass flow increased from 9% to 14% and CBF improved by only 5%. CONCLUSIONS: CFD analysis suggested that the neurological complications were caused by insufficient CBF rather than embolic events, and in tandem carotid stenoses, CAS for an extracranial lesion alone may not always sufficiently increase CBF. CFD enabled the noninvasive quantitative estimation of the effects of CAS of each stenotic segment on carotid flow.

Determining the Presence of Thin-Walled Regions at High-Pressure Areas in Unruptured Cerebral Aneurysms by Using Computational Fluid Dynamics.

BACKGROUND: Thin-walled regions (TWRs) of cerebral aneurysms are at high risk of rupture, and careful attention should be paid during surgical procedures. Despite this, an optimal imaging technique to estimate TWRs has not been established. Previously, pressure elevation at TWRs was reported with computational fluid dynamics (CFD) but not fully evaluated. OBJECTIVE: To investigate the possibility of predicting aneurysmal TWRs at high-pressure areas with CFD. METHODS: Fifty unruptured middle cerebral artery aneurysms were analyzed. Spatial and temporal maximum pressure (Pmax) areas were determined with a fluid-flow formula under pulsatile blood flow conditions. Intraoperatively, TWRs of aneurysm domes were identified as reddish areas relative to the healthy normal middle cerebral arteries; 5 neurosurgeons evaluated and divided these regions according to Pmax area and TWR correspondence. Pressure difference (PD) was defined as the degree of pressure elevation on the aneurysmal wall at Pmax and was calculated by subtracting the average pressure from the Pmax and dividing by the dynamic pressure at the aneurysm inlet side for normalization. RESULTS: In 41 of the 50 cases (82.0%), the Pmax areas and TWRs corresponded. PD values were significantly higher in the correspondence group than in the noncorrespondence group (P = .008). A receiver-operating characteristic curve demonstrated that PD accurately predicted TWRs at Pmax areas (area under the curve, 0.764; 95% confidence interval, 0.574-0.955; cutoff value, 0.607; sensitivity, 66.7%; specificity, 82.9%). CONCLUSION: A high PD may be a key parameter for predicting TWRs in unruptured cerebral aneurysms. ABBREVIATIONS: CFD, computational fluid dynamicsMCA, middle cerebral arteryPave, average pressurePD, pressure differencePmax, maximum pressureTWR, thin-walled regionWSS, wall shear stress.

Fluid structure interaction analysis reveals facial nerve palsy caused by vertebral-posterior inferior cerebellar artery aneurysm.

Cranial nerve palsy caused by aneurysmal compression has not been fully evaluated. The main causes of symptoms are considered to be direct mechanical compression and aneurysm pulsations. Recent studies indicate that nerve dysfunction is mainly induced by pulsation rather than by direct compression, and successful cases of endovascular surgery have been reported. We describe a patient with an unruptured vertebral artery-posterior inferior cerebellar artery (VA-PICA) aneurysm compressing the facial nerve at the root exit zone (REZ). The patient presented with peripheral facial nerve palsy but not hemifacial spasm and was successfully treated by coil embolization. To investigate the mechanisms underlying peripheral facial nerve palsy, fluid structure interaction (FSI) analysis can approximate displacement and the magnitude of aneurysmal wall motion due to hemodynamic forces. In our case, maximum mesh displacement was observed at the aneurysmal wall attached to the facial nerve inside the pons rather than the REZ, which explains the clinical manifestation of facial nerve palsy in the absence of hemifacial spasm. This preliminary report demonstrates the utility of FSI analysis for investigating cranial nerve neuropathy.