Faculty Bibliography

OBJECT: The goal of this study was to quantify the reduction in velocity, vorticity, and shear stresses resulting from the sequential placement of stents across the neck of sidewall cerebral aneurysms. METHODS: A digital particle image velocimetry (DPIV) system was used to measure the pulsatile velocity field within a flexible silicone sidewall intracranial aneurysm model and at the aneurysm neck-parent artery interface in this model. The DPIV system is capable of providing an instantaneous, quantitative two-dimensional measurement of the velocity vector field of 'blood' flow inside the aneurysm pouch and the parent vessel, and its changes at varying stages of the cardiac cycle. The corresponding vorticity and shear stress fields are then computed from the velocity field data. Three Neuroform stents (Boston Scientific/Target), each with a strut thickness between 60 and 65 microm, were subsequently placed across the neck of the aneurysm model and measurements were obtained after each stent had been placed. The authors measured a consistent decrease in the values of the maximal averaged velocity, vorticity, and shear stress after placing one, two, and three stents. Measurements of the circulation inside the sac demonstrated a systematic reduction in the strength of the vortex due to the stent placement. The decrease in the magnitude of the aforementioned quantities after the first stent was placed was remarkable. Placement of two or three stents led to a less significant reduction than placement of the first stent. CONCLUSIONS: The use of multiple flexible intravascular stents effectively reduces the strength of the vortex forming in an aneurysm sac and results in a decrease in the magnitude of stresses acting on the aneurysm wall

A major challenge in stem cell biology is to study the underlying mechanisms of tissue specific homing and differentiation. Recent results suggest that bone marrow derived stem cells can give rise to multiple cell types. Because chemokines and chemokine receptors are associated with development, differentiation and homing of immune cells, we undertook efforts to study the chemokine receptor expression profile of human adult stem cells to identify their potential role in tissue specific homing prior to transdifferentiation. Using human bone marrow-derived stem cell lines, we could demonstrate functional chemokine receptor expression of various chemokine receptors. The expression of CXCR5 and CCR7, associated with secondary lymphoid organ homing as well as CXCR4 and CCR10, involved in organ specific homing and CXCR3, CCR5 and CCR1, which are involved in inflammation events, suggested a role of chemokine receptors in tissue specific homing of stem cells. To proof the specific homing of stem cells in vivo, we used murine stem cell lines, stably introduced green fluorescent protein under control of CMV promotor into the cells and injected them intravenously into mice. We demonstrate the homing of these stem cells to lymphnode and thymus as well as mucosal tissue, while stem cells home exclusively to a site of lesion during wound healing and tissue regeneration. Our data suggest that chemokine biology may play a pivotal role in the homing of stem cells to specific tissues and niches prior to (trans)differentiation, while the homing changes during tissue damage and other adequate lesions

Summary: The pathogenesis of dural arteriovenous fistulas (DAVFs) is currently unknown, with multiple DAVFs being rare. For patients with limited venous access secondary to sinus thrombosis, or for patients where parent sinus occlusion would not be tolerated, transvenous embolization may not be possible and other treatment methods must be considered. A 69-year-old female patient with a two-year history of progressive headaches, memory loss, and unsteady gait underwent cerebral angiography that revealed three separate DAVFs with congested cortical venous drainage overlying both frontal lobes. Using an application of a transarterial wedged-catheter, flow-arrest technique, N-butyl cyanoacrylate was deposited across all three pathologic arteriovenous connections providing a definitive cure. Transarterial NBCA embolization may provide curative treatment of DAVFs, and is of particular utility in situations where access to the draining venous structures is limited

OBJECT: The aim of this study was to describe the application of a novel transarterial approach to curative embolization of complex intracranial dural arteriovenous fistulas (DAVFs). This technique is particularly useful in patients harboring high-grade DAVFs with direct cortical venous drainage or for whom transvenous coil embolization is not possible because of limited sinus venous access to the fistula site due to thrombosis or stenotic changes. METHODS: Twenty-three DAVFs in 21 patients were treated using a transarterial N-butyl cyanoacrylate (NBCA) embolization technique with the aid of a wedged catheter. In all patients, definitive treatment involved two critical steps: 1) a microcatheter was wedged within a feeding artery, establishing flow-arrest conditions within the catheterized vessel distal to the microcatheter tip; and 2) NBCA was injected under these resultant flow-arrest conditions across the pathological arteriovenous connection and into the immediate draining venous apparatus, definitively occluding the fistula. Patient data were collected in a retrospective manner by reviewing office and inpatient charts and embolization reports, and by directly analyzing all procedural and diagnostic angiograms. Eight patients presented with the principal complaint of tinnitus/bruit, five with intracranial hemorrhage, four with cavrnous sinus syndrome, and one each with seizures, ataxia, visual field loss, and hiccups. The parent (recipient) venous structure of the DAVFs in this study included 11 leptomeningeal veins, eight transverse/sigmoid sinuses, three cavernous sinuses, and one sphenoparietal sinus. The NBCA permeated the arteriovenous shunt, perifistulous network, and proximal draining vein in all DAVFs. Occlusion was confirmed on postembolization angiography studies. No complication occurred in any patient in this series. There has been no recurrence during a mean follow up of 18.7 months (range 2-46 months). CONCLUSIONS: Transarterial NBCA embolization with the aid of a wedged catheter in flow-arrest conditions is a safe and an effective treatment for intracranial DAVFs

The authors present the case of a patient who suffered from progressive cranial nerve dysfunction, radiographically documented brainstem compression, and peduncular hallucinosis after undergoing endosaccular coil placement in a giant basilar apex aneurysm. Symptom resolution was achieved following clip ligation of the basilar artery. The pathogenesis of aneurysm mass effect due to coil placement is discussed and the pertinent literature is reviewed

OBJECTIVE: To minimize the risks associated with treating cortical cerebral arteriovenous malformations (AVMs), we developed a technique combining functional imaging and cerebral angiography. The functional loci obtained by performing magnetoencephalography (MEG) are projected onto stereoscopic pairs of a stereotactically derived digital subtraction angiogram. The result is a simultaneous three-dimensional perspective of the angioarchitecture of an AVM and its relationship to the sensorimotor cortex. METHODS: Eight patients underwent multimodality brain imaging, including magnetic resonance imaging, functional mapping via MEG, and stereotactic angiography using a modified Compass fiducial system (Compass International, Rochester, MN). The coordinates derived by performing MEG were superimposed onto stereotactic, stereoscopic, angiographic pairs using custom-made distortion correction and coordinate transfer software. RESULTS: The magnetoencephalographic angiogram allowed simultaneous viewing of the angioarchitecture of the AVM nidus, the feeding vessels, and the draining veins and their relationship to the normal cerebral vasculature and functional cortex. This imaging technique was particularly valuable in identifying en passant vessels that supplied functional cortex and was used during the treatment of these lesions. CONCLUSION: The techniques of MEG and cerebral angiography were combined to provide simultaneous viewing of both modalities in a three-dimensional perspective. This technique can aid in risk stratification in the management of patients with cerebral AVMs. In addition, this technique can facilitate the selective targeting of vessels, thus potentially reducing the risks associated with embolization of these formidable lesions

We report a case of a 19-year-old woman who underwent radiosurgical treatment of a residual arteriovenous malformation. Nine months after treatment, repeat angiography revealed a de novo paranidal aneurysm that was treated endovascularly. We postulate that changes in flow dynamics or vessel integrity after radiosurgery contributed to the formation of her de novo aneurysm

OBJECTIVE: The availability of non-invasive brain imaging permits the study of normal and abnormal brain development in childhood and adolescence. This paper summarizes current knowledge of brain abnormalities of two conditions, attention deficit hyperactivity disorder (ADHD) and childhood onset schizophrenia (COS), and illustrates how such findings are bringing clinical and preclinical perspectives closer together. METHOD: A selected review is presented of the pattern and temporal characteristics of anatomic brain magnetic resonance imaging (MRI) studies in ADHD and COS. These results are discussed in terms of candidate mechanisms suggested by studies in developmental neuroscience. RESULTS: There are consistent, diagnostically specific patterns of brain abnormality for ADHD and COS. Attention deficit hyperactivity disorder is characterized by a slightly smaller (4%) total brain volume (both white and grey matter), less-consistent abnormalities of the basal ganglia and a striking (15%) decrease in posterior inferior cerebellar vermal volume. These changes do not progress with age. In contrast, patients with COS have smaller brain volume due to a 10% decrease in cortical grey volume. Moreover, in COS there is a progressive loss of regional grey volume particularly in frontal and temporal regions during adolescence. CONCLUSIONS: In ADHD, the developmental pattern suggests an early non-progressive 'lesion' involving neurotrophic factors controlling overall brain growth and selected dopamine circuits. In contrast, in COS, which shows progressive grey matter loss, various candidate processes influencing later synaptic and dendritic pruning are suggested by human post-mortem and developmental animal studies

Several studies suggest hemispheric lateralization of autonomic cardiovascular control. There is controversy regarding which hemisphere dominates sympathetic or parasympathetic activity. Hemispheric influences on baroreflex sensitivity (BRS) have not yet been evaluated. To determine hemispheric autonomic control in epilepsy patients, we assessed cardiovascular and baroreflex modulation before and during hemispheric inactivation. For 15 patients with drug-refractory epilepsy, we analyzed autonomic heart rate (HR) and blood pressure (BP) modulation and BRS before and during left and right intracarotid amobarbital procedure (IAP). After Blackman-Tukey spectral analysis, we calculated the low-frequency (LF: 0.04-0.15 Hz) and high-frequency (HF: 0.15-0.5 Hz) power of HR and BP as well as BRS as the LF transfer function gain between BP and HR. Right hemispheric inactivation induced a significant decrease of BP and an increase of HF power of HR and BP (p < 0.05). Left inactivation increased HR, BP, and LF power of both signals and decreased BRS by nearly 30% (p < 0.05). The results confirm previous IAP studies showing sympathetic lateralization in the right hemisphere and, moreover, demonstrate parasympathetic predominance and up-regulation of BRS in the left hemisphere. In epilepsy patients, unilateral electrical activity might derange autonomic balance between both hemispheres and contribute to cardiovascular dysregulation and sudden fatalities