1,359 research outputs found
The transmission of inequality across multiple generations: testing recent theories with evidence from Germany
This article shows that across multiple generations, the persistence of occupational and educational attainment in Germany is larger than estimates from two generations suggest. We consider two recent interpretations. First, we assess Gregory Clark's hypotheses that the true rate of intergenerational persistence is higher than the observed rate, as high as 0.75, and time-invariant. Our evidence supports the first but not the other two hypotheses. Second, we test for independent effects of grandparents. We show that the coefficient on grandparent status is positive in a wide class of Markovian models and present evidence against its causal interpretation.Jan Stuhler gratefully acknowledges support from the Ministerio EconomĂa y Competitividad (Spain, MDM 2014-0431 and ECO2014-55858-P) and Comunidad de Madrid (MadEco-CM S2015/HUM-3444)
Territoriality, Border Controls and the Mobility of Persons in a Globalised World
Der vorliegende Artikel beschĂ€ftigt sich mit dem Zusammenhang von Territorialgrenzen, Personenkontrollen und Staatlichkeit. Im Zentrum der Betrachtung stehen der Wandel des Nationalstaates alter PrĂ€gung sowie die VerĂ€nderung der staatlichen Grenz- und Personenkontrolle unter den Bedingungen der Globalisierung. Unter Globalisierung wird ĂŒblicherweise die Zunahme grenzĂŒberschreitender Transaktionen und die AbschwĂ€chung der KontrollfĂ€higkeit des Staates fĂŒr ein ganzes Spektrum von Faktoren und Ressourcen verstanden. Diese Behauptung wird fĂŒr den Bereich der PersonenmobilitĂ€t auf Basis einer SekundĂ€ranalyse empirischer Studien ĂŒberprĂŒft, wobei zugleich hinterfragt wird, ob eine Zunahme an GrenzĂŒberschreitungen mit einer Abnahme staatlicher Kontrolle gleichgesetzt werden kann. In der Debatte zur Globalisierung stehen Thesen zur abnehmenden KontrollkapazitĂ€t des Staates und zum Bedeutungsverlust von Grenzen kontrĂ€ren Thesen ĂŒber eine anhaltend wichtige Rolle nationalstaatlicher Grenzen und Grenzkontrollen gegenĂŒber. In Abgrenzung dazu deuten unsere gesammelten Hinweise darauf hin, dass diese allgemeinen Thesen zu kurz greifen, um die Breite der Entwicklungen zu beschreiben. Die Reaktionen des Staates auf VerĂ€nderungen im Kontext der Globalisierung scheinen den ersten Befunden nach vielfĂ€ltiger zu sein als oftmals behauptet wird: Wir finden eine Gleichzeitigkeit von Ăffnung und selektiver SchlieĂung, was auf eine Ausdifferenzierung der Grenzkontrollfunktion hindeutet. Zugleich wenden Staaten sowohl Strategien zwischenstaatlicher Kooperation und Makroterritorialisierung von Grenzen bei gleichzeitig erhöhtem Einsatz technischer Mittel und neuer Technologien als auch integrierte AnsĂ€tze der inneren und Ă€uĂeren Sicherheit an. Ein allgemeiner Kontrollverlust des Staates kann auf der Basis unserer Erkenntnisse nicht ausgemacht werden, vielmehr zeigt sich eine VerĂ€nderung der Formen und Inhalte staatlicher Grenzregime
Change impact and risk analysis (CIRA) : combining the CPM/PDD theory and FMEA-methodology for an improved engineering change management
The change process is one of the most critical tasks of the product development process. Misinterpretation or lack of knowledge about impacts or risks of changes can cause serious disadvantages to companies, e.g. high failure or change costs or image losses caused by products with a quality that is unacceptable. Supervising the change process is a challenging task; an important part of this task is the analysis and assessment of risks and impacts of changes. This contribution presents an approach to support the process of analysing and assessing the effects of changes in the product development process. The approach is based on two methods: First on the CPM/PDD theory developed at the Institute of Engineering Design/CAD in order to synthesise potential solutions to change requests and to ana-lyse their impacts; second on the common Failure Modes and Effects Analysis (FMEA)-method in order to assess the risks and impacts of changes and to document the analysis
Comparison of knowledge representation in PDM and by semantic networks
\u27Nowadays, computer-aided tools have enabled the creation of electronic design documents on an unprecedented scale, while determining and finding what can be reused for a new design is like searching for a \u27needle in a haystack\u27. (âŠ) The availability of such extensive knowledge resources is creating new challenges as well as opportunities for research on how to retrieve and reuse the knowl-edge from existing designs.\u27 [1] If the requested knowledge is implicit (which means that it is only in the minds of the employees of a company) the retrieval and reuse of knowledge is even more com-plicated. By representing the (engineering) data backbone of a company, PDM systems are the software implementation which should support the designer to retrieve information about existing and successful design projects. This paper shows that the known data classification approaches of common PDM systems are not applicable to represent implicit (tacit) knowledge. Furthermore a new approach to knowledge representation is introduced by using Semantic Networks. The feasibility of the presented work is shown by a use-case scenario in which the conventional PDM system supported product development process is compared with the proposed way by using the soft-ware \u27The Semaril\u27 â a software tool developed at the Institute of Engineering Design/CAD based on Semantic Networks [2]
On the Nature of the Debye-Process in Monohydroxy Alcohols: 5-Methyl-2-Hexanol Investigated by Depolarized Light Scattering and Dielectric Spectroscopy
The slow Debye-like relaxation in the dielectric spectra of monohydroxy
alcohols is a matter of long standing debate. In the present work, we probe
reorientational dynamics of 5-methyl-2-hexanol with dielectric spectroscopy and
depolarized light scattering (DDLS) in the supercooled regime. While in a
previous study of a primary alcohol no indication of the Debye peak in the DDLS
spectra was found, we now for the first time report clear evidence of a Debye
contribution in a monoalcohol in DDLS. A quantitative comparison between the
dielectric and DDLS manifestation of the Debye peak reveals that while the
dielectric Debye process represents fluctuations in the end-to-end vector
dipole moment of the transient chains, its occurrence in DDLS shows a more
local signature and is related to residual correlations which occur due to a
slight anisotropy of the -relaxation caused by the chain formation.Comment: 5 pages, 5 figures; accepted in Phys. Rev. Let
Accept Me as I Am or See Me Go: A Qualitative Analysis of User Acceptance of Self-Sovereign Identity Applications
Self-sovereign identity represents a novel phenomenon aiming to innovate how entities interact with, manage, and prove identity-related information. As with any emerging phenomenon, user acceptance represents a major challenge for the adoption of Self-sovereign identity. Since previous initiatives for digital identity management solutions have not been successfully adopted while at the same time their benefits are largely driven by network effects, user acceptance research is of particular importance for Self-sovereign identity. Therefore, we investigate the user acceptance of Self-sovereign identity by conducting a qualitative interview study. We contribute novel variables to existing theory and offer guidelines for building Self-sovereign identity systems
An integrative clinical database and diagnostics platform for biomarker identification and analysis in ion mobility spectra of human exhaled air
Over the last decade the evaluation of odors and vapors in human breath has gained more and more attention, particularly in the diagnostics of pulmonary diseases. Ion mobility spectrometry coupled with multi-capillary columns (MCC/IMS), is a well known technology for detecting volatile organic compounds (VOCs) in air. It is a comparatively inexpensive, non-invasive, high-throughput method, which is able to handle the moisture that comes with human exhaled air, and allows for characterizing of VOCs in very low concentrations. To identify discriminating compounds as biomarkers, it is necessary to have a clear understanding of the detailed composition of human breath. Therefore, in addition to the clinical studies, there is a need for a flexible and comprehensive centralized data repository, which is capable of gathering all kinds of related information. Moreover, there is a demand for automated data integration and semi-automated data analysis, in particular with regard to the rapid data accumulation, emerging from the high-throughput nature of the MCC/IMS technology. Here, we present a comprehensive database application and analysis platform, which combines metabolic maps with heterogeneous biomedical data in a well-structured manner. The design of the database is based on a hybrid of the entity-attribute-value (EAV) model and the EAV-CR, which incorporates the concepts of classes and relationships. Additionally it offers an intuitive user interface that provides easy and quick access to the platform's functionality: automated data integration and integrity validation, versioning and roll-back strategy, data retrieval as well as semi-automatic data mining and machine learning capabilities. The platform will support MCC/IMS-based biomarker identification and validation. The software, schemata, data sets and further information is publicly available at \urlhttp://imsdb.mpi-inf.mpg.de
The Influence of Molecular Architecture on the Dynamics of H-Bonded Supramolecular Structures in Phenyl-Propanols
The relaxation behaviour of monohydroxy alcohols (monoalcohols) in broadband
dielectric spectroscopy (BDS) is usually dominated by the Debye process. This
process is regarded as a signature of the dynamics of transient supramolecular
structures formed by H-bonding. In phenyl propanols the steric hindrance of the
phenyl ring is assumed to influence chain formation and thereby to decrease or
even suppress the intensity of the Debye process. In the present paper we study
this effect in a systematic series of structural isomers of phenyl-1-propanol
in comparison with 1-propanol. It turns out that by combining BDS, Photon
Correlation Spectroscopy (PCS) and calorimetry the dynamics of supramolecular
structures can be uncovered. While light scattering spectra show the same
spectral shape of the main relaxation for all investigated monoalcohols, the
dielectric spectra differ in the Debye contribution. Thus it becomes possible
for the first time to unambiguously disentangle both relaxation modes in the
dielectric spectra. It turns out that the Debye relaxation gets weaker the
closer the position of phenyl ring is to the hydroxy group, in accordance with
the analysis of the Kirkwood-Fr\"ohlich correlation factor. Even in
1-phenyl-1-propanol, which has the phenyl group attached at the closest
position to the hydroxy group, we can separate a Debye-contribution in the
dielectric spectrum. From this we conclude that hydrogen bonds are not
generally suppressed by the increased steric hindrance of the phenyl ring, but
rather an equilibrium of ring and chain-like structures is shifted towards
ring-like shapes on shifting the phenyl ring closer to the hydroxy group.
Moreover, the shape of the alpha-relaxation as monitored by PCS and BDS remains
unaffected by the degree of hydrogen bonding and is the same among the
investigated alcohols.Comment: 9 pages, 7 figure
Rekanalisierungsrate von Basilariskopfaneurysmen nach endovaskulÀrem Coiling mit und ohne Stent : eine retrospektive Datenerhebung an 52 Patienten
Einleitung
Seit die Ergebnisse der groĂen, multizentrischen Studien ĂŒber die Therapieentscheidungen einer
operativen oder endovaskulÀren Behandlung vorliegen, werden Gehirnaneurysmen vorwiegend
neuroradiologisch behandelt. Zwar konnte auch nach zehnjÀhriger Nachuntersuchung
der International Subarachnoid Aneurysm Trial eine erhöhte Reblutungsrate in der endovaskulÀren
Gruppe festgestellt werden, doch war die Wahrscheinlichkeit nach einem neurochirurgischen
Eingriff auf Hilfe angewiesen zu sein signifikant erhöht (1. Molyneux AJ, et.
al., 2014).
In der vorliegenden retrospektiven Arbeit wurden ĂŒber den Zeitraum von bis zu 5 Jahren Patienten
untersucht, die sich einer endovaskulĂ€ren Intervention aneurysmatischer GefĂ€ĂverĂ€nderungen
des Basilariskopfes unterzogen haben. Besonders bei Aneurysmen deren chirurgischer
Zugang als risikoreich und komplikationsanfÀllig gilt, versucht man neue endovaskulÀre Behandlungstechniken
zu etablieren und auf ihren Verlauf hin zu untersuchen. Entzogen sich
frĂŒher die breitbasigen, komplex konfigurierten oder riesigen Aneurysmen der endovaskulĂ€ren
Therapie, entwickelte man sukzessive Techniken, auch solche GefĂ€Ăe zu behandeln. Die
erste Gruppe der vorliegenden Studie unterzog sich einem Coiling (n=34), die Aneurysmen
der zweiten Gruppe wurden zusÀtzlich unter Zuhilfenahme eines Stentes (n=18) embolisiert.
Dabei stellten wir uns die Fragen
ob das neuroradiologische Prozedere wesentlich techniksensitiver ist,
inwieweit Okklusions â und Rekanalisierungsraten verĂ€ndert sind und
ob das StentâgestĂŒtzte Coiling mit einer erhöhten Reeingriffsrate verbunden ist.
Patienten und Methode
In einem Zeitraum von 2008â2012 wurden an der Klinik fĂŒr diagnostische und interventionelle
Neuroradiologie der UniversitĂ€tskliniken des Saarlandes zweiundfĂŒnfzig Patienten an Aneurysmen
der A. basilaris endovaskulÀr behandelt. 76,9% der Patienten waren weiblichen und 23,1% mÀnnlichen Geschlechtes.
Das Durchschnittsalter der Patienten zum Zeitpunkt des Ersteingriffes betrug 57,65 Jahre.
5 der behandelten Patienten waren unter 40 Jahren, 39 Patienten zwischen 41 und 69 Jahren
und 9 Ă€lter als 70 Jahre. Der jĂŒngste Patient war 23, der Ă€lteste 86.
9 Aneurysmen waren 2â6mm, 34 6â15mm, 8 15â25mm und 1 gröĂer als 25mm. Die durchschnittliche
AneurysmagröĂe lag bei 9mm.
13 Aneurysmen waren zum Zeitpunkt des Ersteingriffes symptomatisch, 39 asymptomatisch.
34 Basilarisaneurysmen wurden gecoilt, 18 wurden zusÀtzlich mit einem Stent versorgt.
Anhand der RaymondâKlassifikation wurden die Okklusionraten der Aneurysmen sĂ€mtlicher
zur VerfĂŒgung stehender Angiografiedaten eingeteilt. Das Aneurysmavolumen wurde bestimmt,
mit Hilfe der Interventionsbögen Fabrikat und GröĂe der verwandten Coils registriert
und die Packungsdichte berechnet. Das durchschnittliche Aneurysmavolumen betrug
750,16mm3, die Packungsdichte lag bei 29,15%.
Insofern verfĂŒgbar wurden die behandelten Aneurysmen bis zu fĂŒnf Jahren nachuntersucht
und im Hinblick auf periprozedurale Komplikationen, Rekanalisierungsâ und Re-Eingriffsrate
untersucht und verglichen.
Ergebnisse
Die initialen Okklusionsraten lagen in der CoilingâGruppe bei 76,5% (Klasse I), 14,7%
(Klasse II) und bei 8,8% (Klasse III). In der StentâGruppe konnten Okklusionsraten von
83,3%, 16,7% und 0% erreicht werden.
Innerhalb des ersten Jahres konnten noch 26 (76,5%) gecoilte Aneurysmen nachuntersucht
werden. Die Verschlussraten betrugen 52%, 33% und 15%. Die reperfundierten Aneurysmen
der Klasse III und eines der Klasse II wurden nachbehandelt (14,7%) und kamen im Anschluss
komplett verschlossen zur Darstellung. Jeder der Patienten hatte im Vorhinein eine
Subarachnoidalblutung, weshalb die initiale Intervention zunÀchst der Ausschaltung der Blutung
diente. In zwei FĂ€llen bestand nach der ersten Intervention eine inkomplette Okklusion.
14 der StentâgestĂŒtzt behandelten Aneurysmen wurden im ersten Jahr nachuntersucht. Die
Okklusion betrug 58%, 28% und 14%. Ein Re-Eingriff ereignete sich in 16,6% an zuvor symptomatischen
Aneurysmen. Zwei waren zudem primĂ€r Klasse II verschlossen. In der zweiten Nachuntersuchung betrug die Verschlussrate in der CoilingâGruppe 80%,
20% und 0% und in der StentâGruppe 71,5%, 28,5% und 0%.
In den bis zu fĂŒnf Jahren nachuntersuchten Aneurysmen der CoilingâGruppe ist noch eine
Verschlussrate in Höhe von 71,5%, 28,5% und 0% registriert worden. Der Grund fĂŒr die lange
angiografische Nachuntersuchung liegt in der vorangegangen Subarachnoidalblutung oder in
primÀr nicht zufriedenstellenden Okklusionsraten und Packungsdichten.
Schlussfolgerung
Die Behandlung von Aneurysmen des Gehirns unter Zuhilfenahme von Stents stellt eine funktionierende,
sichere Methode dar auch schwierige Konfigurationen erfolgreich zu embolisieren.
Dabei stehen Arterien wie die Basilaris unter besonderem wissenschaftlichen Interesse,
da ihr chirurgischer Zugang schwierig bis unmöglich und die endovaskulĂ€re Therapie bei ungĂŒnstigen
Konfigurationen problembehaftet ist. Besonders inzidentelle Aneurysmen der hinteren
Zirkulation in der GröĂe 7â12mm unterliegen laut ISUIA einer erhöhten Rupturwahrscheinlichkeit
gegenĂŒber GefĂ€Ăerweiterungen im vorderen Hirnkreislauf. (14,5% versus
2,6%) In unserer Studie stellte sich heraus, dass die initialen Okklusionsraten in der Stent â
Gruppe höher, die Rekanalisierungsraten geringer und die Re-Eingriffs- und Reblutungsraten
vergleichbar sind. Das neuroradiologische Prozedere ist vor allem bei Patienten deren GefĂ€Ăe
elongiert und geknickt sind techniksensitiver. Innerhalb dieser Studie konnte aber keine erhöhte
periprozedurale Komplikationsrate im Vergleich zu der CoilingâGruppe gefunden werden.
Dennoch existieren FĂ€lle bei denen die Aneurysmen hĂ€ufig rekanalisieren, weshalb ĂŒber weitere
Einflussfaktoren diskutiert werden muss.Introduction
Cerebral aneurysms have mostly been treated with neuroradiology ever since the results of the
big, multicentre studies dealing with therapeutic decisions about operational versus intravascular
treatments are known. A follow-up examination in the endovascular group, realised by
the International Subarachnoid Aneurysm Trial after ten years, showed increased bleedings â
however, the proability of needing help after a neurosurgical intervention was significantly
higher. (1. Molyneux AJ, et. al., 2014)
This retrospektive thesis shows a five-year-examination of patients that had undergone an endovascular
intervention of basilar tip aneurysms. Scientists are trying to establish new endovascular
treatment techniques and analyse their process, especially for aneurysms whose surgical
accesses are seen as risky and prone to complications. In the past, broad-based,
complexly configured, or giant aneurysms were impossible to treat with endovascular means.
Over time, however, scientists have gradually developed techniques to treat even these vessels.
Group 1 of this study was treated with coiling (n=34), the aneurysms of group 2 were additionally
embolised with a stent (n=18).
Thus, we tried to answer the following questions:
Is a neuroradiological procedure signifcantly more technique sensitive?
To what extent do the occlusion- and the recanalisation-rates change?
Is coiling supported by stents connected to a higher reintervention-rate?
Patients and method
Between 2008 and 2012, 52 patients with aneurysms of the arteria basilaris have undergone
endovascular therapy at the Clinic for Diagnostic and Interventional Neuroradiology of the
University Hospital Saarland.
76.9% of the patients were women, 23.1% were men.
The average age of all patients was 57.65 years at the time of initial intervention. Five of them
were younger than 40 years, 39 were between 41 and 69 years and 9 were older than 70 years.
The youngest patient was 23 years of age, the oldest was 86. Nine aneurysms were 2â6mm, 34 were 6â15mm, eight were 15â25mm, and one was bigger
than 25mm. The average size of the aneurysms was 9mm.
13 aneurysms were symptomatic, 39 were asymptomatic at the time of initial intervention.
34 basilar aneurysms were coiled, 18 were additionally treated with a stent.
Based on the Raymond-classification, we grouped occlusation rates of the aneurysms of all
available angiographic data. We determined the aneurysm volume, recorded brand and size of
the coils used (by means of intervention forms), and computed packing densitiy. The average
aneurysm volume amounted to 750.16mm3, packing density was at 29.15%.
Wherever possible, the treated aneurysms were checked regularly for up to five years. They
were examined and compared with regard to periprocedural complications, recanalisational
and reinterventional rates.
Results
In the coiling-group, the initial occlusation rates were at 76.5% (class I), 14.7% (class II), and
8.8% (class III). In the stent-group, we were able to reach occlusation rates of 83.3%, 16.7%,
and 0%.
Within year one, we were able to do follow-up examinations of 26 (76.5%) of the coiled aneurysms.
The closure rates amounted 52%, 33%, and 15%. We post-treated the reperfused aneurysms
of class III and one of class II, which then were completely closed. Each patient had
had a subarachnoid hemorrhage before treatment, which is why the initial interventionâs priority
was to stop the bleeding. In two cases the occlusion was inclomplete after initial intervention.
Fourteen of the aneurysms treated with a stent had a follow-up examination within the first
year. Occlusation amounted to 58%, 28%, and 14%. A reintervention took place in 16.6% of
formerly symptomatic aneurysms. Additionally, two of them were primarily closed class II.
During the second follow-up examination the closure rate of group 1 was at 80%, 20%, and
0%, in group 2 it amounted to 71.5%, 28.5%, and 0%.
In the aneurysms of group 1 examined over up to five years, we recorded closure rates of
71.5%, 28.5%, and 0%. The reasons for such a long angiographic follow-up examination were
either subarachnoid hemorrhage or occlusion rates and packing densities that were not satisfying
at first. Conclusion
Treating aneurysms of the brain with stents is a functional, safe method to successfully embolise
even difficult configurations. Here, arteries like the basilar are of special scientific interest,
as a surgical access is difficult or impossible and endovascular therapy of unfavourable
configurations is problematic. Especially incidental eneurysms of the anterior circulation and
of 7â12mm in size have an increased probability to rupture compared with vascular dilations
in the posterior cerebral circulation (14.5% versus 2.6%), according to ISUIA. Our study
concluded in the initial occlusion rates of the stent-group being higher, the recanalisation rates
being lower, and the reintervention- and rebleeding-rates being comparable. Especially for patients
with elongated and flexed vessels, the neuroradiological procedure is more technique
sensitive. However, we did not find any increased periprocedural complication rate, compared
to the coiling-group.
Nevertheless, there are cases in which aneurysms recanalise often, which is why further discussion
is still of great importance
Rekanalisierungsrate von Basilariskopfaneurysmen nach endovaskulÀrem Coiling mit und ohne Stent : eine retrospektive Datenerhebung an 52 Patienten
Einleitung
Seit die Ergebnisse der groĂen, multizentrischen Studien ĂŒber die Therapieentscheidungen einer
operativen oder endovaskulÀren Behandlung vorliegen, werden Gehirnaneurysmen vorwiegend
neuroradiologisch behandelt. Zwar konnte auch nach zehnjÀhriger Nachuntersuchung
der International Subarachnoid Aneurysm Trial eine erhöhte Reblutungsrate in der endovaskulÀren
Gruppe festgestellt werden, doch war die Wahrscheinlichkeit nach einem neurochirurgischen
Eingriff auf Hilfe angewiesen zu sein signifikant erhöht (1. Molyneux AJ, et.
al., 2014).
In der vorliegenden retrospektiven Arbeit wurden ĂŒber den Zeitraum von bis zu 5 Jahren Patienten
untersucht, die sich einer endovaskulĂ€ren Intervention aneurysmatischer GefĂ€ĂverĂ€nderungen
des Basilariskopfes unterzogen haben. Besonders bei Aneurysmen deren chirurgischer
Zugang als risikoreich und komplikationsanfÀllig gilt, versucht man neue endovaskulÀre Behandlungstechniken
zu etablieren und auf ihren Verlauf hin zu untersuchen. Entzogen sich
frĂŒher die breitbasigen, komplex konfigurierten oder riesigen Aneurysmen der endovaskulĂ€ren
Therapie, entwickelte man sukzessive Techniken, auch solche GefĂ€Ăe zu behandeln. Die
erste Gruppe der vorliegenden Studie unterzog sich einem Coiling (n=34), die Aneurysmen
der zweiten Gruppe wurden zusÀtzlich unter Zuhilfenahme eines Stentes (n=18) embolisiert.
Dabei stellten wir uns die Fragen
ï· ob das neuroradiologische Prozedere wesentlich techniksensitiver ist,
ï· inwieweit Okklusions â und Rekanalisierungsraten verĂ€ndert sind und
ï· ob das StentâgestĂŒtzte Coiling mit einer erhöhten Reeingriffsrate verbunden ist.
Patienten und Methode
In einem Zeitraum von 2008â2012 wurden an der Klinik fĂŒr diagnostische und interventionelle
Neuroradiologie der UniversitĂ€tskliniken des Saarlandes zweiundfĂŒnfzig Patienten an Aneurysmen
der A. basilaris endovaskulÀr behandelt. 76,9% der Patienten waren weiblichen und 23,1% mÀnnlichen Geschlechtes.
Das Durchschnittsalter der Patienten zum Zeitpunkt des Ersteingriffes betrug 57,65 Jahre.
5 der behandelten Patienten waren unter 40 Jahren, 39 Patienten zwischen 41 und 69 Jahren
und 9 Ă€lter als 70 Jahre. Der jĂŒngste Patient war 23, der Ă€lteste 86.
9 Aneurysmen waren 2â6mm, 34 6â15mm, 8 15â25mm und 1 gröĂer als 25mm. Die durchschnittliche
AneurysmagröĂe lag bei 9mm.
13 Aneurysmen waren zum Zeitpunkt des Ersteingriffes symptomatisch, 39 asymptomatisch.
34 Basilarisaneurysmen wurden gecoilt, 18 wurden zusÀtzlich mit einem Stent versorgt.
Anhand der RaymondâKlassifikation wurden die Okklusionraten der Aneurysmen sĂ€mtlicher
zur VerfĂŒgung stehender Angiografiedaten eingeteilt. Das Aneurysmavolumen wurde bestimmt,
mit Hilfe der Interventionsbögen Fabrikat und GröĂe der verwandten Coils registriert
und die Packungsdichte berechnet. Das durchschnittliche Aneurysmavolumen betrug
750,16mm3, die Packungsdichte lag bei 29,15%.
Insofern verfĂŒgbar wurden die behandelten Aneurysmen bis zu fĂŒnf Jahren nachuntersucht
und im Hinblick auf periprozedurale Komplikationen, Rekanalisierungsâ und Re-Eingriffsrate
untersucht und verglichen.
Ergebnisse
Die initialen Okklusionsraten lagen in der CoilingâGruppe bei 76,5% (Klasse I), 14,7%
(Klasse II) und bei 8,8% (Klasse III). In der StentâGruppe konnten Okklusionsraten von
83,3%, 16,7% und 0% erreicht werden.
Innerhalb des ersten Jahres konnten noch 26 (76,5%) gecoilte Aneurysmen nachuntersucht
werden. Die Verschlussraten betrugen 52%, 33% und 15%. Die reperfundierten Aneurysmen
der Klasse III und eines der Klasse II wurden nachbehandelt (14,7%) und kamen im Anschluss
komplett verschlossen zur Darstellung. Jeder der Patienten hatte im Vorhinein eine
Subarachnoidalblutung, weshalb die initiale Intervention zunÀchst der Ausschaltung der Blutung
diente. In zwei FĂ€llen bestand nach der ersten Intervention eine inkomplette Okklusion.
14 der StentâgestĂŒtzt behandelten Aneurysmen wurden im ersten Jahr nachuntersucht. Die
Okklusion betrug 58%, 28% und 14%. Ein Re-Eingriff ereignete sich in 16,6% an zuvor symptomatischen
Aneurysmen. Zwei waren zudem primĂ€r Klasse II verschlossen. In der zweiten Nachuntersuchung betrug die Verschlussrate in der CoilingâGruppe 80%,
20% und 0% und in der StentâGruppe 71,5%, 28,5% und 0%.
In den bis zu fĂŒnf Jahren nachuntersuchten Aneurysmen der CoilingâGruppe ist noch eine
Verschlussrate in Höhe von 71,5%, 28,5% und 0% registriert worden. Der Grund fĂŒr die lange
angiografische Nachuntersuchung liegt in der vorangegangen Subarachnoidalblutung oder in
primÀr nicht zufriedenstellenden Okklusionsraten und Packungsdichten.
Schlussfolgerung
Die Behandlung von Aneurysmen des Gehirns unter Zuhilfenahme von Stents stellt eine funktionierende,
sichere Methode dar auch schwierige Konfigurationen erfolgreich zu embolisieren.
Dabei stehen Arterien wie die Basilaris unter besonderem wissenschaftlichen Interesse,
da ihr chirurgischer Zugang schwierig bis unmöglich und die endovaskulĂ€re Therapie bei ungĂŒnstigen
Konfigurationen problembehaftet ist. Besonders inzidentelle Aneurysmen der hinteren
Zirkulation in der GröĂe 7â12mm unterliegen laut ISUIA einer erhöhten Rupturwahrscheinlichkeit
gegenĂŒber GefĂ€Ăerweiterungen im vorderen Hirnkreislauf. (14,5% versus
2,6%) In unserer Studie stellte sich heraus, dass die initialen Okklusionsraten in der Stent â
Gruppe höher, die Rekanalisierungsraten geringer und die Re-Eingriffs- und Reblutungsraten
vergleichbar sind. Das neuroradiologische Prozedere ist vor allem bei Patienten deren GefĂ€Ăe
elongiert und geknickt sind techniksensitiver. Innerhalb dieser Studie konnte aber keine erhöhte
periprozedurale Komplikationsrate im Vergleich zu der CoilingâGruppe gefunden werden.
Dennoch existieren FĂ€lle bei denen die Aneurysmen hĂ€ufig rekanalisieren, weshalb ĂŒber weitere
Einflussfaktoren diskutiert werden muss.Introduction
Cerebral aneurysms have mostly been treated with neuroradiology ever since the results of the
big, multicentre studies dealing with therapeutic decisions about operational versus intravascular
treatments are known. A follow-up examination in the endovascular group, realised by
the International Subarachnoid Aneurysm Trial after ten years, showed increased bleedings â
however, the proability of needing help after a neurosurgical intervention was significantly
higher. (1. Molyneux AJ, et. al., 2014)
This retrospektive thesis shows a five-year-examination of patients that had undergone an endovascular
intervention of basilar tip aneurysms. Scientists are trying to establish new endovascular
treatment techniques and analyse their process, especially for aneurysms whose surgical
accesses are seen as risky and prone to complications. In the past, broad-based,
complexly configured, or giant aneurysms were impossible to treat with endovascular means.
Over time, however, scientists have gradually developed techniques to treat even these vessels.
Group 1 of this study was treated with coiling (n=34), the aneurysms of group 2 were additionally
embolised with a stent (n=18).
Thus, we tried to answer the following questions:
ï· Is a neuroradiological procedure signifcantly more technique sensitive?
ï· To what extent do the occlusion- and the recanalisation-rates change?
ï· Is coiling supported by stents connected to a higher reintervention-rate?
Patients and method
Between 2008 and 2012, 52 patients with aneurysms of the arteria basilaris have undergone
endovascular therapy at the Clinic for Diagnostic and Interventional Neuroradiology of the
University Hospital Saarland.
76.9% of the patients were women, 23.1% were men.
The average age of all patients was 57.65 years at the time of initial intervention. Five of them
were younger than 40 years, 39 were between 41 and 69 years and 9 were older than 70 years.
The youngest patient was 23 years of age, the oldest was 86. Nine aneurysms were 2â6mm, 34 were 6â15mm, eight were 15â25mm, and one was bigger
than 25mm. The average size of the aneurysms was 9mm.
13 aneurysms were symptomatic, 39 were asymptomatic at the time of initial intervention.
34 basilar aneurysms were coiled, 18 were additionally treated with a stent.
Based on the Raymond-classification, we grouped occlusation rates of the aneurysms of all
available angiographic data. We determined the aneurysm volume, recorded brand and size of
the coils used (by means of intervention forms), and computed packing densitiy. The average
aneurysm volume amounted to 750.16mm3, packing density was at 29.15%.
Wherever possible, the treated aneurysms were checked regularly for up to five years. They
were examined and compared with regard to periprocedural complications, recanalisational
and reinterventional rates.
Results
In the coiling-group, the initial occlusation rates were at 76.5% (class I), 14.7% (class II), and
8.8% (class III). In the stent-group, we were able to reach occlusation rates of 83.3%, 16.7%,
and 0%.
Within year one, we were able to do follow-up examinations of 26 (76.5%) of the coiled aneurysms.
The closure rates amounted 52%, 33%, and 15%. We post-treated the reperfused aneurysms
of class III and one of class II, which then were completely closed. Each patient had
had a subarachnoid hemorrhage before treatment, which is why the initial interventionâs priority
was to stop the bleeding. In two cases the occlusion was inclomplete after initial intervention.
Fourteen of the aneurysms treated with a stent had a follow-up examination within the first
year. Occlusation amounted to 58%, 28%, and 14%. A reintervention took place in 16.6% of
formerly symptomatic aneurysms. Additionally, two of them were primarily closed class II.
During the second follow-up examination the closure rate of group 1 was at 80%, 20%, and
0%, in group 2 it amounted to 71.5%, 28.5%, and 0%.
In the aneurysms of group 1 examined over up to five years, we recorded closure rates of
71.5%, 28.5%, and 0%. The reasons for such a long angiographic follow-up examination were
either subarachnoid hemorrhage or occlusion rates and packing densities that were not satisfying
at first. Conclusion
Treating aneurysms of the brain with stents is a functional, safe method to successfully embolise
even difficult configurations. Here, arteries like the basilar are of special scientific interest,
as a surgical access is difficult or impossible and endovascular therapy of unfavourable
configurations is problematic. Especially incidental eneurysms of the anterior circulation and
of 7â12mm in size have an increased probability to rupture compared with vascular dilations
in the posterior cerebral circulation (14.5% versus 2.6%), according to ISUIA. Our study
concluded in the initial occlusion rates of the stent-group being higher, the recanalisation rates
being lower, and the reintervention- and rebleeding-rates being comparable. Especially for patients
with elongated and flexed vessels, the neuroradiological procedure is more technique
sensitive. However, we did not find any increased periprocedural complication rate, compared
to the coiling-group.
Nevertheless, there are cases in which aneurysms recanalise often, which is why further discussion
is still of great importance
- âŠ