What is flow diversion therapy of intracranial aneurysms?

The endovascular treatment of intracranial aneurysms has rapidly evolved during the past 2 decades. However, our ability to achieve a durable and complete occlusion of aneurysms remains, in some cases, limited especially large and wide-necked or blister aneurysms.

During the past 3-4 years, a new generation of endovascular devices—the flow diverters—has been developed. These are essentially stents designed to reconstruct the parent artery and divert blood flow along the normal anatomical course of the vessel and away from the aneurysm neck. Complete aneurysm occlusion is not achieved at the time of the procedure.  There is slow progressive thrombosis and the stent provides a scaffolding over which endothelium grows to ultimately seal off the aneurysm.

What are the different stents used?

There are two stents specifically made for flow diversion: SILK and PIPELINE.

However, ENTERPRISE or SOLITAIRE stents which are usually used for stent assisted coiling of aneurysms can also be used and can be effective in certain situations.

Is the treatment established

The PIPELINE device is currently an investigational device in the United States, which is only available within the context of ongoing US Food and Drug Administration (FDA) clinical trials. 

It has received CE Mark approval in Europe on the basis of the Pipeline Embolization Device in the Intracranial Treatment of Aneurysms (PITA) study.

In addition, Dr. Pedro Lylyk in Argentina an Dr Saruhan Cekirge from Turkey have continued to treat patients under individual compassionate use provisions.

The Silk stent (Balt Extrusion, Montmorency, France) is a braided, self-expanding, high metal surface area coverage construct that also has CE Mark approval in Europe for the treatment of intracranial aneurysms. Other similar flow-diverting constructs are at earlier stages of development and are currently without published clinical data.

However, it is important to acknowledge that flow-diversion technology is at a very early stage, and in the Unites States, the PED remains an investigational device. As such, the available data do not provide a sufficient foundation on which to make firm recommendations regarding patient selection.

 The PIPELINE stent

See three case examples below and an animation of the PIPELINE stent being used.

Rupture of a cerebral aneurysm following carotid endarterectomy

This study to date is the largest registry of the flow diversion devices: PIPELINE or SILK.
The authors, here too, like all other smaller studies, have said that the complication rates are acceptable.
This study had 6 major complications in the 90 aneurysms followed up, only 52% had complete occlusion, 66% needed multiple stents which are exorbitantly costly...wonder what the definition of 'acceptable complication rate' is...which most of these studies say...no doubt industry sponsored.
But where ever feasible why not do a parent vessel sacrifice, which is much more safe, durable and cheap...or...use stent grafts/enterprise stent which are much cheaper than the flow diverters..

Pipeline embolization device (PED) for neurovascular reconstruction: initial experience in the treatment of 101 intracranial aneurysms and dissections:

• Authors
  
  
  • Sebastian Fischer, Neuroradiologische Klinik, Neurozentrum, Klinikum Stuttgart, Stuttgart, Germany
  • Zsolt Vajda, Neuroradiologische Klinik, Neurozentrum, Klinikum Stuttgart, Stuttgart, Germany
  • Marta Aguilar Perez, Neuroradiologische Klinik, Neurozentrum, Klinikum Stuttgart, Stuttgart, Germany
  • Elisabeth Schmid, Neurologische Klinik, Neurozentrum, Klinikum Stuttgart, Stuttgart, Germany
  • Nikolai Hopf, Neurochirurgische Klinik, Neurozentrum, Klinikum Stuttgart, Stuttgart, Germany
  • Hansjörg Bäzner, Neurologische Klinik, Neurozentrum, Klinikum Stuttgart, Stuttgart, Germany
  • Hans Henkes, Neuroradiologische Klinik, Neurozentrum, Klinikum Stuttgart, Stuttgart, Germany
  
  
• Journal Neuroradiology
• Online ISSN 1432-1920
• Print ISSN 0028-3940

Treatment of intracranial aneurysms. Reconstruction of the parent artery with flow-diverting (Silk) stent:

• Content Type Journal Article
• Category Interventional Neuroradiology
• Pages 1-10
• DOI 10.1007/s00234-011-0949-9
• Authors
  
  
  • Aase Wagner, Department of Neuroradiology, University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
  • Marie Cortsen, Department of Neuroradiology, University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
  • John Hauerberg, Department of Neurosurgery, University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
  • Bertil Romner, Department of Neurosurgery, University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
  • Mathias Pedersen Wagner, Department of Neuroradiology, University Hospital Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark
  
  
• Journal Neuroradiology
• Online ISSN 1432-1920
• Print ISSN 0028-3940




This is a small patient group who underwent flow diversion with the SILK stent. 1/22 died and 1/22 had clinical deficits. 18/22 aneurysms occluded at 1 year. I do not think these results are really very good

Three cheers for non invasive imaging...

The value of magnetic resonance imaging for the detection of the bleeding source in non-traumatic intracerebral haemorrhages: a comparison with conventional digital subtraction angiography:

• Content Type Journal Article
• Category Diagnostic Neuroradiology
• Pages 1-8
• DOI 10.1007/s00234-011-0953-0
• Authors
  
  
  • Nina Lummel, Department of Neuroradiology, University of Munich, Marchioninistrasse 15, 81377 Munich, Germany
  • Jürgen Lutz, Department of Neuroradiology, University of Munich, Marchioninistrasse 15, 81377 Munich, Germany
  • Hartmut Brückmann, Department of Neuroradiology, University of Munich, Marchioninistrasse 15, 81377 Munich, Germany
  • Jennifer Linn, Department of Neuroradiology, University of Munich, Marchioninistrasse 15, 81377 Munich, Germany
  
  
• Journal Neuroradiology
• Online ISSN 1432-1920
• Print ISSN 0028-3940

• P. Mordasini,M. El-Koussy,C. Brekenfeld,G. Schroth,U. Fischer,J. Beck,and J. Gralla. Applicability of Tableside Flat Panel Detector CT Parenchymal Cerebral Blood Volume Measurement in Neurovascular Interventions: Preliminary Clinical Experience AJNR Am J Neuroradiol 2011 originally published online on September 29, 2011, 10.3174/ajnr.A2715.
  

CBV is a vital perfusion parameter in estimating the viability of brain parenchyma (eg, in cases of ischemic stroke or after interventional vessel occlusion). Recent technologic advances allow parenchymal CBV imaging tableside in the angiography suite just before, during, or after an interventional procedure. The aim of this work was to analyze our preliminary clinical experience with this new imaging tool in different neurovascular interventions.

FPD-CBV measurement was performed on a biplane FPD angiographic system. Eighteen patients (11 women, 7 men) were examined (age range, 18–86 years; median, 58.7 years). In the 10 patients with stroke, the extent of intracranial hypoperfusion was evaluated. The remaining 8 patients had an intracranial hemorrhage; periprocedural CBV was evaluated during the course of interventional treatment.

In the 18 cases studied, 23 CBV measurements were performed. Twenty acquisitions were of sufficient diagnostic quality. The remaining 3 acquisitions failed technically, 1 due to motion artifacts and 2 due to injection technique and/or hardware failure.

FPD-CBV measurement in the angiography suite provides a feasible and helpful tool for peri-interventional neuroimaging. It extends the intraprocedural imaging modalities to the level of tissue perfusion. However, the technique has technical limitations and shows room for improvement in the future.

CME ARTICLE

Neurologic/Head and Neck Imaging:

• Rajiv Mangla,
• Balasubramanya Kolar,
• Jeevak Almast,
• and Sven E. Ekholm

Border Zone Infarcts: Pathophysiologic and Imaging Characteristics Radiographics September-October 2011 31:1201-1214; doi:10.1148/rg.315105014

The causal mechanisms and anatomic locations of external (cortical) and internal (subcortical) border zone infarcts are reviewed, and their appearances at MR imaging, CT, and transcranial Doppler US are described in detail.

Border zone or watershed infarcts are ischemic lesions that occur in characteristic locations at the junction between two main arterial territories. These lesions constitute approximately 10% of all brain infarcts and are well described in the literature. Their pathophysiology has not yet been fully elucidated, but a commonly accepted hypothesis holds that decreased perfusion in the distal regions of the vascular territories leaves them vulnerable to infarction. Two types of border zone infarcts are recognized: external (cortical) and internal (subcortical). To select the most appropriate methods for managing these infarcts, it is important to understand the underlying causal mechanisms. Internal border zone infarcts are caused mainly by hemodynamic compromise, whereas external border zone infarcts are believed to result from embolism but not always with associated hypoperfusion. Various imaging modalities have been used to determine the presence and extent of hemodynamic compromise or misery perfusion in association with border zone infarcts, and some findings (eg, multiple small internal infarcts) have proved to be independent predictors of subsequent ischemic stroke. A combination of several advanced techniques (eg, diffusion and perfusion magnetic resonance imaging and computed tomography, positron emission tomography, transcranial Doppler ultrasonography) can be useful for identifying the pathophysiologic process, making an early clinical diagnosis, guiding management, and predicting the outcome.