Flow diverter

Common sites (intracranial) of saccular aneurysms (treated with flow diverter)

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Flow diverter is an endovascular prosthesis used to treat intracranial aneurysms. It is placed in the parent artery of the aneurysm, covering the neck of the aneurysm, in order to divert blood flow and facilitate progressive thrombosis of the aneurysmal sac. Flow diverters are primarily used to treat aneurysms that are challenging to treat with traditional methods like coil embolization.

Medical Usage

Flow diverters serve as an alternative to traditional treatments such as endosaccular coil embolization, though these techniques can sometimes be combined, especially in the case of larger or giant aneurysms. Flow diverters are particularly effective for wide-necked, unresected saccular aneurysms, which are difficult to treat with coils due to the tendency of the coils to prolapse into the parent artery. Other situations where flow diverters may be used include fusiform or circumferential aneurysms. Before the introduction of flow diverters, many intracranial aneurysms went untreated due to the lack of viable options for their management.

The flow diverter works by diverting the blood flow from the aneurysm sac, promoting thrombosis and eventual occlusion of the aneurysm. This process helps prevent the aneurysm from rupturing and minimizes the risk of bleeding in the brain.

Risks and Complications

While flow diverters offer promising treatment for intracranial aneurysms, they come with certain risks and complications, including:

• Thromboembolic complications – to reduce the likelihood of peri-procedural and post-procedural thromboembolic events, patients are placed on dual antiplatelet therapy for an extended period after receiving a cerebral flow diverter.
• Parent artery occlusion – improper placement or malfunctioning of the flow diverter can result in occlusion of the parent artery, which may lead to ischemia or other complications.
• Incomplete occlusion – there is a possibility of incomplete obliteration of the aneurysm, which would require further intervention.

The efficacy of flow diverters is often assessed using a grading system developed by researchers at the Oxford Neurovascular and Neuroradiology Research Unit (Kamran et al., 2011), known as the Kamran grading system. This system evaluates the degree of aneurysm occlusion on a five-point scale, ranging from:

• Grade 0 – no change in endoaneurysmal flow
• Grade 4 – complete obliteration of the aneurysm

The patency of the parent artery is also graded on a three-point scale, from no change in the diameter of the parent artery to complete occlusion of the parent artery.

This grading system is used widely in clinical practice to evaluate the effectiveness of flow diverters and to monitor patient progress.

See Also

• Blood flow
• Interventional neuroradiology
• Intracranial aneurysm
• Endovascular procedures
• Aneurysm treatment
• Stroke prevention