Interventional Neurosurgery: Advances Offer Safe Alternatives

Paul Camarata, MD, Chair, Neurosurgery
Koji Ebersole, MD, Director, Endovascular Neurosurgery 
Douglas Girod, MD, Otolaryngology

Recent advances in technology and procedures for using catheter-based and other interventional methods in neurosurgery are providing faster, safer, more effective treatments. We now have more options for treating certain aneurysms, strokes and other head and neck issues that may have been untreatable in the past. The best news, however, is that we have only just begun.

Each innovation in materials, procedures and skill development holds the promise of even broader application, giving us hope for continuing to dramatically increase the survivability of these potentially devastating events. This is a review of some of the latest developments in:

  • Treatment of cerebral aneurysms
  • Mechanical thrombectomy
  • Other interventions in neurosurgery and otolaryngology

Embolization device virtually erases evidence of aneurysm

About 1 or 2 percent of the U.S. population likely has a cerebral aneurysm. That equates roughly to the entire population of the state of Kansas or Missouri. Yet only a very small percentage – about 30,000 of these aneurysms – will rupture each year. Smaller aneurysms are often better left alone; depending on the patient’s risk characteristics, they are not likely to rupture. But larger, more complex aneurysms often warrant treatment.

Open surgical treatment of aneurysm, most recently using surgical clips, has been available for more than 60 years and has proven very successful, with low recurrence rates. But interventional procedures have surpassed open surgery by two or three to one over the past 25 years, due to their attractive minimally invasive nature.

The most common interventional aneurysm repair attempts to “pack” the aneurysm, causing thrombosis that will reduce the pressure and inhibit rupture. The primary method is coiling: platinum wires delivered via catheter to fill the aneurysm as tightly as possible, leading to clot formation and occlusion.

This much less invasive technique worked best initially on spherical aneurysms with small necks. Over time, we found better ways to fit the coils more tightly into oddly shaped aneurysms and to more effectively bridge the neck. We also have seen the development of balloons that inflate temporarily in the vessel, giving us more time to make the coils fit complex shapes. And new coiling materials and liquids are able to increase the density of the packing. Still, the recurrence rate with coiling can average around 15 percent.

The new Pipeline™ embolization device relies on a completely different thought process. Instead of packing the aneurysm and allowing the blood flow to continue stressing that spot with each pulsation, the Pipeline relies on diverting blood flow away from the weakened vessel wall.

Unlike the usual stent, which is designed to be as light as possible, the Pipeline is like a dense hose, consisting of 48 braided wires made of 75 percent cobalt chromium and 25 percent platinum tungsten. It is placed inside the vessel from which the aneurysm arises, providing supportive scaffolding across the aneurysm neck and keeping the blood flow in a favored vector down the barrel of the device. It immediately decreases the pressure on the arterial wall, and the vasculature remodels in response to this reduction in stress. After six months, most aneurysms are undetectable and the vessels look normal. Approximately 85 percent are undetectable at one year and recurrence rates are currently at 0 percent.

In the past, the major limitation of endovascular treatment for brain aneurysms was the recurrence rate and the complexity of the aneurysm. This technique overcomes both of those limitations in a major way. In fact, during clinical trials on a specific set of complex aneurysms, Pipeline demonstrated superiority to previous treatment options and therefore the FDA stopped the trial prematurely and awarded full clearance for the device.

The Pipeline shines for large, complex aneurysms, which may have required open surgery in the past or may have presented prohibitive surgical risks. For example, we often resorted to conservative management for large aneurysms in the cavernous carotid because the recurrence rate for coiling was so high, and surgical options carried too much risk. Now, we can often consider Pipeline.

And, while the concept of treating aneurysm by “flow diversion” is very promising, we will need more time and experience with it before it supplants previously proven technologies. But we expect Pipeline to become a go-to tool in the future, potentially having application for as many as 50 percent of all cerebral aneurysms.

Intense credentialing required

To achieve credentialing in the Pipeline procedure, a neurosurgeon must first treat 10 very specific aneurysm types under the direct observation of a certified proctor. The University of Kansas Hospital was the first, and currently is the only, hospital in the region with Pipeline certified physicians.

New mechanical thrombectomy device quickly replaces existing technology

The small percentage of stroke patients who were candidates for mechanical clot retrieval in the past now have a better option, thanks to research on an aneurysm coiling technique.

Intravenous tPA is still the primary treatment for most stroke patients who make it to the emergency department in time. But some patients are not good candidates for tPA, do not respond well to it or arrive too late for tPA to be effective. These patients are sometimes good candidates for mechanical retrieval.

The first mechanical retrieval device in common use was the Merci® Retrieval System, which delivers a corkscrew-shaped wire to the clot and pulls it into the catheter as the wire is retracted. Next was the Penumbra device, which works with a vacuum pump to suction the clot out while macerating it with a teardrop-shaped mandrel. It was more effective, faster than and just as safe as Merci.

Recently, a number of very important randomized clinical trials have demonstrated no clear benefit to mechanical clot retrieval. These results were very disappointing to the stroke community across the board. However, evolution in technology has garnered new hope.

A new class of mechanical retrieval devices has been developed. The new systems deliver a stent-like device made of nitinol, which has shape-memory properties, through a micro-catheter, which temporarily bypasses the occluded vessel. We remove the catheter, leaving the stent imbedded in the clot for about five minutes. As it assumes its desired shape – apposing the walls of the vessels – it expands through and traps the clot. When we retract the device, the clot comes along with it. The new systems appear twice as fast, safe and effective as our past options. The stroke community is extremely excited about these developments and is working to prove their efficacy in randomized controlled trials.

It is important to understand that the indications for clot retrieval are evolving. In the past, we sought this option only within the first three hours of stroke occurrence. But, in certain circumstances, that time window may be extended to six hours and even beyond. Mechanical clot retrieval is thought to be most beneficial when the core ischemic zone – where damage is permanent – is small, and the ischemic penumbra – where the tissue is still potentially viable – is relatively large. These patients may benefit from reperfusion through clot retrieval beyond the previous absolute time marks.

The bottom line, as with cerebral aneurysms, is to offer stroke patients the greatest number of options for treatment. As one of the first five healthcare facilities in the nation – and the only one in the region – to be named an Advanced Comprehensive Stroke Center, The University of Kansas Hospital can offer the greatest number and quality of treatment possibilities.

Technology and experience expand use of other interventional techniques

  • New treatment for pseudotumor cerebri
    Broadened understanding of pathophysiology coupled with advances in neuroendovascular technology has increased treatment options for patients with this difficult diagnosis. A subset of patients develop pseudotumor as a consequence of stenosis in the intracranial venous sinus system. A growing body of evidence suggests that intracranial stenting in the region of stenosis can result in normalization of venous sinus pressures. The subsequent clinical improvement in these select cases can be very satisfactory for both patients and clinicians alike.
  • Managing vascular lesions
    Growing expertise and improved technology also are expanding our ability to embolize head and neck lesions via endovascular and percutaneous routes. Innovations in interventional sclerotherapy offer additional options for benign lesions such as hemangiomas and lymphangiomas. The application of these adjuvant techniques improves surgical safety, decreases blood loss and operating times, and renders rare the necessity to prescribe gross total resection for benign vascular head and neck lesions.
To consult with a specialist at the Center for Advanced Brain & Neurological Care, call 913-588-5862 or toll free 877-588-5862. Read more about the interventional alternatives available at the Center for Advanced Brain & Neurological Care

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