Archive for the 'Neurosurgery' Category

Advances in thrombolysis

Bill Likosky, MD, FAAN, FAHA, Director for Stroke and Telestroke, Swedish Neuroscience Institute

 

 

Washington State has one of the high­est stroke mortality rates in the nation. To improve this situation, acute intervention­al therapies for stroke are being employed to restore circulation to ischemic brain tissue that surrounds areas of completed infraction, while avoiding risk of hemor­rhage due to reperfusion of large areas of infracted brain tissue.

Urgent thrombolysis with intrave­nous alteplase is the only therapy known to improve clinical outcomes following acute stroke. Unfortunately, alteplase has had limited usage because many patients arrive in an emergency department after the three-hour treatment window. The FDA has also approved two clot removal devices based on the ability to restore circulation. These devices are used up to eight hours after symptom onset. Several approaches to improved acute stroke care are now under way, including extension of the thrombolysis window to 4.5 hours, identification of safer thrombolytic agents and research identifying brain at risk of in­farction following a stroke.

A recent European study demonstrat­ed the efficacy of alteplase up to 4.5 hours after ischemic stroke in patients younger than age 80 years who have neither dia­betes mellitus or prior stroke. The safety profile during this longer window for these patients appears similar to that at three hours.

Another promising advance employs a new thrombolytic agent called des­moteplase. Derived from the saliva of the vampire bat, this agent has a longer half life than alteplase and does not break down basement membranes, leading to a lower risk of hemorrhagic complica­tions. The Swedish Stroke Program is part of an international effort to test this drug in a nine-hour window.

Todd Czartoski, M.D., and Bart Keogh, M.D., Ph.D., are collaborat­ing with the stroke team at Stanford University to identify patients with vi­able ischemic tissue regardless of time from onset of symptoms. Perfusion MRI identifies impaired blood flow in brain (the “penumbra”) surrounding an infarct. In cases where there is a large area at risk, the use of alteplase or clot retrieval may prove beneficial long after the three-hour window has elapsed.

Telestroke is another important development in acute stroke care. This program enables the timely alteplase treatment of patients in emergency rooms around the Pacific Northwest that lack onsite neurological expertise.

For more information about the Swedish Stroke Program, contact Sherene Schlegel, R.N., FAHA, at 206-320-3484. For information about telestroke, contact Tammy Cress, R.N., MSN, at 206-320-3112.

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Detecting cerebral microemboli with transcranial doppler.

 

David W. Newell, MDCerebrovascular Surgery, Neurosurgery, Swedish Neuroscience Institute 

 

 

 

 

Colleen Douville, RVT, Director, Cerebrovascular Ultrasound, Swedish Neuroscience Institute

 

 

Since its introduction in 1982, transcranial doppler ultrasound (TCD) has evolved into a por­table, multimodality, noninvasive method for real-time imaging of intracranial vasculature.

The detection of cerebral microemboli is among the more remarkable capabilities of TCD. Emboli create countable signals in the ultrasound display due to the higher reflection of sound waves compared to the blood cells. Experimental mod­els have shown a high sensitivity and specificity for detection of a variety of substrates, including thrombotic, platelet and atheromatous emboli.

Microembolic signals (MES) within the in­tracranial vasculature are most frequently identi­fied in patients with large-vessel atherosclerotic disease, such as carotid stenosis. They have also been reported in intracranial arterial stenosis, ar­terial dissection, cardiac disease and atheroaortic plaque. Additionally, they have been seen in arter­ies distal to coiled aneurysms.

There is strong evidence that MES detection predicts future ipsilateral stroke risk in patients with symptomatic carotid stenosis (Markus HS, et al.; King A, et al.). A recent study of patients with asymptomatic carotid stenosis demonstrated that MES predicted subsequent ipsilateral stroke and TIA, and also ipsilateral stroke alone, and that it is helpful in selecting patients who will benefit from carotid endarterectomy (Markus, HS et al.).

Identification of active embolization provides crucial patho­physiological information to the neurologist and can also aid in the selection of tailored therapy aimed at reducing the risk of stroke. Emboli from different sources have unique compositions and re­quire specific therapy, such as antiplatelet agents for emboli from large artery atherosclerotic plaque and anticoagulants for cardiac emboli.

Future advances in TCD technology will permit full automa­tion and better identification of the composition and size of circu­lating embolic materials, thus improving its value for patients with cerebrovascular disease.

Contact Colleen Douville, RVT, at colleen.douville@swedish.org or 206-320-4080, for more information about TCD for detec­tion of cerebral microemboli.

 

Options widening for wide-necked aneurysms

 

Yince Loh, MD, Interventional Neuroradiology, Neurosurgery, Swedish Neuroscience Institute 

 

Intracranial aneurysms are present in up to 4 percent of the population. These potentially dangerous vascular lesions are being detected with increasing frequency in asymptomatic patients by advances in noninvasive imaging techniques, such as magnetic resonance angiography (MRA). Appearing like blisters on the wall of the brain’s blood vessels, aneurysms develop when the blood vessel’s native repair ability is exceeded by the mild, but constant, injury created by flowing blood under high pressure. The five most common risk factors for developing an aneurysm are: smoking, female gender, high blood pressure, middle age and family history.

Intracranial aneurysms are complex lesions that require a highly specialized, multidisciplinary approach that is individualized for each patient. Key members of the care team for these patients include endovascular neuroradiologists, neurosurgeons with special expertise in aneurysm surgery and neuroanesthesiologists. Availability of dedicated neurocritical care units is an essential care component. A consensus recommendation by these specialists may include close observation, obliteration of the aneurysm with a surgical clip, or filling the vascular outpouching with filamentous coils that are introduced by endovascular microcatheters via an artery in the leg. This latter process is called “coiling.”

Those aneurysms that have a balloon-like opening, or neck, from the parent vessel are typically good candidates for coiling. Not infrequently, however, the aneurysm’s shape does not permit safe coiling. When the aneurysm’s neck is wide, it appears more like a molehill than a balloon. A molehill configuration is often referred to as a “wide-necked aneurysm.” The wide neck allows an unwanted protrusion of coils back into the artery. This can lead to a number of problems, including failure to obliterate the aneurysm and stroke. Thus, in situations where an aneurysm is not surgically accessible or the patient cannot undergo surgery, no therapeutic options can be offered.

Until recently, wide-neck aneurysms could not be treated by coiling. The U.S. Food and Drug Administration, however, has approved a tubular device called an intracranial stent to be used for such situations.

Once a stent is deployed across the neck of the aneurysm, coils are placed into the aneurysm through the stent wall. The stent struts prevent the coils from falling back into the artery by essentially creating a “chain link fence” across the neck of the aneurysm.

Stenting, however, produces another set of problems. A stent is a foreign body that can promote the formation of a blood clot inside the vessel, which is why patients are placed on two antiplatelet medications to thin the blood, usually aspirin and clopidogrel (Plavix®), after placement of a stent. The length of time required to thin the blood after stent placement is unclear, although stents may become incorporated into the vessel wall and covered with endothelium within weeks.

SNI Fellowship Opportunities

The Swedish Neuroscience Institute (SNI) at Swedish Medical Center in Seattle, Washington, is committed to improving the delivery of neurologic care through evidence-based protocols, research and education.

SNI offers advanced training through five fellowships:

Applications are reviewed as received, with fellowships beginning bi-annually on January 1 and July 1.

For one hundred years Swedish has been the premier health-care provider in the Pacific Northwest and a trusted resource for people when it truly counts. As a high-volume, urban medical center located at the epicenter of the Puget Sound area, Swedish attracts nationally recognized physicians and scientists, and provides a broad population base that enhances the patient care, research and education efforts at SNI.

Applying for an SNI fellowship

You can also email your inquiries to SNIFellowships@swedish.org

Neuromodulation Symposium

The symposium “Advances in Neuromodulative Therapies: 2010 and Beyond” will be held August 27, 2010 starting at 7:15 am in the Swedish Education and Conference Center at the Cherry Hill campus.

See more information

A broad array of local and national experts will speak on current and future applications of neuromodulation in the treatment of neurological disorders.

The poet and thinker David Whyte will start off the symposium by addressing some of the philosophical and ethical issues raised by our increasingly dynamic interaction with the human brain and spinal cord.

We hope you will be able to join us for what should be a fun, informative, and inspirational symposium.

 

Ryder Gwinn, MD
Director of Epilepsy Surgery
Functional Neurosurgery
Swedish Neuroscience Institute