|On the Cover|
The Top of the Brain
|By Nick Charles
A platinum-based coil can be used to fill and seal a weak spot in a blood vessel in the brain to prevent rupture.
Neurological surgeons give patients their lives back through proven
treatments and groundbreaking clinical trials.
“In the last five years, all of the physicians that we have recruited have been chosen based on their subspecialty expertise to provide excellent clinical care for our patients. In addition, our physician specialists are also better qualified to train our residents,” says Steven L. Giannotta, M.D., professor and chairman of the Department of Neurological Surgery at the Keck School of Medicine.
The department currently comprises 12 full-time clinician-scientists who are dedicated to personalized clinical care, improving outcomes with translational research, and training the neurological surgeons of tomorrow.
“We work through the femoral artery in the groin and use the arterial system of the body as our road map to get to the arteries of the brain and the spinal cord. We either open the arteries that should be open or close the arteries that should be closed by using catheters and image-guided mechanisms,” Larsen says.
Treatment of an aneurysm (or a weakened bulge in a blood vessel) is aimed at preventing rupture of the aneurysm, which could cause severe hemorrhage. If an aneurysm is deep in the brain, it may be less risky to perform an endovascular procedure called brain aneurysm embolization, as opposed to surgically clipping the aneurysm in an open surgical treatment. The neurosurgeons and neuroradiologists at USC perform the embolization, or closing of the artery, by guiding catheters into the aneurysm itself with the assistance of angiographic guidance and fluoroscopy.
If the opening of the aneurysm is small enough, endovascular coiling (also known as coil embolization) can be used to fill the aneurysm with specially designed platinum-based coils. These tiny coils are pushed one at a time through the catheter over a stainless steel wire until the aneurysm is filled with as many coils as it can hold. This causes a clot to form in the aneurysm and essentially seals it off from future rupture.
USC is investigating two newer devices in order to provide patients with additional state-of-the-art treatment options – Onyx® and Vitesse™.
When the neck of the aneurysm is too wide to hold the embolic coils, a new treatment, called the Onyx HD-500 Liquid Embolic System, is used. Larsen, along with Giannotta; Gene Y. Sung, M.D., assistant professor of clinical neurology; and Arun Amar, M.D., assistant professor of neurological surgery, were on the Food and Drug Administration advisory team when the Onyx system was in the early stages of FDA approval.
“Onyx has been approved by the FDA for brain aneurysms with wide necks that prohibit them from being treated with traditional embolization procedures,” Larsen says. “It is a polymer that is injected into the aneurysm through a tiny catheter as a viscous liquid. We prevent it from coming out of the aneurysm by putting in a special balloon catheter that crosses the neck of the aneurysm and keeps it in place until it hardens. Once the aneurysm is completely filled with the hardened agent, the blood circulates safely past the aneurysm.”
As Larson explained, interventional neuroradiologists close arteries that should be closed, as with the Onyx system - or they open arteries that should be open, as they are doing in a clinical trial called the Vitesse Intracranial Stent Study for Ischemic Therapy, or simply VISSIT.
Larsen and Amar are recruiting patients for the VISSIT clinical trial to treat narrowing in the arteries of the brain. The Pharos Vitesse Balloon Expandable Stent has not been approved by the FDA for general use; it is limited by federal law to investigational use, such as this clinical trial. USC University Hospital is the only West Coast site for the randomized international trial that will compare clinical outcomes between patients treated with the Vitesse Balloon Expandable Stent to open blocked arteries and the current best medical practice of treatment with aspirin or Plavix, a medication that helps prevent blood clots.
“This expandable stent treatment is for patients who have an atherosclerotic narrowing in one of the arteries of the brain, which can cause a stroke,” Larsen says. The full medical treatment will include a low cholesterol diet, hypertension management, and a smoking cessation program, if necessary, in addition to the blood-thinning drugs. The patients who receive the device also will receive the maximum medical therapy.
The goal of the trial is to determine if the device plus medical management will result in improved outcomes compared to solely medical management therapy.
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“There are certain disease processes in neurosurgery that are very linear in the way that we approach their care,” Liu says, “but epilepsy is highly complicated. There are so many facets to this disease. We need the involvement of expert neurologists, radiologists and neuropsychologists. Every one of our epilepsy patients has benefited from the effort and expertise of all of these departments.” Epilepsy causes abnormal discharges from certain areas of the brain that result in seizures, Liu says. When patients continue to have seizures despite taking anti-seizure medication, the most successful alternative is the surgical removal of the parts of the brain that are causing the seizures. For the most difficult group to treat - those in whom the seizure focus cannot be identified, or the focus is in a part of the brain that controls a necessary function - there is neuromodulation. Electrical stimulation of the vagus nerve, a peripheral nerve in the neck, is one form of neuromodulation. “It has been shown that the stimulation of this nerve reduces seizures,” Liu says. “For the management of this group of patients that medicine can’t help and that don’t have a surgically resectable lesion, the outcomes of this treatment strategy have been quite good.”
While vagus nerve stimulation, which involves the implantation of a pacemaker-like device, reduces the frequency of seizures, it does not eliminate them. “For patients to get on with their lives in a completely normal way, they almost invariably have to be seizure free,” Liu says. “For example, whether you have 10 seizures a day or one a month, you still can’t drive a car.”
Luckily, for patients with treatment-resistant epilepsy, USC is one of 32 sites across the country involved in a clinical trial for an investigational device called the NeuroPace Responsive NeuroStimulator. Principal investigator for the clinical trial is Christi Heck, M.D., associate professor of clinical neurology. “With this newest neuromodulation strategy, we place stimulation electrodes on the brain itself, rather than on the vagus nerve in the neck,” Liu says. “By putting the stimulation electrodes right on the area where the seizures are occurring, we have had very good results.”
Liu stressed that epilepsy patients shouldn’t give up, because new treatment strategies continue to be developed to improve their lives. “If we can get rid of their seizures, we can give patients their lives back,” Liu says, “and that is truly satisfying.”
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DEEP BRAIN STIMULATION
The DBS procedure involves surgically implanting an electrode in the brain of the patient and a pacemaker-like device in the upper chest, under the skin near the collar bone. The device delivers continuous, high frequency stimulation to parts of the brain that control movement.
“Deep Brain Stimulation affects an abnormal circuit in the brain that is causing a movement disorder,” says Mark Liker, M.D., assistant professor. “It is left in place for life, and it provides constant stimulation. These are not diseases that are cured by the DBS. These are diseases that if you turn off the DBS, which we can easily do, you can see the symptoms of the disease return. “I tell patients that we’re doing this for your Parkinson’s disease, but if a new technology comes out next week that offers you a cure, we can take out the stimulator, and you’re no worse off. The stimulator doesn’t damage the brain,” Liker says. “Some patients have tried everything before they come to me,” he says, “and they’re really functionally quite disabled. To be able to help them by performing this treatment is a real privilege.”
TREATMENT OF SPINE TUMORS
One of the nonsurgical and noninvasive procedures available for spine patients is the high-tech CyberKnife Stereotactic Radiosurgical System. While it may be referred to as a knife, and it uses cutting-edge technology, the CyberKnife is not a knife at all. It is a system that uses a sophisticated robot to deliver larger than normal doses of radiation with pinpoint accuracy to certain types of tumors. When the CyberKnife was acquired in October 2002, USC was the first institution in Southern California to offer this technology, which is used by several faculty physicians in the department.
“The CyberKnife is sort of a bridge between traditional radiation therapy and surgery,” Hsieh says. “When we are dealing with metastatic tumors, which are tumors that have spread from other parts of the body to the spine, the CyberKnife is one of the options that we offer patients. It is an effective treatment for these types of tumors because it doesn’t require incision, it can shrink the tumor, and it can reduce the patient’s pain. One of the main advantages of the CyberKnife is that you can deliver high doses of radiation very precisely to a specific area. It is very effective in shrinking and controlling tumor growth, but it’s not meant to replace traditional open surgery.”
For treating primary spinal tumors, such as chordoma (malignant bone tumor), chondrosarcoma (cancer of the cartilage) and other sarcomas (cancers of the connective tissue including bone, cartilage and fat), USC is one of only a handful of centers in the country to offer a radical resection procedure called Total En Bloc Spondylectomy. Since most primary spinal tumors have a poor response rate to chemotherapy and radiation, including the radiation delivered with the CyberKnife, complete tumor excision is necessary to obtain long-term survival for patients and to provide them with the hope for cure.
“The traditional method for dealing with most spinal tumors, including primary spinal tumors, was to go inside the tumor and remove as much of it as possible from the inside without increasing the risk of spinal cord or vascular injury. The down side is that you are always leaving microscopic cells behind, putting the patient at high risk for tumor recurrences, which are going to shorten life expectancy,” Hsieh says.
“With this more advanced technique of en bloc tumor excision, we take the tumor out in whole, along with a rim of surrounding healthy tissues, essentially eliminating the risk of leaving any microscopic disease behind,” he says. “By removing the entire tumor as a single piece we’ve been able to show that people have less of a chance of tumor recurrences, which prolongs their survival.”
The surgical result of one of the largest clinical series of sacral chordomas and chondrosarcoma treated using this method by Hsieh and his colleagues was recently published in the journal Spine. “Our data consistently show that we can significantly improve patients’ disease-free survival with en bloc sacral tumor excision with negative margins. Our studies have shown that surgery is really the only way to treat those primary spinal tumors, and the best type of surgery is to take the whole tumor out without leaving malignant cells behind,” he says.
BEST FOR PATIENTS
“Partnering with the experts in neurology and radiology, our team of specialists provides efficient and multidisciplinary solutions for patients,” Giannotta says. “Our patients’ safety and well-being are always at the forefront of decision-making as we carefully weigh risks and benefits of treatments.”
Subspecialty divisions of Neurological Surgery include: cerebrovascular surgery, neuro-oncology, stereotaxic radiosurgery, movement disorders, endovascular neurosurgery, skull base surgery, neuroendocrine surgery, complex spine surgery, interventional neuroradiology, peripheral nerve surgery, neurotrauma and pediatric neurosurgery. For more information or an appointment, visit www.DoctorsOfUSC.com.