Embolization of brain and spine arteriovenous malformations (AVMs) and arteriovenous fistulas (AVFs)
An arteriovenous malformation or dural arteriovenous fistula is an abnormality of the blood vessels that causes shunting of blood from an artery to a vein, bypassing normal tissue. This high-flow system may pose a risk for bleeding. Many characteristics of the abnormality may be important in deciding the best management approach. Endovascular embolization therapy is a method of injecting a “liquid embolic” or glue-like material into the target vessel to stop blood flow through the abnormality. A microcatheter (a very small hollow plastic tube) is carefully navigated to the abnormal connection between the artery and the vein. A glue material is then injected through the catheter to fill the abnormal collection of blood vessels, effectively closing the communication. The catheter is removed and the solidified glue remains within the blood vessels to permanently close the abnormality. This procedure may be performed alone or in conjunction with other treatments including open surgical resection or radiosurgery therapy.
Brain Aneurysm Coiling and Flow Diverter Implantation
Some brain aneurysms can be closely observed with periodic surveillance imaging. For aneurysms that require treatment, endovascular therapy can be performed from inside the blood vessel. Access to the inside of the aneurysm is achieved with the same techniques used in diagnostic catheter cerebral angiography, by advancing a catheter (a hollow plastic tube) through an artery in the leg and navigating it to the blood vessels in the brain. After the catheter is positioned at the site of the brain aneurysm, several techniques are used to close the aneurysm and prevent any further blood flow entry. Coil embolization, or “coiling,” is the most commonly practiced endovascular treatment for brain aneurysms. In this procedure, a very small catheter is advanced into the aneurysm and platinum coils are sequentially introduced to create a tightly packed coil mass within the aneurysm, thereby promoting clot formation within the aneurysm, and preventing entry of blood flow. In some cases, a stent or balloon is required to remodel the neck of the aneurysm for safe coil placement and to promote healing. A balloon is temporarily inflated at the aneurysm neck, while a stent is permanently implanted to provide continuous support at the opening of the aneurysm. Newer technology and techniques now include flow diversion devices for endovascular aneurysm treatment. In this method, a mesh stent-like device is placed within the vessel and across the neck of the aneurysm to divert blood flow away from the aneurysm and down the normal course of the blood vessel. This promotes aneurysm closure and scaffolding for healing of the blood vessel wall. The rapid pace of technology development and evolution of techniques for endovascular repair of brain aneurysms will likely continue to advance safety and efficacy of minimally invasive therapies.
Carotid Artery Balloon Angioplasty and Stenting
Carotid artery narrowing is a known cause of ischemic stroke. Treatment options for selected patients include a minimally invasive endovascular approach to restore normal blood flow. In balloon angioplasty, a small balloon is temporarily inflated across the region of narrowing to expand the artery to normal diameter and restore blood flow. This procedure is usually accompanied by placement of a permanent stent over the narrowed region. During the procedure a temporary filter is placed in the internal carotid artery, downstream from the plaque, to capture debris that might be dislodged during the procedure.
Carotid Cavernous Fistula Embolization
A carotid cavernous fistula can develop after trauma or spontaneously. Symptoms can include swelling and injury to nerves that control eye function. Imaging tests such as CT or MRI can provide clues to the diagnosis, but often a diagnostic catheter cerebral angiogram is necessary to confirm the diagnosis. Treatment options include endovascular therapy in which a small catheter is advanced into the blood vessels where the abnormal communication exists. Glue or a similar liquid embolic material is injected through the catheter and forms a plug at the abnormality to close the fistula.
Cerebral and Spinal Angiography
A diagnostic catheter cerebral or spinal angiogram is a procedure that is performed to acquire high-resolution images of the blood vessels of the head and neck or spine. This is also the foundation to all endovascular interventional procedures. After administering local anesthesia (usually lidocaine), an incision approximately 1/8 of an inch is made in the crease of the groin and a small sheath (a hollow plastic tube) is advanced into the femoral artery in the leg. A smaller catheter (a hollow plastic tube) is advanced through the sheath and navigated under x-ray guidance through the arterial system to the arteries that serve the head and the neck. Contrast dye is injected through the catheter into selected vessels and a series of x-ray images are rapidly acquired using two cameras positioned around the patient’s head. Catheter angiography affords the unique capability of evaluating dynamic and functional anatomy of the brain and spine with far greater resolution than non-invasive imaging such as CT or MRI. Characteristics of the circulation system including blood vessel anatomy and blood flow can be interpreted from the images.
The procedure is commonly performed with the patient awake but very sleepy, under “conscious sedation.” Sedation medications are administered to achieve patient comfort. During contrast injections, a patient may experience a sensation of warmth, flashes of lights, intermittent dizziness, or unusual tastes. These symptoms are well-tolerated, brief, and pass within seconds.
At the completion of the procedure, the catheter and sheath are removed, and pressure is applied to the leg or a small plug is placed to close the artery access site. The patient then recovers with flat bed rest for approximately 3 to 6 hours before returning home the same day.
Emergent Acute Stroke Therapy
The impact of ischemic stroke upon healthcare in the United States is staggering. Extensive research has attempted to unlock methods of safely restoring blood flow to the brain and protect patients from progression to permanent brain damage. In 1996, the United States Food and Drug Administration approved the use of intravenous tissue plasminogen activator (IV tPA) for use in the treatment of acute ischemic stroke in selected patients. This “clot-busting” medicine has been shown to improve patient outcomes when it is administered within the first few hours of a stroke. Among those patients who are not candidates for an intravenous medication, some may benefit from an endovascular method of removing a blood clot. Endovascular methods include navigating a small catheter (a hollow plastic tube) through the blood vessels to the location of the blockage and using one of several therapies. After a catheter is positioned within the blocked artery, tPA can be injected to dissolve the clot, or a device can be used to suction the clot (aspiration) or trap the clot and remove it from the body. Time is brain, which is why methods of opening a blocked artery are performed in the first few hours of an ischemic stroke.
Epistaxis Embolization Therapy
Epistaxis, or excessive bleeding from the nose, can be caused by various underlying conditions. In cases of severe bleeding that is not controlled with conventional surgical techniques, endovascular embolization therapy can be performed. In this procedure, a small catheter is advanced under x-ray guidance to the arteries that serve the nose. Small particles are then injected to intentionally plug the arteries and stop the bleeding.
Inferior Petrosal Sinus Sampling
Cushing syndrome results from excess production of the hormone cortisol. The release of cortisol is controlled by adrenocorticotropic hormone (ACTH), which can be produced in several locations throughout the body. One location is the pituitary gland, which is located in a region behind the eyes and inside the skull. An evaluation for a patient with Cushing syndrome may include inferior petrosal sinus sampling (IPSS). In this procedure, two microcatheters are navigated under x-ray guidance to venous sinuses in the region of the skull base deep behind the nose, the location where the pituitary gland drains. A medication (corticorelin) is then administered and serial blood samples are obtained and tested for levels of hormone to determine the location of abnormal ACTH release.
Intracranial Balloon Angioplasty and Stenting
Ischemic stroke can have multiple causes including clot migration from the heart, narrowing of arteries in the neck, and plaque buildup leading to narrowing of the blood vessels in the brain, which is known as intracranial atherosclerotic disease. Management for patients who have had a stroke due to intracranial atherosclerotic disease includes aggressive medical management with vigilant control of risk factors such as hypertension, diabetes and elevated cholesterol, as well as smoking cessation and antiplatelet medicines. Some patients may be candidates for additional therapies known as intracranial balloon angioplasty or stenting. Balloon angioplasty utilizes endovascular techniques to access the inside of the blood vessel at the region of narrowing, where a balloon is temporarily inflated to expand the narrowed region and restore normal blood flow. A similar technique involves the additional placement of a stent within the blood vessel at the region of narrowing.
Intracranial Venous Sinus Stenting
Intracranial venous sinus abnormalities can obstruct the outflow of blood from the head. In some patients who have chronically elevated intracranial pressures, venous outflow obstruction may be a related finding. For evaluation, patients often undergo diagnostic brain imaging such as MRI or MR angiography, detailed eye examination, and an endovascular procedure to perform manometry testing to evaluate intracranial pressures in several locations. Selected patients may benefit from placement of a stent within a dural sinus of the head to improve venous outflow. The stent is delivered using standard neuroendovascular techniques and on occasion a balloon is also inflated within the stent to ensure optimal placement.
Preoperative Tumor Embolization
Preoperative Embolization of Head, Neck, and Spine Tumors
Tumors can be highly vascularized structures and this large amount of blood vessels can lead to excessive bleeding during surgical removal. In some cases, patients undergoing a surgical resection of a tumor of the head, neck, or spine are referred for a procedure to reduce blood supply to the tumor. This procedure is known as pre-operative tumor embolization. A small catheter is advanced under x-ray guidance into the region of the blood vessels supplying a tumor. After angiographic evaluation of the blood supply, blood vessels can be intentionally plugged by injecting small particles or glue-like material into the arteries. This technique aims to “devascularize,” the tumor and reduce intra-operative bleeding.
Vertebral Artery Balloon Angioplasty and Stenting
Stenosis at the origin of the vertebral artery is a recognized risk factor for ischemic stroke. Patients who have symptoms of stroke or transient ischemic attack (TIA) may undergo diagnostic imaging to evaluate the blood vessels of the head and neck. Patients with severe stenosis at the origin of the vertebral artery may benefit from endovascular treatment. After a catheter is navigated to the area of narrowing, a small wire is advanced through the region of stenosis and positioned in the vertebral artery. A balloon-mounted stent is typically used, which is advanced over the wire to the area of narrowing and the balloon is inflated to both expand the narrowing and implant the stent. Additional balloon inflations can be performed before and after the stent placement if needed to ensure adequate expansion of the narrowed region. This procedure is commonly performed with temporary placement of a filter downstream from the region of plaque to capture any debris that may become dislodged during the stent placement.
Vertebral Body Fracture Kyphoplasty and Vertebroplasty
Vertebral body compression fractures can be identified on plain x-ray or CT imaging and appears as collapse of the vertebral body. A minimally invasive treatment is vertebral body augmentation with kyphoplasty or vertebroplasty. The back is cleaned with sterile technique and under local anesthesia and with conscious sedation, a small needle is advanced under x-ray guidance into the vertebral body. A balloon is inflated inside the bone to improve vertebral body height, and then cement is injected into the bone to increase structural stability of the vertebral body.
A Wada test is used for pre-operative surgical planning in epilepsy. Patients who have epilepsy that is refractory to medications, and who are selected as candidates for surgical resection of a region of abnormal brain tissue, may undergo a Wada test. The test is performed in the angiography suite, similar to all other neurointerventional procedures. Electroencephalogram (EEG) leads are placed on the head to measure brain wave recordings and a diagnostic catheter cerebral angiogram is performed to evaluate the intracranial blood supply. A medication (sodium amytal) is then injected into a blood vessel to temporarily put half of the brain to sleep. The patient is then engaged in a series of memory and language tests. The medication wears off in a few minutes and the procedure is then repeated for the other half of the brain. This test is intended to determine which side of the brain controls language function and identify the role that each hemisphere plays in memory.