Blood normally flows through arteries under high pressure to supply all the organs including the brain. From the arteries it passes through thin-walled capillaries to supply the tissue of the brain and then enters the veins under low pressure to be carried back to the heart and lungs.
Arteriovenous malformations are abnormal collections of blood vessels that directly connect arteries to veins and bypass the capillary bed. Without a capillary bed the AVM blood vessels see an increase in flow and blood pressure. Over the years this causes them to dilate and become thin-walled, and more likely to rupture. AVM’s are thought to be congenital in nature. AVM’s are usually not inherited and other members of the family are not at increased risk for having an AVM.
An AVM can cause headache, weakness, numbness, visual problems, or seizures. They often first show symptoms when there is a bleed or rupture from one of the blood vessels making up the AVM.
An AVM is usually diagnosed with a CT (computed tomography) scan or MRI (magnetic resonance imaging). A patient usually requires an angiogram to then fully identify the anatomy of the AVM and make decisions about treatment. AVMs can be treated using three different techniques. Often more than one technique is used to treat the same AVM because the combination of techniques may prove safer or more successful than one technique alone. These techniques are embolization, surgery and radiation therapy or radiosurgery. Surgery is done by opening the skull and removing the blood vessels that make up the AVM.
Radiosurgery involves using beams of focused radiation to injure the blood vessels of the AVM and cause them to close off. Embolization is done by placing a tiny catheter directly into the AVM vessels within the brain. Material is then injected into the blood vessel to block them up. The material that is usually used is a glue-like material that leaves the catheter as liquid and solidifies within the AVM blood vessel to block it up. Embolization of an AVM is often done in advance of surgery or radiosurgery to help improve the likelihood these techniques will be successful.
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AVM pretreatment:
Angiogram of a patient with a large AVM involving the temporal and parietal lobes of the brain. |
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AVM post treatment:
Angiogram of the same patient after treatment with embolization and radiosurgery shows complete obliteration of the AVM. |
Atherosclerosis (Carotid, Vertebral, Intracranial)
Atherosclerosis is hardening of the arteries that can result in narrowing (stenosis) or blockage (occlusion) of an artery. This can occur in any artery in the body.
When an interventional neuroradiologist is involved in treating this problem it involves the larger arteries going to the brain (carotid or vertebral arteries) or the arteries inside the head (intracranial arteries).
Atherosclerosis of the carotid arteries often causes transient ischemic attacks (TIAs) because the blood flow may be interrupted to the point that a portion of the brain is not working. Typical symptoms include weakness or numbness on one side of the body, inability to speak or understand speech, and changes in vision. If the blood flow is only decreased for a short time a TIA occurs, but if the interruption is sufficiently long a stroke occurs.
Medical treatment may be recommended if the narrowing is not severe. If the narrowing is greater than 70% surgery or endovascular therapy may be recommended. Surgery involves opening the artery and removing the atherosclerotic plaque that is narrowing it.
Endovascular therapy involves using a balloon or stent to push open the wall of the artery from within. Surgery is often done on the carotid artery in the neck, but endovascular treatment may be recommended. Endovascular therapy is often in other location such as the vertebral artery and the intracranial arteries.
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Carotid Stenting pretreatment: Angiogram of a patient with frequent transient ischemic attacks demonstrates a severe narrowing of the internal carotid artery. |
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Carotid Stenting post treatment:
Angiogram following carotid stent placement shows opening of the narrowing by the stent with improved blood flow to the brain. |
Carotid-Cavernous Fistula
Carotid-cavernous fistulae are a specific kind of dural fistula that involves the carotid artery (or its branches) and a large vein (cavernous sinus) behind the eye. These fistulae can occur because of trauma, if there is an aneursym in the carotid that breaks and causes the communication, or they can happen spontaneously without a definite reason.
Symptoms can include eye pain, swelling and redness of the eye, double vision or loss of vision if untreated. These fistulae are usually difficult to treat surgically. They are often treated by an endovascular approach, putting a catheter in the artery or vein and using material to block up the connection between the artery and vein. This material can include balloons, coils, and liquid glue.
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CC Fistula post treatment:
Angiogram after treatment with a small balloon placed at the site of the arrow shows complete closure of the fistula. |
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CC Fistula pretreatment: Angiogram from a patient who fell at a construction site causing a tear in the carotid artery and a carotid cavernous fistula. Arrows and arrowheads show the veins draining the fistula. |
Dural Arteriovenous Fistulas
Dural arteriovenous fistulae are blood vessels that represent abnormal connections between arteries veins that are found in the covering of the brain. This covering is known as the dura, hence the name. There is a direct connection between the arteries and the sinus without any vessels between.
These fistulae or connections are usually acquired and can occur after trauma, infection or thrombosis (clotting-off) of veins in the dura. The fistula may cause abnormal noises in the head due to the high flow of blood. They can also cause headaches or result in bleeding into the brain.
The treatment is similar to those available for AVMs and can include embolization, surgery and in some cases radiosurgery. Embolization is often used as the primary therapy to treat this problem.
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Dural AVF pretreatment:
Angiogram from a young woman with a dural AVF causing increasing pressure in the brain and headaches. |
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Dural AVF post treatment:
Angiogram following treatment with embolization shows complete closure of the fistula. |
Spinal Compression Fractures
The spinal column is made up of thirty-one individual bones called vertebrae. When they become weakened either because of disease or secondary to medications, they can break or collapse. This is called a compression fracture.
Since it is not possible to immobilize the vertebra completely, patients can have severe pain with any patient movement or secondary to nerve compression. Until the late 1980’s, the only way that this problem was treated was with bed rest, narcotic medication and in some cases back bracing.
Now we are able to offer a procedure called percutaneous vertebroplasty. This procedure is done with high tech x-ray equipment to provide optimal visualization. The physician then inserts a small needle directly into the vertebral body that is compressed. Once needle placement has been confirmed, Polymethylmethacrylate, a type of bone cement, is injected. This essentially strengthens the bone from within.
This procedure has been very effective in decreasing pain, decreasing medication usage, and increasing patient mobility, and is also very safe.
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Vertebroplasy pretreatment:
CT scan of a patient with a painful compression fracture of the lumber spine. Patient had failed treatment with pain medicine and bed rest. |
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Vertebroplasty post treatment:
CT scan after vertebroplasty treatment shows bone cement stabilizing the fracture. Patient experienced complete pain relief several hours after treatment.
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Vascular Tumors
(Hemangioblastomas, Juvenile, Nasoangiofibromas, Meningiomas, Metastatic Tumors)
Vascular tumors that come to the attention of the Interventional Neuroradiologist may be inside the skull (intracranial) or outside, in the head and neck region (extracranial).
Endovascular embolization of vascular tumors is often done as a pre-operative procedure. The goal of this embolization is to reduce the amount of blood loss that is experienced at the time of surgery and also to make the removal of the tumor easier and potentially more complete.
The types of tumors that may respond favorably to this technique include:
The embolization is performed by placing a catheter directly into the blood supply of the tumor (this is also done by starting at the femoral artery as in most interventional procedures). Embolic material is then injected through the catheter to close off the blood vessels supplying the tumor and embolize the capillary bed of the tumor. This embolic material can include particles such as polyvinyl alcohol as well liquid glue, which leaves the catheter as a liquid and solidifies within the blood vessel.
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Tumor pretreatment:
Angiogram of a patient with a large vascular brain tumor. Arrows and arrowhead point to prominent blood vessels feeding this tumor. |
| Tumor post treatment: Angiogram following embolization shows complete removal of blood flow to the tumor. Patient then underwent an uncomplicated resection of the tumor. |
Vein of Galen Malformations
The Vein of Galen malformation is a congenital communication between arteries and veins. In this case the communication specifically occurs between a set of deep arteries in the brain called the choroidal arteries and a deep midline vein, the Vein of Galen.
Often a Vein of Galen Malformation will present with symptoms in early infancy or in childhood. In early infancy these symptoms can include congestive heart failure. Symptoms may occur somewhat later in childhood and the child can manifest enlargement of the head (macrocrania) or a neurocognitive development delay.
In general, the treatment of this disease depends upon the size of the Vein of Galen malformation and the symptoms experienced by the patient. Endovascular therapy is often a mainstay of treatment. This usually involves embolization, often with liquid embolic material (glue) or platinum coils to help occlude the abnormal communications between the arteries and the veins.
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Vein of Galen Malformation pretreatment:
Angiogram of a young child who presented with enlarging head size shows a large vein of Galen malformation. |
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VOG post treatment:
Angiogram following treatment with embolization shows obliteration of the malformation. |