Conditions that can be treated through vascular or endovascular techniques – or a combination of both – include:
Neurosurgeons trained in both vascular and endovascular techniques may best explain and treat these challenging lesions.
Two to ten percent of the population have cerebral aneurysms. Some individuals are genetically predisposed to the condition. Cerebral aneurysms occur more commonly in those with collagen vascular diseases, such as Marfan’s syndrome, or in women with disorders such as scleroderma or fibromuscular dysplasia. Patients with polycystic kidney disease have 25% incidence. If an aneurysm ruptures, death occurs in 30 to 50 percent of patients.
Cerebral aneurysms usually occur at a branching point of two vessels in the brain, where a “soft” spot bulges out as an enlarging balloon. The risk of aneurysm rupture (or the balloon bursting) is commonly proportional to the size of the aneurysm and sometimes its location. Risk is also associated with female gender, cigarette smoking and uncontrolled hypertension (high blood pressure).
Treatment can be either open craniotomy and clipping or endovascular coiling. Each option has benefits and drawbacks, which are best discussed between the patient and family and a neurosurgeon trained in both techniques. Sometimes only one or other treatment is suitable.
In coiling, a catheter is guided into the aneurysm dome with computer-assisted X-ray guidance, and platinum coils are deployed into the aneurysm one by one until the it (balloon) is obliterated. Again, the obvious advantage to coiling is that the patient’s head is not opened. A disadvantage is that future retreatment may be required, depending on a number of conditions.
Craniotomy and clipping consist of opening the head aided by an operating microscope and placing a titanium clip or clips along the “neck” of the aneurysm (bottom of the balloon) while preserving the normal cerebral vasculature. The advantage of clipping is that it is usually permanent.
[back to top]
Arteriovenous malformations (AVMs) are genetically derived miscommunications between arteries and veins in the brain. Normally, arteries in the brain divide into smaller and smaller branches, much like limbs on a tree; arteries divide into arterioles, then arterioles divide into capillaries.
Capillaries supply blood and nutrients to the brain, and waste products are borne back to the heart via venules, then larger veins. The typical pressure within an artery is approximately 120 mmHg (systolic blood pressure) and within veins, about 5 mm Hg. Clearly, directly connecting an artery to a vein, without the intervening capillary network to dissipate the pressure from 120 to 5mm Hg, could be problematic, comparable to hooking a fire hose to a garden hose.
AVMs, then, have approximately a 4 percent chance per year of intracranial hemorrhage (bleeding within the skull), which increases over time, so that over 10 years, the chance of an AVM bleeding can be as high as 40 percent. Patients may experience severe headache, weakness, stroke-like symptoms, seizures or, in the worst cases, coma and death. Unlike aneurysms, AVMs do not have an increased rate of re-hemorrhage; it remains about 4 percent per year.
Treatment options depend on location and size of the AVM. Conservative treatment remains an option for those patients with extremely large AVMs or AVMs that lie in very deep, inaccessible locations. More often, however, diagnostic angiography (imaging of the blood vessel) followed by embolization may be preferable. As with aneurysms, embolization is performed via an endovascular route, but instead of coils, plastic polymers, most of which are permanent agents, are injected into the blood vessel. Occasionally an AVM can be cured angiographically without surgery.
More customarily, the AVM’s size and blood flow through it can be decreased to make open surgery safer or to allow future therapeutic focused-beam radiation. Newer endovascular techniques have made certain previously untreatable AVMs treatable.
[back to top]
Dural fistulas are acquired miscommunications between arteries that normally supply the surface coverings of the brain (the dura) and the venous drainage system of the brain (the dural sinuses). They most commonly result from trauma or infection, and patients may experience stroke-like symptoms (TIAs), seizures or intracranial hemorrhage, or simply hear a loud noise in the head (bruit). They can be diagnosed by noninvasive studies, like magnetic resonance imaging, but are best seen angiographically.
The hemorrhage rate depends on severity, so treatment options are tailored to each case. Both endovascular and open surgical options exist, and the options should be discussed by the neurological surgeon with the patient and the patient’s family.
[back to top]
Carotid Cavernous Fistulas
Carotid cavernous fistulas (CCFs) are direct miscommunications between the carotid artery at the skull base and a complex network of veins adjacent to the carotid artery in this location, which is known as the cavernous sinus. CCFs most often result from trauma, but can be spontaneous. Patients experience swelling (proptosis) and redness (chemosis) of one or both eyes, which can cause painful ophthalmoplegia (inability to move the eye) or, at worst, blindness. Ideally, treatment is endovascular, but a direct transocular approach is possible with the assistance of an eye surgeon. All patients are seen by the hospital’s Ophthalmology Service so that intraocular pressure and visual acuity can be assessed.
[back to top]
Cavernous malformations, sometimes called cavernous angiomas, are also genetic miscommunications between arteries and veins in the brain or spinal cord. However, unlike AVMs, they are low-flow, low-pressure abnormalities. They grow slowly, if at all, via a series of small micro-hemorrhages, and the blood products give the malformations a characteristic appearance on magnetic resonance imaging. Patients usually have no symptoms and require no treatment. Because angiography does not reveal the vascular malformation, it has been historically termed “angiographically occult.”
Nevertheless, if cavernomas “macro” hemorrhage (blood easily visible on computed tomorgraphy (CT), they have a much greater incidence of re-hemorrhage and will require treatment. Patients with hemorrhage in the spinal cord or deep in the brain stem can present with overt weakness, paraplegia or quadriplegia or, more often, with seizures.
Because they can not be seen angiographically, cavernomas cannot be embolized, but depending on location, they may be surgically removed, often with restoration of function. If they are surgically inaccessible, focused-beam radiation or “gamma knife” may be an alternative treatment.
[back to top]
When the carotid arteries in the neck become blocked or ulcerated by atherosclerotic plaque (bacon and eggs) or vascular conditions such as fibromuscular dysplasia (FMD) or arteritis, patients are at increased risk for transient ischemic attacks (TIAs) or a cerebrovascular accident (CVA), otherwise known as stroke. Symptoms occur quickly and consist of weakness of the face, arm or leg, usually on one side, that may dissipate (TIA, mini stroke) or progress to neuronal cell death and permanent stroke (CVA). If a TIA or stroke occurs, patients are studied for cardiac and cerebrovascular disease in the neck and brain.
If the carotid arteries in the neck are narrowed more than 70 percent in women or, at times, more than 50 percent in men, carotid endarterectomy may be used to open up the artery and remove plaque.
As an alternative for patients with multiple medical problems or fibromuscular dysplasia (FMD), carotid stenting may be done successfully endovascularly without opening the neck.
[back to top]
Atherosclerosis (hardening of the arteries) can occur in any vessel in the body, including inside the brain. Patients who are already on aspirin therapy and suffer TIAs despite best medical therapy may be candidates for intracranial stenting, which is the placement of a small metal lattice tube in the vessel to keep it open and allow uninterrupted circulation. Patients failing medical therapy with intracranial stenosis have a very high risk of recurrent stroke and morbidity within 6 months. With a recently available intracranial stent, the procedure has been shown to be more effective than medicine alone in decreasing the risk of major stroke. The intracranial stent is placed endovascularly through a small incision (nick) over the femoral artery in the leg and then navigated by computer-assisted X-ray guidance into the narrowed vessel in the brain, where it is then opened with a small balloon.
Ultimately, the carotid artery in the neck may close so that an endovascular stent cannot reach into the skull. In this case, the patient may undergo a bypass procedure, in which a vessel that normally supplies the face is reattached into a vessel in the brain. A vein in the leg may also be used.