Arteriovenous Malformations (AVM)
EMBOLIZATION OF VASCULAR LESIONS
There
are many abnormalities of the blood vessels that affect the brain,
head, neck, and spine. These include arteriovenous malformations
(abnormal vessels forming a connection between the arteries and veins of
the brain, spinal cord, or surrounding structures), dural arteriovenous
fistulas (direct connections between the arteries and one of the large
draining veins contained in the covering of the brain, without any
abnormal vessels in between), traumatic vascular lesions (holes in
vessels with bleeding or an expanding clot, fistulas between the
arteries and veins of the head and neck, or tears in the lining of the
vessels), carotid-cavernous fistulas (direct connections between the
carotid artery and a surrounding vein [cavernous sinus] behind the eye),
spinal vascular malformations (abnormal vessels forming abnormal
connections between the arteries and veins of the spinal cord, its
coverings, the bones or the spine, and/or the surrounding structures),
and extracranial vascular malformations (abnormal vessels forming
abnormal connections between the arteries and veins of the structures of
the head and neck).
These lesions can be very difficult to treat. When surgery is
planned, a catheter can be placed into an artery (usually in the leg,
similar to an angiogram of the heart) and a smaller catheter is then
threaded through to the artery or arteries supplying the
lesion. Material is then injected to block off the blood supply to the
lesion; this is called embolization. There are many different
materials available, depending on the location and size of the vessels
to be blocked off. Sometimes, embolization is performed before radiation
therapy for an arteriovenous malformation. In other instances, surgery
is not possible and embolization is performed to cure the lesion. In
these cases, a catheter may also be placed into the veins draining the
lesion for embolization of the veins. In the case of carotid-cavernous
fistulas, traumatic arteriovenous fistulas, and certain holes in the
walls of major vessels, material may be injected to try to plug the hole
or the fistula. Occasionally, a stent (a metal tube designed to hold a
vessel open) may be used as well. In some cases, it may be necessary to
block a major artery (such as a carotid artery) to treat the problem. If
this is necessary, a small balloon attached to a catheter is placed in
the vessel and blown up to stop the blood flow temporarily (test
occlusion). The patient is examined constantly to see if they tolerate
this or develop any symptoms (such as those of a stroke).
It there are no symptoms, the artery is blocked by injection of
material (permanent occlusion). Depending on the circumstances, the
patient may be able to go home the next day or may be kept for
observation.
Figure 1: AP angiograms demonstrate a large
arteriovenous malformation of the left parietal region. The film on the
left demonstrates the feeding arteries from the middle cerebral artery
system with a large draining vein medially to the sagittal sinus. The
film on the right demonstrates several large feeding vessels from the
posterior cerebral artery on the left side.
Figure 2: The AVM of the patient shown in Figure 1
after endovascular embolization using N-butyl-cyanoacryalate glue for
part of the AVM. As can be seen, the AP angiogram on the carotid
circulation (left) shows a greatly diminished arterial to venous shunt.
As well, the film of the right demonstrates decreased filling from the
posterior cerebral supply to the AVM.
Figure 3: AP angiograms following surgical resection
of the large AVM of the patient shown in Figures 1 and 2. Preoperative
embolization made the operation safer with a minimum of blood loss at
the time of operation. As can be seen on the carotid injection (left
film), there is no arterial to venous shunting. The vertebral injection
(right film) shows no AV shunting. The patient made an excellent
recovery from surgery with no neurologic deficits.
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Brain Aneurysms
A
brain aneurysm, also called a cerebral or intracranial aneurysm, is an
abnormal bulging outward of one of the arteries in the brain. It is
estimated that up to one in 15 people in the United States will develop a
brain aneurysm during their lifetime.
Brain aneurysms are often discovered when they rupture, causing a subarachnoid hemorrhage, or bleeding into the brain and the space closely surrounding the brain called the subarachnoid space. Subarachnoid hemorrhage from a ruptured brain aneurysm can lead to a hemorrhagic stroke, brain damage, and death.
The main goals of treatment once an aneurysm has ruptured are to stop the bleeding, to prevent potential permanent damage to the brain, and to reduce the risk of recurrence. Unruptured brain aneurysms are sometimes treated to prevent rupture.
Surgery or minimally-invasive endovascular
coiling techniques can be used in the treatment of brain aneurysms. It
is important to note, however, that not all aneurysms are treated at the
time of diagnosis or are amendable by either forms of treatment.
Patients need to consult a neurovascular specialist to determine if they
are candidates for either treatment.
Diagnosis of Brain Aneurysms
Diagnosis of a ruptured cerebral aneurysm is commonly made by finding signs of subarachnoid hemorrhage on a CT scan. The CT scan is a computerized test that rapidly X-rays the body in cross-sections as the body is moved through a large, circular machine. If the CT scan is negative but a ruptured aneurysm is still suspected, a lumbar puncture is performed to detect blood in the cerebrospinal fluid that surrounds the brain and the spinal cord.
To determine the exact size and shape of an aneurysm (ruptured or unruptured), neuroradiologists use either cerebral angiography or tomographic angiography.
Cerebral angiography, the traditional method, involves introducing a catheter (small plastic tube) into an artery, usually in the leg, and steering it through the blood vessels of the body to the artery involved with the aneurysm. A special dye, called a contrast agent, is injected into the patient's artery, and its distribution is shown on X-ray projections. This method may not detect some aneurysms due to overlapping structures or spasm.
Computed Tomographic Angiography (CTA) is an alternative to the traditional method and can be performed without the need for arterial catheterization. This test combines a regular CT scan with a contrast dye injected into a vein. Once the dye is injected into a vein, it travels to the brain arteries, and images are created using a CT scan. These images show exactly how blood flows into the brain arteries.
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Minimally-Invasive Treatment Coil Embolization or Endovascular Coiling Endovascular therapy is a minimally
invasive procedure that accesses the treatment area from within the
blood vessel. In the case of aneurysms, this treatment is called coil
embolization, or "coiling". In contrast to surgery, endovascular
coiling does not require open surgery. Instead, physicians use real-time
X-ray technology, called fluoroscopic imaging, to visualize the
patient's vascular system and treat the disease from inside the blood
vessel.
Surgical Treatment To get to the aneurysm, surgeons must first remove a section of the skull, a procedure commonly known as a craniotomy. The surgeon then spreads the brain tissue apart and places a tiny metal clip across the neck of the vessel to stop blood flow into the aneurysm. After clipping the aneurysm, the bone is secured in its original place, and the wound is closed. |
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Endovascular Coiling v. Surgical Clipping
Treatment of Ruptured Aneurysms
Until recently, most of the studies
regarding surgical clipping and endovascular treatment of brain
aneurysms were either small-scale studies or were retrospective studies
that relied on analyzing historical case records. The only multi-center
prospective randomized clinical trial - considered the gold-standard in
study design - comparing surgical clipping and endovascular coiling of
ruptured aneurysm is the International Subarachnoid Aneurysm Trial
(ISAT).
The study found that, in patients equally suited for both
treatment options, endovascular coiling treatment produces
substantially better patient outcomes than surgery in terms of survival
free of disability at one year. The relative risk of death or
significant disability at one year for patients treated with coils was
22.6 percent lower than in surgically-treated patients.
The study
results were so compelling that the trial was halted early after
enrolling 2,143 of the planned 2,500 patients because the trial steering
committee determined it was no longer ethical to randomize patients to
be treated with neurosurgical clipping. However, long-term follow-up
will be essential to assess the durability of the substantial early
advantage of endovascular coiling over conventional neurosurgical
clipping for the treatment of brain aneurysms.
It is important to
note that patients enrolled in the ISAT were evaluated by both a
neurosurgeon as well as an endovascular coiling specialist, and both
physicians had to collaborate and agree that the aneurysm was treatable
by either technique. This study provides compelling evidence that, if
medically possible, all patients with ruptured brain aneurysms should
receive an endovascular consultation as part of the protocol for the
treatment of brain aneurysms.
Treatment of Unruptured Aneurysms
Although no multi-center randomized clinical trial comparing endovascular coiling and surgical treatment of unruptured aneurysms has yet been conducted, retrospective analysis has found that endovascular coiling is associated with less risk of negative outcomes, shorter hospital stays and shorter recovery times compared with surgery.
Studies have shown that:
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EXTRACRANIAL (BRACHIOCEPHALIC) ANGIOPLASTY
Extracranial (brachiocephalic) atherosclerosis is a hardening of the arteries that supply blood to the head and neck (carotid and vertebral arteries), thus causing narrowing and eventually blockage of these vessels. Atherosclerosis of the carotid arteries often cause transient ischemic attacks (TIAs or ministrokes) because pieces of the material that forms the blockage (plaque) and blood clots that form on the plaque break off and are carried into the head where they can block vessels supplying blood the brain. If the blockage produced by this material is small and breaks up quickly, a TIA occurs. If there is blockage of a larger vessel or the blockage doesn't break up right away, a stroke results. Blockage of the vertebral arteries usually causes symptoms because of decreased blood flow to part of the brain, not because of pieces of plaque and clot breaking off. The symptoms of blockage of these vessels may get better and worse, or they may suddenly appear if a stroke occurs. Extracranial atherosclerosis should be treated when it is found. If there are reasons why medical therapy or surgery is not recommended (such as a severe narrowing (especially in a location that cannot be safely reached by the surgeon), poor health, or previous radiation therapy to the neck), angioplasty and possibly stenting may be recommended. A catheter is placed into an artery (usually in the leg, similar to an angiogram of the heart) and threaded up to the vessel with the blockage. A small catheter with a balloon on the tip is inserted at the site of the blockage and inflated to open the vessel; occasionally a stent (a metal tube designed to keep the vessel open) is placed. Blood thinners are given during the procedure and for a short time after to prevent blood clots as it starts to heal. Patients can usually go home later the same day or the next day.Carotid angioplasty with stenting (CAS):
What to expect:
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Carotid Angioplasty and Stenting - before and after angiography
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| Carotid angiography at baseline | Carotid angiography post angioplasty and stent |
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Intracranial Angioplasty for Stroke Prevention
Blockages
in blood vessels in the head (intracranial) are usually caused by
hardening of the arteries (atherosclerosis); treatment with medicines is
not as effective in keeping the vessel open as it is elsewhere in the
body. If the blockage gets too severe, not enough blood will get to that
part of the brain, and a stroke may occur. Intracranial angioplasty is a
method of opening narrowed or blocked blood vessels (arteries) in the
head to increase blood flow and decrease the chance of a stroke. A
catheter is placed into an artery (usually in the leg, similar to an
angiogram of the heart) and threaded up to the vessel with the blockage.
A very small catheter with a balloon on the tip is put across the
blockage and inflated to open the vessel; sometimes a stent (a metal
tube designed to keep the vessel open) is placed. Blood thinners are
given during the procedure and for a short time after to keep the vessel
open as it starts to heal. Patients can usually go home the next day.
Figure 4.
This
is a 63-year-old man who experienced vertebrobasilar TIAs despite
therapeutic doses of warfarin. (A) The lateral projection of the right
vertebral artery injection of the angiogram revealed a severe proximal
basilar artery stenosis (arrow). Imaging (B) immediately after
angioplasty revealed a small intimal tear which was (C) healed at 3
months with minimal residual stenosis.
Figure 5.
This
44-year-old man presented with persistent severe vertebrobasilar TIAs
with gait unsteadiness, blackout spells, and visual disturbances despite
oral anticoagulation. The cerebral angiogram revealed a high-grade left
vertebral artery stenosis (arrows, A and B) with (C) the right-sided
vertebral artery ending in PICA and no visible posterior communicating
arteries. He underwent angioplasty of the left vertebral artery stenosis
(arrow, E) and a right-sided OA (arrow) to (D) PICA revascularization
procedure. His vertebrobasilar TIAs resolved. TIAs, transient ischemic
attacks; PICA, posterior inferior cerebellar artery; OA, occipital
artery.
Treatment of Vasospasm after Aneurysm Bleeding
Vasospasm
(narrowing) of the vessels that supply the brain can occur after a
bleed from an aneurysm in the head (subarachnoid hemorrhage). The spasm
can be severe enough to prevent enough blood from reaching the brain,
causing a stroke. This is usually initially treated by medical therapy,
including giving medication to increase the blood pressure and giving
intravenous fluids. If this does not work, then other treatments can be
used. A catheter is placed into an artery (usually in the leg, similar
to an angiogram of the heart) and threaded up the artery or arteries
that are affected. Medication can be injected through the catheter to
dilate the arteries. A tiny catheter with a soft balloon on the tip can
be threaded through the catheter and gently inflated to stretch the
narrow spots in the arteries (angioplasty). More than one artery may
need to be treated and, in severe cases, the procedure may need to be
repeated.
Angiograms are performed by interventional radiologists (IR). Angiography is an X-ray exam of the arteries and veins to diagnose blockages and other blood vessel problems. A cerebral angiogram is an X-ray of the blood vessels in your brain.
During an angiogram, the doctor inserts a thin tube (catheter) into the artery through a small nick in the skin (usually femoral artery) about the size of the tip of a pencil. A substance called a contrast agent (X-ray dye) is injected to make the blood vessels visible on the X-ray. You do not feel the catheter going through your body; you may feel a flushing sensation as the dye is injected, this will only last a few seconds.
You
will be asked to lie very still while your doctor gets the pictures he
needs. At times you will be asked to hold your breath while a picture is
being taken; this does not last longer than a few seconds.
Your doctor can treat a blocked blood vessel or a bulge (aneurysm) without surgery; this will be scheduled for another time as you may receive' general anesthesia to ensure you do not move during this procedure. Techniques called angioplasty (balloon catheter), stent (a metal tube placed in the blocked area), and thrombolysis (clot-busting medication), and many more are all tools your doctor has for treatment. If this is the case you will be admitted over night to the ICU for observation.
Preparation for your angiogram:
It is very important that you bring a complete list of your medications with you each time you go to the hospital or doctor's office. You will be asked to have nothing to eat or drink from 12 midnight the night before your angiogram. Your doctor's office will instruct you on your medications before your angiogram. It is VERY important to let them know if you are taking Coumadin/Warfarin (or any other blood thinners) and to receive special instructions regarding these medications. You will be asked to arrive one or one-and-a-half hours before your procedure depending on the facility.
You will be asked if you are allergic to any medications of foods; it is important that you tell your doctor if you are allergic to anything.
You must have someone drive you home as it is not safe to drive after
receiving medication that helps you relax. You will be asked to rest
after discharge with heavy lifting or driving for 24 hours. You will be
asked to increase your fluid intake (water is best) to help flush the
dye from your system. A Band-Aid will be placed on your groin which you
should remove after 24 hours. Your doctor will tell you when you can
return to work.
Side effects:
As we are accessing an artery there is a chance of bleeding from the artery. You may have some bruising around the insertion site. This is not uncommon, if you have a large amount of bruising or a hard area (blood collection under the skin, hematoma) you need to contact you doctor or seek immediate medical attention. While the risk of stroke is low (.5%), it is not zero. Infection, while uncommon, can occur; you should inform your doctor if you show any signs of infection.
Follow up:
It is important that you return to our office for your follow up appointment so we can check your groin (area of catheter insertion) and answer any questions you may have. It is always a good idea to write down your questions so you won’t forget and to have another person come with you to your visit.