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CNI Neurovascular Surgery Service
Patient Care
Conditions
WARNING: Some of the photos below are graphic in nature; view them at your own discretion.
Brain Ischemia
Stroke is generally thought of in the medical community as the presence of severe brain ischemia, which may lead to death of brain tissue. Ischemia occurs when the brain, or an area of it, does not have enough oxygen (blood flow) to supply the demand. If the blood flow to a given area decreases low enough, infarction -- or death of tissue -- occurs, (i.e., a stroke). Surgery can sometimes prevent a stroke in patients at risk, and can also alleviate the symptoms of ischemia in an area of the brain before infarction occurs.
Types of Brain Ischemia
Extracranial
Narrowing of the carotid artery in the neck is nearly always caused by atherosclerosis, fatty deposition in the wall of an artery that may cause its narrowing. Pieces of this plaque material may break off and flow downstream, where blood flow may be disturbed, or clot may form on the surface and lead to complete blockage of the artery. Less often, the artery may be narrowed due to dissection, which can be spontaneous or due to trauma. The flow of blood 'dissects' into the wall of the artery, which narrows the channel available for blood flow.
If a person has symptoms such as brief inability to speak or inability to move one arm or hand, such episodes, may be termed Transient Ischemic Attacks, or TIAs. They may herald an increased risk for stroke, and merit urgent evaluation by a neurologist or neurosurgeon. In other instances, one might experience a sudden transient loss of vision in one eye, often described as the sensation of a curtain being pulled down in that eye. If the carotid arteries are examined using ultrasound, and the narrowing is subsequently proven to be greater than 50%, surgery is often helpful in preventing a stroke from occurring.
Treatment for extracranial ischemia includes carotid endarterectomy. This procedure involves surgically exposing the carotid artery, temporarily clamping it, removing the atherosclerotic material, and stitching the artery closed (Figure 1). Following removal of the clamps, flow is restored. Sometimes, narrowing of the carotid is discovered in the absence of symptoms. In certain circumstances, it is helpful to perform endarterectomy for non-symptomatic narrowing.
| Figure 1 |
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| a. Here, an angiogram demonstates significant narrowing of the carotid artery |
b. An operative photo showing the carotid artery and
its branches dissected out. Incision at artery being extended with scissors.
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| c. Closure of the artery following removal of the plaque. |
d. Completion of the artery closure |
Intracranial
In rare circumstances, one or both carotid arteries become 100% blocked, the brain being fed variably by alternative 'collateral' pathways. In some instances, the amount supplied is inadequate, and TIA's result. Very severe cases may progress on to stroke. Typically this situation is managed by long-term anticoagulation with Coumadin, in hopes that more collateral circulation may develop in time.
Other patients may benefit from cerebral revascularization via a surgery called extracranial to intracranial (EC-IC) bypass. This is a specific type of cerebral revascularization that involves dissecting the superficial temporal artery (STA) from the scalp, and 'plugging it in' to a brain vessel, usually a branch of the middle cerebral artery (MCA). These grafts directly provide new blood flow to the ischemic area of brain, and may reverse the symptoms that are occurring (Figure 2). TFigure hey may also prevent stroke, although this conclusion is somewhat controversial. A large study completed in the early 1980's assessed the surgery's ability to prevent stroke, but findings indicated that it did not prevent stroke. The conclusion of this study led to Medicare and insurance companies no longer providing reimbursement for this procedure. As a result, very few surgeons today know how to perform it. Currently, however, new efforts were initiated to organize an updated study to evaluate the results of this procedure for stroke prevention.
With these diseases, it is sometimes necessary to intentionally sacrifice, or occlude, a carotid artery, usually in the case of otherwise inoperable giant brain aneurysms. Prior to actually occluding the vessel, a temporary balloon occlusion test is performed to assess the patient's response to losing a carotid artery. The majority of the time, this is well tolerated, but occasionally, severe ischemia results. If occlusion is not tolerated, it is necessary to perform EC-IC bypass prior to carotid sacrifice.
| Figure 2 |
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a. Preoperative Brain SPECT scan showing markedly reduce flow to the brains right hemisphere (arrow).
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b. Postoperative Brain SPECT scan showing near-normalization of flow in the right hemisphere (arrow).
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c. Postoperative angiogram showing the bypass graft (arrow) delivering flow to the brain.
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Spinal cord hemorrhage usually results from a vascular malformation, such as an AVM or a Cavernous Malformation. Such hemorrhagic events are usually heralded by the sudden onset of weakness of both legs or all four extremities. Surgical principles are similar to those applied to vascular malformations of the brain.
Brain Hemorrhage
Hemorrhage, or bleeding inside the cranium, is the other type of disease that is sometimes thought of as stroke. When a blood vessel ruptures, bleeding may occur in the brain, or in the space between the brain and skull. Brain injury may result, and the situation can be life-threatening. Surgery may in some instances be life-saving, or in other circumstances, prevent the occurrence of additional hemorrhages.
Types of Brain Hemorrhage
Hypertension
The most common cause of bleeding into the brain substance, or parenchyma, is uncontrolled hypertension. Blood pressures in excess of 200 are usually seen, and usually the patient is unable to move one side of the body. Treatment is directed best at prevention. When a large clot is present, a life-threatening situation exists which requires emergent removal of the blood (Figure 3). Unfortunately, such surgery cannot reverse the damage that has already been done, and severe deficits, such as paralysis on one side, likely will persist.
| Figure 3 |
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a. Brain CT scan showing a large hematoma (blood clot) deep within the brain
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b. Postoperative CT scan showing removal of the hematoma
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Vascular Malformations
Bleeding into the brain substance may also be caused by malformed blood vessels, called vascular malformations. These may be high pressure, high flow lesions called arteriovenous malformations (AVM's), or smaller, low pressure ones called cavernous malformations. Surgery to remove the malformation is preventative in nature, but the malformation may also be removed if a life-threatening hemorrhage is present and surgery is required to remove the blood clot (Figure 4). Surgery for removal of an AVM is often performed in conjunction with embolization to reduce the blood inflow. Embolization is performed by CNI’s Interventional Neuroradiology Service.
| Figure 4 |
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| a .CT scan demonstrating a large hematoma |
b. Preoperative angiogram showing
the AVM in the dark, round mass as the top. |
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c. Postoperative CT scan showing
removal of the hematoma |
d. Postoperative angiogram following
removal of the AVM
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Intracranial Aneurysms
Aneurysms are a common cause of intracranial bleeding. An aneurysm is a balloon-like dilation or pouch, which usually occurs at the branch point to an artery. They enlarge until the wall becomes so thin that there is a hemorrhage (Figure 5). The blood usually fills the grooves on the brain's surface. This space is called the subarachnoid space. The bleeding continues until the body's mechanisms for stopping the bleeding take effect, or until the pressure inside the cranium reaches the blood pressure, and blood flow to the brain ceases. A significant portion of the patients sustaining a subarachnoid hemorrhage die immediately, and significant portion of those who make it to the hospital will eventually die as well.
| Figure 5 |
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a. Angiogram demonstrating
this left-sided aneurysm |
b. CT scan showing the
subarachnoid blood (white) |
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c. Operative photograph using the
operating microscope-Left Middle
Cerebral Artery Aneurysm |
d. Clip placed across aneurysm neck |
When possible, surgery is performed to prevent further re-bleeding episodes. Surgery is the established standard for direct treatment of brain aneurysms. The aneurysm is dissected out using microdissection techniques, and a metal clip is placed across the aneurysm neck (Figure 5), so that no more blood flows into it. The aneurysm subsequently shrivels up and scars down. The current standard clips are made from titanium and are safe for use with MRI scanning machines. Even if surgery is carried out without any complications, the patient is still at risk for 14 days following the initial hemorrhage. The blood that leaked out is very irritating to the major arteries supplying the brain, and in approximately 35% of patients, these vessels narrow down due to spasm. If the spasm is severe enough, stroke or death may result. Vasospasm may be treated by a variety of techniques ranging from fluid management to catheter-based angioplasty (Figure 6). The latter is the most state of the art treatment and is available at the CNI. Learn more about aneurysms.
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a. This patient suffered a subarachnoid hemorrhage;
the aneurysm was treated by platinum coils |
b. On day 5, spasm ensued, which resulted in
inability to speak or move the right side of the body. |
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| c. Following angioplasty, most of these symptoms reversed. |
Spinal Cord Ischemia
Ischemia involving the spinal cord may result from a vascular entity called a Dural Arteriovenous Fistula. Symptoms typically include progressive weakness and spasticity of the legs. With a fistula, an abnormal connection develops in which high-pressure arterial flow connects into a vein, which isn't accustomed to such high pressures. This abnormal pressure can actually reduce blood flow to the area of the spinal cord that is otherwise normally drained by that vein. Surgery for these entities is not generally complex, and involves dividing the abnormal vein.
Spinal Cord Hemorrage
Spinal cord hemorrhage usually results from a vascular malformation, such as an AVM or a Cavernous Malformation. Such hemorrhagic events are usually heralded by the sudden onset of weakness of both legs or all four extremities. Surgical principles are similar to those applied to vascular malformations of the brain.
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