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Definitions

Aneurysm	A weakening in an artery wall. Cerebral aneurysms can form in any of the major cerebral arteries. An aneurysm may rupture or it can be discovered before it ruptures. A ruptured cerebral aneurysm causes bleeding into the space around the brain (subarachnoid hemorrhage). Unruptured aneurysms may be discovered incidentally- and so are called incidental, or asymptomatic, aneurysms- or because they are causing symptoms- so called symptomatic unruptured aneurysm. Ruptured cerebral aneurysms, and symptomatic unruptured aneurysms, require emergency treatment and are best treated at hospitals that specialize in treating this type of patient. It is controversial whether or not to treat incidental (asymptomatic) aneurysms. Aneurysms can be treated by one of two methods: "aneurysm coiling" using a catheter, and "aneurysm clipping" that requires a craniotomy (opening the skull). Each method has its advantages and disadvantages. Patients with aneurysms should be treated at hospitals that have both methods available.
Angiogram	A view of body arteries. A cerebral angiogram can be performed using three different techniques: conventional angiogram (catheter angiogram), MR angiogram, and CT angiogram. A catheter angiogram gives the best details. It is performed by placing a small tube (catheter) into the femoral artery in the groin and threading the catheter into the arteries of the brain, typically the carotid or vertebral artery. Once there, a dye (contrast) is injected and an X-Ray of the skull is taken. These X-ray images show where the dye goes within the blood vessels and gives us the best view of the brain's arteries. Also, one can perform surgery (endovascular surgery) through this catheter; for example, one can place platinum coils into an aneurysm, or inject glue into an AVM.
AVM- Arteriovenous Malformation	A congenital (born with) abnormal connection between an arteries and veins. AVMs can occur anywhere in the body, but when they affect the brain or spinal cord they can produce problems if they bleed (hemorrhage). If the AVM ruptures and bleeds the blood that escapes puts pressure on the surrounding brain region or spinal cord region. This is usually a sudden event and causes neurological symptoms like headache, seizure and weakness. AVMs that have hemorrhaged should be evaluated for treatment (removal). This can be done by first embolizing the AVM (injecting glue or other material into the AVM with a catheter during an angiogram), then having a skilled surgeon remove the AVM. Alternatively, the AVM can be treated with radiation using a gamma-knife that focus radiation to the center of the AVM. Following gamma-knife treatment the AVM will shrink and disappear. It is controversial whether or not AVMs that have not hemorrhaged should be treated at all. Deciding whether to treat, and how to treat, requires expert consultation at center that has neurointerventional surgeons (endovascular surgeons), vascular neurosurgeons, gamma-knife and neurointensive care.
ASD- Atrial Septal Defect	A hole in the wall that separates the two chambers (atria) of the heart. This hole can allow blood to flow directly from veins into the arterial system bypassing the lungs. If a blood clot arises in a leg vein, this clot can travel through the heart and be sent to the brain. This produces a paradoxical embolism and can cause a stroke. An ASD is a persistent hole in the heart wall (septum) while a patent foramen ovale (PFO) is a potential hole that acts like a check valve, only opening when the pressures between the venous side of the heart (right side) exceeds the arterial side (left side). If a patient has a stroke and all that can be found is an ASD, or PFO, the neurologist has to make a judgment about whether the ASD or PFO has anything to do with the stroke. If it does, the hole can be closed by surgery (open heart surgery) or by a closure device placed with a catheter. Since many strokes happen for unknown reasons, and because nearly 20% of people have a PFO, many physicians may ascribe the cause of stroke to a PFO when in fact it has nothing to do with the stroke. Before the heart condition is repaired, expert neurological consultation should happen to be sure this the right thing to do.
Atrial Fibrillation	A chaotic contraction of the heart leading to cardioembolic stroke. Atrial fibrillation can be caused by a number of conditions including high blood pressure (hypertension). Atrial fibrillation allows blood clots to form on the heart chamber walls leading to release of a blood clot that travels (embolus) to the brain or other organ. This condition produces one-third of stroke in patients over 85 years of age but can cause stroke at any age. Stroke can be prevented by taking warfarin (Coumadin), and less so by taking aspirin. Patients with atrial fibrillation should discuss stroke prevention with their physicians and seriously consider taking warfarin. Most importantly, any patient who has atrial fibrillation and experiences a TIA needs medical attention immediately.
Atrial Septal Aneurysm	A weakened heart wall (septum) between two heart chambers (atria) that if associated with a patent formen ovale may further increase stroke risk. See discussion about ASD.
Cardioembolic Stroke	A stroke produced by a blood clot that forms in or near the heart and travels (embolus) to the brain and then blocking a blood vessel in the brain. Atrial fibrillation is a chief cause of this form of stroke.
Carotid Artery	A paired artery that travels in the front of the neck (the artery you feel in someone's neck to see if they have a pulse, just lateral to the Adams apple). The carotid arteries branch within the neck. This branch point (carotid bifurcation) is a site the frequently becomes blocked by atherosclerosis (hardening of the arteries). As the degree of blockage rises, so does the risk that the blockage can produce a thrombus that embolizes to the brain. This type of stroke is called a carotid embolic stroke and is best prevented by performing a carotid endarterectomy. Alternately, the artery can be repaired by stenting the artery. Patients with narrowing of the carotid artery who have not experienced a TIA or stroke have "asymptomatic carotid stenosis (narrowing)". It is controversial whether or not to treat asymptomatic patients. If the narrowed artery produces a stroke or TIA it is called "symptomatic carotid stenosis" and the artery should be repaired. Repairing the artery requires a skilled surgeon to perform an endarterectomy or endovascular specialist to stent the artery. Referral to a center that has a proven track record with these procedures is the best way to ensure low risk to the patient.
Carotid Endarterectomy	Surgical repair of an artery with atherosclerosis (hardening of the arteries). This is typically done for symptomatic carotid stenosis, and is controversial for asymptomatic carotid stenosis. The procedure is delicate and requires a skilled surgeon because the surgery can result in a stroke- exactly what was sought to prevent. Skill is largely a function of the number of cases the surgeon does a year. A patient should inquire about the number of cases per year the surgeon performs and the surgeon's complication rate. Typically specialty centers have more than one highly skilled vascular surgeon or vascular neurosurgeon so referral to such a center reduces surgical complication rates.
Cavernous Angioma	A brain vascular malformation that can produce a stroke if it hemorrhages (bleeds). Some patients have several cavernous malformations and these are likely genetic. Surgical removal of these malformations is controversial and should be done only after seeking a second opinion.
Clipping Aneurysm	Neurosurgical technique used to prevent an aneurysm from bleeding. This is done by opening the skull (craniotomy), locating the aneurysm, and placing a metal clamp (clip) across the neck of the aneurysm. It is like placing a tight hairpin (clip) across the neck of an inflated balloon (aneurysm neck). This is one of the most difficult neurosurgical procedures and the surgical outcome is highly dependent upon the skill of the surgeon. Highly experienced vascular neurosurgeons may treat over 100 patients a year. This level of experience is only found at specialty centers.
Coiling Aneurysm	An endovascular (from inside the blood vessel) technique whereby the aneurysm is closed by filling it with material like platinum or a polymer. These is a different approach than the traditional technique of clipping an aneurysm and does not require a craniotomy. Only a few centers in the United States have this technique, but the field is expanding rapidly especially in light of new data that it is safer than aneurysm clipping. Referral to centers that have this technique gives the patient the best chance of a good outcome.
Craniotomy	Surgical opening of the skull as is necessary for clipping an aneurysm.
CT (CAT) Scan	An X-Ray technique whereby the head or body region is imaged as a series of slices. The technique is widely available and essential in the emergency setting, especially during stroke. A CT scan can reveal if a patient is having a bleeding stroke or a non-bleeding stroke. Additionally, an angiogram of the brain's arteries can be performed with the CT scanner giving the clinician more information about the cause of stroke. MRI gives better resolution and if often necessary following a CT scan to better determine the cause of stroke.
CTA (CT Angiography)	A special type of CT scan whereby the patient is given an intravenous dye (contrast) that illuminates the arteries and veins of the brain. This technique gives the clinician a detailed view of the brain blood vessels and can detect aneurysm, artery blockage during stroke, and extent of atherosclerosis (hardening of the arteries) of brain blood vessels.
Dissection	A tear in an artery to the brain. This is a significant cause of stroke in young (age < 60 years) patients and the cause is usually never determined. It is usually painful, and produces a stroke several hours or days following the onset of neck pain. Some dissections are caused by neck injury and spinal manipulative therapy (chiropractic). Immediate use of anticoagulation (heparin and Coumadin) can prevent a stroke or a second stroke.
Dural Fistula (dural AVM)	An abnormal connection between an artery and a vein; normally, an artery and vein are connected by a series of capillaries where oxygen exchange occurs. Fistula form for a number of reasons (trauma, clotting) and can lead to brain hemorrhage. Patients with dural fistula often can hear their own heart beat within their head. Many can be repaired by catheter based techniques and some require neurosurgery.
Echocardiogram	An ultrasound technique used to image the heart. This can be performed by placing an ultrasound probe on the chest (transthoracic echocardiogram- TTE) or down the throat (transesophageal echocardiogram- TEE). An echocardiogram is often performed following a stroke to look for a source of blood clots that may have traveled (embolus) to the brain.
Embolus	A blood clot that has traveled within an artery to the brain.
Endarterectomy	See carotid endarterectomy.
Intracranial hemorrhage	Bleeding within the brain. A principle cause is high blood pressure, but this can also occur from a ruptured AVM, aneurysm, or several other conditions. The cause of the bleeding needs to be determined rapidly because the exact treatment differs between causes. Determining the cause may require brain imaging studies like CT, MRI and angiography.
MRA (Magnetic Resonance Angiography)	An MRI based technique that uses a magnetic field to view the arteries of veins of the brain. These images can detect blood vessel narrowing or blockage of any artery in the head or neck. Sometimes, the radiologist will administer intravenous gadolinium, a drug that improves the imaging ability of the MRI machine to view blood vessels.
MRI (Magnetic Resonance Imaging)	An imaging technique that uses strong magnetic fields to view the brain or other body structures. This produces the most superior images of the brain and can help determine the exact cause of stroke, the site of bleeding from a blood vessel, and a number of other types of studies. This technique has revolutionized the neurologists ability to both treat patients and prevent a second stroke.
Paradoxical Embolus	A blood clot arising within a vein that instead of landing in the lung (where venous blood typically flow toward) the blood clot passes through a hole in the heart and can go directly to the brain. See ASD.
PFO (Patent Foramen Ovale)	An potential hole between two chambers of the heart. See ASD.
Stent	A metal tube that is placed across a narrowed artery and expanded to restore a normal caliber to the blood vessel. Stents can be placed in the carotid arteries offering an alternative to endarterectomy. Small stents can be placed within the blood vessels inside the skull and offer a treatment for patients who have narrowed blood vessels in these regions.
Stroke	A stroke is a sudden change in a neurological function caused either by a blood vessel occlusion (blockage, or non-bleeding stroke) or a blood vessel rupture (intracranial hemorrhage) within the brain. Blockage of blood flow to the brain for even a few minutes results in death of brain tissue. Restoration of blood flow can salvage brain tissue. The most common method for restoring blood flow is administering t-PA, a thrombolytic (thrombus dissolving) drug by vein, or by catheter, to break up the clot. However, the drug must be given within the first several hours of stroke to be effective and is only offered at specialty hospitals. Certain conditions place people at risk for stroke including high blood pressure (hypertension), diabetes, high cholesterol, cigarette smoking, and heart disease (especially atrial fibrillation). People at risk for stroke should know what hospitals near their home or work give t-PA so they can direct paramedics to these hospitals. Call 911 if you experience signs and symptoms of stroke that include: Sudden inability to move one side of the body Sudden loss of sensation of one half of the body Sudden loss of speech or inability to understand others or read Sudden severe headache Sudden loss of ability to walk or balance Sudden change in vision If you experience any of the above symptoms and they only last for a few minutes (except headache), this is called a transient ischemic attack, or TIA. If the symptoms last for more than an hour to 24 hours, then it is called a stroke. Doctors will perform a brain imaging study (CT or MRI) first and will determine if you are eligible for t-PA. After this, the cause of the stroke or TIA needs to be defined so that proper medications or other treatments can be prescribed to prevent a second event. Rehabilitation of the stroke victim is essential to help restore function. Specialty consultation with neurologists who spend their time mostly seeing patients is useful for initial treatment, establishing the cause, and prescribing methods to prevent the next event.
Subarachnoid hemorrhage	Bleeding around the surface of the brain typically from rupture of an aneurysm. This is a neurological emergency and the cause of the bleeding should be determined rapidly using some form of angiography. If an aneurysm is found, it can be clipped or coiled. Patient outcome is a strong function of the experience of the treating center. Patients with subarachnoid hemorrhage should be evaluated at specialty centers.
Thrombosis	Clotting of blood. A thrombus is a blood clot and the thrombus can directly block an artery (arterial thrombosis) causing stroke, or can break loose and travel to another vessel and block it (embolus).
TIA (Transient Ischemic Attack)	A sudden loss of neurological function that goes away typically in 10-15 minutes. Symptoms of TIA are the same as stroke except that the symptoms clear rapidly with TIA and stay for hours or days with stroke. The neurological symptoms of TIA are Sudden inability to move one side of the body Sudden loss of sensation of one half of the body Sudden loss of speech or inability to understand others or read Sudden loss of ability to walk or balance Sudden change in vision A TIA signals that a stroke may be coming and should be treated as an emergency. A patient with a TIA should contact their physician immediately and be satisfied that the cause is determined and that proper preventive measures have been taken. Specialty consultation is often helpful at identifying the exact cause and determining the best preventitive measures.
Venous malformation	An abnormal development of the venous system of the brain. These are often associated with cavernous malformations and of little significance.
Venous Sinus Thrombosis	Blood clotting within the normal veins or venous regions within the brain and skull. This causes a build-up in pressure within the vein leading to reduced blood flow to the brain and potentially stroke. Anticoagulation (blood thinners, heparin and Coumadin) can alleviate this blockage and prevent stroke.
Vertebral Artery	Paired arteries that travel up the back of the neck and supply blood flow to the brainstem and back of the brain. The two vertebral arteries and the two carotid arteries supply all of the blood flow to the brain.