Cerebrovascular Specialties

Intracranial aneurysm

Aneurysm of the brain, also called cerebral aneurysm, is a common cerebrovascular disorder caused by a weakness in the wall of a cerebral artery or vein. The disorder may result from congenital defects or from preexisting conditions such as hypertensive vascular disease and atherosclerosis (build-up of fatty deposits in the arteries), or from head trauma. Cerebral aneurysms occur more commonly in adults than in children and are slightly more common in women than in men, however they may occur at any age. When an aneurysm ruptures, the individual may experience such symptoms as a sudden and usually severe headache, nausea, vision impairment, vomiting, and loss of consciousness, or the individual may be asymptomatic experiencing no symptoms at all. Onset is usually sudden and without warning. Rupture of a cerebral aneurysm is dangerous and usually results in bleeding in the brain or in the area surrounding the brain, leading to an intracranial hematoma (a mass of blood within the skull). Rebleeding, hydrocephalus (the excessive accumulation of cerebrospinal fluid), vasospasm (spasm of the blood vessels), or multiple aneurysms may also occur.  Very large and giant aneurysms are commonly referred to the cerebrovascular surgery team at the Stanford. Any brain aneurysm greater than 2.0 cm fits into this category and is more difficult to treat than smaller aneurysms. Specialized techniques for treating these have been developed at Stanford, including microsurgical clipping using temporary vessel occlusion with mild hypothermia, endovascular coiling and stenting, or arterial bypass with deliberate parent artery occlusion.

Emergency treatment for individuals with a ruptured cerebral aneurysm generally includes restoring deteriorating respiration and reducing intracranial pressure. Surgery is usually performed within the first 3 days to microsurgically clip or endovascularly coil the ruptured aneurysm, to reduce the risk of rebleeding. Other treatments may include bed rest, drug therapy, or hypertensive-hypervolemic therapy to treat vasospasm.

Arteriovenous malformation

Arteriovenous malformation (AVM) is an abnormal cluster of blood vessels in the brain that can cause devastating neurological deterioration or even death. It is most commonly diagnosed between ages fifteen to forty, and left untreated, can cause a progression of symptoms that can lead to permanent disabilities or death. The most common presenting symptom for patients with AVMs is brain hemorrhage. In addition, patients can have seizures, headaches and progressive neurological symptoms such as weakness or difficulty with speaking or swallowing. Intellectual functions, such as short or long term memory, may be impaired. All of these symptoms can affect a patient's ability to perform in school, work or simple daily activities.

It is believed that most people who have AVMs are born with them. They can occur in many locations throughout the brain and spine. Many are asymptomatic and will never even be diagnosed. Usually, the presenting symptoms help identify the part of the brain where the AVM is located. For example, if the AVM is in one of the brain's visual areas, there may be changes in vision. If an AVM is located in a part of the brain that controls motor skills, weakness on one side of the body may become apparent. If a hemorrhage occurs from the AVM, there may be severe neurologic impairments related to the location of the resulting clot. Patients often improve dramatically over a period of a few days to months after a hemorrhage, depending on the location and size of the bleed. Some patients have seizures related to these AVMs and require medication to prevent the seizures from reoccurring. Sometimes these seizures can be difficult to control with medications, but may improve dramatically when the AVM is treated.

Diagnosis of AVMs is confirmed with an MRI and angiogram. These studies allow the team to look at the exact size, location and architecture of an AVM in order to offer the best treatment options, taking into consideration the patient's symptoms, age, and treatment preferences.

The treatment for AVMs has improved in recent years. The goal of treating AVM-related lesions is to close off completely the vessels, thereby curing the patient. This is achieved in a variety of ways and requires a large number of specialists to provide the optimal methods available to safely treat the patient and prevent further problems. The methods available for treating AVMs at the Stanford Cerebrovascular Surgery program include stereotactic computer assisted microsurgery, embolization, stereotactic radiosurgery using CyberKnife. Over the past 30 years, we have treated more than 1,000 patients with AVMs.

Carotid stenosis

Carotid stenosis is narrowing of the carotid arteries (blood vessels within the neck leading to the brain). Build up of plaque, known as atherosclerosis, is the usual cause of this narrowing. If severe enough, it can cause strokes resulting in left or right sided body weakness, speech impairment, visual impairment, and even death. Strokes can also be caused by little pieces of this plaque breaking off and floating upwards into the smaller blood vessels of the brain. Treatment is usually recommended when patients become symptomatic from the narrowing or when the loss of vessel diameter is greater than 70%. This is diagnosed by radiological studies, including carotid duplex (ultrasound), CT/CTA, MRI/MRA, and angiography. The most common treatment is currently carotid endarterectomy (cleaning out the plaque with surgery). Another technique offered to some patients is carotid angioplasty with endovascular stenting, which involves the use of metal-mesh sheaths to open up the narrow portion of the blood vessel. Since 1987 at Stanford, our neurosurgical cerebrovascular service has treated more than 900 patients who have carotid stenosis. We use electrophysiologic (nerve) monitoring, EEG (brain wave) monitoring and ultrasound during surgery to minimize patient risk. Most patients who undergo this type of surgery are able to go home the next day.

Cavernous carotid fistula

Cavernous carotid fistula or (C-C fistula) is an abnormal connection or shunt between the carotid artery and the veins at the base of the skull. These fistulas can form spontaneously, but most are caused either by head trauma or by the rupture of a cerebral aneurysm. The most common presenting symptoms include a buzzing sound in the head, double vision, and a red, swollen bulging eye (proptosis). These fistulas can shunt blood away from the brain, hence depriving the brain of some of its blood supply. Most cavernous carotid fistulas should be treated to prevent further neurologic deficit. The most common form of treatment is obliteration of the fistula with endovascular techniques. During a cerebral angiogram, the neuroradiologists often can block off the fistula using tiny platinum coils. For the small percentage of patients that cannot be cured in this fashion, microsurgery can be used to surgically eliminate the fistula. The treatment of the fistula almost invariably reverses the symptoms, and most patients with this diagnosis do well in the long run.

Dural arteriovenous fistula (AVF)

Dural arteriovenous fistula, also sometimes known as dural AVM, are vascular malformations involving the dura (a protective, leather-like layer surrounding the brain). They differ from AVMs in that they do not directly involve brain tissue. They are actually an abnormally fast shunting of blood through the arteries and veins of the dura. Although dural AVF may be present at birth, many are considered to be acquired lesions. They may be associated with abnormal clotting of veins in the area, known as venous sinus thrombosis. Some result from traumatic head injury. The danger of leaving these untreated is that they can enlarge and possibly hemorrhage, resulting in stroke. In addition, they may cause blockage of veins and buildup of fluid in the brain, thereby increasing the pressure within the skull. The most common symptom of a dural AVM is a pulsating ringing in the ear. Others are headaches and worsening neurological function. Cerebral angiography provides the most definitive diagnosis. Treatment options for these malformations include embolization (blocking the abnormal blood vessels with platinum coils or adhesive glue), surgical resection, and focused stereotactic CyberKnife radiosurgery. Unless these lesions are completely obliterated as documented by an angiogram, they can recur and continue to cause symptoms.

Intracranial hemorrhage

Intracranial hemorrhage is bleeding into brain tissue. Symptoms are generally related to the size and location of the hemorrhage. They include a wide variety of stroke-like symptoms such as difficulty with speech or comprehension, paralysis, numbness, visual disturbances, seizures, coma, and even death. Common causes of intracranial hemorrhage include high blood pressure, arteriovenous malformations (see above), intracranial aneurysms (see above), brain tumors, disorders of blood coagulation, and bleeding into a previous stroke. Intracranial hemorrhage is evident on CT and MRI scans. MRI and cerebral angiography are used to determine the cause of the hemorrhage. Small hemorrhages often do not require surgical removal. Larger hemorrhages may require treatment, particularly if the blood is compressing normal brain and if the blood clot comes to the surface of the brain where it can be removed without causing further neurologic injury. Blood clots within the center of the brain are much more difficult to treat, since surgery would involve cutting through normal brain tissue to access the blood, and thus risk additional brain injury. At Stanford, we are participating in a nationwide protocol for the treatment of large, deep-seated brain hemorrhages. This involves injecting medications that dissolve the blood clot through special catheters (thin tubes) surgically placed in the center of the blood clot. This attempts to reduce the size of the blood clot to promote better neurologic recovery and outcome.

Moyamoya disease

Moyamoya disease causes blood vessels leading to the brain to narrow and close. It is rare and can occur during childhood or adulthood. It usually presents with either stroke-like symptoms or brain hemorrhage such as speech difficulty, weakness, or numbness in the extremities. It usually affects both sides of the brain, but may affect only one side. Patients often experience decline in their intellectual capabilities. Although moyamoya is more common in Asians, it may occur in all races. A thorough evaluation of the blood flow pattern in the brain is essential to developing a treatment plan for each patient. This includes cerebral angiography, MRI, and cerebral blood flow studies. The most common treatment is a bypass procedure known as an Intracranial-Extracranial Bypass Graft (EC-IC Bypass). This involves the connection of normal blood vessels in the scalp to blood vessels on the surface of the brain in an effort to increase the blood flow to the brain. Other surgical procedures sometimes performed for revascularization include EDAS (encephalo-duro-arterio-synangiosis), EMS (encephalo-myo-synangiosis) and omental transposition. We have treated over 800 moyamoya patients over the last 24 years at Stanford, with excellent results.

Spinal AVM and dural AV fistula

Spinal AVM is a rare abnormality of the blood vessels within the spinal cord that is present at birth. Arteries and veins without a network of capillaries form a tangled mass. These are more common in males who are 20-60 years old. Spinal dural AV fistula represents a direct connection between the spinal arteries and veins. The average age of onset is 50-60 years old. Symptoms are usually a combination of back pain and progressive sensory loss and weakness in the legs, which develops over months to years. Sudden back pain and loss of leg function can result from bleeding of the AVM. These lesions require careful planning for treatment. They can be treated with embolization that uses special catheters to block the abnormal vessels, a direct surgical approach to remove the lesion, stereotactic CyberKnife radiosurgery or a combination of these techniques.


Stroke is the permanent loss of neurologic function. There are two types: hemorrhagic (bleeding; see intracranial hemorrhage above) and ischemic (inadequate blood flow; see cerebral ischemia above). In the former, the blood itself disrupts or compresses normal brain tissue resulting in neurologic injury. In the latter the tissue, receiving inadequate blood flow and oxygen, dies. The symptoms of a stroke depend upon the region of the brain involved and include speech difficulties, numbness or weakness in the arms and legs, difficulty with swallowing or facial movement, or visual disturbances. Large strokes, or smaller strokes within critical regions of the brain, can result in coma or even death. Once a stroke occurs, it is important to identify the cause. Tests that are commonly performed to diagnose the causes of stroke include CT and MRI scans of the brain, an echocardiogram of the heart, a carotid ultrasound of the neck arteries, various blood tests, and occasionally, a cerebral angiogram. Treatment of stroke is primarily focused on correcting the cause so as to prevent further strokes. This may include a carotid endarterectomy if the stroke is due to narrowing of the carotid artery. Other causes of stroke which can be treated include occlusive cerebrovascular disease. Stroke caused by intracranial aneurysms or AVMs bleeding into the brain are treated in various ways.

Subarachnoid hemorrhage

Subarachnoid hemorrhage is bleeding on the surface of the brain under the arachnoid layer. This often results from rupture of an intracranial aneurysm (see above). Intracranial aneurysms are a weakened, blister-like area of the artery that can cause catastrophic neurologic impairment or death when it ruptures and bleeds. They are most commonly diagnosed after they rupture. Occasionally they can present prior to rupture with signs such as headache, visual changes, droopy eyelid and various other neurologic symptoms. They are more likely to be diagnosed between the ages of 20 and 40 but can present at any age. We treat approximately 170 patients each year who have intracranial aneurysms. Our team works collaboratively to minimize risk to the patient by individualizing the treatment program based on the size, shape and location of the aneurysm and the neurologic condition and age of the patient. One method of treatment includes microsurgical clipping utilizing special surgical instruments and techniques such as mild hypothermia (lowering the body temperature to protect the brain) and electrophysiologic monitoring of brain function during surgery. Another treatment modality is coil embolization: tiny platinum coils are placed within the aneurysm, from the inside of the vessel during angiography, to promote aneurysm clotting so it can no longer rupture. Sometimes a stent is used with or without coils. The risk of permanent neurologic deficit and death from an aneurysm are greatly reduced by treating it before it ruptures, rather than after it has bled. Following a subarachnoid hemorrhage, patients are at risk for developing delayed narrowing of their blood vessels (vasospasm) within the brain, leading to strokes. No single treatment is available to prevent vasospasm, but the Cerebrovascular Surgery Division of the Stanford Stroke Center has been involved in multiple clinical trials aimed at halting the complications related to vasospasm. In addition, early diagnosis of vasospasm, including transcranial Doppler (TCD) may allow for earlier treatment and prevention of brain injury. In addition, for patients who have been diagnosed with an intracranial aneurysm, we offer preventative screening for other family members to ensure that they do not have an intracranial aneurysm.

Angiographically occult vascular malformation

Angiographically occult vascular malformations (AOVM) represent a group of various types of vascular malformations which are not visible on a cerebral angiogram. The most common type of AOVM is cavernous malformation (see below). Occasionally very small AVMs (see above) also do not appear on angiography. Two other types of AOVMs that are not usually symptomatic and do not require treatment are venous malformations (an abnormal appearing vein) or capillary telangiectasias. It is important when dealing with an AOVM that the appropriate neurologic and radiographic evaluation be performed to determine whether a patient has an AOVM that needs treatment.

Basilar artery stenosis

Basilar artery stenosis is narrowing or closure of a major artery at the base of the brain which supplies blood to the deep center of the brain and the brainstem (the structure which connects the brain to the spinal cord). Stenosis can reduce the blood flow to the brainstem resulting in a stroke. Common symptoms of basilar artery stenosis include dizziness, double vision, difficulty with speaking or swallowing, and weakness or numbness in the arms or legs. Less common but more serious symptoms include complete paralysis or coma. The narrowing within the basilar artery is usually due to atherosclerosis, the build up of fatty deposits within the walls of the artery. The current treatment of basilar artery stenosis generally involves angioplasty (inflating a balloon within the region of stenosis) or stenting (with a thin metal-mesh) to open the narrowing. Both angioplasty and  stent placement occur in the angiography suite during a cerebral angiogram. For patients in which angioplasty and stenting are not possible, certain types of medication (e.g. coumadin, which slows blood clotting) may be useful. Rarely is surgery indicated in these patients.

Carotid dissection

Carotid dissection occurs when the wall of the carotid artery (a major blood vessel in the neck that supplies blood to the brain) is injured. Part of the inner wall of the blood vessel can peel off and this can result in severe strokes from occlusion or blockage of the carotid artery. The most common cause of carotid dissection is trauma to the neck. This usually results in headache or neck pain, stroke like symptoms, and sometimes a droopy eyelid and small pupil. Carotid dissection is usually treated with medication (such as aspirin) that slows blood clotting, as most of these dissections will heal on their own with time. Other forms of treatment include placement of a carotid stent (a metal-mess sheath) that holds the injured wall of the blood vessel back in place allowing it to heal, direct surgical repair of the carotid artery, or occasionally extracranial-to-intracranial arterial bypass.

Cavernous malformation

Cavernous malformation (CM) (also known as cavernous angioma, cavernous hemangioma, and cavernous vascular malformation) is a type of angiographically occult vascular malformation. Cavernous malformations consist of tiny blood vessels without encompassing brain tissue. Most people who have CM are born with them. There may be a genetic predisposition, particularly in Hispanic families for having this type of vascular malformation. Cavernous malformations can be asymptomatic. Others cause symptoms either from bleeding that results in headaches, strokes, or seizures. Cavernous malformations can occur anywhere in the brain or spinal cord. They are best diagnosed by MRI, where they often have a popcorn type appearance. Treatment involves microsurgical resection using stereotactic computer assisted navigation. The Cerebrovascular Surgery section  is participating in an investigation of genetic risk factors in an effort to identify families at risk for these lesions. Over the past 28 years, the cerebrovascular surgery section has treated more than 500 patients who had cavernous malformations with excellent overall results. We have also developed special expertise in treating deep-seated cavernous malformations, including more than 230 in the brainstem, thalamus, and basal ganglia; recently using a CO2 laser.

Cerebral ischemia

Cerebral ischemia occurs when the brain does not receive enough blood flow to maintain normal neurologic function. Common causes of cerebral ischemia include clots in intracranial arteries (see Stroke above), carotid artery stenosis (see above), basilar artery stenosis (see above), vertebral artery stenosis (see below), and cerebral occlusive disease (see below). Other rare causes of cerebral ischemia include moyamoya disease and Takayasu's arteritis (both discussed below). The symptoms of cerebral ischemia can include deficits in speech, movement, sensation, vision, or understanding, and be temporary (TIA or transient ischemic attack) or permanent (a completed stroke).  The treatment of cerebral ischemia involves correction of the underlying cause of the ischemia, which is discussed in each of the individual disease descriptions.

Fibromuscular dysplasia

Fibromuscular dysplasia is a disease that causes progressive narrowing of the blood vessels in certain regions of the body including those in the neck leading to the brain. This narrowing can result in stroke-like symptoms and carotid dissections (see above). The treatment of fibromuscular dysplasia is generally limited to blood thinning medications such as aspirin or coumadin. Angioplasty (balloon dilation of the narrowed vessels) or stenting are occasionally required. Patients with fibromuscular dysplasia may be prone to develop intracranial aneurysms.

Occlusive cerebrovascular disease

Occlusive cerebrovascular disease describes narrowing of the major blood vessels of the brain. Vessels affected can include the carotid artery (within the brain or neck), the basilar artery (see basilar stenosis) and the vertebral arteries (see vertebral stenosis). Other arteries that can be involved are the middle cerebral artery and the anterior cerebral artery, both branches of the internal carotid artery inside the skull. Symptoms of occlusive cerebral vascular disease are those commonly associated with stroke or TIA, including numbness of the extremities, weakness or paralysis, speech difficulties, or visual loss. Treatment for this disease includes medications initially, and then endovascular treatment or surgery for those patients who continue to have symptoms. Since occlusive cerebrovascular disease causes symptoms by reducing blood flow to specific regions of the brain, a thorough evaluation of the blood flow patterns in the brain is essential to developing a treatment plan for each patient with this disease. This is done with cerebral angiography, MRI, and blood flow studies. 

Sinus thrombosis

Sinus thrombosis is clotting of the dural venous sinuses, major veins in the lining of the brain. They drain blood from the brain back to the heart. Sinus thrombosis occurs when the blood within the vein clots and blocks the vein. Venous sinus thrombosis is more common in females than males, and has been linked to certain blood clotting disorders, oral contraceptives, dehydration, and head trauma. Symptoms may be absent or severe headaches, seizures, and neurologic deficits may occur. The treatment chosen depends upon the particular vein involved. It often includes medications to break up the blood clot and restore flow within the vein. This is sometimes performed during an intracranial angiogram that confirms the diagnosis of venous sinus thrombosis and allows infusion of the clot dissolving medication into the specific vein that is occluded.

Spinal cavernous malformation

Spinal cavernous malformation/spinal CM is similar to a cavernous malformation within the brain (see cavernous malformation above). It carries the same risk of hemorrhage as a brain cavernous malformation. Hemorrhage can result in significant neurologic deficits by injuring the spinal cord. These deficits include weakness or numbness in the arms or legs, difficulty walking, and loss of bladder or bowel control. The diagnosis of a spinal cavernous malformation is made with an MRI scan. Occasionally a spinal angiogram is performed to exclude the possibility of a spinal cord AVM (see above). Once diagnosed, symptomatic spinal cavernous malformations are usually treated to prevent the risk of further hemorrhage and neurologic injury. Treatment primarily consists of surgical resection using a microscope and electrophysiologic monitoring.


Vasculitis is the inflammation of blood vessels within the brain. The main causes of vasculitis are infection, such as meningitis, or autoimmune diseases such as lupus. When blood vessels are inflamed, they can narrow and even occlude. This produces symptoms of stroke, including speech difficulty and weakness or numbness of the extremities. The diagnosis of vasculitis is made on the basis of several tests, including blood tests, MRIs, biopsies, and cerebral angiograms. The treatment of vasculitis is directed to the cause. In the case of infection, antibiotics are administered, and in the case of autoimmune inflammation, steroid medication and immunosuppressants are useful. Surgical biopsy is performed only when necessary.

Vertebral artery stenosis

Vertebral artery stenosis is narrowing of the vertebral arteries, which are paired major arteries at the base of the brain. They join to form the basilar artery as it supplies blood to the deep center of the brain and the brainstem (the structure which connects the brain to the spinal cord). Stenosis often reduces the blood flow to the brainstem resulting in a stroke. Common symptoms of vertebral or basilar artery stenosis include dizziness, double vision, difficulty with speaking or swallowing, or weakness and numbness in the arms or legs. Less common, but more serious symptoms, include complete paralysis or coma. The narrowing within the vertebral artery is usually due to atherosclerosis, the build up of fatty deposits within the walls of the artery. The current treatment of vertebral artery stenosis usually starts with medication that thin the blood. If symptoms persist despite medication treatment involves angioplasty (inflating a balloon within the region of stenosis) or stenting (with a thin metal-mesh) to dilate the narrow segment. Both angioplasty and stent placement are performed in the angiography suite during a cerebral angiogram. Rarely is surgery indicated in these patients.