Arteriovenous malformations (AVMs). These are defects of the circulatory system that are generally believed to arise during embryonic or fetal development or soon after birth. AVMs damage the brain or spinal cord through three basic mechanisms: by reducing the amount of oxygen reaching neurological tissues; by causing bleeding (hemorrhage) into surrounding tissues; and by compressing or displacing parts of the brain or spinal cord. The greatest potential danger posed by AVMs is hemorrhage. Researchers believe that each year 2%–4% of all AVMs hemorrhage. However, even in the absence of bleeding or significant oxygen depletion, large AVMs can damage the brain or spinal cord simply by their presence.
Neurosurgeons now use a variety of traditional and new imaging technologies to uncover the presence of AVMs. These include angiography, computed axial tomography (CT) and magnetic resonance imaging (MRI) scans. Today, three surgical options exist for the treatment of AVMs: conventional surgery, endovascular embolization, and radiosurgery. The choice of treatment depends largely on the size and location of the anomaly. Surgery is most appropriate when an AVM is located in a superficial portion of the brain or spinal cord and is relatively small in size. Endovascular embolization and radiosurgery are less invasive than conventional surgery and offer safer treatment options for some AVMs located deep inside the brain.
A cerebral aneurysm is the dilation, bulging, or ballooning out of part of the wall of a vein or artery in the brain. Cerebral aneurysms can occur at any age, although they are more common in adults than in children and are slightly more common in women than in men. Signs and symptoms of an unruptured cerebral aneurysm will partly depend on its size and rate of growth. A larger aneurysm that is steadily growing may produce symptoms such as loss of feeling in the face or problems with the eyes. Immediately before an aneurysm ruptures, an individual may experience such symptoms as a sudden and unusually severe headache (the ‘worst’ headache ever), nausea, vision impairment, vomiting, and loss of consciousness.
Emergency treatment for individuals with a ruptured cerebral aneurysm generally includes restoring deteriorating respiration and reducing intracranial pressure. Microvascular clipping is usually performed within the first 3 days to clip the ruptured aneurysm and to reduce the risk of rebleeding. Clipping has been shown to be highly effective, depending on the location, shape, and size of the aneurysm. In general, aneurysms that are completely clipped surgically do not return. When aneurysms are discovered before rupture occurs, microcoil thrombosis or balloon embolization may be performed on patients for whom surgery is considered too risky. These procedures may have to be repeated throughout the patient’s lifetime.
A related procedure is an occlusion, in which the surgeon clamps off (occludes) the entire artery that leads to the aneurysm. This procedure is often performed when an artery is damaged by a condition (for example, an aneurysm). An occlusion is sometimes accompanied by a bypass in order to reroute the flow of blood away from the section of damaged artery.
The prognosis for a patient with a ruptured cerebral aneurysm depends on the extent and location of the aneurysm, the person's age, general health, and neurological condition. Therefore, early diagnosis and treatment are important.
Non-skull base. Tumors of this type include gliomas and metastatic tumors.
Glioma is a generalized term for any tumor that develops from the glia, the supportive structure that help keep the neurons of the brain in place. There are three types of glial cells: astrocytes (including gliobastomas), oligodendrocytes, and ependyomas. Names that refer to such tumors such as brain cell glioma are derived from the location of the tumor itself, not the type of tissue cell that gave rise to them. A specific diagnosis is only possible if a biopsy of the tumor is obtained.
Metastatic brain tumors are secondary tumors formed from cancer cells that migrate to the brain from a primary cancer found elsewhere in the body. Cancers that frequently do this are lung cancer, breast cancer, melanoma (a form of skin cancer), kidney cancer and colon cancer.
Skull base tumors include acoustic neuromas and meningiomas.
An acoustic neuoma is a benign tumor of the 8th cranial nerve (hearing nerve). In most cases these are slow growing tumors. These typically occur in middle-aged adults, and affect women twice as often as men. Acoustic neuomas are relatively rare and account for 7.5% of all brain tumors
Meningiomas arise from the arachnoid matter, one of the layers of the meninges that line the brain. These tumors account for about 27% of all primary brain tumors, and are seen most frequently in middle-aged women. The majority of meningiomas are benign, slow-growing tumors that are localized and noninfiltrating.
A good primer on brain tumors can be found at the web site of the American Brain Tumor Association (www.abta.org).
As a leading cause of death and disability in patients across the world, stroke is a problem that plagues both neurosurgeons and neurologists alike. Stroke affects more than 750,000 persons in the United States each year. A stroke is caused by blockage of blood flow to the brain, or by bleeding into the brain itself. The most common type of stroke is due to a blockage, which may be the result of a clot forming in the brain, or one that has traveled from another part of the body, such as the neck or the heart. There are a number of risk factors that can lead to stroke, including hypertension, smoking, elevated levels of cholesterol, diabetes, homocysteine, heart disease, and carotid artery disease.
There are two prominent types of surgery for stroke prevention and treatment: carotid endarterectomy and extracranial/intracranial (EC/IC) bypass.
Carotid endarterectomy is a surgical procedure in which a doctor removes fatty deposits (plaque) from the inside of one of the carotid arteries, which are located in the neck and are the main suppliers of blood to the brain. A newer surgical procedure for carotid stenosis, called stenting, involves inserting a long, thin catheter tube into an artery in the leg and threading the catheter through the vascular system into the narrow stenosis of the carotid artery in the neck. Once the catheter is in place in the carotid artery, the radiologist expands the stent with a balloon on the tip of the catheter.
Extracranial-to-intracranial (EC/IC) bypass surgery is generally not recommended for patients with transient ischemic attacks. However, research is ongoing to determine whether there may be a subgroup of patients who might benefit from this treatment.
Cerebral bypass. A cerebral bypass is similar to a heart bypass. It involves rerouting blood flow around a blocked or damaged blood vessel so that the region of brain affected can continue to get blood supply.
f the bypass is from outside of the head to inside of the head, it is referred to as an extracranial-to-intracranial (EC/IC) bypass. This can be a helpful procedure in select patients with appropriate clinical circumstances. Brain bypass operations are carried out by a relatively few neurosurgeons with experience in this area of neurovascular surgery. There are two types. The first type is called a superficial temporal artery to middle cerebral artery bypass or STA-MCA. The superficial temporal artery (STA) normally provides blood to the face and scalp and can safely be surgically disconnected from the scalp and attached to the affected brain vessels. This operation is performed to decrease the risk of stroke in a small subset of patients. The second type of bypass utilizes a transplanted vessel from the leg (saphenous vein bypass graft or SVBG) or arm (radial artery bypass graft or RABG) to connect an artery in the neck to a large brain vessel. These types of bypasses provide more flow than STA-MCA. SABG or RABG are utilized primarily when a large vessel of the brain needs to be removed in order to cure an untreatable aneurysm, or a skull base tumor that involves a major brain vessel.
Hydrocephalus is a condition in which the primary characteristic is excessive accumulation of cerebrospinal fluid fluid (CSF) in the brain. The excessive accumulation of CSF results in an abnormal dilation of the spaces in the brain called ventricles, which potentially can result in harmful pressure on the tissues of the brain. Hydrocephalus may be congenital or acquired. Congenital hydrocephalus is present at birth and may be caused by genetic abnormalities or developmental disorders such as spina bifida and encephalocele. Acquired hydrocephalus develops at the time of birth or at some point afterward (after a brain injury) and can affect individuals of all ages. Normal pressure hydrocephalus occurs most often among the elderly. It may result from either a subarachnoid hemorrhage, head trauma, infection, tumor, or complications of surgery, although many people develop this condition without an understandable cause.
Symptoms of hydrocephalus vary with age, disease progression, and individual differences in tolerance to CSF. In infancy, the most obvious indication of hydrocephalus is often the rapid increase in head circumstance or an unusually large head size. In older children and adults, symptoms may include headache followed by vomiting, nausea, papilledema (swelling of the optic disk, which is part of the optic nerve), downward deviation of the eyes (called "sunsetting"), problems with balance, poor coordination, gait disturbance, urinary incontinence, slowing or loss of development (in children), lethargy, drowsiness, irritability, or other changes in personality or cognition, including memory loss.
Hydrocephalus is diagnosed through clinical neurological evaluation and by using cranial imaging techniques such as ultrasound, computer tomography (CT), magnetic resonance imaging (MRI), or pressure-monitoring techniques.
Hydrocephalus is most often treated with the surgical placement of a shunt system, which diverts the flow of CSF from a site within the central nervous system to another area of the body where it can be absorbed as part of the circulatory process. A limited number of patients can be treated with an alternative procedure called third ventriculostomy. In this procedure, a small hole is made in the floor of the third ventricle, allowing the CSF to bypass the obstruction and flow toward the site of resorption around the surface of the brain.