Surgery for Brain Tumors

Overview

Surgery is the primary treatment for brain tumors that can be removed without causing severe damage. Many benign (non-cancerous) tumors are treated only by surgery. Most malignant (cancerous) tumors, however, require treatment in addition to the surgery, such as radiation therapy and/or chemotherapy.

The goals of surgical treatment for brain tumors are multiple and may include one or more of the following:

• Confirm diagnosis by obtaining tissue that is examined under a microscope.
• Remove all or as much of the tumor as possible.
• Reduce symptoms and improve quality of life by relieving intracranial pressure caused by the cancer.
• Provide access for implantation of internal chemotherapy or radiation.
• Provide access for delivering intra-surgical treatments, including hypertherapy or laser surgery.

The following is a general overview of surgical treatment for brain tumors. There are different types of surgeries and techniques available, particularly in institutions that conduct many similar procedures. Circumstances unique to each patient’s situation may influence which approach is applied. The potential benefits of specific procedures must be carefully balanced with potential risks. The information on this web site is intended to help educate patients about their treatment options and to facilitate a mutual or shared decision-making process with their cancer physician.

• Choosing a Surgeon and/or Institution
• Types of Surgery for Brain Tumors
• Imaging and Monitoring Techniques
• Surgical Techniques
• Strategies to Improve Treatment

Choosing a Surgeon and/or Institution: Experience and Volume are Important

Surgical procedures for the treatment of brain tumors can be complicated and may involve significant risk. Research indicates that patients who require complex surgical procedures have better outcomes (fewer surgery-related deaths and complications) if they are treated in high-volume institutions (hospitals that perform a high number of such procedures). 1,2,3,4,5It is thought that the more favorable outcomes at high-volume institutions are due to more skilled surgeons as well as a more skilled and dedicated team.

These findings highlight the importance of choosing an experienced surgeon. Outcomes may vary between large and small institutions. However, researchers agree that it is important to select a surgeon with a great deal of experience conducting the specific procedure in question. Often these doctors work at large, specialized institutions.

Types of Surgery for Brain Tumors

Biopsy: A biopsy is a surgical procedure to remove a small piece of tumor in order to confirm the diagnosis. The sample is examined under the microscope by a pathologist who determines the type of the tumor. A biopsy can be performed as part of the surgery to remove the tumor or as a separate procedure.

There are two different approaches for performing a biopsy for brain tumors. An open biopsy involves exposing the tumor and then removing a small portion of it. A needle biopsy is performed by making an incision in the skin, drilling a small hole into the skull, inserting a narrow, hollow needle through the hole and into the tumor, and drawing up a small amount of tumor into the needle.

A needle biopsy may also be conducted with the assistance of computers and scanning equipment, including MRI or CT, in order to increase the precision of the procedure. This procedure is called stereotactic needle biopsy and is useful for patients with deep or multiple tumors. Stereotactic techniques are discussed further in the Surgical Techniques section.

Craniotomy: The most commonly performed surgery for removal of a brain tumor is called a craniotomy. “Crani” means skull, “otomy” means cutting into. In preparation for a craniotomy, a portion of the scalp is usually shaved, and an incision is made through the skin. Using specialized equipment, a surgeon removes a piece of bone to expose the area of brain over the tumor. The dura mater (the outermost layer of the brain tissue) is opened, the tumor is located and then removed (resected). After the tumor is removed, the bone is usually replaced and the scalp stitched shut.

In a conventional craniotomy, surgeons guide themselves by what they see, their knowledge of anatomy, and their interpretation of the pre-operative scans. During stereotactic surgery, surgeons may rely on a computer to help direct the craniotomy. This approach is discussed further in the Surgical Techniques section below.

Shunt: Some patients with brain tumors develop increased intracranial pressure. To relieve the pressure, a procedure is conducted to drain excess or blocked fluid. A shunt is a narrow piece of flexible tubing (called a catheter) that is inserted into a ventricle in the brain. The other end of the tubing is threaded under the scalp toward the neck, then, still under the skin, threaded to another body cavity where the fluid is drained and absorbed. The body cavities used for drainage are the right atrium of the heart and, more commonly, the abdominal cavity. Compared to other surgical treatments for brain tumors, the procedure to implant a shunt is relatively minor. A small hole is drilled in the skull through which the catheter is threaded into a ventricle. A small incision is made in the abdomen or the chest, depending on which cavity is used for drainage. The other end of the catheter is threaded under the skin to the cavity and then fastened. Some shunts can be temporary and are removed after treatment is completed. Other shunts are left in place after surgery. Following shunt insertion, many patients, particularly children, show dramatic improvement within days. In others, symptoms of intracranial pressure, such as headaches, might remain for a period of several weeks.

Imaging and Monitoring Techniques (Brain Mapping)

Doctors use a variety of techniques to determine what a brain tumor looks like both before and during surgery. Specialized images can be generated that shows what functions the brain tissue near the cancer is responsible for. Generating images both before and during surgery can increase the likelihood that extensive tumor removal can be achieved while avoiding these critical areas.

Before surgery, the location of the brain tumor in relation to other structures and blood vessels must be determined as precisely as possible. To achieve this, a variety of tests are performed. These may include:

• Computerized tomography (CT),
• Magnetic resonance imaging (MRI),
• Positron emission tomography (PET), and
• Angiography (to map blood vessels).

Using the information obtained from these tests, the surgeon can plan and even rehearse the operation in order to obtain optimal results. Evaluation of outcomes in elderly patients who had undergone surgery for brain tumors indicates that those who underwent preoperative MRI experienced better outcomes than those patients who were not evaluated with MRI before surgery.6

The scans taken before surgery yield a great deal of information, but they don’t always provide the precision needed to avoid critical areas of the brain during the operation. Sophisticated mapping techniques can improve the safety and effectiveness of surgery by locating the exact areas of the brain responsible for speech, comprehension, sensation, or movement. Brain mapping is also used to help identify the margin of the tumor and to differentiate between tumor, swelling (edema), and normal tissue.

Techniques for brain mapping include:

• Direct cortical stimulation,
• Evoked potentials,
• Functional MRI,
• Intraoperative ultrasound imaging, and
• Microsurgery.

Direct cortical stimulation: In direct cortical stimulation, a probe passes a tiny electrical current into the brain and delicately stimulates a specific area. The result is a response from the body, such as a visible movement of the corresponding body part. This technique may be employed during surgery to help identify important functional areas. For example, direct cortical stimulation has been used during surgery for gliomas to successfully identify and preserve cortical areas responsible for language and minimize damage to motor function.

In a group of 30 patients who underwent direct cortical stimulation, surgeons were able to effectively identify and preserve language centers. Additionally, the brain tumor was completely removed in 14 of the patients.7 Of 294 patients with gliomas near motor centers of the brain, 60 patients (20%) experienced deficits in motor ability after surgery and cortical stimulation. Of these 60 patients, 76.7% regained their baseline function within the first 90 days after surgery.8

Evoked potentials: The electrical response of the brain can be measured by stimulating the brain and measuring the resulting activity, or evoked potentials, on brain scanning equipment. Evoked potentials may be used to map and continuously monitor areas of the brain during surgery.

Research indicates that the use of evoked potentials can help doctors identify potential damage to motor function in time for repairs to be made. Researchers evaluated the use of motor evoked potentials (MEPs) in 51 patients who underwent surgery for gliomas. Using corrective measures, all intraoperative changes in MEPs were reversed in time to prevent an irreversible, complete injury to the motor system. None of the patients involved in this clinical trial lost motor function at the end of the operation.9

Researchers have also reported that evoked potentials are useful for accurately identifying the part of the brain that controls sensation in the lower lip, which can be damaged during surgery to remove tumors in patient with gliomas in that region of the brain.10

Functional MRI: MRI is a high-speed imaging device that generates images of the tumor’s use of oxygen. This helps distinguish between active, normal brain, and non-active tumor or dead tissue (necrosis). Functional MRI can be an alternative to direct cortical stimulation. Research indicates that motor and sensory areas identified with functional MRI are very similar to locations identified with direct cortical stimulation.11 This technique is reliable but requires sophisticated and expensive equipment.

Intraoperative ultrasound imaging: The use of ultrasound during surgery can help determine the depth of the tumor and its diameter. Ultrasound works by sending ultrasonic wave pulses into the brain, which then reflect back to a device. A computer measures the amount of time it takes for the “echoes” to return, and the results are displayed as a TV image. Surgeons can monitor their movements to verify positioning and results during surgery. The waves can also reflect motion such as blood flow. Ultrasound can make it easier for the surgeon to locate the margins of the tumor so that more extensive tumor removal can be achieved. It helps distinguish between tumor, necrosis (dead tumor cells), cysts, edema, and normal brain. Because ultrasound does not readily penetrate bone, it cannot be used preoperatively.

Researchers from Germany who have used intraoperative ultrasound imaging routinely since 1987 have reported that it is a reliable method for determining the size, shape, and location of lesions, and can differentiate between solid tumor, cyst, and necrosis (dead tissue).12

Microsurgery: Microsurgery involves the use of a high-powered microscope during surgery, which allows the surgeon to obtain a magnified view of the surgical field. Microsurgery is widely used for brain tumor surgery.

Surgical Techniques

Many different surgical techniques are utilized in the treatment of brain tumors, particularly in large medical centers that treat a significant number of patients. The technique utilized for a particular patient depends on the type of tumor and its location as well as the preference of the surgeon. The surgical techniques most commonly employed in the treatment of brain tumors include:

• Stereotactic surgery,
• Embolization,
• Endoscopy,
• Laser surgery,
• Photodynamic laser surgery, and
• Ultrasonic aspiration.

Stereotactic surgery: The use of computers to create a three-dimensional image is called stereotaxy. The purpose of this technique is to provide precise information about the location of a tumor and its position relative to the many structures in the brain. Stereotaxy can be used by the surgeon to map out the surgical procedure beforehand so that the neurosurgeon can “rehearse” the procedure or to allow the radiation specialist to plan radiation therapy.

While conventional X-ray pictures depict tumors in two dimensions, stereotaxy provides the third dimension—depth—by obtaining readings in both left to right and front to rear directions, and then using a computer to analyze the information. It is the third dimension that allows the surgeon to accurately insert the needle for biopsy, the laser beam for vaporization, the scalpel for cutting, or the suction device for aspiration.

Stereotactic surgical techniques are used to perform biopsies, remove tumors, implant radiation pellets or other local treatments, or to provide a navigational system during surgery (frameless stereotaxy). These techniques are particularly useful for reaching a tumor located deep within the brain, such as the brain stem or thalamus. Stereotaxy can also help limit the extent of surgery. Some stereotactic systems can project images of the surgery as it is being performed (“real-time” imaging). Stereotaxy is performed either with or without a head frame.

• Steriotaxy with a head frame involves placing the patient’s head in a rigid frame so the attached scanning devices can accurately pinpoint the tumor location in three-dimensional space. The rigid frame holds the patient’s head in place during the pre-surgical scans and the surgery itself. The information from the CT and/or MRI scans, along with coordinate information from the headframe, is entered into a computer system. The images produced, with their relational coordinates, are used to plan the surgery and guide the surgeon’s tools during the procedure.
• Frameless steriotaxy utilizes an imaging hand-held device rather than CT or MRI. With this approach, the head must be stabilized in a frame. The surgeon touches structures in the patient’s brain with an imaging “wand” that superimposes that location in the brain on a computer monitor showing a recent scan or three-dimensional image of the brain. This tool is used to orient the surgeon as to the exact location of the tumor as compared to a specific point on the exterior of the brain. The wand provides quick and continuous “real-time” information about its location during surgery. This tool is particularly useful during skull base surgery, which is an especially complicated area. It is also of value when multiple tumors are to be removed. The viewing wand can shorten the surgical time by quickly identifying parts of the brain and localizing the tumor.

Researchers anticipate that, in the not too distant future, a significant portion of neurosurgical procedures, as well as many general surgical procedures will involve stereotaxy.13

Embolization: Embolization is used to reduce the amount of blood supply to a tumor by blocking the flow of blood in selected arteries. This procedure is conducted prior to surgery. Results from an arteriography, which is an X-ray taken after radiolabeled dye has been injected into the circulatory system, help determine whether embolization is necessary and which blood vessel or vessels may need to be blocked. Surgery follows as soon as possible to avoid re-growth of blood vessels. This technique might be used with vascular tumors such as meningiomas, meningeal hemangiopericytomas, and glomus jugulare tumors.

Endoscopy: Endoscopes are long, narrow, flexible lighted tubes that are inserted into the surgical area. They provide the surgeon with light and visual access. Preoperative scans help determine the location of tumors and enable the surgeon to plan surgery using relatively small openings. These small openings (sometimes called keyhole approaches) make it difficult for the surgeon to see. The endoscope helps solve that problem. The neuro-endoscope is particularly useful for surgery that involves correcting a malfunctioning shunt, removing scar tissue blocking a shunt, or removing intra-ventricular tumors. It can also be useful for removing brain cysts.

Laser surgery: Using a laser during brain surgery is a relatively routine practice. The aim of laser surgery is to direct the laser beams at the cancer and destroy it with heat. Because the light beams cannot penetrate bone, the laser can be used only during surgery. Lasers are used in addition to, or in place of, a scalpel. Lasers are capable of immense heat and power when focused at close range. Lasers destroy tumor cells by vaporizing them. Stereotactic, or computer-assisted techniques, are frequently used to direct the laser. Lasers are chiefly used in the treatment of tumors that have invaded the skull base or are deep within the brain, with hard tumors that cannot be removed by suction, or with tumors that break apart easily.

Photodynamic laser surgery: A laser is also used in photodynamic therapy. Photodynamic therapy combines a drug that increases a tissue’s sensitivity to light and laser surgery. Prior to surgery, the photosensitizing drug is injected into a vein or artery. It travels through the blood system to the tumor, accumulating in the cells of the tumor. The patient is then taken to surgery for removal of the tumor. During the operation, the treated tumor cells appear fluorescent. The physician aims a laser at the tumor cells, activating the drug. The activated drug then kills the tumor cells. Only operable tumors can be treated with this procedure. Tumor cells not seen by the surgeon or not sensitive to the drug are not affected by this treatment. This is a local form of therapy because some parts of the tumor might not be exposed to the light. Because of the danger of swelling, tumors near the brain stem cannot be treated with this technique.

Ultrasonic aspiration: Ultrasonic aspiration uses ultrasonic sound waves to fragment and break the tumor into small pieces, which are then aspirated, or suctioned out. This technique causes fewer disturbances to adjacent tissue than other types of suction devices because it causes less heat and destruction of normal tissue. This is particularly helpful with tumors that would be difficult to remove with cautery and suction because of their firmness and location. As with the laser, the use of ultrasound has permitted the removal of tumors that would otherwise have been inoperable.

Strategies to Improve Treatment

The development of more effective cancer treatments requires that new and innovative therapies be evaluated with cancer patients. Clinical trials are studies that evaluate the effectiveness of new approaches. Future progress in the surgical treatment of brain tumors will result from the continued evaluation of new treatments in clinical trials. Participation in a clinical trial may offer patients access to better treatments and advance the existing knowledge about treatment of this cancer. Patients who are interested in participating in a clinical trial should discuss the risks and benefits of clinical trials with their physician. Areas of active investigation aimed at improving the surgical treatment of brain tumors include the following:

Fluorescent-guided surgery: The use of a compound that collects in glioblastoma cells and emits fluorescent light may make it easier for surgeons to detect and remove cancer cells during surgery. The compound—called 5-aminolevulinic acid (5-ALA) is administered orally and is converted by normal metabolic processes in the body to a substance that has been shown to accumulate in glioblastoma cells. Physicians have determined that using this technique may enable them to detect glioblastoma cells that cannot be detected through standard methods.

Physicians in Germany have reported that fluorescence-guided surgery using 5-ALA improves the chance that a cancer can be completely removed with surgery and improves progression-free survival in the treatment of patients with malignant glioma (see table). This trial included 322 patients with newly diagnosed malignant gliomas who were eligible for surgery. Approximately half of the patients underwent fluorescence-guided surgery with 5-ALA, while the other half underwent standard surgery. Patients undergoing fluorescence-guided surgery had significantly improved outcomes.

Table 1 More cancer is removed with fluorescent-guided surgery

	Fluorescent-guided surgery	Standard surgery
Complete removal of cancer	65%	36%
Progression-free survival	41%	21%

 
Older patients experienced improved survival (14.1 months) when treated with fluorescence-guided surgery compared to those treated with standard surgery (11.5 months); however, patients younger than 55 years did not have a survival benefit. 14

References

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