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Surgery is typically performed both to diagnose and treat low-grade glioma when the tumor can be reached without causing severe injury to normal tissue. Removing the tumor, either in part or completely, can lessen some of the pressure within the skull. Surgery can also help to relieve symptoms, enhance neurologic function, and improve your quality of life.

However, because low-grade gliomas often occur in areas of the brain controlling vital activities such as speech and movement, surgery to remove these brain tumors requires an advanced approach and expertise.

Studies suggest that, on average, greater surgical experience leads to better patient outcomes. At Memorial Sloan Kettering, neurosurgeons operate on more than 600 patients with brain tumors each year, using the most sophisticated diagnostic and treatment methods available.

Our neurosurgeons are experienced in removing as much of the tumor as possible, while preserving the highest possible quality of life. They are able to do this by using advanced imaging technologies both before and during an operation. Being able to see the brain in such fine detail has enabled doctors to improve the precision with which they operate, making surgery safer and more effective.

Although not all technologies are used in treating each person, doctors at the Brain Tumor Center now routinely use the following approaches during brain surgery.

Functional MRI Brain Mapping for Planning Surgery

To plan brain surgery, our surgeons use an imaging test called a functional MRI, or fMRI, performed in the days before the procedure. This is a specialized MRI that can create a functional “map” of your brain. During the MRI, you are asked to perform simple tasks such as moving your hands and feet, counting in your head, or thinking of words that begin with a particular letter.

These tests result in a scan that can show which areas of your brain are important to everyday functions such as vision, speech, touch, and movement. From this scan, your surgeon can determine whether the tumor involves these functional areas of the brain, and figure out how much of the tumor can be safely removed during the surgery.

Surgical Navigation during the Procedure

Our surgeons use a very precise technique called frameless stereotaxy – sometimes referred to as surgical navigation — to plan operations and guide the team during surgery.

Technicians begin by attaching six plastic self-adhesive dots around the scalp. At the start of surgery, they register the exact location of these dots via MRI, and then relay the position of the patient’s head to the computer system.

The team directs a wand-like viewing device at the brain, which projects an image onto a monitor in the operating room. The image is synchronized with the MRI scan, giving your neurosurgeon up-to-the-second information about the positioning of your brain and the tumor during the procedure.

The neurosurgeon can also use the viewing wand to help see through the tumor to the outermost edges of the tissue to be removed, known as the tumor’s margins. This helps the surgeon to remove the entire tumor whenever possible.

By using this surgical navigation, our surgeons can more accurately remove the tumor, are more likely to be able to perform the procedure using a smaller incision, and can often finish the surgery in a shorter amount of time.

MRI during Surgery

Memorial Sloan Kettering’s neurosurgeons perform brain surgery in an operating room equipped with an MRI scanner. At any point during the procedure, the neurosurgeon can perform an MRI to determine whether your tumor has been removed completely. If the surgeon finds any remaining tumor tissue, surgery can be resumed immediately to remove it.

The power to reevaluate your tumor with MRI during surgery enables neurosurgeons to operate with remarkable precision, and to detect and address any complications immediately during the procedure.

Awake Surgery for Low-Grade Gliomas

In some cases, the tumor is so close to a delicate area that the surgeon performs mapping of the brain during the operation, which may require you to be awake during part of the procedure. Also called awake craniotomy, the procedure involves local anesthesia and intravenous medications that result in sedation but not loss of consciousness.

Electrodes are used to stimulate the brain surface and identify with great precision the areas of the brain that are involved in specific tasks and therefore need to be preserved. During parts of the procedure, you are awakened and asked to speak or to demonstrate certain movements to help guide removal of the tumor, ensuring that areas of the brain critical to speech or movement remain intact.


Neuroendoscopy is a type of minimally invasive surgery for the removal of some low-grade glioma tumors, depending on their location. Using this technique, only a small opening is made in the skull. The surgeon performs the operation using a thin tube with a powerful lens, a high-resolution video camera, and tiny surgical instruments on its tip.

This minimally invasive procedure enables doctors to use a smaller incision than in conventional surgery, enhances their ability to perform microsurgical procedures, and usually results in less injury to healthy tissue.