Moffitt Onco Update

Surgical Navigation Between Brain Tumors: A Balancing Act

November 15, 2015

Surgical Navigation Between Brain Tumors.jpg White matter tractography for neurosurgical planning is a 3D modeling technique used to visually represent neural tracts

The brain’s natural defense mechanism, the blood-brain barrier (BBB), normally prevents entry of harmful substances, but also hinders penetration of beneficial medications into the brain. Whereas, invasive treatment options could potentially damage normal surrounding brain tissue, thus impacting quality of life. Fortunately, technological advances in neurosurgery have paralleled the shift towards more aggressive surgical treatment of primary brain tumors and brain metastasis. Using tractography and other innovative technologies, we can safely remove tumors that are located next to movement, speech and vision pathways with very good outcomes. 

Figures: MRI-guided stereotactic images for tumor resection. The tumor (orange object) is located in the movement area. The movement fibers are appreciated (blue). Knowing the relationship of fibers to the tumor, as well as performing the surgery while patients are awake is essential for safe maximum resection of tumor.
Figures: MRI-guided stereotactic images for tumor resection. The tumor (orange object) is located in the movement area. The movement fibers are appreciated (blue). Knowing the relationship of fibers to the tumor, as well as performing the surgery while patients are awake is essential for safe maximum resection of tumor.

Brain tumors can either destroy or displace critical white matter pathways that control important functions such as movement, speech or vision. Prior to removing brain tumors, it is very important for the neurosurgeon to have an idea of the location of critical white matter fibers with respect to the tumor. Such information enables the surgeon to select a surgical path to the tumor that minimizes damage and therefore improves outcomes for patients.

Advanced Techniques for Brain Tumor Resection

Image-guided stereotactic navigation is a technology that has revolutionized minimally invasive brain surgery. By optically matching the patient’s anatomic features (e.g., facial features) with a pre-operative high-resolution MRI, we can pinpoint within millimeter accuracy the location of the patient’s tumor. More precise, smaller surgical openings translate into less disruption of surrounding brain tissue, less pain and lower risk of infections. 

More recent innovations include functional MRI, which non-invasively localizes eloquent brain centers (e.g., language and motor centers). Through this advanced MRI-guided neurosurgery, Moffitt Cancer Center employs 3-D representations of both tumor and critical white matter pathways (see Figures) that enable the neurosurgeons to navigate in real-time during surgery, thereby staying cognizant of the relationship between tumor and white matter pathways.

Diffusion tensor imaging (DTI) is a highly specialized MRI technique that maps nerve fiber tracts necessary for different functions, including movement and vision. DTI can help determine how nearby nerve fiber tracts are being displaced by the tumor. We are then able to plan surgical trajectories that avoid critical brain structures and pathways. These technologies are usually only available at tertiary care centers with access to high strength magnet MRIs like Moffitt Cancer Center. 

Another critical adjunct includes intraoperative neuro-monitoring. By placing electrodes on the brain surface, or within the deep white matter tracts, we can stimulate and determine in real-time the proximity of important brain structures.

Taken together, these advances have brought once unresectable tumors into the realms of maximally safe resection. Neurosurgeons at Moffitt perform a substantial number of surgeries in eloquent and non-eloquent regions of the brain with image-guided stereotactic techniques like functional MRI and DTI tractography neuro-navigation.