Surgical Management of Patients with Brain Tumor
By Brian Andrews, M.D., FACS, Chair, California Pacific Medical Center Neuroscience Institute
The majority of primary and metastatic tumors of the brain and its coverings require consideration of surgical treatment. When a diagnosis is unclear, tissue biopsy is invaluable. Surgical removal, or debulking, are useful for treatment purposes, often combined with subsequent radiation therapy. The major types of tumors we treat include primary parenchymal brain tumors (usually grades II-IV gliomas), meningiomas, pituitary adenomas, and metastatic tumors. Among the most common metastatic tumors for us to treat surgically are those related to breast and lung cancer and melanomas.
The surgical techniques we employ are image-guided, with contrast-enhanced preoperative magnetic resonance imaging on our 3-Tesla magnet used for planning purposes (Figures 1 & 1A). Often, these images are fused with the BrainLab intraoperative guidance system, which allows us to monitor our exact location inside the head as we access and remove the tumor. This is particularly useful when the tumor is in a deep location within the brain or difficult-to-access site at the base of the skull. The operating microscope is routinely used to illuminate and magnify the access corridor and tumor bed, and often an ultrasonic aspirator (CUSA) provides for safe removal of tougher or calcified tumors. Often, if we are working in an area of particularly eloquent brain, such as the motor cortex, or among the cranial nerves at the base of the skull, intraoperative electrophysiological monitoring is employed, to allow us to readily identify the exact location of motor cortex, or the cranial nerves as they relate to the tumor. In the case of tumors within or near the language centers, the surgery will be performed awake, with our neuropsychologist performing speech assessment during the course of the procedure. Prior to surgery in such cases, a WADA test may be performed, to confirm dominance of the hemispheres for speech and memory.
The usual technique for surgical access is to perform a craniotomy, windowing the skull at an exact location and specific size for optimal tumor removal. In some cases, the skull itself is involved in the tumor. Figure 2 shows a large, transcranial meningioma where the tumor was removed from the exterior and interior of the skull, and then replaced at the end of the surgery (to later be irradiated to complete treatment). The brain is relaxed and retracted away from the access corridor, using self-retaining retractors to gently protect it from injury as the tumor is removed.
In the case of pituitary surgery, a transnasal transsphenoidal approach is used to provide access to the sella turcica, where the tumor is (Figure 2A). The long, deep, and narrow surgical access corridor requires use of an entire set of specific instruments to remove the tumor. In recent years, use of endoscopy has allowed the surgeon to see around corners to optimize tumor removal.
In the case of primary brain gliomas, as much of the tumor as can be removed safely is the goal. This enhances potential survival in most cases, but it is extremely important not to harm function, particularly speech and sensorimotor function. Some gliomas are unresectable due to their depth and location, and only a biopsy can be achieved. In every case, biopsy samples of tissue are sent for pathological analysis, to determine tumor grade, or malignancy. Samples also are sent to California Pacific Medical Center Research Institute, where they are assessed for the presence of cytomegalovirus, a potential cancer-causing virus.
In the case of meningiomas, maximal tumor removal is again the goal, but today, radiation therapy techniques are so effective for residual tumors that the surgeon usually can limit tumor removal to what is optimally safe. For pituitary tumors, and metastatic tumors, maximal tumor removal is optimal, but again is often followed by subsequent radiation therapy for suspected microscopic disease.
Similar to the intraoperative BrainLAB system, image-guidance is used by our radiation oncologists, using another Brainlab system, to provide exacting radiation therapy to the site of residual tumor or microscopic disease. In this way, our treatment of brain tumors is a continuous spectrum often of surgery followed by planned radiation therapy.
Magnetic resonance image showing a large transcranial meningioma extending from the subdural space to the scalp that presents as an expanding scalp mass.