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Neurosciencesupdate MAYO CLINIC NEUROSCIENCE UPDATE 3 volume 1 NEUROSCIENCES UPDATE number 2 2004 NEUROLOGIC SURGERY AND CLINICAL NEUROLOGY NEWS FROM MAYO CLINIC ROCHESTER Treatment Options for Vestibular Schwannoma Acoustic neuromas, The selection of treatment is highly more appropriately individualized—and sometimes subject to called vestibular controversy. The first option is simply to schwannomas, are observe and note the patient's progress with a benign tumors follow-up MRI and a hearing test in 6 months. that arise from This is particularly true for patients older than overproduction of 65 years who have small tumors. perineural Schwann For patients younger than 65 years who have cells. They account small tumors and good hearing, there are 2 main for 6% to 8% of all options. First is stereotactic radiosurgery, a primary intracranial 1-day, outpatient, focused radiation treatment. Colin L. W. Driscoll, MD, and tumors. Within the This treatment does not destroy or remove the Michael J. Link, MD cerebellopontine tumor. Rather, it stops or slows its growth. At angle they represent 80% of tumors. The incidence Mayo Clinic, more than 300 patients have been of vestibular schwannomas is hard to estimate, treated for vestibular schwannoma using but it is probably somewhere between 10 and 15 Gamma Knife stereotactic radiosurgery. The per 1 million population. overall results are very good, with an expected The tumors typically present in patients greater than 95% chance of long-term tumor between 40 and 50 years old. But they can occur in control. The risk of facial weakness is less than 1%. children and occasionally in patients in their 80s. Second is an open surgical approach (Figure 1). Irrespective of the age of the patient, common Mayo Clinic neurologic surgeons operate on all symptoms include unilateral hearing loss, tinnitus, sizes of tumors, ranging from a few millimeters to and impairment or loss of balance. Hearing loss greater than 6 cm. If the tumor measures less that is bilateral and symmetric is unlikely to be than 2 cm and the patient has useful hearing in caused by a vestibular schwannoma. the affected ear, an approach that preserves Says otorhinolargyngologist Colin L. W. hearing is attempted—either a retrosigmoid Driscoll, MD: “Irrespective of the age of the approach or a middle fossa approach. The goal of patient, the most common presenting symptom Inside This Issue is gradual or sudden-onset unilateral hearing loss and tinnitus. More rarely, patients may Surgical Management experience vertigo or mild imbalance.” Adds his of Brain Tumors That colleague, neurosurgeon Michael J. Link, MD: Cause Epilepsy . 2 “If a vestibular schwannoma becomes large Interdisciplinary Brachial enough, it can produce facial numbness, severe Plexus Clinic Uses Novel ataxia, and even dysphagia by impinging on the Approaches to Attempt to nerves that mediate those functions.” Restore Hand Function . 4 Diagnosis and Treatment Options Carotid Angioplasty With The best modality available to confirm the Stent Placement . 6 diagnosis of vestibular schwannoma is MRI of the head, with and without contrast. The tumor Figure 1. Left, Preoperative axial T1-weighted image with Physician Directory . 8 gadolinium shows a 2.5-cm right vestibular schwannoma. is almost always seen as a brightly enhancing Right, Postoperative axial T1-weighted image with lesion in the cerebellopontine angle that enlarges gadolinium 2 years after tumor resection shows and extends to the internal auditory canal. complete tumor removal with no evidence of recurrence. PAGE 1 MAYO CLINIC NEUROSCIENCE UPDATE 2 the surgery is to remove all the tumor, thus curing Knife radiosurgery if it shows growth on the patient and preserving useful hearing without future imaging.” adding new neurologic deficits. A neurosurgical and otorhinolarygologic SCHWANNOMA CLINIC Depending on the size and configuration of team performs all operations for vestibular CONSULTANTS the tumor, hearing preservation ranges between schwannomas at Mayo Clinic. These specialists Neurosurgery 10% and 50%. The risk of facial nerve weakness have extensive experience treating tumors of Michael J. Link, MD varies from less than 1% in patients with very this type and a good collaborative approach to Otorhinolaryngology small tumors to 20% to 25% in patients with very treating these patients. The alliance of advanced Colin L. W. Driscoll, MD large tumors. The risk of other surgical specialties working together—neurosurgeons, Charles W. Beatty, MD complications is less than 1%, and the typical otorhinolaryngologists, radiation oncologists— Stereotactic Radiosurgery hospital stay is 3 to 5 days. is a hallmark of the Mayo Clinic approach to the Michael J. Link, MD If the patient does not have useful hearing, a treatment of vestibular schwannomas. Says Dr Bruce E. Pollock, MD translabyrinthine approach may be recommended. Link: “Patients benefit tremendously from Neuro-oncology This involves operating through the inner ear, preoperative consultation by all members of the Terrence L. Cascino, MD and subsequently no hearing is preserved in that team so they have a thorough understanding of Julie E. Hammack, MD ear. This approach has some benefit in that it the treatment options from the very beginning.” David W. Kimmel, MD Daniel H. Lachance, MD exposes the internal auditory Brian P. O'Neill, MD canal well, which tends to Joon H. Uhm, MD make this portion of removal Radiation Oncology of the tumor easier. Paul D. Brown, MD There is a third open Robert L. Foote, MD surgery scenario as well: Yolanda I. Garces, MD Paula J. Schomberg, MD subtotal resection (Figure 2). Scott L. Stafford, MD Says Dr Link: “In some cases we may elect to do subtotal Audiology Christopher D. Bauch, PhD resection on a very large Jodi A. Cook, PhD tumor. We may elect to leave a small portion of the tumor attached to the facial Figure 2. Left, Preoperative coronal T1-weighted image with gadolinium shows a nerve to avoid inducing very large, 4.5-cm right vestibular schwannoma with severe compression of the new facial weakness after brain stem and cerebellum and moderate obstructive hydrocephalus. Right, Coronal T1-weighted image with gadolinium 3 months postoperatively shows a surgery. Then, once we small tumor remnant along the course of the right facial nerve. Hydrocephalus have reduced the tumor to has resolved, and the patient has normal facial nerve function. The tumor an acceptable size, we treat remnant is now a size that could be treated effectively with radiosurgery if it the remnant with Gamma shows signs of growth. Surgical Management of Brain Tumors That Cause Epilepsy Brain tumors are among the possible causes of surgery. An estimated 70% of tumors that cause epilepsy, defined as chronic and recurring epilepsy are slow-growing gliomas. seizure activity, in both adults and children. Favorable surgical outcomes depend on the Various types of brain tumors can be involved completeness of resection of both the lesion and in seizure generation. Common epilepsy-related the epileptogenic zone involved in seizure tumors arise from glial cells and include low- initiation. Complete resection requires a highly grade gliomas such as pilocytic astrocytoma, skilled, experienced, and integrated surgical ganglioglioma, dysembryoplastic epithelial neuroscience team accustomed to working together tumors, and oligodendrogliomas. These tumors throughout the continuum of care. Individualized are generally slow growing, tend to be benign and care—from presurgical evaluation to planning and well defined, and are successfully removed by executing a specific surgical strategy unique to each Neurosurgical Consultation 507-284-8008 www.mayoclinic.org/neuro-update-rst PAGE 2 MAYO CLINIC NEUROSCIENCE UPDATE 3 patient through postoperative care and follow-up—is the hallmark of the Mayo Clinic Epilepsy Center neurosurgical team. EPILEPSY CENTER Because of advances in neuroimaging, CONSULTANTS epilepsy-associated brain tumors are more Neurosurgery easily detected. However, these may not For adults: be visualized by CT scan. MRI is W. Richard Marsh, MD Fredric B. Meyer, MD indispensable for visualizing exact anatomic details of the tumor. Says W. For children: Richard Marsh, MD, Mayo Clinic Corey Raffel, MD neurosurgeon: “Every patient with a Neurology chronic seizure disorder deserves to have MRI scans of left temporal lobe preoperatively (left) and postoperatively Jeffrey W. Britton, MD an MRI scan. If a brain tumor can be Gregory D. Cascino, MD (right) after successful removal of tumor. Terrence D. Lagerlund, MD identified as a cause of the seizure Cheolsu Shin, MD disorder, good surgical treatment exists.” eloquent areas, surgery proceeds with the patient Elson L. So, MD Adds neuropsychologist Max R. Trenerry, PhD: “In Barbara F. Westmoreland, MD under general anesthesia. Gregory A. Worrell, MD, PhD addition to the anatomic detail that MRI can Precision during the surgery is assured by provide, neuropsychological evaluation helps computer-assisted monitoring. This technology Neuropsychology patients understand the nature and extent of Max R. Trenerry, PhD provides information about the volume, shape, cognitive changes associated with the tumor and and configuration of the tumor and is used to seizure disorder.” identify the margins of the tumor, which may not be Evaluating the Epileptic Patient apparent under direct visualization. With this At Mayo Clinic, a patient seeking care for understanding of the physical space within the brain-tumor-caused epilepsy sees at least patient's
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