The Neurofibromatosis and Benign Tumors Program (NBT) of Cleveland Clinic Brain Tumor and Neuro-Oncology Center focuses primarily on the management of benign brain tumors. These include meningiomas, schwannomas, craniopharyngiomas, dermoids, epidermoids, hemangioblastomas, choroid plexus papillomas and pineal region tumors. In addition, those tumors associated with neurofibromatosis types 1 and 2, and tumors occurring along the skull base, are also treated.
As part of Cleveland Clinic Brain Tumor and Neuro-Oncology Center, the Neurofibromatosis and Benign Tumors Program comprises specialists from the Departments of Neurosurgery, the Brain Tumor and Neuro-Oncology Center, Neurology, Otolaryngology, Ophthalmology, Plastic Surgery, Radiation Oncology, Hematology/Oncology and Pediatric Oncology, offering the highest-quality interdisciplinary care.
In 2005, the Neurofibromatosis and Benign Tumors Program neurosurgeons saw over 300 new patients with benign tumors, the two most common tumors being meningiomas and schwannomas. More than 200 new patients with meningiomas were seen in 2005. Of these patients, approximately 100 underwent surgery, 20 had Gamma Knife radiosurgery, and the remaining 80 were treated conservatively. Over 70 new patients with schwannomas were evaluated this past year. Fifty patients had surgery, approximately 15 had Gamma Knife radiosurgery, and the remaining had conservative treatment. These numbers represent one of the largest in the country for specialized benign tumor management.
Dr. Lee, Head of NBT, had six articles and nine papers accepted for publication. He currently is editing a major landmark textbook on meningiomas consisting of 70-plus chapters, with contributions from more than 50 international leaders in all the basic and clinical disciplines related to meningiomas. This book is planned for early 2007 publication. Additionally, a three-year research grant was awarded to Dr. Lee by the Integra Neurosciences Foundation for the study of dural reconstruction following skull base and meningioma surgery. Dr. Lee was also an invited lecturer at annual meetings of the Korean Skull Base Society, the European Skull Base Society and the North American Skull Base Society.
Our specialists are at the forefront of development, application and refinement of microsurgical techniques such as minimally invasive microsurgery, computer-assisted surgery and "high-tech" medical armamentaria, including brain navigation systems, intraoperative MRI, Gamma Knife radiosurgery, NOVALIS radiosurgery, and intensity-modulated radiation therapy.
Meningioma
Meningiomas are typically benign brain tumors arising from the cells (arachnoid cap cells) that form the middle layer of the brain covering, called the "meninges." Meningiomas are the most common primary brain tumors. In 94 percent of cases, the tumors are benign, with only two percent of meningiomas showing "malignant" characteristics and four percent revealing "aggressive/atypical" features.
Because these are slow growing tumors, not all meningiomas need to be treated immediately at the time of detection. For many patients with benign meningiomas, especially in elderly patients not having any neurological symptoms or deficits, initial observation may be a reasonable option. When this type of tumor has reached a significant size and causes neurological problems, meningioma surgery is the preferred option. Meningioma surgery would usually be recommended if the tumor was found to be enlarged or was detected in a young patient.
Although "total" removal or resection theoretically can provide a "cure" for benign meningiomas, total resection is not always possible. The tumor’s location, or the site of origin (where it arises in the brain), determines how much can be safely resected or removed through meningioma surgery. This in turn determines the risks of surgery and the patients' immediate and long-term outcome. Radiosurgery (such as the Gamma Knife) may be offered for patients whose poor health prohibits conventional surgery. Also, post-operative residual tumors or surgically inoperable tumors may be treated with Gamma Knife radiosurgery or conventional radiation therapy, depending on the tumor size and location. The 10-year recurrence-free survival rates are: 80 percent after total resection, 45 percent following subtotal removal, and 77 percent after a combination of subtotal resection and radiation. At our center, we usually recommend removal of incidental meningiomas at the time of detection for patients who have at least 10-15 years of remaining life expectancy.
Tumorigenesis, or the mechanism responsible for tumor formation, is not well understood currently. However, accumulating evidence suggests that the NF2 gene (tumor suppressor) and various oncogenes coding for several growth factors and their receptors may play a role in meningioma formation.
Schwannoma
Schwannomas arise from Schwann cells that form the insulating cover of nerve fibers. These are benign tumors, and total surgical removal provides "cure". The most common schwannomas occur along the 8th cranial nerve, which have two main components, the cochlear (auditory/acoustic) and vestibular (balance) nerves. In the past, these tumors were also known as "acoustic neuromas," or "acoustic schwannomas." However, we now know that these grow from the vestibular nerve of the eighth cranial nerve complex, and therefore, these are now more correctly referred to as "vestibular schwannomas." The 8th cranial nerve courses with the seventh cranial nerve (the facial nerve). As the vestibular schwannoma grows, it adheres to and stretches the cochlear and facial nerves, both of which are at risk of injury during surgery. Less common schwannomas may arise from the trigeminal nerve (fifth cranial nerve), facial nerve (seventh cranial nerve), and glossopharyngeal nerve (ninth cranial nerve).
As is true of meningiomas, schwannomas are relatively slow-growing brain tumors, so observation is a reasonable treatment option in select patients. Observation is indicated in patients with small tumors and stable, mild hearing loss, and for elderly patients and/or those in poor health.
Microsurgery carries minimal complications today, and the risks are mainly related to the tumor size. In our experience with small tumors, hearing preservation is possible, with an approximate success rate of 50 percent. The risk of permanent facial nerve damage is two to five percent for small brain tumors, five to 10 percent for medium size, and 10-25 percent for large tumors.
There is growing experience with Gamma Knife radiosurgery, an outpatient procedure that does not involve open surgery, as a primary treatment option for small-to-medium vestibular schwannomas less than three centimeters in diameter. Gamma Knife radiosurgery has become a proven treatment option in controlling the brain tumor from further growth. Gamma Knife radiosurgery is also utilized if microsurgery fails to remove the tumor completely and the residual tumor is noted to be re-growing on follow-up imaging studies.
The exact mechanism of tumor formation is not known for schwannomas. However, present understanding is that its tumorigenesis may involve similar pathways (NF2 gene, growth factors, receptors) as meningiomas.
Neurofibromatosis (NF)
Neurofibromatosis type 1 (NF1), also known as von Recklinghausen Disease, is a hereditary disease seen in approximately 1 in 4,000 live births in the U.S. Neurofibromatosis 1 is characterized by a triad of café-au-lait spots (skin discolorations), cutaneous neurofibromata and iris Lisch nodules. Other features of the disorder may include skeletal dysplasia, vascular dysplasias, learning disabilities, seizures and other tumors of the neural crest origin, such as pheochromocytomas. In addition, about 10 to 15 percent of neurofibromatosis1 patients have low-grade astrocytomas, and less commonly, ependymomas or meningiomas.
Neurofibromatosis type 2 (NF2), the hallmark of which is bilateral vestibular schwannomas, is a much less common disorder than neurofibromatosis1, with the incidence of approximately 1 in 40,000 live births in the U.S. In addition, retinal astrocytomas and childhood cataracts are seen in 50-80 percent of NF2 patients.
To schedule an evaluation with a Cleveland Clinic Brain Tumor and Neuro-Oncology Center specialist, please call our Patient Access Coordinator at 216.445.8971, or toll-free at 800.223.2273, ext. 58971.
