- Department of Neurosurgery Hospital Clinicas Caracas, Venezuela/Department of Radiation Oncology Hospital Clinicas Caracas, Venezuela/Gammaknife Unit, CDD Las Mercedes, Caracas, Venezuela
Department of Neurosurgery Hospital Clinicas Caracas, Venezuela/Department of Radiation Oncology Hospital Clinicas Caracas, Venezuela/Gammaknife Unit, CDD Las Mercedes, Caracas, Venezuela
DOI:10.4103/2152-7806.110663Copyright: © 2013 Lustgarten L. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Lustgarten L. The impact of stereotactic radiosurgery in the management of neurofibromatosis type 2-related vestibular schwannomas. Surg Neurol Int 17-Apr-2013;4:
How to cite this URL: Lustgarten L. The impact of stereotactic radiosurgery in the management of neurofibromatosis type 2-related vestibular schwannomas. Surg Neurol Int 17-Apr-2013;4:. Available from: http://sni.wpengine.com/surgicalint_articles/the-impact-of-stereotactic-radiosurgery-in-the-management-of-neurofibromatosis-type-2-related-vestibular-schwannomas/
Although there is an ongoing debate about the ideal management of vestibular schwannomas, radiosurgical treatment has become popular in the past decade with good to excellent results reported. Given the young age at presentation, the bilateral nature of vestibular schwanomas, the presence of other associated central nervous system tumors, patients with neurofibromatosis Type 2 (NF2) are very complex and present significant management challenges. Although results do not seem to be as good as for patients with sporadic unilateral tumors, stereotactic radiosurgery has proven a safe, attractive, and effective management modality for NF2 vestibular schwannomas. An overview of the impact stereotactic radiosurgery has had in the management of these tumors is discussed.
Keywords: Hearing preservation, local tumor control, neurofibromatosis type 2, stereotactic radiosurgery gamma knife, vestibular schwanomas
Medical advances and the availability of high technology have revolutionized the way we practice medicine today, and are indispensable for people's health and better quality of life. Given that we use a wide variety of technologies in assessing, diagnosing, and treating patients, our practice is inherently dependent upon health technology. The decision to implement a new medical technology requires that it not only increases survival and/or quality of life, but also be economically sound. Despite the fact that neurosurgeons in general welcome new technologies all the time, this is naturally accompanied with some degree of skepticism, as any change that might modify our traditional standard practice tend to shake our “comfort zone” and therefore generate anxiety. This was even more so at the beginnings of the stereotactic radiosurgical era for brain lesions as the results and success of the technique were not immediately evident.
The management of vestibular schwannomas has suffered an interesting evolution from traditional microsurgery to less invasive “technological” procedures, namely, cerebral stereotactic radiosurgery. Ever since the first patient with an acoustic schwannoma was treated with gammaknife in 1969, no one probably imagined the real impact stereotactic radiosurgery would have in the management of central nervous system (CNS) tumors. From that moment on, and after decades and hundreds of thousands of patients treated, neurosurgeons have debated as to which treatment, radiosurgery or microsurgery is most convenient for a patient with a tumor that is accessible to both procedures. For many years, only those tumors critically located and therefore surgically inaccessible were considered ideal candidates for radiosurgery. As experience and knowledge in this field have grown and long-term results have been published, the trend for radiosurgical procedures has also grown and our practice has been changed accordingly.
Almost three decades later, in 1998, and already witnessing the power of the technology and potential success of this procedure, Pollock et al.[
This is an autosomal dominant genetic disorder caused by mutations on chromosome 22.[
The classical management of neurofibromatosis (NF)-related schwannomas has been standard microsurgical resection,[
Published data on the different treatment alternatives for sporadic vestibular schwannomas and those NF2 related will support our understanding of why radiosurgery has become such a huge impact in the management of these patients. Even though the level of tumor control and hearing preservation is not quite the same as for their sporadic counterparts, gammaknife and Linear accelerator (LINAC-) based radiosurgery have proven to be excellent tools for the treatment for vestibular schwannomas in patients with NF2. In general, excellent local control rates have been achieved and reported in the vast majority of series with minimal facial and trigeminal nerve toxicity.[
Better functional outcomes after stereotactic radiosurgery as compared with surgical resection have been reported,[
Tumor control rates for NF2 vestibular scwannomas have been reported to range roughly between 85% and 80% at 5-10, years respectively.[
The actuarial serviceable hearing preservation rate show a decline over time varying from around Radiosurgery for Neurofibromatosis type 2 vestibular schwanomas 50-70% at 1 year, 45-60% at 2 years, and 33-45% at 5 years after radiosurgery.[
The facial and trigeminal nerve function preservation rate in radiosurgery for NF2-related vestibular schwannomas seems to be as high as that in radiosurgery for sporadic cases with most published series reporting treatment-related toxicity in less than 10% of patients. Radiation dose and tumor volume were predictive of development of new deficits.[
After multivariate analysis, no evident factors have been identified as predictive of growth of vestibular schwannomas in NF2 patients,[
A corollary of the previous paragraphs is that surgical resection is commonly thought to carry a greater risk of functional deterioration, and, even though the level of tumor control and hearing preservation is not the same as for sporadic cases, stereotactic radiosurgery is a less invasive option that provides comparable, if not superior outcomes to resection providing satisfactory tumor control and hearing preservation in these patients.[
A few decades ago, when faced with a young patient with NF2 with demonstrable growing tumor(s), microsurgery was recommended for the bilateral vestibular schwannomas. It was a relatively common but unfortunate event to see these young patients with bilateral scars related to their suboccipital craniectomies and facial disfigurements as a result of surgery and cranial nerve deficits. Needless to say, a natural consensus among all patients and specially the younger ones was their concern about functional preservation of both hearing and facial nerve function. The quality and performance of their personal and professional lives depend on both and the consequences of either dysfunction could be catastrophic. Tumor control and cranial neuropathy are thus crucial goals to achieve, the first one easily be done at the expense of damaging the latter. Before the availability of our current published data on the efficacy of radiosurgery, the decision in a way relied either on observation or microsurgery. Then radiosurgery came along and the procedure created such a dramatic impact that has essentially replaced surgery as the standard of care, especially for NF2 patients. Apart from patient satisfaction, an interesting fact supporting this notion is how most recently published series on NF2-related vestibular schwannomas deal only with radiosurgery as their treatment of choice for this population.
The management of NF2 vestibular schwannomas require a fine and delicate balance between growth control against preservation of hearing and other cranial nerves function. It is therefore very important to know how efficient the treatment will be and how much damage it is capable of producing while maintaining the primary aim of achieving the best possible patient's quality of life. Unfortunately these patients are complex and there are no established guidelines to give recommendations that could cover all situations, leaving experience and perhaps most importantly, common sense, to dictate management. There are, however, numerous factors to consider when deciding the best management options for NF2 patients. The decision between observation and either surgical or radiosurgical intervention, as well as the choice of surgical or radiation procedure to be offered, boils down to patient factors and preferences and on the experience of the treating center.
Current available studies on radiosurgery and stereotactic radiation therapy for sporadic vestibular schwannoma sare abundant with excellent performance[
Truth is, we can actually find evidence in the literature to support anything we wish to hear or tell our patients backing up either treatment alternative we prefer. The real fact is that when NF2 patients are offered different treatment alternatives (with sufficient information on all of them), the vast majority, if not all, will choose the less invasive, less expensive, and less time consuming procedure, especially if treatment final results are similar, and also bearing in mind that these treatments will need to be bilateral. Nowadays, there are no significant differences in treatment results including the long-term growth control rate, hearing preservation rate, and incidence of postoperative cranial nerve disturbance between radiosurgery and microsurgery.
Radiosurgery has become so precise and accurate that the results have even exceeded our best surgical skills.[
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