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Oren Berkowitz, Douglas Kondziolka, David Bissonette, Ajay Niranjan, Hideyuki Kano and L. Dade Lunsford

Object

The first North American 201 cobalt-60 source Gamma Knife surgery (GKS) device was introduced at the University of Pittsburgh Medical Center in 1987. The introduction of this innovative and largely untested surgical procedure prompted the desire to study patient outcomes and evaluate the effectiveness of this technique. The parallel advances in computer software and database technology led to the development of a registry to track patient outcomes at this center. The purpose of this study was to describe the registry's evolution and to evaluate its usefulness.

Methods

A team was created to develop a software database and tracking system to organize and retain information on the usage of GKS. All patients undergoing GKS were systematically entered into this database by a clinician familiar with the technology and the clinical indications. Information included patient demographics and diagnosis as well as the anatomical site of the target and details of the procedure.

Results

There are currently 11,738 patients in the database, which began to be used in August 1987. The University of Pittsburgh Medical Center has pioneered the evaluation and publication of the GKS technique and outcomes. Data derived from this computer database have facilitated the publication of more than 400 peer-reviewed manuscripts, more than 200 book chapters, 8 books, and more than 300 published abstracts and scientific presentations. The use of GKS has become a well-established surgical technique that has been performed more than 700,000 times around the world.

Conclusions

The development of a patient registry to track and analyze the use of GKS has given investigators the ability to study patient procedures and outcomes. The future of clinical medical research will rely on the ability of clinical centers to store and to share information.

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Anthony L. Asher, Paul C. McCormick and Douglas Kondziolka

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Yueh-Ying Han, Oren Berkowitz, Evelyn Talbott, Douglas Kondziolka, Maryann Donovan and L. Dade Lunsford

Object

The authors evaluated the potential role of environmental risk factors, including exposure to diagnostic or therapeutic radiation and to wireless phones that emit nonionizing radiation, in the etiology of vestibular schwannoma (VS).

Methods

A total of 343 patients with VSs who underwent Gamma Knife surgery performed between 1997 and 2007 were age and sex matched to 343 control patients from the outpatient degenerative spinal disorders service at the University of Pittsburgh Medical Center. The authors obtained information on previous exposure to medical radiation, use of wireless phone technologies, and other environmental factors thought to be associated with the development of a VS. Conditional multivariate logistic regression was used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs).

Results

After adjusting for race, education, cigarette smoking, alcohol consumption, occupational exposure to noise, use of cell phones, and family history of cancer, the authors identified only a single factor that was associated with a higher risk of VS: individuals exposed to dental x-rays once a year (aOR = 2.27, 95% CI = 1.01–5.09) or once every 2–5 years (aOR = 2.65, 95% CI = 1.20–5.85), compared with those exposed less than once every 5 years. Of interest, a history of exposure to radiation related to head or head-and-neck computed tomography was associated with a reduced risk of VS (aOR = 0.52, 95% CI = 0.30–0.90). No relationship was found between the use of cell phones or cordless phones and VS.

Conclusions

Patients with acoustic neuromas reported significantly more exposure to dental x-rays than a matched cohort control group. Reducing the frequency of dental x-ray examinations may decrease the potential risk of VS.

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L. Dade Lunsford, Veronica Chiang, John R. Adler, Jason Sheehan, William Friedman and Douglas Kondziolka

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Douglas Kondziolka

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Georgios Zenonos, Douglas Kondziolka, John C. Flickinger, Paul Gardner and L. Dade Lunsford

Object

Microsurgical management of foramen magnum meningiomas (FMMs) can be associated with significant morbidity and mortality. Stereotactic radiosurgery may be an efficient and safe alternative treatment modality for such tumors. The object of this study was to increase the documented experience with Gamma Knife surgery (GKS) for FMMs and to delineate its role in an overall management paradigm.

Methods

The authors report on their experience with 24 patients harboring FMMs managed with GKS. Twelve patients had primary symptomatic tumors, 5 had asymptomatic but enlarging primary tumors, and 7 had recurrent or residual tumors after a prior surgery.

Results

Follow-up clinical and imaging data were available in 21 patients at a median follow-up of 47 months (range 3–128 months). Ten patients had measurable tumor regression, which was defined as an overall volume reduction > 25%. Eleven patients had no further tumor growth. Two patients died as a result of advanced comorbidities before follow-up imaging. One patient was living 8 years after GKS but had no clinical evaluation. Ten of 17 symptomatic patients with at least 6 months of follow-up had symptom improvement, and 7 remained clinically stable. Smaller tumors were more likely to regress. No patient suffered an adverse radiation effect after radiosurgery.

Conclusions

Gamma Knife surgery was a safe management strategy for small, minimally symptomatic, or growing FMMs as well as for residual tumors following conservative microsurgical removal.

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Douglas Kondziolka, Seyed H. Mousavi, Hideyuki Kano, John C. Flickinger and L. Dade Lunsford

Object

Management recommendations for patients with smaller-volume or newly diagnosed vestibular schwannomas (< 4 cm3) need to be based on an understanding of the anticipated natural history of the tumor and the side effects it produces. The natural history can then be compared with the risks and benefits of therapeutic intervention using a minimally invasive strategy such as stereotactic radiosurgery (SRS).

Methods

The authors reviewed the emerging literature stemming from recent recommendations to “wait and scan” (observation) and compared this strategy with published outcomes after early intervention using SRS or results from matched cohort studies of resection and SRS.

Results

Various retrospective studies indicate that vestibular schwannomas grow at a rate of 0–3.9 mm per year and double in volume between 1.65 and 4.4 years. Stereotactic radiosurgery arrests growth in up to 98% of patients when studied at intervals of 10–15 years. Most patients who select “wait and scan” note gradually decreasing hearing function leading to the loss of useful hearing by 5 years. In contrast, current studies indicate that 3–5 years after Gamma Knife surgery, 61%–80% of patients maintain useful hearing (speech discrimination score > 50%, pure tone average < 50).

Conclusions

Based on published data on both volume and hearing preservation for both strategies, the authors devised a management recommendation for patients with small vestibular schwannomas. When resection is not chosen by the patient, the authors believe that early SRS intervention, in contrast to observation, results in long-term tumor control and improved rates of hearing preservation.

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Jason Sheehan and Chun Po Yen

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Jason Sheehan and David Schlesinger

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Jason P. Sheehan, Shota Tanaka, Michael J. Link, Bruce E. Pollock, Douglas Kondziolka, David Mathieu, Christopher Duma, A. Byron Young, Anthony M. Kaufmann, Heyoung McBride, Peter A. Weisskopf, Zhiyuan Xu, Hideyuki Kano, Huai-che Yang and L. Dade Lunsford

Object

Glomus tumors are rare skull base neoplasms that frequently involve critical cerebrovascular structures and lower cranial nerves. Complete resection is often difficult and may increase cranial nerve deficits. Stereotactic radiosurgery has gained an increasing role in the management of glomus tumors. The authors of this study examine the outcomes after radiosurgery in a large, multicenter patient population.

Methods

Under the auspices of the North American Gamma Knife Consortium, 8 Gamma Knife surgery centers that treat glomus tumors combined their outcome data retrospectively. One hundred thirty-four patient procedures were included in the study (134 procedures in 132 patients, with each procedure being analyzed separately). Prior resection was performed in 51 patients, and prior fractionated external beam radiotherapy was performed in 6 patients. The patients' median age at the time of radiosurgery was 59 years. Forty percent had pulsatile tinnitus at the time of radiosurgery. The median dose to the tumor margin was 15 Gy. The median duration of follow-up was 50.5 months (range 5–220 months).

Results

Overall tumor control was achieved in 93% of patients at last follow-up; actuarial tumor control was 88% at 5 years postradiosurgery. Absence of trigeminal nerve dysfunction at the time of radiosurgery (p = 0.001) and higher number of isocenters (p = 0.005) were statistically associated with tumor progression–free tumor survival. Patients demonstrating new or progressive cranial nerve deficits were also likely to demonstrate tumor progression (p = 0.002). Pulsatile tinnitus improved in 49% of patients who reported it at presentation. New or progressive cranial nerve deficits were noted in 15% of patients; improvement in preexisting cranial nerve deficits was observed in 11% of patients. No patient died as a result of tumor progression.

Conclusions

Gamma Knife surgery was a well-tolerated management strategy that provided a high rate of long-term glomus tumor control. Symptomatic tinnitus improved in almost one-half of the patients. Overall neurological status and cranial nerve function were preserved or improved in the vast majority of patients after radiosurgery.