Faculty Bibliography

BACKGROUND: We evaluated the role of Gamma Knife SRS in the multidisciplinary management of metastatic cancer to the pituitary gland. METHODS: We retrospectively reviewed records of 18 consecutive pituitary metastasis patients who underwent Gamma Knife SRS during a 21-year experience. The median patient age was 57.6 years (range, 27.0-81.1 years). There were 5 patients who had initial surgical resection of their pituitary metastasis, 5 who had fractionated radiation, and 7 who had CT before SRS. The median radiosurgery target volume was 3.5 mL (range, 0.2-18.0 mL), and the median marginal dose was 13.0 Gy (range, 9-18 Gy). RESULTS: The overall survival after SRS at 3, 6, and 12 months, respectively, was 66%, 36%, and 18%. The median survival after SRS was 5.2 months. The progression-free survival after SRS was 100% and 66.7% at 6 and 12 months, respectively. The only factor associated with an improved overall survival was younger age at presentation. Diabetes insipidus improved in 3 (42.9%) of 7 patients. Neurological symptoms or signs improved in 4 (50.0%) of 8 patients. Three (16.7%) patients developed new neurological deficits due to tumor progression despite SRS. CONCLUSION: Development of a pituitary metastasis is an ominous finding in the context of systemic cancer. Stereotactic radiosurgery is an effective palliative approach for most patients with pituitary metastasis.

OBJECT: Meningiomas of the cerebral convexity are often surgically curable because both the mass and involved dura mater can be removed. Stereotactic radiosurgery has become an important primary or adjuvant treatment for patients with intracranial meningiomas. The authors evaluated clinical and imaging outcomes in patients with convexity meningiomas after radiosurgery. METHODS: The patient cohort consisted of 125 patients with convexity meningiomas managed using radiosurgery at some point during an 18-year period. The patient series included 76 women, 55 patients who had undergone prior resection, and 6 patients with neurofibromatosis Type 2. Tumors were located in frontal (80 patients), parietal (24 patients), temporal (12 patients), and occipital (9 patients) areas. The WHO tumor grades in patients with prior resections were Grade I in 34 patients, Grade II in 15 patients, and Grade III in 6 patients. Seventy patients underwent primary radiosurgery and therefore had no prior histological tumor diagnosis. The mean tumor volume was 7.6 ml. Radiosurgery was performed using the Leksell Gamma Knife with a mean tumor margin dose of 14.2 Gy. RESULTS: Serial imaging was evaluated in 115 patients (92%). After primary radiosurgery, the tumor control rate was 92%. After adjuvant radiosurgery, the control rate was 97% for Grade I tumors. The actuarial tumor control rates at 3 and 5 years for the entire series were 86.1+/-3.8% and 71.6+/-8.6%, respectively. For patients with benign tumors (Grade I) and those without prior surgery, the actuarial tumor control rate was 95.3+/-2.3% and 85.8+/-9.3%, respectively. Delayed resection after radiosurgery was performed in 9 patients (7%) at an average of 35 months. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 9.6%. Symptomatic peritumoral imaging changes compatible with edema or adverse radiation effects developed in 5%, at a mean of 8 months. CONCLUSIONS: Stereotactic radiosurgery provides satisfactory control rates either after resection or as an alternate to resection, particularly for histologically benign meningiomas. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection. Both temporary and permanent morbidity are related to brain location and tumor volume.

In a drive toward improved quality and safety in medicine, educators have emphasized the importance of lifelong learning and improved pedagogical models to effective continuing education. Scholarly understanding of disciplinary knowledge and expert thought has progressed rapidly in the past 40 years. Lessons from adult learning theory can and should be systematically applied to the design of effective, learner- centered, collaborative, and conceptually driven continuing education for physicians and surgeons. One example of this pedagogical approach is Integrated Medical Learning (IML), an instructional theory that is based on dynamic interaction between each element of the learning process, is learner centered, incorporates self-assessment, uses various formats and media to facilitate learning, and seeks to apply scientific method to educational process development. This article discusses advances in learning, instructional theory, and practice relevant to medical continuing education and outlines the conceptual basis for IML. The first iteration of IML, which took place in part at the General Scientific Sessions of the 2007 Annual Meeting of the Congress of Neurological Surgeons, will be described elsewhere. In addition to advancing goals related to educational effectiveness, IML produces novel and otherwise not easily obtainable data about current clinical knowledge, attitudes, and actual practice patterns that are relevant to clinical equipoise, study design, and medical evidence.

In recent years, the use of radiosurgery or radiotherapy for benign brain tumors has increased significantly. Although long-term follow-up from several centers suggests that radiosurgery or radiotherapy is effective and safe, there are particular concerns regarding development of radiation-induced tumors. This article reviews the use of radiosurgery and fractionated radiation therapy with particular regard to new tumor induction and malignant transformation. The authors have found that the risk of radiation associated tumors after radiosurgery or radiotherapy for benign brain tumors is very low. All patients should be informed about the risks and consequences of radiation and microsurgery. The current practice standards for radiosurgery should not be modified because of this very low risk.

OBJECTIVE: Management options for patients with vestibular schwannoma include observation, surgical resection, stereotactic radiosurgery (SRS), and stereotactic radiation therapy. In younger patients, resection is often advocated because of concern regarding the long-term effects of radiation. We studied tumor response and clinical outcomes after SRS in such patients. METHODS: We reviewed long-term outcomes in 55 patients with vestibular schwannomas. Patients were 40 years of age or younger, underwent gamma knife (GK) SRS between 1987 and 2003, and were followed up for a minimum of 4 years. The median patient age was 35 years (range, 13-40 years). Forty-one patients had Gardner-Robertson class 1 to 4 hearing. Thirteen patients (24%) had undergone surgical removal. The median tumor volume was 1.7 mm. The median tumor margin dose was 13.0 Gy (range, 11-20 Gy). RESULTS: At a median of 5.3 years, (range, 4-20 years), 2 of 55 patients underwent GK SRS for a second time; 1 of these patients had had a recurrence after initial resection. The 5-year rate of freedom from additional management was 96%. Hearing preservation rates (i.e., remaining within the same Gardner-Robertson hearing class) were 93%, 87%, and 87% at 3, 5, and 10 years, respectively. In patients with serviceable hearing before SRS, it was maintained in 100%, 93%, and 93% of patients at 3, 5, and 10 years, respectively. Hearing preservation was related to a margin dose lower than 13 Gy (P = 0.017). At the last assessment, facial and trigeminal nerve function was preserved in 98.2% and 96.4% of patients, respectively; the only facial deficit (House-Brackmann grade III) occurred in a patient who received a tumor dose of 20 Gy early in our experience (1988). None of the patients treated with doses lower than 13 Gy experienced facial or trigeminal neuropathy. All patients continued their previous level of activity or employment after GK SRS. No patient developed a secondary radiation-related tumor. CONCLUSION: Our experience indicates that GK SRS is an effective management strategy for younger patients with vestibular schwannoma, most of whom have no additional cranial nerve dysfunction.