Faculty Bibliography

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.

OBJECTIVE: We report our experience using gamma knife radiosurgery (GKR) for brain metastasis from thyroid cancer, which is extremely rare. METHODS: Between 1995 and 2007, 9 patients with 26 metastatic brain tumor(s) from thyroid cancer underwent GKR. The mean patient age was 58 years (range: 10-78). Seven patients had metastases from papillary thyroid cancer, and two from medullary thyroid cancer. Five patients had solitary tumors, and four patients had multiple metastases. Three patients who had multiple metastases also underwent whole brain radiation therapy (WBRT). The mean tumor volume was 2.4 cc (range: 0.03-14.0). A median margin dose of 18.0 Gy (range: 12-20) was delivered to the tumor margin. RESULTS: Tumor control was obtained in 25 out of 26 tumors (96%). The median progression-free period after GKR was 12 months (range: 4-53). The overall median survival after GKR was 33 months (range: 5-54). There were no procedure-related complications and six patients are still living 5-54 months after GKR. CONCLUSIONS: Radiosurgery is an effective and minimally invasive strategy for management of brain metastases form thyroid cancer.

To assess outcomes after stereotactic radiosurgery (SRS) for newly diagnosed or recurrent pilocytic astrocytomas in pediatric patients. Fifty patients (28 male and 22 females) with juvenile pilocytic astrocytomas (JPA) underwent Gamma knife SRS between 1987 and 2006. The median patient age was 10.5 years (range, 4.2-17.9 years). Three patients had failed prior fractionated radiation therapy (RT) and two had failed RT and chemotherapy. The median radiosurgery target volume was 2.1 cc (range, 0.17-14.4 cc) and the median margin dose was 14.5 Gy (range, 11-22.5 Gy). At a median follow-up of 55.5 months (range 6.0-190 months), one patient died and 49 were alive. The progression free survival after SRS (including tumor growth and cyst enlargement) for the entire series was 91.7, 82.8 and 70.8% at 1, 3 and 5 years, respectively. Stereotactic radiosurgery for pediatric pilocytic astrocytomas should be considered when resection is not feasible, or if there is an early recurrence. The best response was observed in small volume residual solid tumors.

OBJECT: In this study the authors evaluated the role of stereotactic radiosurgery (SRS) in the management of progressive or newly diagnosed small-volume oligodendrogliomas. Tumor control, survival, and complications were assessed in patients with oligodendroglioma who underwent Gamma Knife radiosurgery as a primary or adjuvant procedure. METHODS: The authors retrospectively reviewed 30 patients with oligodendroglioma (12 Grade II and 18 Grade III) who underwent SRS between 1992 and June 2006 at the University of Pittsburgh. The median patient age was 43.2 years (range 10.8-75.4 years). Twenty-four patients had previously undergone resection of the tumor, whereas tumors in 6 were diagnosed based on biopsy findings. The SRS was performed in 25 patients who had imaging-defined tumor progression despite prior fractionated radiation (22 patients) and/or chemotherapy (20 patients). The median target volume was 15.4 cm(3) (range 0.07-48.7 cm(3)) and the median margin dose was 14.5 Gy (range 11-20 Gy). RESULTS: At an average of 39.2 months of follow-up (range 12-133 months), 17 patients were dead and 13 were living. The overall survival rates from diagnosis to 5 and 10 years were 90.9 and 68.2%, respectively, for Grade II and 52.1% at 5 years and 26.1% at 10 years for Grade III. Factors associated with an improved progression-free survival included lower tumor grade and smaller tumor volume. In 13 patients who had loss of heterozygosity testing, patients with 1p19q loss of heterozygosity had a significantly improved survival after diagnosis (p = 0.04). CONCLUSIONS: The SRS modality is a minimally invasive additional option for patients with residual or recurrent oligodendrogliomas. It may also be considered as an alternative to initial resection in small-volume tumors located in the cortical brain region.

OBJECT: To evaluate outcome predictors after stereotactic radiosurgery (SRS) in patients with trigeminal schwannomas, the authors compared tumor control, functional preservation, and complications with tumor grade, tumor volume, patient age, and tumor imaging characteristics. METHODS: The records of 33 consecutive patients with trigeminal schwannoma treated via Gamma Knife surgery were retrospectively reviewed. The median patient age was 49.5 years (range 15.1-82.5 years). Eleven patients had undergone prior tumor resection. Two patients had neurofibromatosis Type 2. Lesions were classified as root type (6 tumors), ganglion type (17 tumors), and dumbbell type (10 tumors) based on their location. The median radiosurgery target volume was 4.2 cm3 (range 0.5-18.0 cm3), and the median dose to the tumor margin was 15.0 Gy (range 12-20 Gy). RESULTS: At an average of 6 years (range 7.2-147.9 months), the rate of progression-free survival (PFS) at 1, 5, and 10 years after SRS was 97.0, 82.0, and 82.0%, respectively. Factors associated with improved PFS included female sex, smaller tumor volume, and a root or ganglion tumor type. Neurological symptoms or signs improved in 11 (33.3%) of 33 patients and were unchanged in 19 (57.6%). Three patients (9.1%) had symptomatic disease progression. Patients who had not undergone a prior tumor resection were significantly more likely to show improvement in neurological symptoms or signs. CONCLUSIONS: Stereotactic radiosurgery is an effective and minimally invasive management option in patients with residual or newly diagnosed trigeminal schwannomas. Predictors of a better treatment response included female sex, smaller tumor volume, root or ganglion tumor type, and the application of SRS as the primary treatment.

This paper proposes an efficient method to acquire sources of tremor in patients with movement disorders based on blind source separation of convolutive mixtures. The extracted sources indicated neural activities that might be generated in the central nervous system. Four patients with essential tremor were tested in a set of movement tasks. Subjects wore a data glove that measured finger movements of the hand. The experimental data were then fed to a convolutive-mixture model, which revealed sources that imbibed in them the tremor frequency components of 2--8 Hz. Time--frequency analysis of these sources might be of potential help to clinicians to devise tasks that can manifest visible tremor from patients.

To assess outcomes when stereotactic radiosurgery (SRS) is used during multimodality management of pilocytic astrocytomas in adult patients. Fourteen patients (six male and eight females) with pilocytic astrocytomas underwent SRS between 1994 and 2006. The median patient age was 32 years (range, 19-52 years). Initial surgical management included stereotactic biopsy (N = 4), gross total resection (N = 1), and partial resection (N = 9). Fractionated radiation therapy had failed in six patients. The median radiosurgery target volume was 4.7 cc (range, 0.6-33.7 cc) and the median margin dose was 13.3 Gy (range, 10-20 Gy). At a median follow-up of 36.3 months (range 6.1-109 months), three patients died and 11 were alive. The overall survival after SRS for the entire series was 100%, 88.9% and 88.9% at 1, 3 and 5 years, respectively. Localized solid tumor progression was seen in two patients. Cyst progression was noted in three of nine patients with cystic tumors and mixed solid and cyst progression was noted in two with cystic tumors. The progression free survival after SRS (including tumor growth and cyst enlargement) for the entire series was 83.9%, 31.5% and 31.5% at 1, 3 and 5 years, respectively. Prior surgical resection was associated with better progression free survival after SRS (P = 0.027). Despite their purported benign nature, pilocytic astrocytomas in adult patients often do not behave benignly. Unresectable pilocytic astrocytomas that are located in critical or deep areas of the brain require additional management approaches. In this preliminary experience obtained over a 12 year interval, SRS is most valuable for patients after maximal feasible surgical resection. Delayed cyst progression contributes to late loss of tumor control.

OBJECTIVE: Radiation-induced meningiomas of the brain are typically managed with surgical resection. Stereotactic radiosurgery (SRS) has become an important primary or adjuvant management for patients with intracranial meningiomas, but the value of this approach for radiation-induced tumors is unclear. METHODS: This series consisted of 19 patients (mean age, 40 years) with 24 tumors. The patients met criteria for a radiation-induced meningioma and underwent gamma knife radiosurgery. Seven patients had undergone a previous resection. The World Health Organization tumor grades for those with prior histology were Grade I (n = 5) and Grade II (n = 2). The median tumor volume was 4.4 cm3. Radiosurgery was performed using a median margin dose of 13 Gy. RESULTS: Serial imaging was evaluated in all patients at a median follow-up of 44 months. The control rate was 75% after primary radiosurgery. Delayed resection after radiosurgery was performed in 5 patients (26%) at an average of 39 months. The median latency between radiation therapy for original disease and SRS for radiation-induced meningiomas was 29.7 years (range, 7.3-59.0 years). The overall survival after SRS was 94.1% and 80.7% at 3 and 5 years, respectively. No patient developed a subsequent radiation-induced tumor. The overall morbidity rate was 5.3% (1 optic neuropathy). Asymptomatic peritumoral imaging changes compatible with an adverse radiation effect developed in 1 patient. CONCLUSION: SRS provides satisfactory control rates either after resection or as an alternative to resection. Its role is most valuable for patients whose tumors affect critical neurological regions and who are poor candidates for resection.

OBJECT: Many patients with acoustic neuromas (ANs) have hearing function at diagnosis and desire to maintain it. To date, radiosurgical techniques have been focused on conformal irradiation of the tumor mass, with less attention to inner ear structures for which there was scant radiobiological information. The authors of this study evaluated tumor control and hearing preservation as they relate to tumor volume, imaging characteristics, and nerve and cochlear radiation dose following stereotactic radiosurgery (SRS) using the Gamma Knife. METHODS: Seventy-seven patients with ANs had serviceable hearing (Gardner-Robertson [GR] Class I or II) and underwent SRS between 2004 and 2007. This interval reflected more recent measurements of inner ear dosimetry during the authors' 21-year experience. The median patient age was 52 years (range 22-82 years). No patient had undergone any prior treatment for the ANs. The median tumor volume was 0.75 cm(3) (range 0.07-7.7 cm(3)), and the median radiation dose to the tumor margin was 12.5 Gy (range 12-13 Gy). At diagnosis, a greater distance from the lateral tumor to the end of the internal auditory canal correlated with better hearing function. RESULTS: At a median of 20 months after SRS, no patient required any other additional treatment. Serviceable hearing was preserved in 71% of all patients and in 89% (46 patients) of those with GR Class I hearing. Significant prognostic factors for maintaining the same GR class included (all pre-SRS) GR Class I hearing, a speech discrimination score (SDS) >or= 80%, a pure tone average (PTA) < 20 dB, and a patient age < 60 years. Significant prognostic factors for serviceable hearing preservation were (all pre-SRS) GR Class I hearing, an SDS >or= 80%, a PTA < 20 dB, a patient age < 60 years, an intracanalicular tumor location, and a tumor volume < 0.75 cm(3). Patients who received a radiation dose of < 4.2 Gy to the central cochlea had significantly better hearing preservation of the same GR class. Twelve of 12 patients < 60 years of age who had received a cochlear dose < 4.2 Gy retained serviceable hearing at 2 years post-SRS. CONCLUSIONS: As currently practiced, SRS with the Gamma Knife preserves serviceable hearing in the majority of patients. Tumor volume and anatomy relate to the hearing level before radiosurgery and influence technique. A low radiosurgical dose to the cochlea enhances hearing preservation.

OBJECTIVE: The safety, efficacy, and morbidity of radiosurgery (RS) must be established before it can be offered as an alternative to open surgery for unilateral mesial temporal lobe epilepsy. We report the 3-year outcomes of a multicenter, prospective pilot study of RS. METHODS: RS was randomized to 20 or 24Gy targeting the amygdala, hippocampus, and parahippocampal gyrus. Seizure diaries evaluated the final seizure remission between months 24 and 36. Verbal memory was evaluated at baseline and 24m with the Wechsler Memory Scale-Revised (WMS-R) and California Verbal Learning Test (CVLT). Patients were classified as having "significant improvement," "no change," and "significant impairment" based on relative change indices. RESULTS: Thirteen high-dose and 17 low-dose patients were treated. Both groups showed significant reductions in seizures by 1 year after treatment. At the 36-month follow-up evaluation, 67% of patients were free of seizures for the prior 12 months (high dose: 10/13, 76.9%; low dose: 10/17, 58.8%). Use of steroids, headaches, and visual field defects did not differ by dose or seizure remission. The prevalence of verbal memory impairment was 15% (4/26 patients); none declined on more than one measure. The prevalence of significant verbal memory improvements was 12% (3/26). INTERPRETATION: RS for unilateral mesial temporal lobe epilepsy offers seizure remission rates comparable with those reported previously for open surgery. There were no major safety concerns with high-dose RS compared with low-dose RS. Additional research is required to determine whether RS may be a treatment option for some patients with mesial temporal lobe epilepsy.