Faculty Bibliography

OBJECTIVE: Tumor control, facial function preservation, and hearing preservation are important criteria for successful management of intracanalicular vestibular schwannomas, whether observation, microsurgery, or radiosurgery is chosen. We collected data prospectively to assess hearing preservation after intracanalicular vestibular schwannoma radiosurgery. METHODS: Between 1987 and 2003, 96 patients (65 men and 31 women) underwent gamma knife stereotactic radiosurgery (SRS) for intracanalicular tumors. The median patient age was 54 years (range, 22-80 years). Hearing was graded using the Gardner-Robertson (GR) and the American Academy of Otolaryngology-Head and Neck Surgery classifications. Dose planning was performed on intraoperative stereotactic images using multiple 4-mm isocenters. The median tumor volume was 0.112 mm3 (range, 0.05-0.447 mm3), and the median margin dose was 13 Gy (range, 10-18 Gy). RESULTS: The mean and median audiologic follow-up periods were 42 months and 28 months (range, 12-144 months), respectively. Serviceable hearing was preserved in 31 of 40 (77.5%) patients with initial American Academy of Otolaryngology-Head and Neck Surgery Class A hearing. Serviceable hearing was preserved in 40 of 79 (64.5%) patients with GR Grade I or II pre-SRS hearing. Ninety-two patients had GR Grade I, II, or III hearing before SRS, and GR Grade I, II, or III hearing was maintained in 78 patients (85%). Hearing grades improved in 7 patients. Facial and trigeminal nerve function was preserved in all patients. The tumor control rate (freedom from additional intervention) was 99.0% (95 of 96) at a median follow-up of 28 months (range, 12-144 months). One patient underwent tumor resection 18 months after radiosurgery. CONCLUSION: SRS is a minimally invasive first-line management option for patients with intracanalicular tumors and provides high rates of hearing preservation with minimal morbidity.

OBJECTIVE: One of the key limitations of gamma knife surgery arises from the radiation safety tolerance limit of the brainstem. The authors conducted an analysis of patients with intra-axial brainstem lesions and documented the incidence of adverse radiation imaging effects (ARIE) and new neurological deficits after gamma knife surgery. METHODS: Thirty-eight patients (39 lesions) with intra-axial brainstem astrocytomas or vascular malformations underwent gamma knife surgery during a 6-year interval. Brainstem exposure volume was calculated by subtracting the volume within the 12-Gy isodose line (12 Gray volume) from the prescription volume. ARIE was defined as a new parenchymal signal alteration on follow-up magnetic resonance imaging sequences. RESULTS: The average prescription volume was 1.46 cm, 12 Gy volume was 2.03 cm, and brainstem exposure volume was 0.57 cm. Seven (18.4%) patients developed ARIE. ARIE correlated only with the presence of new neurological deficits and age younger than 40 years. Three (7.9%) patients developed minor residual deficits without any ARIE. There was no mortality. CONCLUSION: Exposure of the brainstem to more than 12 Gy at volumes as low as 0.1 cm can produce ARIE and new neurological deficits. The tolerance of the brainstem to radiosurgery is related to patient age, lesion volume, and pathology. Analysis of the exposed volume of brainstem tissue may be useful in radiosurgical planning for individual patients.

BACKGROUND: Although uncommon, adverse radiation effects (ARE) are a potentially serious side effect of brain stereotactic radiosurgery (SRS). Corticosteroids are used to treat suspected ARE but side effects may be significant after long-term usage. Oral pentoxifylline (Ptx) and vitamin E therapy (VitE) are reported to benefit ARE seen in other organ systems. We treated 11 patients with suspected ARE after SRS with Ptx and VitE. METHODS: To assess the response, edema was measured using fluid-attenuated inversion recovery magnetic resonance imaging (MRI). Edema volumes were calculated by first determining the three maximum measurements in the X, Y, and Z planes of the image with the largest signal change. Volume was plotted over time for each patient that had serial MRI scans available. Two patients had 2 separate radiosurgeries and 2 patients underwent 3. Three patients received adjuvant whole-brain radiation therapy. RESULTS: The time until clinical detection of ARE after SRS varied from 3 to 18 months (median, 8 months). The change in edema volume varied from 59.6 ml in 1 patient (worse edema) to -324.2 ml (improvement). The average change in edema from pre- to post-treatment was -72.3 ml. One patient had more edema despite treatment; this patient was found to have tumor recurrence, and not an ARE. Two patients discontinued Ptx because of persistent nausea and abdominal discomfort. CONCLUSIONS: Ptx and VitE may be of benefit in the management of adverse radiation effects and should be studied further.

OBJECTIVE: To evaluate the role of stereotactic radiosurgery (SRS) in the management of recurrent or residual intracranial hemangioblastomas, we assessed tumor control, survival, and complications in 32 consecutive patients. METHODS: We retrospectively reviewed records of 32 consecutive hemangioblastoma patients (74 intracranial tumors) who underwent gamma knife SRS. The median patient age was 43.8 years (range, 21.3-79.4 yr). Thirty-one patients had undergone previous surgical resections. Nineteen patients had sporadic lesions (22 tumors), and 13 patients had von Hippel-Lindau disease-associated hemangioblastomas (52 tumors). The median SRS target volume was 0.72 mL (range, 0.08-16.6 mL), and the median marginal dose was 16.0 Gy (range, 11-20 Gy). RESULTS: At a median of 50.1 months (range, 6.0-165.4 mo), seven patients had died from disease progression, and one patient had died secondary to heart failure. The overall survival after radiosurgery was 100%, 94.4%, and 68.7% at 1, 3, and 7 years, respectively. Follow-up imaging studies demonstrated tumor control in 68 tumors (91.9%). The progression-free survival after SRS at 1, 3, and 5 years was 96.9%, 95.0%, and 89.9%, respectively. Factors associated with an improved progression-free survival included von Hippel-Lindau disease-associated hemangioblastoma, solid tumor, lower tumor volume, and greater marginal dose. CONCLUSION: SRS is an important tool in the management of hemangioblastomas and is associated with a high tumor control rate and a low risk of adverse radiation effects.

Management options for patients with vestibular schwannomas (acoustic neuromas) include observation, resection, stereotactic radiosurgery, or fractionated radiotherapy. In this report, we review our experience with radiosurgery over a 20-year interval, and discuss indications and expectations with the different approaches. There has been an evolution in available technologies, and an evolution in both patient and physician approaches to the management of this tumor. Patient decisions must be based on quality information from the peer-reviewed literature. Future concepts for radiosurgery are discussed.

OBJECTIVE: To report the results of gamma knife radiosurgery (GKR) for treatment resistant choroid plexus papillomas. METHODS: Six patients (median age 55 years; range 29-75) with residual (n = 2) or recurrent (n = 4) choroid plexus papillomas underwent GKR. All failed prior surgery and one failed prior proton beam radiation therapy. These six patients had a total of 11 locally or distant recurrent intracranial tumors. The median and mean tumor volumes were 2.7 and 3.9 cc (range, 0.23-21.1). A median margin dose of 12.0 Gy (range, 11.5-15) was prescribed to the tumor margin. RESULTS: The progression-free periods varied from 7 to 108 months (mean: 36.9). Four tumors were stable after GKR but seven showed progression. Four recurrent tumors in two patients were managed with repeat radiosurgery and three were observed. At the second GKR, the tumor volume varied from 1.3 to 12.4 cc, and the marginal radiation dose varied from 11 to 14 Gy. The overall survival after the first GKR varied from 15 to 120 months. Four patients were alive at the end of the study period. CONCLUSIONS: Radiosurgery represents an additional management strategy for patients who progress despite surgical removal. It may especially be useful for patients with small deep seated residual choroid plexus papillomas, and for tumors that recur at a site distant from their origin.

We sought to establish a benchmark for complications using frame-based stereotactic surgery for both deep and lobar brain surgery. During a 28-year interval, we performed frame-based stereotactic surgery in 2,651 patients. Our database was retrospectively used to assess the risks of complications after frame-based stereotactic surgery. Routine immediate intraoperative imaging detected new blood products after diagnostic biopsy in 43 cases (2.6%); only 6 patients (0.36%) required craniotomy for hematoma evacuation. Perioperative seizures occurred in 6 patients (0.36%), and 2 patients developed burr hole site infections. One patient (1%) developed an intra-abscess hemorrhage after biopsy and catheter drainage. Two deaths (0.08%) related to surgery occurred. Some centers are currently migrating to frameless, even pinless, neuronavigation-guided needle procedures for both lobar and deep brain targets. Although experimental accuracy under optimal conditions is reported to be similar to that of frame-based systems, the complication rates from a significant number of cases have yet to be reported. This report establishes the safety profile of frame-based stereotactic surgery based on a 28-year period. These results may serve as a benchmark against which free-hand or guided neuronavigation approaches may be measured, as both the advantages and risks of such procedures are assessed.

PURPOSE: To evaluate adjuvant stereotactic radiosurgery (SRS) in the management of recurrent or residual intracranial hemangiopericytomas (HPCs), we assessed tumor control, survival, and complications in patients who had undergone gamma knife SRS as part of multimodal therapy. METHODS AND MATERIALS: We retrospectively reviewed the records of consecutive 20 HPC patients who had undergone SRS for 29 tumors. The median patient age was 51.5 years (range, 8.9-80.2). All patients had undergone previous surgical resection of their tumors. In addition, 12 patients underwent fractionated radiotherapy before SRS. Of the 20 patients, 16 patients had low-grade HPCs (20 tumors) and 4 had high-grade anaplastic HPCs (9 tumors). The median radiosurgery target volume was 4.5 cm(3) (range, 0.07-34.3), and the median marginal dose was 15.0 Gy (range, 10-20). RESULTS: At an average of 48.2 months (range, 7.2-124.1), 5 patients had died of metastases and 3 patients had died of disease progression. The overall survival after radiosurgery was 100%, 85.9%, and 13.8% at 1, 5, and 10 years, respectively. The follow-up imaging studies demonstrated tumor control in 21 (72.4%) of 29 tumors. The progression-free survival rate after SRS at 1, 3, and 5 years was 89.1% for low-grade HPCs and 88.9%, 66.7%, and 0%, respectively, for high-grade HPCs. The factors associated with improved progression-free survival included lower grade and higher marginal dose. Eight patients had intracranial or extracranial metastasis after the initial diagnosis, which correlated with the shorter survival. CONCLUSION: The results of our study have shown that adjuvant SRS after tumor resection is an important management option for patients with residual or recurrent HPCs and is particularly effective for less-aggressive tumors.

OBJECT: The aim of this paper was to determine prognostic factors for adult medulloblastoma treated with boost Gamma Knife surgery (GKS) following resection and craniospinal irradiation. METHODS: The authors performed a retrospective analysis of 12 adult patients with histologically proven medulloblastoma or supratentorial primitive neuroectodermal tumor who between February 1991 and December 2004 underwent >or=1 sessions of GKS for posttreatment residual or recurrent tumors (6 tumors in each group). Before GKS, all patients had undergone a maximal feasible resection followed by craniospinal irradiation. Nine patients also received systemic chemotherapy. Stereotactic radiosurgery was applied to residual and recurrent posterior fossa tumor as well as to foci of intracranial medulloblastoma metastases. The median time interval from initial diagnosis and resection to the first GKS treatment was 24 months (range 2-37 months). The mean GKS-treated tumor volume was 9.4 cm3 (range 0.5-39 cm3). RESULTS: Following adjunctive radiosurgery, 5 patients had no evidence of tumor on magnetic resonance (MR) imaging, 3 patients had stable tumor burden on MR imaging, and 4 patients had evidence of tumor progression locally with or without intracranial metastases. All patients with tumor progression died. Eight patients survive with a mean cumulative follow-up of 72.4 months (range 21-152 months). No acute radiation toxicity or delayed radiation necrosis was observed among any of the 12 patients. The majority of patients who achieved tumor eradication (80%) and tumor stabilization (67%) after GKS had residual tumor as the reason for their referral for GKS. The best outcomes were attained in patients with residual disease who were younger, had smaller tumor volumes, had no evidence of metastatic disease, and had received higher cumulative GKS doses. CONCLUSIONS: Single or multiple GKS sessions were a well-tolerated, feasible, and effective adjunctive treatment for posterior fossa residual or recurrent medulloblastoma as well as intracranial metastatic medulloblastoma in adult patients.