Faculty Bibliography

BACKGROUND: Stereotactic radiosurgery is the principal alternative to microsurgical resection for acoustic neuromas (vestibular schwannomas). The goals of radiosurgery are the long-term prevention of tumor growth, maintenance of neurologic function, and prevention of new neurologic deficits. Although acceptable short-term outcomes have been reported, long-term outcomes have not been well documented. METHODS: We evaluated 162 consecutive patients who underwent radiosurgery for acoustic neuromas between 1987 and 1992 by means of serial imaging tests, clinical evaluations, and a survey between 5 and 10 years after the procedure. The average dose of radiation to the tumor margin was 16 Gy, and the mean transverse diameter of the tumor was 22 mm (range, 8 to 39). Resection had been performed previously in 42 patients (26 percent); in 13 patients the tumor represented a recurrence of disease after a previous total resection. Facial function was normal in 76 percent of the patients before radiosurgery, and 20 percent had useful hearing. RESULTS: The rate of tumor control (with no resection required) was 98 percent. One hundred tumors (62 percent) became smaller, 53 (33 percent) remained unchanged in size, and 9 (6 percent) became slightly larger. Resection was performed in four patients (2 percent) within four years after radiosurgery. Normal facial function was preserved in 79 percent of the patients after five years (House-Brackmann grade 1), and normal trigeminal function was preserved in 73 percent. Fifty-one percent of the patients had no change in hearing ability. No new neurologic deficits appeared more than 28 months after radiosurgery. An outcomes questionnaire was returned by 115 patients (77 percent of the 149 patients still living). Fifty-four of these patients (47 percent) were employed at the time of radiosurgery, and 37 (69 percent) remained so. Radiosurgery was believed to have been successful by all 30 patients who had undergone surgery previously and by 81 (95 percent) of the 85 who had not. Thirty-six of the 115 patients (31 percent) described at least one complication, which resolved in 56 percent of those cases. CONCLUSIONS: Radiosurgery can provide long-term control of acoustic neuromas while preserving neurologic function.

OBJECTIVE AND IMPORTANCE: We describe the successful treatment of symptomatic giant arteriovenous malformations (AVMs) using staged volume radiosurgery followed by microsurgical resection. CLINICAL PRESENTATION: A 57-year-old man presented with Spetzler-Martin Grade 5 AVMs, with persistent headaches and seizures. He had previously undergone eight attempts at AVM embolization and a craniotomy for attempted AVM resection; he had suffered four episodes of brain hemorrhaging but had made a good neurological recovery. INTERVENTION: Because of the persistent symptoms of the patient and his history of hemorrhaging, a treatment plan based on staged radiosurgical treatments of different portions of the AVMs (three sessions, spaced 6 mo apart), followed by delayed microsurgical removal of the much-reduced residual AVMs (3 years later), was undertaken. The patient did not suffer any additional hemorrhaging episodes, his AVMs were completely removed, and he has made a good recovery. CONCLUSION: Staged volume radiosurgery followed by microsurgical resection of the residual AVMs represents a novel treatment strategy for the management of Grade 5 AVMs that might be untreatable by any single treatment method used alone

PURPOSE: The development of a brain metastasis represents an ominous event for patients with malignant melanoma. We evaluated results after stereotactic radiosurgery (SR) for patients with metastastic melanoma to identify patient outcomes and factors for survival. METHODS: The authors reviewed the management results of 60 consecutive patients with melanoma metastases, with a total of 118 melanoma brain metastases, undergoing SR during a 9-year interval. Of these, 51 also had whole-brain radiation therapy (WBRT). A total of 118 tumors of mean volume of 2.95 ml (range, 0.1-25.5 ml) were treated by SR with a mean margin dose of 16.4 Gy (range, 10 to 20 Gy). Univariate and multivariate analyses were used to determine significant prognostic factors affecting survival in 60 patients. RESULTS: Median survival was 7 months after SR in all 60 patients and 10 months from brain tumor diagnosis (mean follow-up period, 9.3 months). Lack of active systemic disease and a solitary metastasis were associated with improved survival in multivariate analysis (median, 15 months). The imaging-defined local control rate of evaluable tumors (n = 72) was 90% (disappearance = 11%, shrinkage = 44%, and stable = 35%). Local recurrence developed in 7 patients and remote brain disease developed in 14 patients. WBRT combined with radiosurgery did not improve survival nor local tumor control. New brain metastases developed less often when WBRT was added to SR (23% vs. 44%), but this difference was not significant. Only 4 patients (7%) died from progression of a radiosurgery-managed tumor. No patient developed a delayed radiation-related complication, but 3 patients developed delayed intratumoral hemorrhage at the radiosurgery site, 2 of whom had new symptoms. CONCLUSIONS: Stereotactic radiosurgery for melanoma brain metastasis is effective and is associated with few complications. The use of radiosurgery alone is an appropriate management strategy for many patients with solitary tumors.

To evaluate the role of Gamma Knife radiosurgery as the first surgical therapy in the management of medically refractory trigeminal neuralgia, we reviewed outcomes on our first 23 patients who had radiosurgery as primary surgical therapy. These patients represented 19% of our overall series. Mean patient age was 66 years, and mean follow-up after radiosurgery was 12 months (range 5-33 months). For most patients, radiosurgery was performed because the patient had medical contraindications to open surgery. 14 patients had 70-Gy radiosurgery, and 9 patients, 80 Gy. Radiosurgery was performed using a single 4 mm isocenter. Postoperative imaging 6 to 9 months following radiosurgery confirmed regions of enhancement at the radiosurgical target. Nine patients received 70 Gy, and 8 patients had 80 Gy. 17 patients (74%) had an excellent result (total pain relief). Five patients (22%) achieved a good result (50-90% improvement). One patient had a poor result (4%) after 70-Gy radiosurgery and subsequently underwent microvascular decompression. No patient developed facial numbness or any other complication after Gamma Knife radiosurgery. Gamma Knife radiosurgery using 70 or 80 Gy targeted to the proximal trigeminal nerve proved to be a safe and effective primary surgical therapy for medically refractory trigeminal neuralgia. The overall response rate (96%) was similar to that obtained with other surgical therapies performed as a first procedure.

PURPOSE: To evaluate the imaging and pathological correlates of successful or risk-related stereotactic radiosurgery (SR). Methods and Materials. The ten-year Gamma Knife experience in 2,344 patients at the University of Pittsburgh was reviewed. In addition, the results or radiosurgery primate, rat, and mouse models were analyzed. Successful results and untoward complications were evaluated. RESULTS: Dose, volume, location and histology affected the imaging changes seen after SR. Imaging changes range from central loss of contrast ('black holes'), shrinkage with diffuse contrast uptake ('white dwarfs'), or stabilization or growth arrest. Limited pathological data indicates that the prevention of cell division coupled with vascular obliteration results in tumor control, whereas a progressive endothelial proliferative and obliterative response results in arteriovenous malformation (AVM) obliteration. Perilesional imaging changes, especially in vascular malformations, may reflect flow phenomena, interstitial edema, or profound reactive astrocytosis ('supernovas'). CONCLUSION: Imaging changes correlate with both success and risks of stereotactic radiosurgery; however, pathological correlates are limited. High resolution neurodiagnostic imaging provides the best quality control available to assess the response to stereotactic radiosurgery. In the future, additional molecular probes are necessary to assess the radiobiological effects of radiosurgery.

Surgeons perform stereotactic radiosurgery as the main alternative to acoustic tumor (vestibular schwannoma) resection. The goals of radiosurgery include preservation of neurological function and prevention of tumor growth. Longer-term outcomes are not well documented for patients with solitary tumors or those with neurofibromatosis Type 2 (NF2). To define outcomes, the authors evaluated 462 consecutive patients with solitary acoustic tumors and 40 patients with NF2 (total of 45 tumors treated) who underwent radiosurgery between 1987 and 1998. Serial imaging studies, clinical evaluations, and a patient survey were performed. The average tumor margin dose was 15 Gy, and the mean transverse tumor diameter was 22 mm. In patients with solitary tumors, prior resection had been performed in 111 patients (24%); 27 patients experienced tumor recurrence after a "total resection." The clinical tumor control rate (no resection required) was 98%. In non-NF2 patients followed for at least 5 years, 100 tumors (61.7%) were smaller, 53 (32.7%) remained unchanged in size, and nine (5.6%) were slightly larger. Resection was performed in four patients (2.4%). Neurological deficits after radiosurgery all occurred within the first 28 months. The rates of facial and trigeminal neuropathy varied with radiosurgery technique. In patients with NF2, 16 tumors were smaller, 28 remained unchanged, and one enlarged (overall 98% control rate at median 3-year follow up). Resection was performed in three patients (7%). Useful hearing was preserved in six (43%) of 14 NF2 patients who had useful hearing before radiosurgery. Radiosurgery provided long-term tumor control associated with high rates of neurological function preservation. No further tumor surgery was necessary in 98% of patients with solitary tumors followed for a minimum of 5 years.

BACKGROUND: Parasagittal meningiomas, especially when associated with the middle or posterior third of the superior sagittal sinus, pose difficult management challenges. Initial surgical excision is associated with high morbidity and frequent tumor recurrence after subtotal resection. Neurological deficits are cumulative when multiple resections are required. No consistent management approach exists for patients with such tumors. In addition to observation, management options include resection, stereotactic radiosurgery, or fractionated radiation therapy used alone or in combination. METHODS: Sixteen centers where resection, gamma knife radiosurgery, and/or radiation therapy were available provided management data on 203 patients with histologically benign meningiomas from the time of initial diagnosis through follow-up after radiosurgery. The timing of resections, parameters of radiosurgery, rates of tumor control, morbidity, and functional patient outcomes were studied. The median follow-up duration in this study was 3.5 years (maximum, 33 yr after presentation and 6 yr after radiosurgery). RESULTS: The tumors were located in the anterior superior sagittal sinus in 52 patients, at the middle of the sinus in 91, and at the posterior portion of the sinus in 60. The mean tumor volume at the time of radiosurgery was 10 cc. In patients who underwent radiosurgery as the primary therapy (n = 66), the 5-year actuarial tumor control rate was 93 +/- 4%. No clinical failure (need for additional therapy or worsened neurological function) occurred in patients who had smaller tumors (<7.5 cc) and who had never undergone resection (n = 41). The 5-year control rate for patients with previous surgery was only 60 +/- 10%; the control rate for the radiosurgery-treated volume was 85%. Most failures resulted from remote tumor growth. Multivariate analyses identified significantly decreased tumor control with increasing tumor volume (P = 0.002) and previous neurological deficits (P = 0.002). The rate of transient, symptomatic edema after radiosurgery was 16%, was more common with larger tumors, and occurred within 2 years. Of 33 patients who were employed at the time of radiosurgery for whom a minimum of 1 year of follow-up data were available, 30 remained employed (91%). A decrease in functional status after radiosurgery was noted in only 3 of 33 (9%) employed and 7 of 77 (9%) unemployed patients. CONCLUSION: In patients with smaller tumors (<3 cm in diameter) and patent sagittal sinuses, we advocate radiosurgery alone as the first surgical procedure. Patients with larger tumors and those with progressive neurological deficits resulting from brain compression should first undergo resection. Planned second-stage radiosurgery should be performed soon afterward for any residual tumor nodule or neoplastic dural remnant. Multimodality management may enhance long-term tumor control, reduce the need for multiple resections, and maintain the functional status of the patient.

OBJECTIVE: A 10-year prospective clinical and magnetic resonance imaging study was undertaken to determine the natural history of venous malformations. We assessed the hemorrhage rate and morbidity associated with venous malformations of the brain. PATIENTS AND METHODS: From 1986 to 1996, 80 patients with venous malformations were referred to the University of Pittsburgh multidisciplinary vascular malformation study group for evaluation. Observation was recommended for all patients. Follow-up clinical information was obtained from patients or their referring physicians through questionnaire or phone conversation. RESULTS: Twenty-two patients presented with neurological signs or symptoms that were thought to be related to the malformations (nine with headaches, four with seizures, three with sensory symptoms, three with motor deficits, two with trigeminal neuralgia, and one with an extrapyramidal disorder). Twenty-three patients presented with headaches that were not considered to be related to the malformations. The retrospective hemorrhage rate (from birth to study entry) was 0.61% (18 bleeds in 2,949 patient-years). Sixteen patients had sustained previous brain hemorrhage in the region of the venous malformations, two of whom had suffered subsequent hemorrhage. During the prospective follow-up period totaling 298 patient-years of clinical observation, two patients suffered hemorrhage (0.68% per year), but only one had a symptomatic bleed (0.34% per year). This patient had not hemorrhaged previously. One of these patients remained asymptomatic, whereas the second developed temporary worsening of facial paresthesias. No patient died as a result of the venous malformations. CONCLUSION: The hemorrhage rate of a patient with venous malformations is similar to the rates presented in previous reports for patients with cavernous malformations without previous symptomatic hemorrhage. We think that hemorrhage in a patient with venous malformations may be related to an underlying but not yet documented cavernous malformation. Because of the low risk for new neurological events, we advocate conservative management. The risks associated with surgical intervention greatly exceed the low risk of morbidity related to venous malformation hemorrhage.