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Bruce E. Pollock

Object

Stereotactic radiosurgery (SRS) has become an important treatment option for patients with intracranial meningiomas. The author reviews the 12-year experience at a single institution and discusses the relative strengths and weakness of this management approach.

Methods

Between January 1990 and December 2002, 330 patients (with 356 tumors) underwent radiosurgery for intracranial meningiomas. One hundred thirty-eight patients (42%) harbored recurrent/residual tumors after having already undergone resection; 192 patients (58%) underwent radiosurgery as primary treatment. The majority of patients (70%) harbored skull base tumors. The median tumor volume was 7.3 cm3 (range 0.5–50.5 cm3). The median tumor margin dose was 16 Gy (range 12–20 Gy). In 278 patients with 297 lesions the mean clinical and imaging follow-up period was 43 months (range 2–138 months). Two hundred seventy-eight tumors (94%) remained stable or decreased in size, and 19 tumors progressed in size. Factors associated with progression were tumor histological type and prior surgery. Treatment-related complications occurred in 8% of the patients and included cranial neuropathies, symptomatic edema, cyst formation, and stenosis of the internal carotid artery. In three patients (1%) tumor dedifferentiation was noted after SRS.

Conclusions

Radiosurgical treatment of meningioma is safe and it has become the primary treatment for patients with small skull base tumors. Further study is needed to determine the long-term tumor control rates after such treatment, especially for patients treated with doses of 14 Gy or less.

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Bruce E. Pollock

Object

Microsurgical removal of glomus jugulare tumors is frequently associated with injury of the lower cranial nerves. To decrease the morbidity associated with tumor management in these patients, gamma knife surgery (GKS) was performed as an alternative to resection.

Methods

Between 1990 and 2003, 42 patients underwent GKS as the primary management (19 patients) or for recurrent glomus jugulare tumors (23 patients). Facial weakness and deafness were more common in patients with recurrent tumors than in those in whom primary GKS was performed (48% compared with 11%, p = 0.02). The mean tumor volume was 13.2 cm3; the mean tumor margin dose was 14.9 Gy. The mean follow-up period for the 39 patients in whom evaluation was possible was 44 months (range 6–149 months). After GKS, 12 tumors (31%) decreased in size, 26 (67%) were unchanged, and one (2%) grew. The patient whose tumor grew underwent repeated GKS. Progression-free survival after GKS was 100% at 3 and 7 years, and 75% at 10 years. Six patients (15%) experienced new deficits (hearing loss alone in three, facial numbness and hearing loss in one, vocal cord paralysis and hearing loss in one, and temporary imbalance and/or vertigo in one). In 26 patients in whom hearing could be tested before GKS, hearing preservation was achieved in 86 and 81% at 1 and 4 years posttreatment, respectively. No patient suffered a new lower cranial nerve deficit after one GKS session; the patient in whom repeated GKS was performed experienced a new vocal cord paralysis 1 year after his second procedure.

Conclusions

Gamma knife surgery provided tumor control with a low risk of new cranial nerve injury in early follow-up review. This procedure can be safely used as a primary management tool in patients with glomus jugulare tumors that do not have significant cervical extension, or in patients with recurrent tumors in this location.

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Bruce E. Pollock

with propofol as needed. Once adequate sedation had been achieved, a 20-gauge spinal needle was directed through the foramen ovale by using a combination of lateral, anteroposterior, and oblique fluoroscopy After an intracranial needle position had been confirmed, the stylet of the spinal needle was removed to determine whether CSF flow was present. The patient was then placed into a sitting position and cisternography was performed to access the volume of the trigeminal cistern. The amount of glycerol that was injected was based on the size of the trigeminal cistern

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Jonathan M. Bledsoe, Michael J. Link, Scott L. Stafford, Paul J. Park and Bruce E. Pollock

preferred treatment when this can be accomplished safely, 18 but subtotal resection followed by fractionated radiotherapy or SRS is often performed when the risk of total removal is prohibitive. 6 , 10 , 12 , 16 , 19 The dose/volume relationship and how it relates to postradiosurgical complications has been well documented. 5 Nonetheless, the progressive trend to treat benign tumors with lower radiation doses theoretically permits patients with larger lesions to be considered for SRS. 7 In this study, we review the radiosurgical experience at our center for patients

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Brian D. Milligan, Bruce E. Pollock, Robert L. Foote and Michael J. Link

studies have documented increased morbidity following GKS for larger tumors, but the majority of these tumors were treated with higher tumor margin doses (16 Gy) than is generally used today. 4 , 10 , 14 , 20 , 30 One study of VSs treated with contemporary radiosurgical doses (tumor margin doses of 12–13 Gy) reported only a 57% 5-year PFS for patients with tumors larger than 15 cm 3 (24 tumors). 14 A more recent GKS study of larger VSs (5–22 cm 3 , median volume 9 cm 3 ) treated with a median margin dose of 12 Gy demonstrated an 87% tumor control rate at the last

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Aaron A. Cohen-Gadol and Bruce E. Pollock

and are not included in our calculations. The clinical characteristics of the remaining 38 patients (14 boys and 24 girls) are outlined in Table 1 . The median patient age was 15 years (range 7–18 years). Of note, only three patients (8%) were younger than 9 years of age. A radiosurgery-based AVM score was calculated for each patient according to the following formula: AVM score = (0.1 × volume [cm 3 ]) + (0.02 × age [years]) + (0.3 × location [frontal/temporal = 0; parietal/occipital/corpus callosum/cerebellar = 1; basal ganglia/thalamus/brainstem = 2]). 20 The

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Bruce E. Pollock and John C. Flickinger

authors have noted discrepancies between the Spetzler—Martin AVM grade and patient outcomes, especially with regard to Grade III AVMs, 3, 24 the general consensus supports this grading scale as practical and reliable. Unfortunately, this grading scale does not seem to correlate with successful AVM radiosurgery. 22, 28 This should not be surprising because the Spetzler—Martin grading system is insensitive to important factors such as AVM volume and specific location. For example, a 1-cm diameter lesion has an approximate volume of 0.6 cm 3 , whereas a 3-cm diameter

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outcomes: AVM volume (p = 0.001), patient age (p < 0.001), AVM location (p < 0.001), previous embolization (p = 0.02), and number of draining veins (p ≤ 0.001). Regression analysis modeling permitted removal of two significant variables (previous embolization and number of draining veins) and resulted in the following equation to predict patient outcomes after AVM radiosurgery: AVM score = (0.1) (AVM volume in cm 3 ) + (0.02) (patient age in years) + (0.3) (location of lesion: frontal or temporal) = 0; parietal, occipital, intraventricular, corpus callosum, cerebellar

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Nelly Amador and Bruce E. Pollock

-term complication rates for high-volume hospitals and surgeons performing MVD procedures to low-volume hospitals and surgeons. Based on a review of 1590 operations (1326 for TN), they determined that even after adjusting for age, sex, diagnosis, and other medical comorbidities, outcomes at discharge were superior for both high-volume hospitals and high-volume surgeons. Surgeons with the highest caseload (≥ 29 cases/year) had no neurological complications recorded in this study, whereas postoperative neurological morbidity was noted in 2.7% of patients who underwent operations by

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Bruce E. Pollock and Christopher J. Boes

authorization. Radiosurgical Dosimetry Radiosurgery was performed using the Leksell Gamma Knife Perfexion Unit (Elekta Instruments). Dose planning was performed using a combination of stereotactic Gd-enhanced spoiled gradient–recalled acquisition MR imaging and thin-slice CT. The radiosurgical target was the distal portion of the glossopharyngeal nerve at the level of the glossopharyngeal meatus ( Fig. 1 ). In 4 patients 1 isocenter of radiation was used with all 4-mm sectors open (volume 93 mm 3 ); the length of coverage for the 50% isodose line was 5.9 mm. In 1