Pre-existing Vestibular Symptoms Are Associated With Acute Vestibular Symptoms After Gamma Knife Therapy for Vestibular Schwannoma.

OBJECTIVE: To identify pretreatment variables associated with the development of acute vestibular symptoms after Gamma Knife (GK) treatment for Vestibular Schwannoma (VS). STUDY DESIGN: Retrospective case series. SETTING: Tertiary neurotology referral center. PATIENTS: Patients treated with GK radiosurgery for VS between March 2007 and March 2017 were considered for this study. Patients with neurofibromatosis type II, previous VS surgery, follow-up less than 6 months, or the lack of T2 magnetic resonance imaging (MRI) sequences from the day of treatment were excluded. MAIN OUTCOME MEASURES: The presence of acute vestibular symptoms arising within 6 months after GK was the main outcome variable. Tumor, patient, and treatment characteristics were gathered from the medical record. RESULTS: In total, 98 patients met inclusion criteria. The incidence of acute vestibular symptoms occurring within 6 months after GK treatment was 46.9%. Post-GK vestibular symptoms were reported at a significantly higher frequency among subjects who had reported vestibular symptoms before their treatment (p = 0.001). Tumor size was not associated with a propensity to develop acute vestibular symptoms (p = 0.397). The likelihood of receiving a referral to vestibular rehabilitation services was not significantly different among patients with larger versus smaller tumor size, as defined by 1.6 cm and 1.4 cm thresholds (p = 0.896, p = 0.654). CONCLUSIONS: Inquiries aimed at revealing a history of vestibular complaints may prove useful in counseling patients on the likelihood of experiencing acute vestibular symptoms after treatment of Vestibular Schwannoma with Gamma Knife therapy.

A Protective Cap: Fundal Fluid Cap Facilitates a Reduction in Inner Ear Radiation Dose in the Radiosurgical Treatment of Vestibular Schwannoma.

OBJECTIVE: Assess inner ear radiation dose magnitude as it relates to fundal cap length and hearing outcomes in the radiosurgical treatment of vestibular schwannoma. STUDY DESIGN: Retrospective case series. SETTING: Tertiary neurotology referral center. PATIENTS: Patients treated with Gamma Knife radiosurgery for vestibular schwannoma between March 2007 and March 2017 were considered for this study. Exclusion criteria included pretreatment pure-tone average (PTA) >90 dB, neurofibromatosis type II, history of previous surgical resection, and follow-up less than 1 year. MAIN OUTCOME MEASURE: (s): Hearing function was assessed by maintenance of class A/B hearing level and maintenance of baseline hearing (≤20 dB change in PTA following Gamma Knife radiosurgery). RESULTS: Lower radiation doses delivered to the inner ear were associated with longer fundal cap lengths: mean cochlear dose (r = -0.130; p = 0.184), mean labyrinth dose (r = -0.406; p < 0.001), max cochlear dose (r = -0.326; p = 0.001), and max labyrinth dose (r = -0.360; p < 0.001). Kaplan-Meier analysis with log-rank testing revealed that patients with a mean labyrinth dose < 3 Gy achieved higher rates of preserving baseline hearing (≤20 dB change in PTA) following radiosurgery, compared to patients with a mean labyrinth dose ≥3 Gy (p < 0.001). A fundal fluid cap length of 2.5 mm was associated with the 3 Gy mean labyrinth dose threshold. CONCLUSIONS: We report that fundal cap presence facilitated the creation of treatment plans with a lower dose delivered to the labyrinth. By affording this dose reduction, a fundal cap may be associated with a slight improvement in hearing outcomes.

Fundal Fluid Cap Is Associated With Hearing Preservation in the Radiosurgical Treatment of Vestibular Schwannoma.

OBJECTIVE: To evaluate the relationship between fundal fluid and hearing outcomes after treatment of vestibular schwannoma (VS) with Gamma Knife radiosurgery (GKRS). STUDY DESIGN: Retrospective case series. SETTING: Tertiary neurotology referral center. PATIENTS: Patients treated with GKRS for vestibular schwannoma between March 2007 and March 2017 were considered for this study. Exclusion criteria included pretreatment pure-tone average (PTA) >90 dB, neurofibromatosis type II, history of previous surgical resection, and follow-up less than 1 year. MAIN OUTCOME MEASURE(S): Hearing function was assessed both by preservation of serviceable hearing and by preservation of baseline hearing (≤20 dB change in PTA) after GKRS. Hearing preservation comparisons were made between groups of patients with and without a fundal fluid cap. RESULTS: Patients with a fundal cap had significantly higher rates of baseline hearing preservation (≤20 dB change in PTA) according to Kaplan-Meier survival analysis of all 106 patients (p = 0.006). By the 3rd year posttreatment, 70.9% of patients with a fundal cap had maintained a ≤20 dB change in PTA, while only 43.6% of patients without a fundal fluid cap achieved this outcome (p = 0.004). CONCLUSIONS: Fundal fluid present on pretreatment magnetic resonance imaging is predictive of improved baseline hearing preservation rates in patients undergoing GKRS for vestibular schwannoma when considering all patients with PTA ≤90 dB. Fundal fluid cap presence may serve as a favorable prognostic indicator to help set hearing expectations and guide patient selection efforts.

Utility of graded prognostic assessment in evaluation of patients with brainstem metastases treated with radiosurgery.

OBJECTIVES: Prospective data regarding the safety and efficacy of stereotactic radiosurgery (SRS) for patients with metastatic disease involving the brainstem are lacking. The aim of this study was to assess the efficacy and toxicity of SRS for patients with brainstem metastases treated at our institution. PATIENTS AND METHODS: From September 2007 to October 2015, patients treated with SRS for brain metastases were prospectively entered into an institutional database. Forty eight patients with 51 lesions involving the brainstem with clinical follow-up were identified. Local control (LC), elsewhere brain failure (EBF) and overall survival (OS) were assessed from the date of radiosurgery using the Kaplan-Meier method. Univariate and multivariate analyses of factors related to OS were performed using a Cox proportional hazards model. RESULTS: Median clinical follow-up was 4.8 months. Median patient age was 62 (range: 28-87); non-small cell lung and breast cancer were the most common primaries at 54% and 21% respectively. Median brainstem lesion volume was 0.12cm(3) (range: 0.01-3.67cm(3)). Whole brain radiotherapy was previously utilized in 19 patients (40%). The median OS was 7.6 months and the 12 month LC rate was 89%. Only 2 patients (4%) experienced grade 3 motor toxicity secondary to SRS. 11 of the 16 patients (69%) initially presenting with symptoms related to brainstem metastases had symptom improvement or resolution following SRS. On multivariate analysis, graded prognostic assessment (GPA) score>2 was predictive of improved survival (p<0.01) while prior chemotherapy use predicted decreased survival (p=0.049). CONCLUSIONS: SRS is associated with high LC rates and low toxicity for brainstem metastases. Improved OS was seen for patients with GPA score>2. GPA appears to be a useful tool for assessing prognosis in patients with brainstem metastases. Small volume lesions were safely treated with or without prior whole brain radiotherapy.

Surgical Resection of Brain Metastases and the Risk of Leptomeningeal Recurrence in Patients Treated With Stereotactic Radiosurgery.

PURPOSE: Recent prospective data have shown that patients with solitary or oligometastatic disease to the brain may be treated with upfront stereotactic radiosurgery (SRS) with deferral of whole-brain radiation therapy (WBRT). This has been extrapolated to the treatment of patients with resected lesions. The aim of this study was to assess the risk of leptomeningeal disease (LMD) in patients treated with SRS to the postsurgical resection cavity for brain metastases compared with patients treated with SRS to intact metastases. METHODS AND MATERIALS: Four hundred sixty-five patients treated with SRS without upfront WBRT at a single institution were identified; 330 of these with at least 3 months' follow-up were included in this analysis. One hundred twelve patients had undergone surgical resection of at least 1 lesion before SRS compared with 218 treated for intact metastases. Time to LMD and overall survival (OS) time were estimated from date of radiosurgery, and LMD was analyzed by the use of cumulative incidence method with death as a competing risk. Univariate and multivariate analyses were performed with competing risk regression to determine whether various clinical factors predicted for LMD. RESULTS: With a median follow-up time of 9.0 months, 39 patients (12%) experienced LMD at a median of 6.0 months after SRS. At 1 year, the cumulative incidence of LMD, with death as a competing risk, was 5.2% for the patients without surgical resection versus 16.9% for those treated with surgery (Gray test, P<.01). On multivariate analysis, prior surgical resection (P<.01) and breast cancer primary (P=.03) were significant predictors of LMD development. The median OS times for patients undergoing surgery compared with SRS alone were 12.9 and 10.6 months, respectively (log-rank P=.06). CONCLUSIONS: In patients undergoing SRS with deferral of upfront WBRT for intracranial metastatic disease, prior surgical resection and breast cancer primary are associated with an increased risk for the development of LMD.

Trigeminal neuralgia pain relief after gamma knife stereotactic radiosurgery.

OBJECTIVES: To report outcomes of patients with medical and/or surgical refractory trigeminal neuralgia (TN) treated with gamma knife stereotactic radiosurgery (GK SRS). METHODS: One hundred and forty-nine patients with 152 cases of TN treated with GK SRS were analyzed. All patients, except one, received a dose of 40Gy to the 50% isodose volume. The Barrow Neurological Institute (BNI) pain intensity score was used to grade pain. Actuarial rates of pain relief were calculated. Multiple factors were analyzed for association with pain relief. RESULTS: The median follow up was 27 months (4-71 months). Overall 92% of cases achieved a BNI score I-III after GK SRS. Of those who had pain relief after GK SRS, 32% developed pain recurrence defined as a BNI score of IV or V. The actuarial rate of freedom from pain recurrence (BNI scores I-III) of all treated cases at 1, 2 and 3-years was 76%, 69% and 60%, respectively. On univariate analysis age ≥70 was predictive of better pain relief (p=0.046). Type of pain, prior surgery, multiple sclerosis, number of isocenters, treated nerve length, volume and thickness and distance from the root entry zone to the isocenter were not significant for maintaining a BNI score of I-III. Those who achieved a BNI score of I or II were more likely to maintain pain relief compared to those who only achieved a BNI score of III (93% vs 38% at three years, p<0.01). The rate of pain relief of twenty-seven patients who underwent repeat GK SRS was 70% and 62% at 1 and 2 years, respectively. Toxicity after first GK SRS was minimal with 25% of cases experiencing only new or worsening post-treatment numbness. CONCLUSION: GK SRS provides acceptable pain relief with limited morbidity in patients with medical and/or surgical refractory TN.

Tumor volume as a predictor of survival and local control in patients with brain metastases treated with Gamma Knife surgery.

OBJECT: The aim of this study was to examine tumor volume as a prognostic factor for patients with brain metastases treated with Gamma Knife surgery (GKS). METHODS: Two hundred fifty patients with 1-14 brain metastases who had initially undergone GKS alone at a single institution were retrospectively reviewed. Patients who received upfront whole brain radiation therapy were excluded. Survival times were estimated using the Kaplan-Meier method. Univariate and multivariate analyses using Cox proportional hazard regression models were used to determine if various prognostic factors could predict overall survival, distant brain failure, and local control. RESULTS: Median overall survival was 7.1 months and the 1-year local control rate was 91.5%. Median time to distant brain failure was 8.0 months. On univariate analysis an increasing total tumor volume was significantly associated with worse survival (p = 0.031) whereas the number of brain metastases, analyzed as a continuous variable, was not (p = 0.082). After adjusting for age, Karnofsky Performance Scale score, and extracranial disease on multivariate analysis, total tumor volume was found to be a better predictor of overall survival (p = 0.046) than number of brain metastases analyzed as a continuous variable (p = 0.098). A total tumor volume cutoff value of ≥ 2 cm(3) (p = 0.008) was a stronger predictor of overall survival than the number of brain metastases (p = 0.098). Larger tumor volume and extracranial disease, but not the number of brain metastases, were predictive of distant brain failure on multivariate analysis. Local tumor control at 1 year was 97% for lesions < 2 cm(3) compared with 75% for lesions ≥ 2 cm(3) (p < 0.001). CONCLUSIONS: After adjusting for other factors, a total brain metastasis volume was a strong and independent predictor for overall survival, distant brain failure, and local control, even when considering the number of metastases.

Hearing preservation in patients with vestibular schwannoma treated with Gamma Knife surgery.

OBJECT: Hearing loss after Gamma Knife surgery (GKS) in patients with vestibular schwannoma has been associated with radiation dose to the cochlea. The purpose of this study was to evaluate serviceable hearing preservation in patients with VS who were treated with GKS and to determine if serviceable hearing loss can be correlated with the dose to the cochlea. METHODS: Forty patients with vestibular schwannoma with serviceable hearing were treated using GKS with a median marginal dose of 12.5 Gy (range 12.5-13 Gy) to the 50% isodose volume. Audiometry was performed prospectively before and after GKS at 1, 3, and 6 months, and then every 6 months thereafter. Hearing preservation was based on pure tone average (PTA) and speech discrimination (SD). Serviceable hearing was defined as PTA less than 50 dB and SD greater than 50%. RESULTS: The median cochlear maximum and mean doses were 6.9 Gy (range 1.6-16 Gy) and 2.7 Gy (range 0.7-5.0 Gy), respectively. With a median audiological follow-up of 35 months (range 6-58 months), the 1-, 2-, and 3-year actuarial rates of maintaining serviceable hearing were 93%, 77%, and 74%, respectively. No patient who received a mean cochlear dose less than 2 Gy experienced serviceable hearing loss (p = 0.035). Patients who received a mean cochlear dose less than 3 Gy had a 2-year hearing preservation rate of 91% compared with 59% in those who received a mean cochlear dose of 3 Gy or greater (p = 0.029). Those who had more than 25% of their cochlea receiving 3 Gy or greater had a higher rate of hearing loss (p = 0.030). There was no statistically significant correlation between serviceable hearing loss and age, tumor size, pre-GKS PTA, pre-GKS SD, pre-GKS Gardner-Robertson class, maximum cochlear dose, or the percentage of cochlear volume receiving 5 Gy. On multivariate analysis there was a trend toward significance for serviceable hearing loss with a mean cochlear dose of 3 Gy or greater (p = 0.074). Local control was 100% at 24 months. No patient developed facial or trigeminal nerve dysfunction. CONCLUSIONS: With a median mean cochlear dose of 2.7 Gy, the majority of patients with serviceable hearing retained serviceable hearing 3 years after GKS. A mean cochlear dose less than 3 Gy was associated with higher serviceable hearing preservation.

Differentiation between intra-axial metastatic tumor progression and radiation injury following fractionated radiation therapy or stereotactic radiosurgery using MR spectroscopy, perfusion MR imaging or volume progression modeling.

OBJECTIVE: To determine the accuracy of magnetic resonance spectroscopy (MRS), perfusion MR imaging (MRP), or volume modeling in distinguishing tumor progression from radiation injury following radiotherapy for brain metastasis. METHODS: Twenty-six patients with 33 intra-axial metastatic lesions who underwent MRS (n=41) with or without MRP (n=32) after cranial irradiation were retrospectively studied. The final diagnosis was based on histopathology (n=4) or magnetic resonance imaging (MRI) follow-up with clinical correlation (n=29). Cho/Cr (choline/creatinine), Cho/NAA (choline/N-acetylaspartate), Cho/nCho (choline/contralateral normal brain choline) ratios were retrospectively calculated for the multi-voxel MRS. Relative cerebral blood volume (rCBV), relative peak height (rPH) and percentage of signal-intensity recovery (PSR) were also retrospectively derived for the MRPs. Tumor volumes were determined using manual segmentation method and analyzed using different volume progression modeling. Different ratios or models were tested and plotted on the receiver operating characteristic curve (ROC), with their performances quantified as area under the ROC curve (AUC). MRI follow-up time was calculated from the date of initial radiotherapy until the last MRI or the last MRI before surgical diagnosis. RESULTS: Median MRI follow-up was 16 months (range: 2-33). Thirty percent of lesions (n=10) were determined to be radiation injury; 70% (n=23) were determined to be tumor progression. For the MRS, Cho/nCho had the best performance (AUC of 0.612), and Cho/nCho >1.2 had 33% sensitivity and 100% specificity in predicting tumor progression. For the MRP, rCBV had the best performance (AUC of 0.802), and rCBV >2 had 56% sensitivity and 100% specificity. The best volume model was percent increase (AUC of 0.891); 65% tumor volume increase had 100% sensitivity and 80% specificity. CONCLUSION: Cho/nCho of MRS, rCBV of MRP, and percent increase of MRI volume modeling provide the best discrimination of intra-axial metastatic tumor progression from radiation injury for their respective modalities. Cho/nCho and rCBV appear to have high specificities but low sensitivities. In contrast, percent volume increase of 65% can be a highly sensitive and moderately specific predictor for tumor progression after radiotherapy. Future incorporation of 65% volume increase as a pretest selection criterion may compensate for the low sensitivities of MRS and MRP.

Longitudinal assessment of quality of life and audiometric test outcomes in vestibular schwannoma patients treated with gamma knife surgery.

OBJECTIVE: To prospectively assess the quality of life (QOL) and hearing acuity in vestibular schwannoma (VS) patients after gamma knife surgery (GKS). PATIENTS: Fifty-nine VS patients. INTERVENTION: GKS. MAIN OUTCOME MEASURES: Prospective follow-up algorithm included 36-item Short Form Health Survey (SF-36), Hearing Handicap Inventory (HHI), Dizziness Handicap Inventory (DHI), Tinnitus Handicap Inventory (THI), pure-tone average, and speech discrimination hearing scores (Gardner-Robertson and American Academy of Otolaryngology), performed before and after GKS at 1-, 3-, 6-, 12-, and 18-month posttreatment intervals. RESULTS: From December 2006 to November 2008, 59 VS patients were treated with a median follow-up of 15 months. At baseline, mean scores for SF-36, HHI, DHI, and THI were 73, 37, 17, and 23, respectively. Median baseline Gardner-Robertson and American Academy of Otolaryngology hearing acuity scores were 2 and B, respectively. No significant decline in SF-36 health survey was noted after GKS. Mean SF-36 score at baseline was 73, compared with a range of 70 to 77 at predetermined posttreatment intervals. Similarly, no significant changes in DHI, HHI, and THI were noted. Approximately 47% of patients with baseline serviceable hearing maintained serviceable hearing at 12 months. Significant acute and chronic worsening in hearing acuity were noted at 1 and 18 months, respectively. No correlative decline in QOL was noted as assessed by SF-36 or HHI. CONCLUSION: No significant decline in global QOL occurred after GKS with relatively short follow-up and approximately 50% survey completion. When discussing therapy options with VS patients, anticipated treatment-related QOL outcomes should be considered.

Successful treatment of glomus jugulare tumours with gamma knife radiosurgery: clinical and physical aspects of management and review of the literature.

PURPOSE: To demonstrate the feasibility of treatment and early outcomes for patients treated with gamma knife radiosurgery (GKR), with or without surgical resection, for glomus jugulare tumours. METHODS: Between January 2007 and November 2008, 10 patients with glomus jugulare tumours were treated with GKR. Eight had prior surgical resection, seven subtotal resection and one total resection. In two cases GKR was the only definitive therapy. Baseline neurological deficits were prospectively recorded and present in 90% prior to GKR. The median tumour size and volume were 4 cc (0.7-10.9 cc). The median marginal tumour dose was 14 Gy (12-16 Gy). Clinical and radiographic outcomes are reported with a median follow-up of 9.7 months. RESULTS: Stereotactic frame placement allowed treatment of all 10 lesions, although 3-point fixation was sometimes required to avoid collisions. No patients developed worsening of symptoms or new neurological complaints after GKR; symptom relief was achieved in 50% of cases. No cases of clinical or radiographic progression were identified. Radiographically, 80% of lesions were stable and 20% showed significant shrinkage. CONCLUSIONS: GKR is an excellent option for patients with glomus jugulare tumours after complete or subtotal resection or at recurrence. Appropriately planned frame placement allows successful treatment delivery without difficulty. GKR improved symptoms, prevented neurological progression and achieved radiographic stability or regression in all cases.

Gamma Knife radiosurgery for occipital condyle metastasis.

We present a 45 year old female with right occipital condylar metastases who was treated at William Beaumont Hospital in the Gamma Knife Unit. Clinical results at 17 months follow-up and MRI are exposed.

Prospective staged volume radiosurgery for large arteriovenous malformations: indications and outcomes in otherwise untreatable patients.

OBJECTIVE: The obliteration response of an arteriovenous malformation (AVM) to radiosurgery is strongly dependent on dose and volume. For larger volumes, the dose must be reduced for safety, but this compromises obliteration. In 1992, we prospectively began to stage anatomic components in order to deliver higher single doses to symptomatic AVMs > 15 ml in volume. METHODS: During a 17-year interval at the University of Pittsburgh, 1040 patients underwent radiosurgery for a brain AVM. Out of 135 patients who had multiple procedures, 37 patients underwent prospectively staged volume radiosurgery for symptomatic otherwise unmanageable larger malformations. Twenty-eight patients who were managed before 2002 were included in this study to achieve sufficient follow-up in assessing the outcomes. The median age was 37 years (range, 13-57 yr). Thirteen patients had previous hemorrhages and 13 patients had attempted embolization. Separate anatomic volumes were irradiated at 3 to 8 months (median, 5 mo) intervals. The median initial AVM volume was 24.9 ml (range, 10.2-57.7 ml). Twenty-six patients had two stages and two had three-stage radiosurgery. Seven patients had repeat radiosurgery after a median interval of 63 months. The median target volume was 12.3 ml. (range, 4.2-20.8 ml.) at Stage I and 11.5 ml. (range, 2.8-22 ml.) at Stage II. The median margin dose was 16 Gy at both stages. Median follow-up after the last stage of radiosurgery was 50 months (range, 3-159 mo). RESULTS: Four patients (14%) sustained a hemorrhage after radiosurgery; two died and two patients recovered with mild permanent neurological deficits. Worsened neurological deficits developed in one patient. Seizure control was improved in three patients, was stable in eight patients and worsened in two. Magnetic resonance imaging showed T2 prolongation in four patients (14%). Out of 28 patients, 21 had follow-up more than 36 months. Out of 21 patients, seven underwent repeat radiosurgery and none of them had enough follow- up. Of 14 patients followed for more than 36 months, seven (50%) had total, four (29%) near total, and three (21%) had moderate AVM obliteration. CONCLUSIONS: Prospective staged volume radiosurgery provided imaging defined volumetric reduction or closure in a series of large AVMs unsuitable for any other therapy. After 5 years, this early experience suggests that AVM related symptoms can be stabilized and anticipated bleed rates can be reduced.

Prospective staged volume radiosurgery for large arteriovenous malformations: indications and outcomes in otherwise untreatable patients.

OBJECTIVE: The obliteration response of an arteriovenous malformation (AVM) to radiosurgery is strongly dependent on dose and volume. For larger volumes, the dose must be reduced for safety, but this compromises obliteration. In 1992, we prospectively began to stage anatomic components in order to deliver higher single doses to symptomatic AVMs >15 ml in volume. METHODS: During a 17-year interval at the University of Pittsburgh, 1040 patients underwent radiosurgery for a brain AVM. Out of 135 patients who had multiple procedures, 37 patients underwent prospectively staged volume radiosurgery for symptomatic otherwise unmanageable larger malformations. Twenty-eight patients who were managed before 2002 were included in this study to achieve sufficient follow-up in assessing the outcomes. The median age was 37 years (range, 13-57 yr). Thirteen patients had previous hemorrhages and 13 patients had attempted embolization. Separate anatomic volumes were irradiated at 3 to 8 months (median, 5 mo) intervals. The median initial AVM volume was 24.9 ml (range, 10.2-57.7 ml). Twenty-six patients had two stages and two had three-stage radiosurgery. Seven patients had repeat radiosurgery after a median interval of 63 months. The median target volume was 12.3 ml. (range, 4.2-20.8 ml.) at Stage I and 11.5 ml. (range, 2.8-22 ml.) at Stage II. The median margin dose was 16 Gy at both stages. Median follow-up after the last stage of radiosurgery was 50 months (range, 3-159 mo). RESULTS: Four patients (14%) sustained a hemorrhage after radiosurgery; two died and two patients recovered with mild permanent neurological deficits. Worsened neurological deficits developed in one patient. Seizure control was improved in three patients, was stable in eight patients and worsened in two. Magnetic resonance imaging showed T2 prolongation in four patients (14%). Out of 28 patients, 21 had follow-up more than 36 months. Out of 21 patients, seven underwent repeat radiosurgery and none of them had enough follow- up. Of 14 patients followed for more than 36 months, seven (50%) had total, four (29%) near total, and three (21%) had moderate AVM obliteration. CONCLUSIONS: Prospective staged volume radiosurgery provided imaging defined volumetric reduction or closure in a series of large AVMs unsuitable for any other therapy. After 5 years, this early experience suggests that AVM related symptoms can be stabilized and anticipated bleed rates can be reduced.

Radiosurgery of vestibular schwannomas: summary of experience in 829 cases.

OBJECT: Management options for vestibular schwannomas (VSs) have greatly expanded since the introduction of stereotactic radiosurgery. Optimal outcomes reflect long-term tumor control, preservation of cranial nerve function, and retention of quality of life. The authors review their 15-year experience. METHODS: Between 1987 and 2002, some 829 patients with VSs underwent gamma knife surgery (GKS). Dose selection, imaging, and dose planning techniques evolved between 1987 and 1992 but thereafter remained stable for 10 years. The average tumor volume was 2.5 cm3. The median margin dose to the tumor was 13 Gy (range 10-20 Gy). No patient sustained significant perioperative morbidity. The average duration of hospital stay was less than 1 day. Unchanged hearing preservation was possible in 50 to 77% of patients (up to 90% in those with intracanalicular tumors). Facial neuropathy risks were reduced to less than 1%. Trigeminal symptoms were detected in less than 3% of patients whose tumors reached the level of the trigeminal nerve. Tumor control rates at 10 years were 97% (no additional treatment needed). CONCLUSIONS: Superior imaging, multiple isocenter volumetric conformal dose planning, and optimal precision and dose delivery contributed to the long-term success of GKS, including in those patients in whom initial microsurgery had failed. Gamma knife surgery provides a low risk, minimally invasive treatment option for patients with newly diagnosed or residual VS. Cranial nerve preservation and quality of life maintenance are possible in long-term follow up.

Acoustic neuroma radiosurgery with marginal tumor doses of 12 to 13 Gy.

PURPOSE: To define tumor control and clinical outcomes of radiosurgery to marginal tumor doses of 12-13 Gy for unilateral acoustic neuroma patients. METHODS AND MATERIALS: Three hundred thirteen patients with previously untreated unilateral acoustic neuromas (vestibular schwannomas) underwent gamma knife radiosurgery between February 1991 and February 2001 with marginal tumor doses of 12-13 Gy (median, 13 Gy). Median follow-up was 24 months (maximum, 115 months; 36 patients with > or =60 months). Maximum doses were 20-26 Gy (median, 26 Gy), and treatment volumes were 0.04-21.4 mL (median, 1.1 mL). RESULTS: The actuarial 6-year clinical tumor control rate (no requirement for surgical intervention) for the entire series was 98.6 +/- 1.1%. Two patients required tumor resection; one had a complete resection for solid tumor growth and one required partial resection for an enlarging adjacent subarachnoid cyst. Six-year actuarial rates for preservation of facial nerve function, normal trigeminal nerve function, unchanged hearing level, and useful hearing were 100%, 95.6 +/- 1.8%, 70.3 +/- 5.8%, and 78.6 +/- 5.1%, respectively. The risk of developing trigeminal neuropathy correlated with increasing tumor volume (p = 0.038). CONCLUSIONS: Acoustic neuroma radiosurgery with doses of 12-13 Gy provides high rates of tumor control and cranial nerve preservation.

Long-term results after radiosurgery for benign intracranial tumors.

BACKGROUND: Stereotactic radiosurgery is the principal therapeutic alternative to resecting benign intracranial tumors. The goals of radiosurgery are the long-term prevention of tumor growth, the maintenance of patient function, and the prevention of new neurological deficits or adverse radiation effects. Evaluation of long-term outcomes more than 10 years after radiosurgery is needed. METHODS: We evaluated 285 consecutive patients who underwent radiosurgery for benign intracranial tumors between 1987 and 1992. Serial imaging studies were obtained, and clinical evaluations were performed. Our series included 157 patients with vestibular schwannomas, 85 patients with meningiomas, 28 patients with pituitary adenomas, 10 patients with other cranial nerve schwannomas, and 5 patients with craniopharyngiomas. Prior surgical resection had been performed in 44% of these patients, and prior radiotherapy had been administered in 5%. The median follow-up period was 10 years. RESULTS: Overall, 95% of the 285 patients in this series had imaging-defined local tumor control (63% had tumor regression, and 32% had no further tumor growth). The actuarial tumor control rate at 15 years was 93.7%. In 5% of the patients, delayed tumor growth was identified. Resection was performed after radiosurgery in 13 patients (5%). No patient developed a radiation-induced tumor. Eighty-one percent of the patients were still alive at the time of this analysis. Normal facial nerve function was maintained in 95% of patients who had normal function before undergoing treatment for acoustic neuromas. CONCLUSION: Stereotactic radiosurgery provided high rates of tumor growth control, often with tumor regression, and low morbidity rates in patients with benign intracranial tumors when evaluated over the long term. This study supports radiosurgery as a reliable alternative to surgical resection for selected patients with benign intracranial tumors.

Gamma knife radiosurgery of imaging-diagnosed intracranial meningioma.

PURPOSE: To evaluate tumor control and outcome from radiosurgery of meningiomas diagnosed by imaging without pathologic verification. METHODS AND MATERIALS: A total of 219 meningiomas diagnosed by imaging criteria underwent gamma knife radiosurgery to a median marginal tumor dose of 14 Gy (range 8.9-20), a median treatment volume of 5.0 cm(3) (range 0.47-56.5), and a median maximal dose of 28 Gy (range 22-50). The median follow-up was 29 months (range 2-164). RESULTS: Tumor progression developed in 7 cases, 2 of which turned out to be different tumors (metastatic nasopharyngeal adenoid cystic carcinoma and chondrosarcoma). One tumor was controlled, but the development of other brain metastases suggested a different diagnosis. The actuarial tumor control rate was 93.2% +/- 2.7% at 5 and 10 years. The actuarial rate of identifying a diagnosis other than meningioma was 2.3% +/- 1.4% at 5 and 10 years. The actuarial rate of developing any postradiosurgical injury reaction was 8.8% +/- 3.0% at 5 and 10 years. No pretreatment variables correlated with tumor control in univariate or multivariate analysis. The risk of postradiosurgery sequelae was lower (5.3% +/- 2.3%) in patients treated after 1991 (with stereotactic MRI and lower doses; p = 0.0104) and tended to increase with treatment volume (p = 0.0537). CONCLUSION: Radiosurgery of meningioma diagnosed by imaging without tissue confirmation is associated with a high rate of tumor control and acceptable morbidity but carries a small risk (2.3%) of an incorrect diagnosis.

An analysis of the dose-response for arteriovenous malformation radiosurgery and other factors affecting obliteration.

PURPOSE: The aim of this study was to better understand arteriovenous malformation (AVM) obliteration rates after radiosurgery. METHODS AND MATERIALS: We studied obliteration after Gamma knife radiosurgery in 351 AVM patients with 3-11 years of follow-up imaging. The median marginal dose was 20 Gy (range: 12-30) and median treatment volume was 5.7 cm(3) (range: 0.26-24). Stereotactic targeting was with angiography alone in 250 AVMs, and additional magnetic resonance (MR) imaging in 101 AVMs. RESULTS: We documented obliteration by angiography in 193/264 (73%) AVM, and by MR alone in 75/87 (86%) AVM for a 75% corrected obliteration rate. We identified persistent out-of-field nidus in 18% of embolized vs. 5% of non-embolized patients, (P = 0.006). Multivariate analysis correlated in-field obliteration with marginal dose (P < 0.0001) and sex (P < or = 0.026, but not for overall obliteration P = 0.19). A mathematical dose-response model for overall obliteration was constructed to generate a dose-response curve for AVM obliteration with a maximum overall obliteration rate of 88% and minimal improvement above 25 Gy. We could not define the value of alpha/beta for AVM obliteration to a level of statistical significance. CONCLUSION: The rate of AVM obliteration from radiosurgery depends on the marginal dose administered with a dose-response curve that reaches a maximum of approximately 88%. The dose-response plateau reflects problems with target definition which is made more difficult by prior embolization.