Long-Term Outcome of Unilateral Acoustic Neuromas With or Without Hearing Loss: Over 10 Years and Beyond After Gamma Knife Radiosurgery

Background@#Since the long-term outcomes of 162 patients who underwent gamma knife radiosurgery (GKS) as an initial or adjuvant treatment for acoustic neuromas (ANs) with unilateral hearing loss were first reported in 1998, there has been no report of a comprehensive analysis of what has changed in GKS practice. @*Methods@#We performed a retrospective study of the long-term outcomes of 106 patients with unilateral sporadic ANs who underwent GKS as an initial treatment. The mean patient age was 50 years, and the mean initial tumor volume was 3.68 cm 3 (range, 0.10–23.30 cm 3 ).The median marginal tumor dose was 12.5 Gy (range, 8.0–15.0 Gy) and the median follow-up duration was 153 months (range, 120–216 months). @*Results@#The tumor volume increased in 11 patients (10.4%), remained stationary in 27 (25.5%), and decreased in 68 patients (64.2%). The actuarial 3, 5, 10, and 15-year tumor control rates were 95.3 ± 2.1%, 94.3 ± 2.2%, 87.7 ± 3.2%, and 86.6 ± 3.3%, respectively.The 10-year actuarial tumor control rate was significantly lower in the patients with tumor volumes of ≥ 8 cm 3 (P = 0.010). The rate of maintaining the same Gardner-Robertson scale grade was 28.6%, and that of serviceable hearing was 46.4%. The rates of newly developed facial and trigeminal neuropathy were 2.8% and 4.7%, respectively. The patients who received marginal doses of less than 12 Gy revealed higher tumor control failure rates (P = 0.129) and newly occurred facial or trigeminal neuropathy rates (P = 0.040 and 0.313, respectively). @*Conclusion@#GKS as an initial treatment for ANs could be helpful in terms of tumor control, the preservation of serviceable hearing, and the prevention of cranial neuropathy. It is recommended to perform GKS as soon as possible not only for tumor control in unilateral ANs with hearing loss but also for hearing preservation in those without hearing loss.

Frameless Fractionated Gamma Knife Radiosurgery with ICON™ for Large Metastatic Brain Tumors

BACKGROUND: Recently, a new generation of gamma knife radiosurgery (GKRS) equipped with a frameless immobilization system has encouraged the use of fractionated GKRS as an increasingly favorable treatment option. We investigated the preliminary outcome of efficacy and toxicity associated with frameless fractionated gamma knife radiosurgery (FF GKRS) for the treatment of large metastatic brain tumors. METHODS: Fifteen patients with 17 lesions were treated using FF GKRS and included in this study, because of the large tumor size of more than 10 cm3. FF GKRS was performed based on a thermoplastic mask system for 3 to 5 consecutive days. RESULTS: The mean duration of clinical follow-up was 12 months (range, 4–24), and the local control rate was 100%. Tumor volume decreased in 13 lesions (76.5%), and remained stable in 4 lesions (23.5%). One patient was classified as new lesion development because of the occurrence of leptomeningeal seeding regardless of the tumor volume change. Compared with the initial volume at the time of FF GKRS, tumor volume change at the last follow-up was 62.32% ± 29.80%. Cumulative survival rate at 12 months was 93.3% ± 6.4%. One patient died during the follow-up period because of the progression of the primary disease. No patient showed radiation necrosis on the follow-up images. CONCLUSION: Daily FF GKRS by gamma knife ICON™ revealed satisfactory tumor control rate and low morbidity, despite the short follow-up period. Further prospective studies and a longer follow-up of a large cohort of patients diagnosed with brain metastases are required to elucidate the effect of FF GKRS in brain metastases.

Fractionated Gamma Knife Radiosurgery as Initial Treatment for Large Skull Base Meningioma

We present our experience on the hypofractionated Gamma Knife radiosurgery (FGKS) for large skull base meningioma as an initial treatment. We retrospectively reviewed 23 patients with large skull base meningioma ≥10 cm³ who underwent FGKS as the initial treatment option. The mean volume of tumors prior to radiosurgery was 21.2±15.63 cm³ (range, 10.09~71.42). The median total margin dose and marginal dose per fraction were 18 Gy (range, 15~20) and 6 Gy (range, 5~6), respectively. Patients underwent three or four fractionations in consecutive days with the same Leksell® frame. The mean follow-up duration was 38 months (range, 17~78). There was no mortality. At the last follow-up, the tumor volume was stationary in 15 patients (65.2%) and had decreased in 8 patients (34.8%). Six patients who had cranial neuropathy at the time of FGKS showed improvement at the last clinical follow-up. Following FGKS, 4 patients (17%) had new cranial neuropathy. The trigeminal neuropathy was the most common and all were transient. The mean Karnofsky Performance Status score at pre-FGKS and the last clinical follow-up was 97.0±10.4 points (median, 100) and 98.6±6.9 (median, 100) points, respectively. FGKS has showed satisfactory tumor control with functional preservation for large skull base meningiomas. Further prospective studies of large cohorts with long term follow-up are required to clarify the efficacy in the tumor control and functional outcome as well as radiation toxicity.

Brain Edema after Repeat Gamma Knife Radiosurgery for a Large Arteriovenous Malformation: A Case Report

Brain edema due to venous thrombosis following stereotactic radiosurgery for a cerebral arteriovenous malformation (AVM) has rarely been reported. We report a patient with a large AVM in the eloquent area, and brain edema developed in this area after repeat Gamma knife stereotactic radiosurgery (GKRS). An 18-year-old female presented with a 4-year-history of persistent headache. Magnetic resonance imaging and transfemoral carotid angiogram revealed a high-flow large AVM in the left parieto-occipital area. Brain edema developed and aggravated patient's symptoms after time-staged GKRS. The cause of edema was thought to be the failure of the surrounding venous channels to drain the venous flow from the normal brain and the drainage was hampered by the persistent shunt flow from the AVM, which was due to the thrombosis of one huge draining vein of the AVM. The microsurgical resection of the AVM nidus eliminated shunt flow and completely normalized the brain edema. Microsurgical resection of the AVM nidus completely normalized the brain edema due to thrombosis of a draining vein of an AVM develops after SRS.

Fractionated Stereotactic Gamma Knife Radiosurgery for Medial Temporal Lobe Epilepsy: A Case Report

An 18-year-old left-handed male harbored intractable medial temporal lobe epilepsy (MTLE) underwent fractionated gamma knife surgery (GKS) instead of open surgery, considering the mental retardation and diffuse cerebral dysfunction. GKS treatment parameters were: target volume, 8.8 cm3; total marginal dose, 24 Gy in 3 fractionations at the 50% isodose line. The patient has been free from seizures since 9 months after GKS, with notable improvement in cognitive outcome. Fractionated GKS could be considered as a safe tool for seizure control and neuropsychological improvement in patients with MTLE.

Fractionated Stereotactic Gamma Knife Radiosurgery for Medial Temporal Lobe Epilepsy: A Case Report

An 18-year-old left-handed male harbored intractable medial temporal lobe epilepsy (MTLE) underwent fractionated gamma knife surgery (GKS) instead of open surgery, considering the mental retardation and diffuse cerebral dysfunction. GKS treatment parameters were: target volume, 8.8 cm3; total marginal dose, 24 Gy in 3 fractionations at the 50% isodose line. The patient has been free from seizures since 9 months after GKS, with notable improvement in cognitive outcome. Fractionated GKS could be considered as a safe tool for seizure control and neuropsychological improvement in patients with MTLE.

Clinical Application of 7.0 T Magnetic Resonance Images in Gamma Knife Radiosurgery for a Patient with Brain Metastases

In the study we assessed the distortion of 7.0 T magnetic resonance (MR) images in reference to 1.5 T MR images in the radiosurgery of metastatic brain tumors. Radiosurgery with Gamma Knife Perfexion(R) was performed for the treatment of a 54-yr-old female patient with multiple brain metastases by the co-registered images of the 7.0 T and 1.5 T magnetic resonance images (MRI). There was no significant discrepancy in the positions of anterior and posterior commissures as well as the locations of four metastatic brain tumors in the co-registered images between 7.0 T and 1.5 T MRI with better visualization of the anatomical details in 7.0 T MR images. This study demonstrates for the first time that 7.0 T MR images can be safely utilized in Perfexion(R) Gamma Knife radiosurgery for the treatment of metastatic brain tumors. Furthermore 7.0 T MR images provide better visualization of brain tumors without image distortion in comparison to 1.5 T MR images.

Little Response of Cerebral Metastasis from Hepatocellular Carcinoma to Any Treatments

OBJECTIVE: We retrospectively evaluated the survival outcome of patients with brain metastasis from hepatocellular carcinoma (HCC). METHODS: Between 1991 and 2007, a total of 20 patients were diagnosed as having brain metastasis from HCC. The mean age of the patients was 55 +/- 13 years, and 17 (85.0%) were men. Seventeen (85.0%) patients had already extracranial metastases. The median time from diagnosis of HCC to brain metastasis was 18.5 months. Fourteen (70.0%) patients had stroke-like presentation due to intracerebral hemorrhage (ICH). Ten (50.0%) patients had single or solitary brain metastasis. Among a total of 34 brain lesions, 31 (91.2%) lesions had the hemorrhagic components. RESULTS: The median survival time was 8 weeks (95% CI, 5.08-10.92), and the actuarial survival rates were 85.0%, 45.0%, 22.5%, and 8.4% at 4, 12, 24, and 54 weeks. Age < 60 years, treatment of the primary and/or extracranial lesions, and recurrent ICH were the possible prognostic factors (p = 0.044, p < 0.001, and p = 0.111, respectively). The median progression-free survival (PFS) time was 3 months (95% CI, 0.95-5.05). CONCLUSION: The overall survival of the patients with brain metastasis from HCC was very poor with median survival time being only 8 weeks. However, the younger patients less than 60 years and/or no extracranial metastases seem to be a positive prognostic factor.

Introduction to Radiosurgery

Radiosurgery, or stereotactic radiosurgery, is a minimally invasive modality to treat a lesion with stereotactically focused ionizing radiation without surgical incision. Because there are no incision procedures, general anesthesia or transfusion is not required, and complications related to incisional procedures do not occur in radiosurgery. As a result, radiosurgery shows much low rates of complications than conventional open surgery with comparable cure rates. In the beginning, radiosurgery was applied only to a few intracranial diseases because a stereotactic frame was applied to the skull. Along with the development of technologies and accumulation of knowledge on radiosurgery such as medical imaging, computer, radiation physics, and radiobiology, indications of radiosurgery have been expanded in various ways. Nowadays, radiosurgery is accepted as an adjuvant treatment or a primary treatment option for many neurosurgical diseases and cancers. Cranial nerve schwannomas, brain meningiomas, pituitary adenoma, and other benign brain tumors are good indications for radiosurgery. Intracranial arteriovenous malformation, brain metastases from extracranial cancers, and trigeminal neuralgia are also well controlled by radiosurgery. Spinal metastases and various cancers are emerging indications for extracranial radiosurgery, which has been recently introduced. In this article, the authors summarized the basic concept, history, development, and future of radiosurgery as an introduction to radiosurgery.

Radiosurgery for Intracranial Disorders

Stereotactic radiosurgery offers a broad spectrum armamentarium for the safe treatment of various lesions within the central nervous system. Radiosurgery uses stereotactic targeting methods to precisely deliver highly focused, large doses of radiation to small intracranial tumors and arteriovenous malformations (AVMs). It is widely used for the treatment of metastatic brain tumors, non-resectable tumors, residual or recurrent benign and malignant tumors as well as for the treatment of AVMs, functional diseases, and pain disorders. Although radiosurgery has the potential to produce complications, the majority of patients experience clinical improvement with less morbidity and mortality than those occur in surgical resection.

Development of a Stereotactic Device for Gamma Knife Irradiation of Small Animals

OBJECTIVE: The authors developed a stereotactic device for irradiation of small animals with Leksell Gamma Knife(R) Model C. Development and verification procedures were described in this article. METHODS: The device was designed to satisfy three requirements. The mechanical accuracy in positioning was to be managed within 0.5 mm. The strength of the device and structure were to be compromised to provide enough strength to hold a small animal during irradiation and to interfere the gamma ray beam as little as possible. The device was to be used in combination with the Leksell G-frame(R) and KOPF(R) rat adaptor. The irradiation point was determined by separate imaging sequences such as plain X-ray images. RESULTS: The absolute dose rate with the device in a Leksell Gamma Knife was 3.7% less than the value calculated from Leksell Gamma Plan(R). The dose distributions measured with GAFCHROMIC(R) MD-55 film corresponded to those of Leksell Gamma Plan(R) within acceptable range. The device was used in a series of rat experiments with a 4 mm helmet of Leksell Gamma Knife. CONCLUSION: A stereotactic device for irradiation of small animals with Leksell Gamma Knife Model C has been developed so that it fulfilled above requirements. Absorbed dose and dose distribution at the center of a Gamma Knife helmet are in acceptable ranges. The device provides enough accuracy for stereotactic irradiation with acceptable practicality.

Application of IAEA TRS-398 Protocol to Gamma Knife Model C / 의학물리

Although Gamma Knife irradiates much more radiation in a single session than conventional radiotherapy, there were only a few studies to measure absolute dose of a Gamma Knife. Especially, there is no report of application of International Atomic Energy Agency (IAEA) TRS-398 which requires to use a water phantom in radiation measurement to Gamma Knife. In this article, the authors reported results of the experiments to measure the absorbed dose to water of a Gamma Knife Model C using the IAEA TRS-398 protocol. The absorbed dose to water of a Gamma Knife model C was measured using a water phantom under conditions as close as possible to the IAEA TRS-398 protocol. The obtained results were compared with values measured using the plastic phantom provided by the Gamma Knife manufacturer. Two Capintec PR-05P mini-chambers and a PTW UNIDOS electrometer were used in measurements. The absorbed dose to water of a Gamma Knife model C inside the water phantom was 1.38% larger than that of the plastic phantom. The current protocol provided by the manufacturer has an intrinsic error stems from the fact that a plastic phantom is used instead of a water phantom. In conclusion, it is not possible to fully apply IAEA TRS-398 to measurement of absorbed dose of a Gamma Knife. Instead, it can be a practical choice to build a new protocol for Gamma Knife or to provide a conversion factor from a water phantom to the plastic phantom. The conversion factor can be obtained in one or two standard laboratories.

Gamma Knife Surgery for Brain Metastasis from Renal Cell Carcinoma: Relationship Between Radiological Characteristics and Initial Tumor Response

OBJECTIVE: The authors have speculated that metastatic brain lesions from renal cell carcinoma (RCC) show diverse radiological patterns and tumor responses after Gamma knife surgery (GKS), and have hypothesized that these can be predicted from tumor radiological characteristics. The goal of the current study was to identify the radiological characteristics of RCC brain metastases and the predictors of initial radiosurgical response after GKS. METHODS: A retrospective analysis was performed on 48 lesions in 18 patients with RCC brain metastasis treated by GKS. The radiological characteristics of these lesions in magnetic resonance images (MRI) were classified into 3 categories according to enhancement patterns in T1-weighted images and signal intensity characteristics in T2-weighted images. Responses to GKS were analyzed according to these categories, and in addition, other potential predictive factors were also evaluated. RESULTS: MRI findings in the three categories were diverse, though numbers of the lesion were comparable. At 2-month MRI follow-ups after GKS, response rate was 54% and the local tumor control rate 83%. T2 signal intensity was found to be the principal predictive factor of response to GKS, namely negative predictive factor. Other variables such as age, sex, tumor volume, dose, duration from initial diagnosis to GKS, and previous systemic therapies failed to show significant relationships with treatment response by multivariate analysis. CONCLUSION: Careful evaluation of the radiological characteristics of brain metastases from RCC is important prior to GKS because MRI heterogeneity has predictive value in terms of determining initial tumor response.

Long-term Outcomes of Gamma Knife Stereotactic Radiosurgery of Vestibular Schwannomas

OBJECTIVE: Gamma Knife Stereotactic Radiosurgery (GK SRS) has become an important treatment modality for vestibular schwannomas. We evaluated the tumor control rate, patterns of tumor volume change and preservation of hearing following low-dose radiation for vestibular schwannomas in a homogeneous cohort group in which the mean marginal dose was 12 Gy. METHODS: A total of 59 patients were enrolled in this study. All enrolled patients were followed-up for at least 5 years and the radiation dose was 11-13 Gy. Regular MRI, audiometry and clinical evaluations were done and tumor volumes were obtained from MRI using the OSIRIS program. RESULTS: The tumor control rate was 97%. We were able to classify the patterns of change in tumor volume into three categories. Transient increases in tumor volume were detected in 29% of the patients and the maximum transient increase in tumor volume was identified at 6 to 30 months after GK SRS. The transient increases in tumor volume ranged from 121% to 188%. Hearing was preserved in 4 of the 12 patients who had serviceable hearing prior to treatment. There were no other complications associated with GK SRS. CONCLUSION: Low-dose GK SRS was an effective and safe mode of treatment for vestibular schwannomas in comparison to the previously used high-dose GK SRS. Transient increases in tumor volume can be identified during the follow-up period after low-dose GK SRS for vestibular schwannomas. Physicians should be aware that these increases are not always indicative of treatment failure and that close observation is required following treatments. Unfortunately, a satisfactory hearing preservation rate was not achieved by reducing the radiation dose. It is thought that hearing preservation is a more sophisticated problem and further research is required.

Recurrent Juvenile Nasopharyngeal Angiofibroma Treated with Gamma Knife Surgery

Radiosurgery has been rarely applied for juvenile nasopharyngeal angiofibroma (JNA) and cumulative reports are lacking. The authors report a case of successful treatment of recurred JNA with gamma knife surgery (GKS). A 48-yr-old man was presented with right visual acuity deterioration and brain magnetic resonance images (MRI) disclosed a 3 cm-sized intraorbital mass in the right orbit. He underwent a right fronto-temporal craniotomy and the mass was subtotally removed to preserve visual function. Histological diagnosis confirmed JNA in typical nature. However, the vision gradually worsened to fail four years after operation. MRI then showed regrowth of the tumor occupying most of the right orbit. GKS was done for the re-curred lesion. A dose of 17 Gy was delivered to the 50% isodose line of tumor mar-gin. During the following four-year follow-up period, the mass disappeared almost completely without any complications. Usually JNA can be exclusively diagnosed by radiological study alone. So this report of successful treatment of JNA with GKS may provide an important clue for the novel indication of GKS.

Hearing Outcome after Gamma Knife Stereotactic Radiosurgery in Vestibular Schwannoma Patients with Serviceable Hearing

OBJECTIVE: The authors conducted a retrospective study to evaluate the preservation rates of serviceable hearing and to determine its prognostic factors after gamma knife stereotactic radiosurgery(GK SRS) in the patient with vestibular schwannomas. METHODS: Between December 1997 and March 2005, 54 patients with a sporadic vestibular schwannoma and serviceable hearing (Gardner Robertson grade I-II) were enrolled in this study. Electronic database of medical records and radiological examinations before and after GK SRS were investigated to the last follow up. The mean marginal dose was 12.3+/-0.7Gy. The mean maximum dose delivered to the tumor center was 24.7Gy (22~30Gy). The median tumor volume was 2cc (0.1~9.1cc). The median follow-up period of magnetic resonance(MR) imaging was 31 months (6~99 months), and the mean follow-up period of audiometry was 24 months (4~70 months). RESULTS: The tumor control rate was 100% in the patients with the follow up period more than 2 years. The trigeminal and facial nerve preservation rates were 98% and 100%, respectively. Twenty-eight (52%) of the 54 patients preserved serviceable hearing and 16 (30%) patients retained their pre-GK G-R grade level after GK SRS. In the univariate and multivariate analysis, there was no significant prognostic factor in preservation of the serviceable hearing. CONCLUSION: The hearing preservation rate is still unsatisfactory compared with the results of other cranial nerve preservation and tumor control in the treatment of vestibular schwannoma by GK SRS. More sophisticated strategy during and after GK SRS is necessary to improve long-term hearing preservation.

Gamma Knife Surgery for the Pineal Region Tumors

OBJECTIVE: Gamma Knife Surgery(GKS) for the management of pineal region tumors is challengeable strategy as direct access to this area is not easy. The experiences of pineal region tumor patients treated with GKS were analyzed to evaluate the effectiveness. METHODS: Seven patients with tumors in the pineal region were treated with GKS between September 1998 and May 2005. The histological diagnosis were pineal parenchymal tumor (2 patients), low-grade astrocytoma (2 patients), immature teratoma (1 patient), and choriocarninoma (1 patient). One patient was diagnosed as metastatic brain tumor based on histological diagnosis for primary site and brain imaging study. The median marginal dose was 15Gy (range; 11~20) at the 50% isodose line. The median target volume was 2.5cm3 (range; 0.8~12.5). The median clinical follow up period was 29 months (range; 13~93) and the median radiological follow up period was 18 months (range; 6~73). RESULTS: Tumor volume measured in follow-up images showed reduction in six patients, disappearance in one. No adverse effect due to GKS was found during the follow-up period . The performance status was preserved in all patients except one who died due to progression of primary cancer in spite of controlled metastatic brain lesion. CONCLUSION: Gamma Knife Surgery can be applied to pineal region tumors irrespective of their histology whenever surgery is not indicated.

Anatomical Considerations in Gamma Knife Radiosurgery for Idiopathic Trigeminal Neuralgia

OBJECTIVE: The authors conducted this study to present the long-term treatment outcomes (minimum 2 years) of Gamma knife radiosurgery(GKS) for trigeminal neuralgia(TN) and to demonstrate the correlation of treatment outcomes and the anatomical characteristics of TN. METHODS: From 1997 to 2003, 44 consecutive patients suffering from medically intractable pain underwent GKS for TN. A single 4mm collimator was used with a median maximum dose of 80Gy (range 75~80Gy) prescribed to the root entry zone of the trigeminal nerve. Median follow up duration was 30 months (range 24~78 months). Anatomical measurements of trigeminal nerve in magnetic resonance images during GKS planning were correlated with clinical outcome. RESULTS: Twenty-two patients (50%) achieved an excellent outcome (BNI grade I & II), 20 patients (45.5%) a good outcome (grade IIIa & IIIb), and only 2 patients (4.5%) a poor outcome (grade IV & V). Eleven patients (25.0%) experienced pain recurrence after initial pain relief. Smaller volume of trigeminal nerve area irradiated more than 40Gy was significantly correlated with excellent outcome in both univariate and multivariate analyses respectively (P=0.033 and 0.040). CONCLUSION: Anatomical considerations during the planning of GKS would be helpful for predicting clinical outcome in TN.

Korean Medical Citation Index(KoMCI) and Journal of Korean Neurosurgical Society

The authority and reputation of a medical journal is based on the number of received citations. Korean Medical Citation Index (KoMCI) provides information about citations of Korean medical journals since 2002. All six issues of KoMCI (from 2000 to 2005) were used for analysis. Citations, impact factor, and their changes were evaluated. We compared the data of Journal of Korean Neurosurgical Society(JKNS) with other Korean medical journals. The impact factor(IF) of 2005 maintained increased value since 2004, although the impact factor excluding self citation(ZIF) returned previous low value. Improvement in proportion of Korean citations and in proportions of non-self received citations were encouraging changes. Although there were some improvements, the status of JKNS with respect to ZIF is still behind other Korean medical journals selected for comparison. Improvement of the status of JKNS by aid of KoMCI and enhanced reputation of KoMCI by its positive influence on JKNS or other Korean medical journals will be beneficial to members and medical societies of Korea.

What Do You Think about the Journal of Korean Neurosurgical Society?: Survey of Korean Neurosurgical Society Members

The editorial department of Journal of Korean Neurosurgical Society(JKNS) polled more than 1,210 members of the Korean Neurosurgical Society(KNS) to evaluate the present status of JKNS from a viewpoint of readers or authors. The survey form includes questions about the impressions and opinions of JKNS regarding to its contents, style, and service. The responses were collected by means of e-mail and a total of 107 replies could be gathered during 2 months. Analysis of the responses revealed that majority of members of the KNS recognized the efforts to improve the quality of JKNS during recent years. However, there was also apprehensions and discontent about the quality of articles and review process in some KNS members.