[Basic and Advanced Techniques of Anastomosis in Deep Surgical Fields:STA-SCA Anastomosis].

This article detailly describes the subtemporal-transtentorial STA-SCA bypass technique. Through temporal base drilling, copious cerebrospinal fluid evacuation before retraction, and sufficient retraction of the temporal lobe preserving the veins of the temporal base would be primodial to obtain an appropriate surgical field. Refrection of the tentrial free edge and identification of recipient SCA posterior to the entry point of the trochlear nerve into the cavernous sinus is a micro-anatomical key. Bilateral bayonet-type needle holders and forceps should be used not to shadow the surgical corridor with one's hands.

Salvage pemetrexed for brain metastases from ALK-positive lung cancer after Gamma Knife radiosurgery: illustrative case.

BACKGROUND: Systemic therapy for cancer treatment has improved, and therapeutic options for intracranial lesions are increasing. Combinations of treatment modalities are required in certain difficult cases. Gamma Knife radiosurgery (GKS) is effective for the treatment of brain metastases, especially for lesions that are inoperable because of their anatomical or functional location. OBSERVATIONS: The authors report a case of brain metastases in anaplastic lymphoma kinase (ALK)-positive lung adenocarcinoma initially treated with GKS followed by the combination of repeat GKS and ALK tyrosine kinase inhibitors (ALK-TKIs) for tumor recurrence. During the clinical course, acquired resistance to ALK-TKIs due to the long exposure period was suspected. After a great deal of thought and discussion with the oncologist responsible for the treatment of the pulmonary lesions, the authors successfully controlled the lesion for the next 17 months by salvage pemetrexed administration. LESSONS: This is the first report on the effectiveness of pemetrexed for recurrent brain metastasis from ALK-positive lung adenocarcinoma resistant to both radiosurgery and ALK inhibitors. Salvage pemetrexed showed a favorable therapeutic effect in this specific case.

Spontaneous Regression of an Unruptured Arteriovenous Malformation Due to Drainer Vein Thrombosis in a Patient with Protein S Deficiency: A Case Report and Literature Review.

Spontaneous regression of an arteriovenous malformation (AVM) is a rare condition observed in 0.3%-1.3% of patients with AVMs and is most likely caused by hemorrhagic events. The regression of an unruptured AVM is rarer than that of a ruptured AVM. Moreover, due to its low frequency of occurrence, the etiology and natural course of spontaneous regression of an AVM is still unclear. This is the first report presenting a case of a spontaneous regression of an unruptured AVM caused by a gradual drainer vein thrombosis that was suspected to result from hypercoagulability due to protein S deficiency.

Comparing Fractionated and Single-Fraction Gamma Knife Radiosurgery for Brain Metastases From Non-Small-Cell Lung Cancer With a Focus on Driver Alterations.

Background As the overall survival in non-small-cell lung cancer has increased, safer, long-term treatments for brain metastases are increasingly needed. This study aimed to analyze the outcomes of fractionated and single-fraction gamma knife radiosurgery for brain metastases from non-small-cell lung cancer, focusing on driver alteration status. Methodology Patients who underwent gamma knife radiosurgery as their first local treatment for brain metastases from non-small-cell lung cancer between May 2018 and December 2021 at our institution were retrospectively enrolled. Results Among the 98 patients (287 lesions), 45 (130 lesions) harbored driver alterations, including epidermal growth factor receptor mutations in 35 patients and anaplastic lymphoma kinase or ROS1 rearrangement in 10 patients. Overall, 64 and 34 patients underwent single-fraction and fractionated radiosurgery (3-15 fractions), respectively. Large tumor size was a risk factor for recurrence, while fractionated radiosurgery (subdistribution hazard ratio (sHR) = 16.47; confidence interval (CI) = 3.58-75.77; p < 0.001) and small tumor size (sHR = 1.15; CI = 1.04-1.28; p = 0.008) independently protected against radiation necrosis. In the case-matched analyses, the cumulative radiation necrosis rates were significantly lower in the fractionated group than in the single-fraction group among all lesions (p = 0.017) and among those with driver alterations (p = 0.046), whereas no significant difference was confirmed among wild-type lesions (p = 0.382). Conclusions Fractionated gamma knife radiosurgery may be an alternative therapeutic approach for reducing the risk of radiation necrosis, particularly for patients with driver alterations, even when the tumors are small. Further research is necessary to determine the optimal indications for fractionated gamma knife radiosurgery and fractionation methods.

Fractionated versus staged gamma knife radiosurgery for mid-to-large brain metastases: a propensity score-matched analysis.

PURPOSE: To compare treatment results between fractionated gamma knife radiosurgery (f-GKRS) and staged gamma knife radiosurgery (s-GKRS) for mid-to-large brain metastases (BMs). METHODS: We retrospectively analyzed data of patients with medium (4-10 mL) to large (> 10 mL) BMs who underwent s-GKRS or f-GKRS between March 2008 and September 2022. Patients were treated with (i) s-GKRS before May 2018 and (ii) f-GKRS after May 2018. Patients who underwent follow-up magnetic resonance imaging at least once were enrolled. Case-matched studies were conducted by applying propensity score matching to minimize treatment selection bias and potential confounding. Local control (LC) was set as the primary endpoint and overall survival (OS) as the secondary endpoint. RESULTS: This study included 129 patients with 136 lesions and 70 patients with 78 lesions who underwent s-GKRS and f-GKRS, respectively. Overall, 124 lesions (62 lesions in each group) were selected in the case-matched group. No differences were observed in the 6-month and 1-year cumulative incidences of LC failure between the s-GKRS and f-GKRS groups (15.6% vs. 15.9% at 6 months and 25.6% vs. 25.6% at 1 year; p = 0.617). One-year OS rates were 62.6% (95% confidence interval [CI]: 45.4-75.7%) and 73.9% (95% CI: 58.8-84.2%) in the s-GKRS and f-GKRS groups, respectively. The post-GKRS median survival time was shorter in the s-GKRS group than in the f-GKRS group (17 vs. 36 months), without significance (p = 0.202). CONCLUSIONS: This is the first study to compare f-GKRS and s-GKRS in large BMs. Fractionation is as effective as staged GKRS for treating mid-to-large BMs.

Association Between Frontal Lobe Hemodynamics and Neurocognitive Dysfunction in Adults With Moyamoya Disease: Retrospective Cohort Analysis.

BACKGROUND: Adult patients with moyamoya disease (MMD) may present with mild cognitive dysfunction, even those without evidence of conspicuous brain parenchymal damage. This cognitive dysfunction might be caused by local frontal lobe ischemia. OBJECTIVE: To explore the relationship between frontal lobe hemodynamic insufficiency and cognitive dysfunction in patients with MMD. METHODS: Thirty adult patients with MMD without conspicuous brain parenchymal damage were retrospectively examined. Patients with MMD with frontal lobe intracerebral steal phenomenon on single photon emission computed tomography were defined as group S (n = 13) and those without it were defined as group P (n = 17). A comparative group comprising patients with unruptured intracranial aneurysm was defined as group C (n = 30). The results of various cognitive and intelligence tests and a composite cognitive score were compared between groups. RESULTS: The digit span test forward version ( P = .041), frontal assessment battery ( P = .022), and composite cognitive score ( P = .015) z-scores were significantly lower in group S than group C. Adjusting for sex and age, patients in group S had a significantly lower composite cognitive score compared with those in group C in multiple regression analysis ( P = .037). Executive dysfunction and working memory dysfunction may be involved in the cognitive decline observed in group S. CONCLUSION: Mild cognitive dysfunction in MMD was associated with frontal lobe hemodynamic insufficiency. Future studies should examine whether revascularization can improve cerebral hypoperfusion and neurocognitive function in these patients.

Temporo-parietal muscle pedicle flap for reconstruction of the anterior skull base after resection of recurrent olfactory groove meningioma: a technical note.

Reconstruction becomes the main issue in surgery for tumours penetrating the anterior skull base because it faces the nasal cavity. Vascularized flaps are desirable for preventing infection, but in re-opening surgery, tissue availability is limited. We report a case of recurrent olfactory groove meningioma in which the anterior skull base defect was reconstructed using a temporo-parietal muscle (TPM) pedicle flap. A 65-year-old woman presented with recurrent olfactory groove meningioma penetrating the anterior skull base. Because the frontal pericranium had been used in the initial surgery, the temporal fascia was harvested with a TPM pedicle flap from behind the initial bicoronal incision. After removal of the tumour, the pedicle flap reached the sphenoid planum easily and was sutured to the surrounding structures. The fascia lata was sutured as an inlay. The postoperative course was uneventful, and no cerebrospinal fluid leakage was observed. In re-opening surgery, a TPM pedicle flap can be an option for reconstruction of the anterior skull base.

Two adult patients with moyamoya disease presenting with alexia with agraphia limited to kanji: can revascularization improve characteristic symptoms?

Patients with moyamoya disease (MMD) may exhibit higher brain dysfunction due to hypoperfusion, which may be ameliorated by revascularization. However, few studies have examined the relationship between cerebral perfusion and language function or the ameliorating effect of revascularization on language dysfunction. We present two cases with MMD who presented with alexia with agraphia, specifically for Japanese kanji. The patients had impaired perfusion in the left inferior temporal and lateral occipital lobes. Following superficial temporal artery-middle cerebral artery bypass, the symptoms improved dramatically. Thus, correction of hypoperfusion may be effective even in adult patients with MMD presenting with language dysfunction.

VEGFR-TKI treatment for radiation-induced brain injury after gamma knife radiosurgery for brain metastases from renal cell carcinomas.

OBJECTIVE: Antiangiogenic vascular endothelial growth factor receptor tyrosine kinase inhibitors play an essential role in systemic therapy for renal cell carcinoma. Given the anti-edematous effect of bevacizumab, an antiangiogenic antibody targeting vascular endothelial growth factor, vascular endothelial growth factor receptor tyrosine kinase inhibitors should exert therapeutic effects on radiation-induced brain injury after stereotactic radiosurgery. This preliminary study aimed to investigate the therapeutic effect of vascular endothelial growth factor receptor tyrosine kinase inhibitor against radiation-induced brain injury. METHODS: Magnetic resonance images for six patients treated with vascular endothelial growth factor receptor tyrosine kinase inhibitors who were diagnosed with radiation-induced brain injury following gamma knife radiosurgery were retrospectively reviewed. RESULTS: The median brain edema volume and tumour mass volume in the pre-tyrosine kinase inhibitor period were 57.6 mL (range: 39.4-188.2) and 3.2 mL (range: 1.0-4.6), respectively. Axitinib, pazopanib (followed by cabozantinib) and sunitinib were administered in four, one and one cases, respectively. The median brain edema volume and tumour mass volume in the post-tyrosine kinase inhibitor period were 4.8 mL (range: 1.5-27.8) and 1.6 mL (range: 0.4-3.6), respectively. The median rates of reduction in brain edema volume and tumour mass volume were 90.8% (range: 51.9-97.6%) and 57.2% (range: 20.0-68.6%), respectively. The post-tyrosine kinase inhibitor values for brain edema volume (P = 0.027) and tumour mass volume (P = 0.008) were significantly lower than the pre-tyrosine kinase inhibitor values. Changes in volume were correlated with tyrosine kinase inhibitor use. CONCLUSION: This study is the first to demonstrate the therapeutic effects of vascular endothelial growth factor receptor tyrosine kinase inhibitors on radiation-induced brain injury in patients with brain metastases from renal cell carcinoma treated via gamma knife radiosurgery.

Efficacy of Emergent STA-MCA Bypass for Acute Atherosclerotic ICA Stenosis/Occlusion with Concomitant Chronic Contralateral ICA Occlusion/Stenosis: Two Case Reports.

Recombinant tissue-type plasminogen activator with/without endovascular regimen is sometimes not effective for the treatment of acute hemodynamic stroke. Emergent superficial temporal artery-middle cerebral artery (STA-MCA) bypass has been reportedly effective in patients with progressive hemodynamic stroke; however, the effectiveness of urgent STA-MCA bypass for acute internal carotid artery (ICA) stenosis/occlusion with concomitant contralateral chronic ICA stenosis/occlusion, that is considered the worst hemodynamic situations, is unclear. Two cases of acute left ICA stenosis with concomitant right chronic ICA occlusion wherein both developed hemodynamic infarction and were initially treated by maximal medical treatment. Nevertheless, the patients' symptoms had gradually worsened, thus we performed emergency STA-MCA bypass for both cases. Postoperatively, deterioration of imaging and neurological findings was successfully stopped and the patients' condition gradually stabilized. An urgent STA-MCA bypass can be considered as a last resort to prevent progressive neurological deterioration for patients with progressive infarction due to ICA stenosis/occlusion concomitant with contralateral ICA stenosis/occlusion.

Direct Clipping of Paraclinoid Aneurysm in Conjunction with Extradural Anterior Clinoidectomy: Technical Nuance and Functional Outcome.

Objective Because of their anatomical features, treatment for paraclinoid aneurysms has remained to be challenging. Thus, the aim of this report is to prove the validity of our surgical method for unruptured paraclinoid aneurysms, together with surgical videos. Study Design Between August 2017 and November 2019, we were able to perform surgical clipping for 11 patients with unruptured paraclinoid aneurysm using a completely unified method. This study investigated the effect of surgery on multiple measures, including visual impairment, brain contusion, temporalis muscle atrophy, and multiple neurocognitive functions. Results Of the 67 unruptured aneurysms treated at our hospital, 17 were identified to be paraclinoid aneurysm, and 11 of them were treated by direct clipping using anterior clinoidectomy. Three were ophthalmic artery aneurysms, three were superior hypophyseal artery aneurysms, and five were anterior carotid wall aneurysms without branch projection. Only one patient had asymptomatic mild enlargement of the Marriott blind spots postoperatively. No brain contusion and temporalis muscle atrophy were observed in any cases. Only the Trail Making test (TMT) showed a significant worsening in the acute postoperative period: mean pre- and postoperative TMT scores were 59.1 ± 29.1 and 72.7 ± 37.3 for Part A ( p = 0.018) and 80.5 ± 35.5 and 93.8 ± 39.9 for Part B ( p = 0.030), respectively. However, it improved in the chronic phase. Conclusion We can conclude that our surgical method is safe and can be considered an acceptable treatment. Although surgical stress can cause temporary executive dysfunction shortly after surgery, this decline is temporary.

Interfractional change of tumor volume during fractionated stereotactic radiotherapy using gamma knife for brain metastases.

PURPOSE: Fractionated stereotactic radiotherapy (FSRT) using gamma knife is useful for brain metastases. However, several uncertainties derived from fractionation pose issues for maintaining high-level accuracy. This study analyzed interfractional tumor change by performing radiological reassessment at the midterm of FSRT with ≥ 10 fractions, and the significance of replanning was evaluated. METHODS: Data of FSRT using gamma knife with ≥ 10 fractions were retrospectively collected. Interfractional volume changes in MRI at the midterm of the irradiation period were analyzed. Radiological changes after FSRT and final outcomes were also investigated. RESULTS: Overall, 114 lesions in 74 treatments from 66 patients were included, with previously irradiated lesions accounting for 46%. The median interval between planning and the interfractional MRI was 7 days. The interfractional change rates of tumor volume ranged from - 48 to + 72%. Significant interfractional enlargement was observed in 16 lesions (14%); evident regression was confirmed in 17 lesions (15%). Predictive factors for interfractional enlargement were small tumor and cystic lesion; high biologically effective dose was associated with regression. After FSRT, most lesions regressed within 6 months despite interfractional change type. The incidences of tumor control and radiation necrosis indicated no differences between interfractionally-regressed lesions and others. CONCLUSION: This is the first study to evaluate interfractional tumor change in FSRT using gamma knife with ≥ 10 fractions, indicating significant volume changes in 29% of the lesions. These preliminary results suggest that interfractional reassessment of a treatment plan in FSRT with irradiation periods exceeding a week is necessary for more adaptive treatment.

Traumatic pseudoaneurysm resulting from avulsion of the falcine branch of an azygos anterior cerebral artery: a case report.

Traumatic anterior cerebral artery (ACA) aneurysms are extremely rare. Traumatic anterior ACA aneurysms are thought to develop when the ACA at the pericallosal segment travel adjacent to immobile falx cerebri. As the majority of aneurysms are pseudoaneurysms, direct neck clipping is usually not possible, and it is often necessary to carry out direct or endovascular trapping in conjunction with proficient bypass techniques. The authors describe the first reported case of a traumatic ACA pseudoaneurysm resulting from avulsion of the falcine branch of an azygos ACA. In this case, the lacerated aneurysm wall was successfully sutured, without the need for a bypass. Neurosurgeons should be aware that avulsion of the falcine branch arising from the ACA can occur, and that this may cause a traumatic aneurysm on the distal ACA. Furthermore, direct suturing of a lacerated arterial wall should be considered a treatment option for this type of traumatic intracranial aneurysm.

Fractionated Gamma Knife radiosurgery after cyst aspiration for large cystic brain metastases: case series and literature review.

Tumor cyst aspiration followed by Gamma Knife radiosurgery (GKRS) for large cystic brain metastases is a reasonable and effective management strategy. However, even with aspiration, the target lesion tends to exceed the dimensions of an ideal target for stereotactic radiosurgery. In this case, the local tumor control rate and the risk of complication might be a critical challenge. This study is aimed to investigate whether fractionated GKRS (f-GKRS) could solve these problems. Between May 2018 and April 2021, eight consecutive patients with nine lesions were treated with f-GKRS in five or ten sessions after cyst aspiration. The aspiration was repeated as needed throughout the treatment course to maintain the cyst size and shape. The patient characteristics, radiologic tumor response, and clinical course were reviewed using medical records. The mean follow-up duration was 10.2 (2-28) months. The mean pre-GKRS volume and maximum diameter were 16.7 (5-55.8) mL and 39.0 (31-79) mm, respectively. The mean tumor volume reduction achieved by aspiration was 55.4%. The tumor volume decreased for all lesions, and symptoms were alleviated in all patients. The median overall survival was 10.0 months, and the estimated 1-year survival rate was 41.7% (95% CI: 10.9-70.8%). The local tumor control rate was 100%. No irradiation-related adverse events were observed. f-GKRS for aspirated cystic brain metastasis is a safe, effective, and less invasive management option for large cystic brain metastases.

One-Stage Revascularization to the Ipsilateral Middle Cerebral Artery and Contralateral Anterior Cerebral Artery Territories.

BACKGROUND: Patients with multiple intracranial atherosclerotic stenoses often present with hemodynamic instability in 2 remote regions without a reciprocal vascular network. In this situation, revascularization to each region may be required. METHODS: In this report, 2 patients who had coexisting unilateral middle cerebral artery (MCA) and contralateral anterior cerebral artery territory ischemia were treated by using ipsilateral superficial temporal artery (STA)-radial artery graft-contralateral A3 bypass and ipsilateral STA-MCA bypass in one stage. RESULTS: Postoperatively, the bypass conduit was well established, and the patients' hemodynamic instability was improved. CONCLUSIONS: In patients with severe hemodynamic instability in the remote unilateral MCA and contralateral anterior cerebral artery regions, as in our 2 cases, ipsilateral STA-MCA and ipsilateral STA-radial artery graft-contralateral A3 bypasses in one stage can be a treatment option.

Carotid Endarterectomy for Vertebrobasilar Insufficiency Caused by Severe Stenosis of Primitive Hypoglossal Artery: A Technical Case Report and Literature Review.

Persistent primitive hypoglossal artery (PHA) originating from the external carotid artery (ECA) is a rare anomaly. Reports of carotid endarterectomy (CEA) for ECA stenosis associated with this anomaly are even rarer. A 76-year-old woman presented to a medical clinic with a major complaint of refractory dizziness. Carotid ultrasound study suggested severe stenosis of the left cervical carotid bifurcation; therefore, she was referred to our department for a possible CEA. The imaging results indicated severe stenosis of the left carotid bifurcation and that the ECA was a PHA and the origin of the dominant vertebrobasilar artery (VBA). CEA was performed with the special caution of providing VBA collateral flow during clamping and preventing microembolisms during declamping of the ECA. Postoperative head magnetic resonance imaging revealed no new findings of cerebral infarction, and her dizziness disappeared. CEA associated with stenosis of the PHA as the origin of a dominant VBA was safely performed with an appropriate understanding of possible collateral pathways during cross-clamping.

How do I: Venous reconstruction of accidentally injured superficial sylvian vein during the clipping of an unruptured cerebral aneurysm.

BACKGROUND: The transsylvian approach is a versatile treatment method for aneurysms of the anterior circulatory system. Studies have shown that sylvian veins run in various patterns, suggesting the need for dissection between veins to obtain appropriate surgical corridor. In case of inadvertent sylvian vein injury, serious complications such as venous congestion may occur. METHOD: We herein describe the "side-to-side anastomosis reconstruction technique" of the resected superficial sylvian vein. CONCLUSION: This technique can be effective for the reconstruction of other cortical veins, and indocyanine green videoangiography was effective in determining the indications for venous reconstruction.

Superficial temporal artery lengthening technique to prevent postoperative wound complications in direct revascularization to the anterior cerebral artery for Moyamoya disease.

BACKGROUND: Neurocognitive dysfunctions or psychomotor symptoms of Moyamoya disease may improve after direct revascularization to the anterior cerebral artery (ACA). However, long-distance harvest of the frontal branch of the superficial temporal artery (STA) is needed to reach the cortical ACA, frequently resulting in postoperative wound complications. To solve this problem, we devised a novel method (STA lengthening technique). In this study, we compared the STA lengthening technique and the conventional method regarding postoperative wound complications. METHODS: Twenty-five patients who underwent STA-ACA direct bypass from December 2016 to October 2021 were retrospectively reviewed, and postoperative wound complications were recorded. Magnetic resonance angiography was performed to evaluate the patency of the bypass to the ACA and postoperative development of collaterals to the skin flap. RESULTS: Thirty-eight hemispheres (new method [n = 12] vs. conventional method [n = 26]) were treated. Wound complications occurred in 12 surgeries (46%) of the conventional method, and none (0%) of the new method. The anastomosis with the cortical ACA was patent in all surgeries. Postoperative development of collaterals to the skin flap was confirmed after all surgeries (100%) in the new method, whereas after only five surgeries (20%) in the conventional method. CONCLUSION: The STA lengthening technique can enable to preserve the collateral circulation to the skin flap postoperatively, resulting in good wound healing.

Outcomes of Gamma Knife radiosurgery for skull base chondrosarcomas: a multi-institutional retrospective study.

OBJECTIVE: Radiotherapy has an essential role in the management of skull base chondrosarcomas (SBCs) after resection. This multi-institutional study evaluated the outcomes of Gamma Knife radiosurgery (GKRS) for histopathologically proven SBCs. METHODS: Data of patients who underwent GKRS for SBCs at Gamma Knife centers in Japan were retrospectively collected. Patients without a histopathological diagnosis and those who had intracranial metastases from extracranial chondrosarcomas were excluded. Histologically, grade III and some nonconventional variants were identified as aggressive types. The cumulative local control rates (LCRs) and disease-specific survival (DSS) rates were calculated using the Kaplan-Meier method. Factors potentially affecting the LCR were evaluated using the Cox proportional hazards model for bivariate and multivariate analyses. The incidence of radiation-induced adverse effects (RAEs) was calculated as crude rates, and factors associated with RAEs were examined using Fisher's exact test. RESULTS: Fifty-one patients were enrolled, with a median age of 38 years. Thirty patients (59%) were treated with upfront GKRS for residual SBCs after resection (n = 27) or biopsy (n = 3), and 21 (41%) underwent GKRS as a salvage treatment for recurrence. The median tumor volume was 8 cm3. The overall LCRs were 87% at 3 years, 78% at 5 years, and 67% at 10 years after GKRS. A better LCR was associated with a higher prescription dose (p = 0.039) and no history of repeated recurrence before GKRS (p = 0.024). The LCRs among patients with the nonaggressive histological type and treatment with ≥ 16 Gy were 88% at 3 years, 83% at 5 years, and 83% at 10 years. The overall survival rates after GKRS were 96% at 5 years and 83% at 10 years. Although RAEs were observed in 3 patients (6%), no severe RAEs with Common Terminology Criteria for Adverse Events grade 3 or higher were identified. No significant factor was associated with RAEs. CONCLUSIONS: GKRS for SBCs has a favorably low risk of RAEs and could be a reasonable therapeutic option for SBC in multimodality management. A sufficient GKRS prescription dose is necessary for higher LCRs. Histological grading and subtype evaluations are important for excluding exceptional SBCs. Patients with conventional SBCs have a long life expectancy and should be observed for life after treatment.

Stereotactic radiosurgery results for brain metastasis patients with renal cancer: A validity study of Renal Graded Prognostic Assessment and proposal of a new grading index (JLGK2101 Study).

BACKGROUND AND PURPOSE: The Renal Graded Prognostic Assessment (GPA) is relatively new and has not been sufficiently validated using a different dataset. We thus developed a new grading index, the Renal Brain Metastasis Score (Renal-BMS). MATERIALS AND METHODS: Using our dataset including 262 renal cancer patients with brain metastases (BMs) undergoing stereotactic radiosurgery (SRS) (test series), we validity tested the Renal-GPA. Next, we applied clinical factor-survival analysis to the test series and thereby developed the Renal-BMS. This system was then validated using another series of 352 patients independently undergoing SRS at nine gamma knife facilities in Japan (verification series). RESULTS: Using the test series, with the Renal-GPA, 95% confidence intervals (CIs) of the post-SRS median survival times (MSTs) overlapped between pairs of neighboring subgroups. Among various pre-SRS clinical factors of the test series, six were highly associated with overall survival. Therefore, we assigned scores for six factors, i.e., "KPS ≥ 80%/<80% (0/3)", "tumor numbers 1-4/≥5 (score; 0/2)", "controlled primary cancer/not (0/2)", "existing extra-cerebral metastases/not (0/3)", "blood hemoglobin ≥ 11.0/<11.0 g/dl (0/1)" and "interval from primary cancer to SRS ≥ 5/<5 years (0/1)". Patients were categorized into three subgroups according to the sum of scores, i.e., 0-4, 5-8 and 9-12. In the test and verification series, post-SRS MSTs differed significantly (p < 0.0001) with no overlaps of 95% CIs among the three subgroups. CONCLUSIONS: The Renal BMS has the potential to be very useful to physicians selecting among aggressive treatment modalities for renal cancer patients with BMs.