[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.

Carotid endarterectomy for acute carotid thrombosis after carotid artery stenting with CASPER Rx® stent: A case report.

Background: Acute carotid stent thrombosis (ACST) is a rare but devastating complication for carotid artery stenting (CAS). That requires early diagnosis and immediate treatment. Although administration of drugs or endovascular treatment is the most widely used approach for patients with ACST, there is no consensus on the standard treatment of this disease. Case Description: The present study reports on an 80-year-old female patient with the right internal carotid artery stenosis (ICS) that had been followed up by ultrasonography for 8 years. Although the optimal medical treatment was followed, the patient's right ICS worsened, and the patient was subsequently hospitalized for CAS. On the 12th day after CAS, left paralysis and dysarthria were observed. Head magnetic resonance imaging (MRI) showed acute obstruction of the stent and scattered cerebral infarction in the right cerebral hemisphere caused possibly by the discontinuation of temporary antiplatelet drug therapy as a means to prepare for embolectomy of the femoral artery. Stent removal and carotid endarterectomy (CEA) were selected as the appropriate treatment approach. CEA was performed with the precaution of stent removal and distal embolism, and complete recanalization was obtained. Postoperative head MRI showed no new findings of cerebral infarction, and the patients remained symptom-free after 6 months of postoperative follow-up. Conclusion: Stent removal with CEA could be an appropriate curative option in some cases with ACST except in patients at high risk of CEA and in the chronic phase after CAS.

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.

Clinical and Genetic Characteristics of Patients with Moyamoya Disease who Experienced Both Ischemic and Hemorrhagic Events.

OBJECTIVE: Cerebrovascular events in moyamoya disease are mainly classified into ischemic or hemorrhagic onset. It is rare for one patient to develop both ischemia and hemorrhage in moyamoya disease; detailed clinical course and genetic characteristics of such patients have not been elucidated. We aimed to clarify the clinical features of patients with both ischemic and hemorrhagic cerebrovascular events. METHODS: We analyzed the background factors, radiological features, and genotype of ring finger protein 213 c.14429 G > A (p.Arg4810Lys) of patients with moyamoya disease who visited our hospital between 1996 and 2020, and experienced both ischemic and hemorrhagic cerebrovascular events. Additionally, we analyzed factors that caused subsequent hemorrhage in adult-onset ischemic moyamoya disease. RESULTS: Of 262 patients, 12 presented with both ischemia and hemorrhage, of which, 4 exhibited pediatric onset and 8 had adult onset. In pediatric-onset subjects, ischemia was the initial event in all cases. Hemorrhagic events occurred at a median of 24.7 years postoperatively in patients who had undergone bypass surgery. In adult-onset subjects, ischemia preceded hemorrhage in 7 patients. In males, the interval to subsequent hemorrhage was significantly shorter for adult-onset ischemic moyamoya disease, and the hazard ratio for hemorrhagic events was 5.45. The ring finger protein 213 p.Arg4810Lys heterozygous variant was present in 9 patients. CONCLUSIONS: A majority of patients with moyamoya disease with both ischemia and hemorrhage experience an ischemic event first. Patients who developed ischemia in childhood may develop subsequent hemorrhage in approximately 20-25 years after bypass surgery. Male sex is a risk factor for a subsequent hemorrhagic event in adult-onset ischemic moyamoya disease.

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.

Development of a sigmoid sinus dural arteriovenous fistula secondary to sigmoid sinus thrombosis after resection of a foramen magnum meningioma: illustrative case.

BACKGROUND: The precise etiology of dural arteriovenous fistula (DAVF) is still unknown. The authors reported a case of delayed postoperative sigmoid sinus (SS) DAVF secondary to SS thrombosis after resection of a foramen magnum meningioma through a suboccipital craniotomy. OBSERVATIONS: The authors visualized the clear architecture of the DAVF using fusion three-dimensional computer graphics (3DCG) images reconstructed from multimodal imaging studies. These fusion 3DCG images revealed that the feeders of the DAVF had connected through neovascularization to the SS at the previous thrombus site. The authors also reviewed previously reported cases of DAVFs that developed after craniotomy. LESSONS: This study indicated that SS stenosis and occlusion with sinus thrombosis are possible risk factors for delayed postoperative DAVF that demand special consideration.

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.

RNF213 p.Arg4810Lys Heterozygosity in Moyamoya Disease Indicates Early Onset and Bilateral Cerebrovascular Events.

The relationship between RNF213 c.14429G > A (p.Arg4810Lys) heterozygous variants and clinical manifestation in patients with Moyamoya disease (MMD) remains unclear. We performed a retrospective cohort analysis to clarify the genotype-phenotype correlation of this RNF213 hotspot variant in MMD patients, especially between wild-type (GG) and heterozygous (GA) genotypes. Clinical and genetic data were obtained from patients diagnosed with MMD in our institutions between October 2011 and November 2020. Clinical data included age, sex, neurological status at diagnosis, medical history, smoking history, alcohol intake, and family history. Of the 225 enrolled patients, 160 (71.1%) were symptomatic, 3 (1.3%) had the homozygous variant, and 149 (66.2%) had the heterozygous variant (GA). Analysis of all enrolled patients showed that the GA group was prone to present bilateral symptoms (p = 0.008) and progressive status (Suzuki grade ≥ 4; p = 0.017). Analysis limited to symptomatic patients revealed that the GA group had bilateral symptoms (p = 0.017), younger age at onset (p = 0.043), and, in particular, a higher proportion of onset before 25 years of age (p = 0.021). Multivariate logistic regression analysis of overall patients revealed that earlier age at diagnosis (p < 0.001, OR 0.936, 95% CI 0.914-0.959) and GA group (p = 0.017, OR 3.326, 95%CI 1.237-8.941) were significantly associated with bilateral symptoms. MMD patients diagnosed at a young age with the RNF213 heterozygous variant should be followed up with consideration of possible contralateral stroke if one hemisphere is already symptomatic or of early cerebrovascular events if bilateral hemispheres are asymptomatic.

Vein-related Trigeminal Neuralgia: How to Determine the Treatment Method of the Causative Vein: A Technical Note.

Trigeminal neuralgia (TN) is often caused by various vein forms. Herein, we report two cases of vein-related TN. In the first case, the vein of the cerebellopontine fissure (VCPF), along with the thickened surrounding arachnoid, clung to the trigeminal nerve. As the perfusion range of this vein was expected to be wide and its injury might cause extensive venous infarction, the anchor between the trigeminal nerve and the vein was carefully dissected and the vein was successfully transposed. In the second case, the involvement of the vein of the middle cerebellar peduncle (VMCP), which penetrates the nerve bundle of the trigeminal nerve, was suspected. Because vein transposition was impossible, the vein was transected at the nerve penetration site after confirming that there was sufficient collateral venous outflow. The superior petrosal vein and its tributaries are the primary causative veins of vein-related TN, and their contact patterns are infinite. Moreover, their perfusion range and the presence or absence of collateral venous outflow vary from case to case. Therefore, it is necessary to judge the perfusion range as well as collateral venous outflow based on preoperative images and intraoperative findings and to determine the appropriate treatment method for each case.