Embolization of Meningiomas with Ultralow Concentration N-Butyl 2-Cyanoacrylate

Abstract

Objective

Preoperative embolization of meningiomas with n-butyl 2-cyanoacrylate (NBCA) is problematic as its adhesive nature may force termination prior to achieving adequate embolization of intratumoral vessels. Herein, we report the use of ultralow concentration NBCA embolization to address this issue.

Materials and Methods

Seventeen patients with meningiomas underwent embolization with ultralow concentration NBCA. Twenty-four tumor-feeding vessels were embolized with 5% NBCA to allow infiltration of the intratumoral vessels. Overall, this method achieved a reduced operative time and blood loss during the resection as compared with those of the nonembolized group.

Results

Embolization was achieved in all patients at ultralow concentrations. Additionally, 20 vessels (83.3%) were embolized up to the intratumoral level. Warmed 5% NBCA aided in the embolization of intratumoral vessels. Embolization effectively controlled bleeding in all patients, while in 15 patients (88.2%), some form of tumor necrosis or softening was observed, predominantly in the area of dural attachment, demonstrating the efficacy of embolization in tumor removal. No embolization-related complications were observed. The mean operative time for resection was significantly different between the embolization (17 patients) and nonembolization (9 patients) groups (316 vs. 412 minutes, p = 0.0271). In these two groups, the mean blood loss was 349 versus 575 mL, the mean maximum tumor diameter was 56.8 versus 35.4 mm (p = 0.0089), and the mean age was 73.3 versus 72.3 years, respectively, with the significantly larger embolization group having shorter operation time and less blood loss.

Conclusion

Embolization of meningiomas with ultralow concentrations of NBCA can help to reach intratumoral vessels.

Keywords

embolization - intratumoral vessels - meningioma - N-butyl 2-cyanoacrylate - ultralow concentration

Introduction

Feeder embolization of meningiomas is used as preoperative hemorrhage prophylaxis during craniotomy to mitigate intraoperative blood loss and ensure safe removal.[1] Additionally, if the occlusion extends to a portion of the intratumoral vessels, the tumor tissue may undergo necrosis and softening, thereby facilitating easier removal.[2] Preoperative embolization is recognized as a beneficial adjuvant therapy because of its potential to reduce blood loss and shorten the operative time.[3]

Coils, particles, and liquid materials are commonly used in embolization procedures. Among these materials, polyvinyl alcohol (PVA) particles and gel foam powders are frequently employed.[2] Recent reports have described the use of liquid adhesives, such as n-butyl 2-cyanoacrylate (NBCA) (Histoacryl; B. Braun, Melsungen, Germany), compared with particles.[4]

NBCA is commonly used at concentrations of 10 to 13%, balancing fluidity and adhesiveness for effective embolization. However, its inherent adhesiveness can limit deep tumor penetration and occasionally necessitate early termination of embolization to prevent catheter adhesion caused by proximal reflux. To overcome these limitations, we explored the use of an ultralow concentration (5%) NBCA formulation. By reducing adhesiveness, this approach permits a controlled degree of reflux while maintaining sufficient injection pressure, thereby enhancing distal tumor penetration and overall embolization efficacy.

Materials and Methods

Seventeen patients who underwent preoperative embolization of meningiomas using an ultralow concentration (5%) of NBCA between June 2015 and November 2023 were included ([Table 1]). Meningiomas were located in the convexity in nine cases, the parasagittal sinus in five cases, the sphenoidal ridge in two cases, and the tentorial region in one case, with a mean maximum diameter of 56.8 mm (range: 30–85 mm). The patients included eight males and nine females with a mean age of 73.3 years (range: 57–87 years).

Table 1 Patient characteristics

Case	Age	Sex	Tumor location	Tumor size (mm)	Feeding artery	Interval between embolization and surgery (d)
1	86	M	Rt. sphenoid ridge	68	MMA, PA	1
2	82	F	Lt. parasagittal	77	MMA	1
3	60	F	Rt. convexity	60	MMA	1
4	73	F	Lt. convexity	50	MMA	1
5	72	F	Lt. parasagittal	48	MMA, PA	1
6	72	M	Rt. convexity	85	MMA, AMA, STA, PA	1
7	74	M	Lt. parasagittal	54	MMA	1
8	80	M	Rt. parasagittal	56	MMA, PA	1
9	71	M	Lt. convexity	39	MMA, AMA	1
10	83	M	Rt. parasagittal	35	MMA, OA	1
11	87	M	Lt. sphenoid ridge	58	MMA, AMA, PA	15
12	57	M	Rt. convexity	80	MMA, AMA, PA, STA	1
13	72	F	Rt. tentrial	30	OA	1
14	73	F	Rt. convexity	54	MMA, AMA, STA	1
15	60	F	Lt. convexity	48	MMA, OA, PA	1
16	68	F	Rt. convexity	72	MMA	1
17	76	F	Rt. convexity	51	MMA	1

Abbreviations: AMA, accessory meningeal artery; F, female; Lt, left; M, male; MMA, middle meningeal artery; OA, occipital artery; PA, pial artery; Rt, right; STA, superficial temporal artery.

In cases where there was suspicion of involvement of the feeding artery in the cranial neurotrophic branches or anastomosis with normal vessels of the internal carotid artery or vertebrobasilar artery system, known as dangerous anastomosis, embolization was primarily performed using coils alone. These cases were therefore excluded from this study.

The operating time and blood loss were compared with those of nine patients who underwent resection without embolization during the same period (nonembolization group). The nine patients in the nonembolization group had tumors located in the parasagittal area in two cases, the sphenoidal ridge in two cases, the cerebellopontine angle in two cases, and in the olfactory groove, tuberculum sellae, and foramen magnum in one case each, with a mean maximum diameter of 35.4 mm (range: 16–57 mm). This group comprised four males and five females with a mean age of 72.3 years (range: 52–81 years).

Embolization was performed in 24 vessels in 17 patients. All procedures were performed under local anesthesia with access to the transfemoral artery. The guiding catheters (GCs) used were the 4–6Fr FUBUKI (Asahi Intecc, Aichi, Japan) in 12 cases, 6Fr ENVOY (Codman & Shurleff, Johnson & Johnson, Raynham, Massachusetts, United States) in 2 cases, and 8Fr Flowgate2 (Stryker, Kalamazoo, Michigan, United States) in 2 cases ([Table 2]).

Table 2 Characteristics of preoperative meningioma embolization assessed using n-butyl 2-cyanoacrylate

Case	Target artery	Guiding catheter	Triple coaxial	MC	MG	Total amount of NBCA (mL)	NBCA penetration into the tumor	Embolic result	Effect of embolization on surgical removal	Complication of NBCA embolization
1	MMA	6Fr ENVOY	No	SL	GT	0.1	Yes	Fair	Fair	No
2	MMA	4Fr FUBUKI	No	MA	CH10	0.1	Yes	Good	Good	No
3	MMA	4Fr JB2	No	MA	CH10	0.2	No	Poor	Poor	No
4	MMA	4Fr FUBUKI	No	SL	CH10	0.21	Yes	Fair	Fair	No
5	MMA	4Fr FUBUKI	No	MA	CH10	0.18	Yes	Fair	Fair	No
5	MMA	4Fr FUBUKI	No	MA	CHX	0.05	No	Poor	−	−
6	MMA	4Fr FUBUKI	No	MA	CH10	0.17	Yes	Good	Fair	No
6	AMA	4Fr FUBUKI	No	SL	CH10	0.1	Yes	Good	−	−
6	MMA	4Fr FUBUKI	No	MA	CH10	0.2	Yes	Good	−	−
7	MMA	4Fr FUBUKI	Yes	SL	CH10	0.15	Yes	Good	Good	No
8	MMA	6Fr FUBUKI	No	MA	CHX	0.12	Yes	Fair	Fair	No
9	MMA	4Fr FUBUKI	No	MA	CH10	0.37	Yes	Good	Good	No
10	MMA	6Fr ENVOY	Yes	DF	CHX	0.05	Yes	Good	Good	No
11	MMA	8Fr Flowgate	Yes	MA	CHX	0.35	Yes	Good	Fair	No
12	MMA	5Fr FUBUKI	Yes	MA	CHX	0.17	Yes	Good	Good	No
13	OA	4Fr FUBUKI	Yes	MA	CHX	0.08	Yes	Excellent	Good	No
14	MMA	5Fr FUBUKI	Yes	HD	CH10	0.03	Yes	Good	Fair	No
15	MMA	5Fr FUBUKI	Yes	DF	CH10	0.03	Yes	Good	Fair	No
15	MMA	5Fr FUBUKI	Yes	DF	CH10	0.03	Yes	Fair	−	−
15	OA	5Fr FUBUKI	Yes	SL	CH10	0.01	No	Poor	−	−
16	MMA	8Fr Flowgate	Yes	MA	CH10	0.27	Yes	Good	Good	No
17	MMA	5Fr FUBUKI	No	DF	CH10	0.13	Yes	Excellent	Excellent	No
17	MMA	5Fr FUBUKI	No	MA	CH10	0.02	Yes	Fair	−	−
17	MMA	5Fr FUBUKI	No	DF	CHX	0.08	No	Fair	−	−

Abbreviations: AMA, accessory meningeal artery; CH10, CHIKAI 10; CHX, CHIKAI X 010; DF, defibrillator; GT, GT wire; MA, Marmpions; MC, microcatheter; MG, microguidewire; MMA, middle meningeal artery; NBCA, n-butyl 2-cyanoacrylate; OA, occipital artery; SL, SL 10.

Distal access catheters (DACs) were used to distally improve GC support and microcatheter (MC) accessibility distally: 3.4Fr TACTICS (Technocrat Corporation, Aichi, Japan) or Guidepost (Tokai Medical Products, Aichi, Japan) in eight cases.

The MCs used included Marathon (eV3 Covidien, Irvine, California, United States) in 13 vessels (54.2%), Excersior SL-10 (Stryker) in 8 vessels (33.3%), Defrictor (Medicos Hirata, Osaka, Japan) in 5 vessels (20.8%), and Headway Duo (Terumo, Tokyo, Japan) in 1 vessel (4.2%). The MC was advanced as far as possible to the more distal tumor-feeding vessels without involving the dangerous anastomoses. Selective imaging was performed on MC prior to NBCA injection to confirm tumor staining and the absence of dangerous anastomoses.

A solution of 5% NBCA was prepared using NBCA and lipiodol (Lipiodol Ultra-Fluide, Guerbet, Roissy, France) at a ratio of 1:19 (0.05 and 0.95 mL). The liquid drug was mixed in a 1-mL Medallion syringe (Merit Medical, Utah, United States) and heated with a heat gun (Robert Bosch, Gerlingen, Germany) set at 100°C for at least 2 minutes to reduce viscosity. A 5% glucose solution was prewarmed prior to use. Two 1-mL syringes of the warmed glucose solution were injected sequentially, immediately followed by the injection of the warmed 5% NBCA. As the total injection time did not exceed 1 minute, significant temperature reduction during the procedure was considered unlikely. NBCA (5%) was injected using the continuous column method to reach the intratumor vessels. The ultralow concentration of NBCA allowed it to flow back proximally, approximately 2 cm beyond the apical marker of the MC, owing to its low adhesiveness. The MC was subsequently removed by applying negative pressure to the syringe when sufficient embolization was achieved, when 5% NBCA was injected into an unintended dural branch, or when 5% NBCA flowed back by more than 2 cm beyond the apical marker of the MC.

The outcomes of NBCA injection from the target vessel of the external carotid artery system were classified as follows: Excellent, NBCA reached the entire intratumor vessels; good, more than 50% of the intratumor vessels were reached; fair, less than 50% of the intratumor vessels were reached; and poor, only proximal occlusion was achieved. For tumor resection, embolization outcomes were classified as follows: Excellent, the entire tumor was necrotic and softened, making it easily removable; good, the tumor was extensively necrotic and softened around the dural attachments; fair, the embolization was partially effective against the tumor; and poor, embolization reduced bleeding during craniotomy, but was ineffective against the tumor itself. As coil embolization was performed in patients with suspected dangerous anastomoses, we did not perform a provocative test.

Statistical Analysis

Statistical analyses were performed using JMP 14.2.0. The Wilcoxon nonparametric test was used to compare two groups. Statistical significance was set at p < 0.05.

Results

Embolization was successful in all patients, allowing NBCA to reach the intratumoral vessels in 15 of 17 patients (88.2%) and 20 of 24 vessels (83.3%) ([Table 2]). Of the 10 vessels embolized using DAC, such as TACTICS or Guidepost, intratumoral vessel embolization was achieved in nine. Embolization status was classified as excellent in 2 vessels, good in 12, fair in 7, and poor in 3. Angiographic impressions further showed that the average embolization rate (disappearance of tumor staining) was 86.8%. All tumor staining from feeding vessels in the middle meningeal artery (MMA) and occipital artery (OA) embolized with ultralow concentration NBCA disappeared, whereas tumor staining from feeding vessels that were not embolized, such as the superficial temporal artery and pial artery, were retained.

The most common combination of MC and microguidewire was Marathon + CHIKAI 10 in eight vessels, and CHIKAI X 010 in seven vessels. The NBCA infusion time was almost within 1 minute, and the removal time was within 3 seconds. There were no cases in which the MCs were trapped by 5% NBCA and the extraction was time-consuming. There were no complications from embolization, including rupture of the MC, in any of the patients. Sixteen patients underwent total resection 1 day after embolization, while one patient underwent total resection 15 days after embolization due to postponement of the procedure because of fever. All patients experienced some hemorrhage control, while the softening effect of embolization at the time of resection was classified as excellent in one case, good in seven cases, fair in eight cases, and poor in one case. In cases where NBCA was able to embolize the tumor, partial softening of the tumor was observed, facilitating resection. However, embolization was less effective only in cases of proximal occlusion, and in cases with a strong feeder from the pial artery.

Comparing the 17 patients in the embolization group with the 9 patients in the nonembolization group, the mean operative time for resection was significantly longer in the nonembolization group (316 vs. 412 minutes, p < 0.05). The mean blood loss was 349 versus 575 mL (p = 0.1865), showing a nonsignificant difference, but indicating more blood loss in the nonembolization group. The mean age was 73.3 versus 72.3 years (p = 0.8924), showing no age bias. The mean maximum tumor diameters were 56.8 versus 35.4 mm (p < 0.05); therefore, the significantly larger tumor size in the embolization group was correlated with shorter operative times and less blood loss.

Representative Cases

Case 4

Case 4 was a 73-year-old female who presented with loss of consciousness and transient right hemiplegia. Examination at another hospital revealed a brain tumor; therefore, she was referred to our hospital. On admission, no specific neurological findings were observed. Magnetic resonance imaging (MRI) revealed a tumor with a maximum diameter of 50 mm in the left convexity, which was suspected to be a meningioma ([Fig. 1A]). Cerebral angiography revealed strong tumor staining, with MMA as a feeder ([Fig. 1B, C]). No staining was observed in the pial artery. A 4Fr FUBUKI (dilator kit) was placed at the origin of the external carotid artery as a guiding sheath, while Excelsior SL-10 and CHIKAI 10 were used to guide the MMA to a bend that could not be crossed. Embolization was performed using 5% NBCA ([Fig. 1D]). Slow injection allowed embolization to reach the intratumor vessels before refluxing to the proximal MMA, completely eliminating tumor staining ([Fig. 1E]). Postembolization computed tomography (CT) revealed NBCA within the tumor ([Fig. 1F]). Surgery was performed on the day after embolization. Bleeding control during surgery was good, and tumor removal was easy ([Fig. 1G]). The intraoperative blood loss was 50 mL. Postoperative MRI revealed complete tumor removal ([Fig. 1H]). The final diagnosis was fibrous meningioma, and the patient was discharged without any neurological symptoms.

Fig. 1 Case 4. (A) Preembolized gadolinium (Gd)-enhanced T1-weighted magnetic resonance imaging (MRI) showing a well-enhanced tumor in the left frontal lesion. (B) Angiogram of the left external carotid artery showing a tumoral blush fed by the middle meningeal artery. (C) Selective angiogram of the middle meningeal artery showing tumoral blush. The arrow indicates the tip of the microcatheter. (D) Injection of 5% n-butyl 2-cyanoacrylate (NBCA) through the microcatheter showing deep penetration to the tumor vessels. (E) Postembolization of the left external carotid artery showing no tumoral feeding. (F) Postembolization computed tomographic imaging showing good penetration of the NBCA to the tumor (arrowhead). (G) Intraoperative view showing achievement of less bleeding, allowing easy removal of the tumor. (H) Postoperative Gd-enhanced T1-weighted MRI showing successful removal of the tumor.

Case 13

Case 13 was a 72-year-old female. MRI revealed a brain tumor in the right posterior fossa during a headache, which increased during follow-up and caused discomfort in the right lower extremity. On admission, neurological findings included slight ataxia of the right lower extremity. MRI showed a tumor with a maximum diameter of 30 mm in the right tentorium, which was suspected to be a meningioma ([Fig. 2A]). Cerebral angiography revealed strong tumor staining with the OA as a feeder ([Fig. 2B, C]). No staining was observed in the pial artery. A 4Fr FUBUKI (dilator kit) was placed at the origin of the external carotid artery as a guiding sheath, and a 3.4Fr Guidepost was placed in the OA as a DAC, from which Marathon and CHIKAI X 010 were used. The Marathons were guided to the vicinity of the tumor in the OA using the DAC, and embolization was performed with 5% NBCA ([Fig. 2D]). NBCA was injected into the entire intratumor vasculature before refluxing to the MC tip marker, thus completely eliminating tumor staining ([Fig. 2E]). Postembolization CT revealed NBCA within the tumor ([Fig. 2F]). Surgery was performed on the day after embolization. During surgery, necrosis and softening of the tumor were observed, and the tumor was easily removed ([Fig. 2G]). The intraoperative blood loss was 50 mL. Postoperative MRI revealed complete tumor removal ([Fig. 2H]). The final diagnosis was fibrous meningioma, and the patient was discharged without any neurological symptoms.

Fig. 2 Case 13. (A) Preembolized gadolinium (Gd)-enhanced T1-weighted magnetic resonance imaging (MRI) showing a well-enhanced tumor in the suboccipital lesion. (B) Angiogram of the right external carotid artery showing the tumoral stain. (C) Selective angiogram of the distal branch of the occipital artery showing a tumoral blush. The arrow indicates the tip of the microcatheter. (D) Injection of 5% n-butyl 2-cyanoacrylate (NBCA) through the microcatheter showing deep penetration to the tumor vessels. (E) Postembolization image of the right common carotid artery showing no tumoral feeding. (F) Postembolization computed tomographic imaging showing good penetration of the NBCA to the tumor (arrowhead). (G) Intraoperative view showing the achievement of tumor necrosis, allowing easy removal of the tumor. (H) Postoperative Gd-enhanced T1-weighted MRI showing successful removal of the tumor.

Discussion

The embolization of meningiomas was first reported in 1973, and has since become widely used in recent years owing to advances in endovascular equipment, embolic materials, and treatment techniques.[5] [6] [7] In one review of 459 meningioma embolizations extracted from 36 studies published between 1990 and 2011, Shah et al found that the target sites were predominantly supratentorial, with the occipital area being the most common site of embolization.[7] The embolization materials used were PVA (31.4%), porous cellulose beads (30.3%), onyx (0.9%), and NBCA (0.2%).[5] Complications from embolization were observed in 21 patients, including 2 deaths due to cerebral infarction and infection. A further 18 patients experienced mild complications, such as cranial nerve palsy and cerebral edema. The risk of complications associated with embolization necessitates that the procedure be performed safely, as it is intended to be an adjunct to resection.

PVA, sponzel, and porous gelatin sponge gel (Nippon Kayaku, Tokyo, Japan) are the most commonly used granular embolization materials for meningiomas.[8] Granular embolization materials are easy to use, but those smaller than 100 μm carry the risk of tumor hemorrhage due to ischemia in the neurotrophic branches of the brain, straying of the embolized material through the external carotid artery system, internal carotid artery, and vertebrobasilar artery system via dangerous anastomosis, in addition to occlusion of the small arteries and outflow veins in the tumor.[9] [10] Additionally, larger granular embolization material is more likely to occlude the MC, requiring an 18-type MC with a larger lumen, making it more difficult to guide material to the distal feeding vessel or over the bend, potentially resulting in proximal arterial occlusion. Furthermore, the granular embolic material is mixed with contrast media, but its visibility is poor. In contrast, NBCA allows the selection of small-diameter MCs, including flow-guided catheters, as well as the use of a DAC enables the MCs to be guided more distally to the feeding vessel.[11] There was no difference in the occlusive effect of NBCA at different concentrations,[12] and if the intratumor vessels could be sufficiently embolized using low concentrations of NBCA, tumor softening and necrosis may occur, making it very effective for performing craniectomy.[13] In a recent report comparing PVA and NBCA, there was no difference in the relationship between the degree of embolization and the embolizing material, while the NBCA was found to be useful.[5]

NBCA is a cyanoacrylate-based drug, and its main component, cyanoacrylate, polymerizes upon contact with anions in the blood to form a polymer that hardens and adheres.[14] [15] NBCA is a permeable substance; as such, it is usually mixed with lipiodol, a contrast material. The lower the concentration of NBCA, the lower the adhesion, while the average polymerization time increases from 3.2 seconds at 50% to 11.8 seconds at 20%.[16] However, lower concentrations increase the mixing ratio of lipiodol, which increases the viscosity and makes it more difficult for lipiodol to flow distally. As such, simply decreasing the NBCA concentration reduces the risk of catheter adhesion to the vessel, but fails to reach the inside of the tumor, resulting in proximal arterial occlusion. Conversely, increasing the NBCA concentration increased the adhesiveness of the catheter, necessitating immediate removal of the MC in the event of backflow into the catheter. As such, NBCA with low adhesion and viscosity is ideal for the adequate embolization of tumors. Lipiodol can be heated to lower its viscosity, while Kora et al reported that the viscosity ratio of a suspension of the anticancer drug miriplatin and lipiodol can be markedly reduced to 0.77 at 30°C and 0.51 at 40°C compared with 25°C, which is room temperature.[17] To reduce the viscosity of lipiodol, we warmed a syringe of mixed NBCA and lipiodol with a heat gun at 100°C for approximately 2 minutes immediately prior to injection. Additionally, another two 1-mL syringes of warmed 5% dextrose solution were injected immediately prior to NBCA injection to heat the MCs, allowing the NBCA to reach more distal sites following a longer injection time. Similar efficacy has been reported with low concentrations of 13 or 14% NBCA[18] [19]; however, our search revealed no prior reports of ultralow concentrations of 5%. The 4Fr DAC is useful not only for guiding the MC distally but also for supporting the removal of the MC if it is trapped by the NBCA by advancing the DAC.[11] Although we encountered no issues with catheter adhesion in our study, it was necessary to pay attention to the dispersion of NBCA into the proximal vessel during catheter removal as low-concentration NBCA is quite soft.[20] Negative pressure is applied to the syringe to remove the catheter. As such, in the present study, we achieved good results with distal embolization of a very low concentration of NBCA (5%), particularly in regard to tumor embolization and its effect on surgery. However, to achieve effective embolization within the tumor, it is important to guide the distal vessels to avoid unintended entry. In some cases, the MC cannot be guided close to the tumor, particularly in the case of a strongly bent artery serving as a feeding artery or a feeding artery from the contralateral side, leading to only proximal vessel occlusion. Additionally, in cases involving only the external carotid artery system, embolization of the external carotid artery softens the entire tumor and has a sufficient effect on surgery; however, when the pial artery is strongly involved, embolization of this region is not achieved, resulting in poor surgical outcomes.[2] [3]

Comparing the 17 patients in the embolization group and 9 patients in the nonembolization group, we hypothesized that the operation time would be shorter in the nonembolization group because of the smaller tumor size. However, the operative time was shorter in the embolization group, which may be due to the fact that the nonembolization group included more patients with posterior cranial fossa tumors, which may influence the operation time depending on the tumor's location.

In addition to reducing intraoperative bleeding and shortening operative time, several reports have suggested that preoperative embolization may also contribute to the suppression of tumor recurrence,[21] [22] indicating its potential utility in cases where total resection is anatomically difficult. Furthermore, there have been reports of tumor shrinkage following penetration embolization with low-concentration NBCA,[23] [24] suggesting that this technique could serve as a palliative treatment option for patients who are not candidates for surgery. However, the number of reported cases remains limited, and further accumulation of clinical experience is necessary. To achieve meaningful outcomes such as recurrence suppression or tumor volume reduction, a higher level of embolization efficacy may be required. In this context, the use of ultralow concentration NBCA, owing to its superior intratumoral penetration, may play a significant role in improving therapeutic outcomes.

Although ultralow concentration NBCA was used in this study at safe sites without dangerous anastomosis and complications, it is reasonable to increase the concentration or consider other embolic materials, such as coils, to avoid unintended straying in shunt disease or in situations where catheter guidance is insufficient. The limitations of this study include the small sample size, different tumor localization in the two groups, and the lack of comparison with high-concentration NBCA.

Conclusion

Embolization with an ultralow concentration of 5% NBCA is expected to allow NBCA to effectively reach the intratumoral vessels, potentially shortening the operative time and reducing blood loss during tumor resection. For effective embolization using NBCA, it is crucial to understand its properties, particularly the relationship between concentration, adhesiveness, and viscosity. Additionally, performing a thorough anatomical study prior to the procedure is essential to avoid dangerous anastomoses and cranial neurotrophic branches, thus preventing complications.

Conflict of Interest

None declared.

Ethical Approval

The study protocol was approved by the Ethics Committee of the Kansai Medical University (No. 2023093).

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Publication History

Article published online:
02 June 2025