Preoperative embolization of brain, head, and neck tumors: Single center experience and literature review
Article information
Abstract
Objective
The management of highly vascularized tumors in the brain, head, and neck regions poses significant challenges. This review aims to provide practical insights into using preoperative embolization to improve surgical outcomes and guide healthcare centers with limited expertise in this technique.
Methods
A literature review was conducted using PubMed, Scopus, and Web of Science databases with keywords related to preoperative embolization and highly vascularized tumors, detailing its definition, indications, diagnostic considerations, procedural aspects, clinical and surgical implications, and associated complications. The findings are supported by data from 309 patients with brain, head, and neck tumors treated with preoperative embolization at Hospital Clínica Kennedy in Guayaquil, Ecuador, from 2015 to 2023. Cases without embolization or those below the clavicular border were excluded. Illustrations and photographs, based on the authors’ surgical experience, are included with informed consent.
Results
Preoperative embolization has proven effective in reducing morbidity, enhancing surgical outcomes, and palliating symptoms in inoperable cases by decreasing tumor size. While complications are rare, they can be minimized with careful planning. Despite its efficacy, the lack of randomized controlled trials due to the rarity of hypervascular tumors limits the ability to establish standardized practices.
Conclusions
Preoperative embolization is a valuable tool in managing highly vascularized tumors. However, further research and uniform reporting are essential to optimize outcomes and develop clear guidelines for this critical procedure.
INTRODUCTION
The management of highly vascularized tumors in the brain, head, and neck region often presents a challenge and requires a multimodal treatment approach. Embolization is a technique that can be performed before planned surgical resection in an attempt to minimize morbidity and improve the chances of controlled and successful tumor resection. Although tumor embolization has been described since the 1970s, advancements in embolization techniques, materials, and specialist training have significantly expanded the progress of this technique today [12].
Preoperative embolization of intra- and extracranial tumors has become an adjunct to surgical excision with the following primary objectives: 1) Facilitate tumor resection by limiting blood loss and inducing lesion necrosis through the selective occlusion of arterial feeding vessels. Limited blood loss makes surgical resection safer, more controlled, and effective, improving visualization as tumor margins become easier to identify. 2) Necrosis leads to tumor softening, facilitating resection and reducing the forces exerted on adjacent neurovascular structures [28].
The ultimate purpose is not merely to control blood flow but to minimize overall morbidity and maximize the effectiveness of the surgical treatment. An overly conservative embolization may prove inefficient, while a more aggressive embolization may be riskier and more effective. Therefore, the patient and physicians should consider embolization and resection as a combined approach in treatment.
MATERIALS AND METHODS
A literature review was conducted using databases such as PubMed, Scopus, and Web of Science, employing keywords such as “Preoperative Embolization,” “Highly Vascularized Tumors,” “Brain Tumor Embolization,” “Head and Neck Tumor,” “Embolization,” and “Tumor Resection.” This review details the definition, indications, diagnostic considerations, procedural details, clinical and surgical implications, as well as the complications associated with preoperative embolization (Supplementary Table 1).
We illustrate our findings using data from our center, Hospital Clínica Kennedy in Guayaquil, Ecuador, where a total of 309 patients with brain, head, and neck tumors, aged over 18 years who underwent preoperative embolization from 2015 to 2023 were included. Patients who did not meet the criteria, tumors that were not treated with embolization before resection, and those below the superior clavicular border were excluded. The photographs and illustrations provided are based on the author’s surgical experience and have been accompanied by informed consent.
RESULTS
1. Multidisciplinary approach
Advances in surgical techniques have reduced the mortality associated with the resection of specific brain, head, and neck tumors. Complete tumor resection requires a multidisciplinary approach involving techniques from multiple specialties, including vascular and endovascular, otolaryngology, and neurosurgery. Ideally, patients with vascular tumors in the head and neck should be evaluated through a multidisciplinary team approach for optimal staging and therapeutic planning.
2. Definition
Tumor embolization refers to any percutaneous procedure, either through direct puncture of the tumor or via an endovascular approach in which particles, liquid embolic agents, coils, gel foam, or other materials are injected to reduce tumor vascularization. The direct puncture technique for preoperative embolization of hypervascular head and neck tumors has traditionally been performed with gel foam, fibrin glue polyvinyl alcohol, or permanent materials such as ethanol or N-butyl-cyanoacrylate [26]. It is a viable alternative to transarterial embolization, offering improved tumor penetration and potentially fewer arterial complications. While direct puncture embolization is safe and effective for hypervascular head and neck tumors, its use in intracranial pathologies requires caution due to the potential risk of venous complications [13].
The key recommendation for successful embolization is that the procedure be performed by a physician experienced in neuroendovascular techniques, angiographic image interpretation and with in-depth knowledge of relevant vascular and surgical anatomy (venous flow patterns, involvement of dural sinuses, anatomical variations, and regional anastomoses) [28].
3. Indications
The primary objective of tumor embolization is to facilitate the successful surgical resection of the lesion. Controlling bleeding during surgery can be challenging, particularly in highly vascularized tumors. In certain cases, embolization may be employed as a palliative treatment to reduce tumor size and alleviate pain in patients with tumors deemed inoperable [1]. Examples of tumors (brain, head, neck, and spine) typically characterized by significant vascularization include hemangioblastomas, meningiomas, juvenile nasoangiofibromas, aneurysmal bone cysts, paragangliomas (carotid body, glomus vagale, glomus jugulare), solitary fibrous tumors, and vascular metastases from renal cell carcinoma, thyroid cancer, and choriocarcinoma [30].
Table 1 summarizes the specific tumors commonly treated with adjuvant embolization prior to surgical resection. This list may exclude other tumor types where embolization could be indicated based on the tumor’s vascularity. It is recommended that the indication for tumor embolization be clearly defined before the procedure.
Vascular tumors that may benefit from pre-surgical embolization
In the brain, meningiomas fulfill most of the objectives of preoperative embolization as they are hypervascular and primarily supplied by dural feeding vessels. While most convexity meningiomas do not require embolization, even if highly vascular, those located at the skull base or in the posterior fossa can present significant differences. (Fig. 1) [2,5]
(A) and (B) Pre- and post-embolization angiographic study of a right sphenoid wing meningioma. Onyx was used as the embolic agent to occlude blood flow from the middle meningeal artery. (C) Brain CT showing the size and extent of the highly vascularized tumor. (D) Postoperative CT after a pterional transzygomatic approach was performed for complete resection of the meningioma. No hemorrhagic complications occurred. STA, Superficial temporal artery; MaxA, Maxillary artery; MMA, Middle meningeal artery; CT, computed tomography
4. Angiographic study
Digital subtraction angiography provides additional information to complement clinical evaluation and findings from computed tomography or magnetic resonance imaging studies. Angiography enables the identification of feeding vessels supplying the tumor, facilitating their localization and ligation during surgery. Other critical information includes the extent of tumor growth around vessels (e.g., the internal carotid artery) and collateral flow distal to the affected vessel. Combined with a balloon occlusion test, angiography can assist in determining the feasibility of carotid artery sacrifice during surgery, if necessary [5].
The blood supply to a tumor can be predicted based on its location, extent, and type. For instance, paragangliomas are almost universally supplied by branches of the ascending pharyngeal artery. In the case of nasoangiofibromas, the vascular supply primarily arises from the distal branches of the internal maxillary artery, particularly the sphenopalatine, descending palatine, and posterior superior alveolar branches [22,35]. Therefore, selective catheterization of the external and internal carotid artery branches is required to delineate the blood supply properly. Additionally, super-selective catheterization of external carotid artery branches may reveal dangerous intracranial anastomoses, necessitating caution during embolization.
An evaluation of the contralateral carotid artery branches should be performed to rule out their contribution to the tumor, particularly in cases where the tumor has crossed the midline. Intracranial tumors, particularly those located in the posterior fossa, may require additional imaging of the posterior circulation (Fig. 2). It is important to note that anastomoses may exist between the external carotid artery branches (particularly the occipital artery) and the posterior circulation. These vascular connections can pose potential risks during embolization if they are not documented and thoroughly understood [12].
Angiographic study before the embolization of a left posterior fossa hemangioblastoma (A) (1, hemangioblastoma mural nodule; 2, hemangioblastoma vascularity), and seven days post-embolization prior to tumor excision (B) (3, Mural nodule after embolization; 4, PICA aferences post embolization; 5, AICA aferences post embolization). During the surgical procedure, complete excision of the hemangioblastoma was achieved. The patient experienced reduced intraoperative blood loss. BA, basilar artery; LVA, left vertebral artery; PICA, posteroinferior cerebellar artery; AICA, anteroinferior cerebellar artery; SUCA, superior cerebellar artery; PCA, posterior cerebral artery
A comprehensive understanding of extracranial-to-intracranial arterial anastomoses is vital for minimizing complications during neuroendovascular procedures. Among the most clinically relevant pathways is the connection between the facial artery or the internal maxillary artery (IMAX) and the ophthalmic artery (OA), which arises from the internal carotid artery (ICA). The facial artery, via its terminal angular branch, forms anastomoses with the supratrochlear and supraorbital arteries-distal branches of the OA. This vascular linkage creates a potential conduit for unintentional embolic material to reach the intracranial anterior circulation, including the retinal territory, particularly during embolization of nasal or facial vascular lesions [15]. Similarly, the IMAX establishes communications with the OA through orbital branches such as the zygomaticotemporal artery, presenting additional risk during procedures involving the maxillofacial region [15].
Another important anatomical connection involves the middle meningeal artery (MMA), a branch of the IMAX, which communicates with branches of the meningohypophyseal trunk (MHT) of the ICA. Notably, the marginal tentorial artery may anastomose with the petrosquamosal branch of the MMA [17,29]. This pathway poses a considerable risk for retrograde embolization into the intracranial circulation, especially when liquid embolic agents are employed for treating dural arteriovenous fistulas or meningeal tumors [15]. Such events may result in significant neurological deficits.
A third noteworthy route is established via the vidian artery, which links the IMAX to the petrous segment of the ICA. This artery may originate from the IMAX as part of the pterygoid canal vasculature and anastomose with a corresponding branch from the ICA. This pathway is particularly relevant in the context of nasopharyngeal tumors such as juvenile angiofibromas, where these arteries are often hypertrophied [24]. Failure to identify these anastomoses during embolization can lead to the inadvertent delivery of embolic agents into critical intracranial structures.
Finally, the occipital artery (OccA) forms frequent and robust connections with the vertebral artery (VA) through radicular and muscular branches at the C1 and C2 levels. These segmental anastomoses are capable of providing collateral flow to the vertebrobasilar system in cases of proximal vertebral artery occlusion (15). Additionally, the stylomastoid branch of the OccA may communicate with the posterior meningeal artery, itself a branch of the VA. These connections pose a potential risk for embolization into the posterior fossa or brainstem, necessitating careful consideration during interventions in the upper cervical spine or posterior skull base.
Though often not visible on conventional angiography, these anastomoses can become functionally significant in altered hemodynamic states, such as elevated intraluminal pressure or downstream vascular occlusion. Consequently, meticulous knowledge of these arterial pathways is essential to safely navigate neurointerventional procedures and avoid inadvertent intracranial complications [15,21].
5. Procedure details
1) Embolization material and particle size
The specific attributes of each material provide various options for tumor devascularization. Embolic agents are classified into three main categories, each with advantages and disadvantages. The choice of material may be determined by several factors, including anatomical considerations or the operator’s preference and experience.
Among the commonly used agents are polyvinyl alcohol (PVA), microspheres, and Gelfoam. Liquid agents include n-Butyl Cyanoacrylate (nBCA) and the ethylene-vinyl alcohol copolymer (Onyx), while the most recent embolizing agent is coiling [2,8]. In the case of particles such as polyvinyl alcohol (PVA) or tris acryl gelatin microspheres (TAGM), particle size has been associated with both efficacy and complication rates. Smaller particles can penetrate more distally into tumor capillary beds but may also cause injury to the vasa nervorum, resulting in cranial nerve damage, or enter the intracranial circulation through anastomoses between the external and internal carotid arteries. A comparison between tris acryl gelatin microspheres (TAGM) and polyvinyl alcohol (PVA) particles suggests that TAGM particles may achieve deeper penetration into the tumor’s vascular beds [34].
Highly effective embolization can result in significant tumor reduction, sometimes surpassing the effects of radiation, which can be highly beneficial. Except for lesions with a single feeding pedicle, the efficacy of embolization is directly related to the deposition of embolic material as deeply as possible within the intrinsic tumor vasculature. For this reason, optimal tumor embolizations require small particles capable of penetrating vessels with diameters of 100 micrometers or smaller [12,30].
PVA particles provide controlled occlusion of larger vessels, making them safer for proximal embolization with a lower ischemic risk. However, their limited penetration may lead to partial recanalization and a slightly higher recurrence rate than n-BCA. In contrast, n-BCA creates a permanent occlusion, reaching deeper MMA branches for better long-term hematoma reduction, but with a higher risk of nontarget embolization and cranial nerve ischemia if injected distally. While both are effective, the choice depends on vascular anatomy, treatment goals, and operator expertise, balancing PVA’s safety with n-BCA’s stronger but riskier occlusion [37].
6. Embolization route
There are three main embolization techniques: the transarterial approach, direct puncture, and a combination of both. Any of these methods is feasible, and there are no established guidelines regarding the preferred route [2]. However, advancements in endovascular therapy, particularly in embolic materials and microcatheter technology, have expanded the window of opportunity for adjuvant treatment of challenging-to-resect neoplasms [1].
Traditionally, embolization is performed through the transarterial route using super-selective catheterization and embolization of the feeding vessels via microcatheter-guided injection of one or more agents. Additionally, occlusion of the main tumor-feeding vessel with coils is also a viable option [10,30] (Figs. 3, 4). This method can be challenging when the vascular anatomy involves tortuous or small-caliber vessels, which may hinder attempts to achieve the necessary microcatheter positioning. The presence of local collaterals also poses a risk of material migration into adjacent normal branches. Moreover, injection into a single feeding vessel may be insufficient to achieve complete tumor devascularization, often needing additional selective catheterizations. These challenges prolong the total procedure time and increase the risk of unintended arterial embolization.
(A) Pre-embolization angiographic study of a carotid body tumor as part of preoperative management. (B) Post-embolization angiographic study of the tumor using SQUID 12 as the embolic agent before tumor resection (** representing carotid body tumor after embolization). (C) CT scan with 3D reconstruction of the head and neck showing the tumor in the carotid body of the left carotid artery (* representing carotid body tumor vascularity before embolization). (D) Tumor resection through a left cervical-lateral approach. CCA, common carotid artery; ICA, internal carotid artery; ECA, external carotid artery; STh, superior thyroid artery; FA, facial artery; MAx, Maxillary artery; CT, computed tomography
(A) and (B) Pre- and post-embolization angiographic study of a left juvenile nasoangiofibroma, Fisch stage IIIb. Onyx was used as the embolic agent. (C) Preoperative MRI showing intra- and extracranial tumor extension. (D) Complete resection of the previously embolized tumor was performed using a craniofacial approach, successfully reducing surgical time and blood loss (* representing intracranial portion of tumor: after removal, anterior fossa with frontal lobe covered by dura mater; ** representing extracranial portion of the tumor after removal). ICA C4, internal carotid artery cavernous segment; ICA C2, internal carotid artery petrous segment; MRI, magnetic resonance imaging
Direct puncture embolization has been proposed as an alternative to address these challenges and can also be used as a complement to the transarterial method. Using an 18-25 Fr gauge needle, a liquid embolic agent is directly injected into the tumor bed under fluoroscopic guidance. While this approach achieves a higher concentration of the embolic agent within the tumor and eliminates the need for endovascular catheterization, it carries a higher likelihood of inadvertent trans-tumoral embolization of venous structures due to the shorter distance to the venous system. Additionally, direct tumor injection poses the risk of unintended migration to surrounding normal structures [14]. Generally, the method choice is determined by factors such as tumor location, the number of arterial feeding vessels, vascular access, vascular anatomy, individual tumor characteristics, presenting symptoms, the patient’s age, and clinical condition.
In rare cases where vascular anatomy or pathology complicates endovascular access, direct puncture embolization may be the only option for preoperative embolization. While there are no systematic comparisons of the two techniques, some authors have suggested that direct puncture allows for better tumor penetration, thereby reducing intraoperative blood loss when liquid embolic agents are used. Additionally, it may facilitate resection by delineating the tumor from surrounding tissue [12,28]. However, this technique also includes significant complications. Further comparisons between these techniques are needed before definitive recommendations regarding their relative merits can be made.
7. Anesthesia and pharmacological provocation testing
Tumor embolization can be performed under either general or local anesthesia. Local anesthesia with conscious sedation allows for neurological examination during provocation maneuvers and avoids potential complications associated with intubation and exposure to general anesthetic agents. General anesthesia, on the other hand, eliminates risks related to patient agitation and movement during the procedure, which could be hazardous during critical phases of the embolization [5,12,16]. In general, embolization can be safely performed using either method; therefore, the choice of anesthesia should be guided by the patient’s specific characteristics, such as the presence of airway obstruction caused by the tumor or coexisting medical conditions, at the discretion of the endovascular operator.
8. Clinical and radiological efficacy of embolization
As previously mentioned, the goal of tumor embolization is to reduce its vascularization to facilitate surgical resection or provide palliation. However, some authors have questioned the utility of preoperative embolization [5,6]. The literature supports the efficacy of tumor embolization in reducing intraoperative blood loss, surgical times, and recurrence rates [20,23,33]. Despite the additional resources required for embolization procedures compared to resection alone, the benefits of embolization are promising. However, conclusive randomized studies are still needed. It is clear that, while feasible and beneficial, embolization may not be necessary in all cases. The decision should be individualized based on various factors, as previously mentioned.
When reporting efficacy, the amount of tumor “blush” is used as a radiographic measure of vascularization. The goal of embolization should be to reduce tumor blush by 80% or more [28,33]. Digital subtraction angiography (DSA) images should be reviewed after completing embolization, and the percentage of reduction should be quantified. Magnetic resonance angiography (MRA) images (indicating lack of contrast uptake or diffusion restriction) or intraoperative computed tomography (CT) have also been employed to quantify the extent of vascularization following embolization. Intraoperative parameters such as blood loss, transfusion requirements, and surgical duration are additional quantitative measures that should be evaluated. For embolization procedures performed with palliative intent, the presenting symptoms and their subsequent regression or improvement have been reported as efficacy measures [2,12].
9. Timing of surgery following embolization
Tumor embolization is optimally performed 1 to 7 days before surgery. This timing facilitates 1) maximum thrombosis of the embolized vessels, 2) ideal tumor necrosis, and 3) tumor softening [7,18]. If delayed beyond this time frame, tumor inflammation and neovascularization may occur.
The radiographic and clinical effects of embolization can be transient or permanent, depending on the embolic material used. Therefore, the timing of the embolization of surgery is crucial. Very early tumor resection (<24 hours) after embolization may negate the benefits of embolization by not allowing sufficient time for devascularization and tumor necrosis to occur, leading to increased surgical blood loss [3,9]. Histological examination of tumors embolized with particles reveals thrombus formation and multinucleated giant cell reactions within 7 days post-embolization. Subsequently, partial recanalization and revascularization can be observed in approximately 30% of the embolized vessels [25].
It has been demonstrated that the change in tumor consistency and ease of resection are maximized 7–9 days following embolization of meningiomas [9,34]. Therefore, surgical resection should be performed 1 to 8 days after embolization to maximize the benefits of the latter procedure. Steroids should be administered for large tumors at risk of post-embolization edema, such as meningiomas, particularly if surgery is delayed. Transarterial embolization for meningiomas and other vascular tumors of the skull base may lead to infarction, inflammation, and even brain herniation. In such cases, embolization immediately before surgery should be seriously considered [18].
10. Complications
Complications can be classified as either procedure-related or non-procedure-related. The most common complications associated with tumor embolization are outlined in Table 2 and include cranial nerve paralysis, skin or mucosal necrosis, and unintended vascular occlusions [2,28]. Procedure-related complications can be further subclassified based on their clinical relevance and impact into minor or major complications.
Complications of tumor embolization
1) Major complications
Major complications are rare in extracranial tumor embolizations [12]. However, ischemic or hemorrhagic cerebrovascular events have been reported in 3–6% of cases during intracranial embolization procedures [16,18]. Major complications are defined as those requiring additional therapy, higher levels of care, prolonged hospitalization, permanent sequelae, or death. These may include cerebrovascular events, cranial nerve paralysis, tissue damage, or fatal outcomes. Table 3 summarizes the frequency of complications in a case series presented by the authors of this article.
Complications of embolized tumors
2) Minor complications
Minor complications are those that do not require specific treatment beyond observation and have no clinical consequences. These may include puncture site complications that do not affect neural structures, as well as localized pain and swelling. However, when tumor embolization is performed prior to surgical resection, complications may be attributed to either the embolization procedure or the resection.
3) Strategies for preventing complications in tumor embolization
Tumor embolization is a valuable technique for minimizing blood loss during surgery and enhancing the feasibility of tumor resection. However, it is not without risks. One of the primary concerns for neurointerventionists is the inadvertent migration of embolic agents into cerebral circulation, which can result in serious complications such as cerebral infarction and cranial nerve damage. These potential outcomes highlight the need for thorough anatomical understanding, meticulous technique selection, and the implementation of protective measures to ensure patient safety and optimize clinical results.
The migration of embolic material has been identified as a key contributor to adverse neurological outcomes following embolization procedures. A multicenter retrospective analysis revealed that this complication was the strongest predictor of decline in modified Rankin Scale (mRS) scores three months after treatment. Notably, embolization involving high-risk vessels, such as the accessory meningeal artery and the distal segment of the internal maxillary artery, was significantly correlated with increased risk of embolic migration [31]. These results highlight the critical need for meticulous procedural planning and thoughtful selection of target vessels to minimize complications.
To reduce the likelihood of embolic reflux and unintentional migration, the use of balloon protection techniques has gained prominence. By temporarily occluding the external carotid artery with balloon guide catheters, neurosurgeons can effectively prevent retrograde flow into the internal carotid artery as well as forward embolization into non-target branches. This method improves procedural accuracy and control, enabling safer and more targeted delivery of embolic materials and thereby lowering the incidence of stroke and cranial nerve injuries [27].
Understanding vascular anatomy is crucial, especially in areas with complex anastomotic networks between the external and internal carotid arteries. In such anatomically challenging regions, embolization of vessels like the MHT and inferolateral trunk (ILT) can be particularly difficult. To address this, a novel technique involving distal balloon protection has been developed, allowing safe embolization even in cases where microcatheter navigation is not possible. This method includes temporary balloon occlusion of the internal carotid artery at the ophthalmic segment, combined with careful injection of embolic agents and aspiration of any reflux before deflation. Although postprocedural imaging revealed subclinical infarcts in approximately 69% of cases, no patients exhibited clinical symptoms, suggesting that this approach may be a viable and safe option for high-risk embolizations [38].
Dual balloon protection has also proven effective in the embolization of posterior fossa meningiomas supplied by the MHT. In a cohort of eight patients, this technique enabled complete or near-complete devascularization of the tumor without any cases of cerebral infarction resulting from distal embolic spread. Despite these favorable outcomes, one patient experienced a worsening of a pre-existing abducens nerve palsy, underscoring that while balloon protection can significantly enhance safety, the risk of cranial nerve ischemia cannot be eliminated [32].
When embolic migration occurs despite the use of preventive strategies, salvage interventions such as thromboaspiration may serve as effective rescue options. Commonly utilized in managing complications during arteriovenous malformation embolization, thromboaspiration allows for the retrieval of migrated embolic material and the re-establishment of cerebral perfusion. This technique can be instrumental in mitigating the risk of infarction and reducing procedure-related morbidity [4].
In addition, meticulous technique remains essential in transvenous embolization (TVE), where excessive coil packing has been associated with complications such as trigeminal nerve palsy and ischemic cranial neuropathy. These adverse events are often the result of mechanical compression or ischemia caused by obstruction of the vasa nervorum. Therefore, precise control of coil volume and a thorough understanding of venous sinus anatomy are fundamental to reducing the incidence of such complications [19].
DISCUSSION
A hypervascular brain tumor presents a significant challenge for neurosurgeons, as excessive bleeding during its removal can pose a life-threatening risk [11,36]. In the article by Deshmukh et al., as well as in most of the studies cited in this review, preoperative embolization is described as a procedure that significantly enhances the surgical process and outcomes by facilitating bleeding control, particularly in highly vascularized tumors. The vascular tumors that derive the greatest benefit from preoperative embolization include hemangioblastomas, hemangiopericytomas, meningiomas, juvenile nasoangioblastomas, glomus tumors, and metastases [2].
The effectiveness of embolization is closely linked to the deposition of embolic material; therefore, optimal tumor embolization requires small particles capable of penetrating vessels with diameters of 100 micrometers or less. When performed with appropriate guidance, sufficient expertise, and a multidisciplinary approach, embolization is considered a safe procedure. Beyond its role in reducing tumor vascularization to facilitate surgical resection, embolization is also widely employed for palliative purposes, aiming to alleviate symptoms related to tumor mass effect [8,34]. Despite the promising benefits of embolization, further conclusive randomized studies are necessary to establish its efficacy definitively.
Regarding the route of embolization delivery, although the transarterial approach with super-selective catheterization remains the preferred method, it is associated with certain risks. These include the potential migration of embolic material through local collateral vessels and the necessity for additional selective catheterization in tumors supplied by multiple feeding vessels. Conversely, direct puncture embolization offers the advantage of achieving a higher concentration of embolic agent within the tumor but is associated with an increased risk of trans-tumoral embolization into venous structures [6,14,16].
Currently, no systematic reviews directly compare the transarterial approach with direct puncture embolization. Further studies are required to clarify the specific indications and relative advantages of each technique.
In the same context, the timing of surgery following tumor embolization is critical. Surgery is ideally performed within 1-7 days post-embolization to maximize vessel thrombosis, tumor necrosis, and softening. Delaying the procedure beyond 7 days may result in severe inflammation and neovascularization while performing tumor resection less than 24 hours after embolization may not allow sufficient time for adequate devascularization and necrosis to occur [9,18].
The most common major complications associated with tumor embolization include cranial nerve paralysis, skin or mucosal necrosis, and distal vascular thrombosis, which can lead to ischemic or hemorrhagic stroke. However, these complications are rare in cases of extracranial tumor embolization, such as in nasofibromas and carotid glomus tumors [12,16,28,34].
Most studies emphasize the heterogeneity of indications and specific contexts for performing preoperative embolization. This review, combined with our surgical experience, offers a more targeted perspective, which is particularly valuable for healthcare centers with limited expertise in this procedure. Furthermore, it lays the groundwork for future qualitative and quantitative studies aimed at better defining the clinical and surgical scenarios in which preoperative embolization provides the greatest benefit.
One limitation of this study is the absence of recent systematic reviews or meta-analyses to consolidate existing knowledge and establish a more objective framework. The lack of significant advancements in recent years, both for adult and pediatric populations, highlights this gap. Addressing this limitation through comprehensive studies will undoubtedly contribute to improved safety, efficacy, and patient outcomes.
CONCLUSIONS
In conclusion, preoperative embolization is a procedure that demands a multidisciplinary approach, meticulous planning, and the individualization of patient care within a comprehensive framework. Its precise indications are essential to achieving optimal outcomes. Endovascular techniques play a significant role in the management of intracranial and head and neck vascular tumors, effectively reducing tumor blood flow and serving as a reliable method to minimize intraoperative hemorrhagic complications.
However, randomized controlled trials assessing the safety and efficacy of these techniques remain scarce, primarily due to the rarity of hypervascular tumors. Establishing standardized definitions and uniform reporting practices will be crucial in developing best practice measures and advancing the field.
Notes
Disclosure
The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
Supplementary figure and table
Summary of authors included