Embolization of the middle meningeal artery as a treatment of chronic subdural hematoma – a single-center experience

Summary

Introduction: Chronic subdural hematoma (CSDH) is almost the most frequent neurosurgical diagnosis. In particular, with an aging population and the use of antiplatelet and anticoagulant therapy, these cases are on the rise. Surgical treatment, usually managed by simple burr-hole evacuation is a relatively simple and effective method of treatment. Despite the successful primary surgery, there is an increase in CSDH recurrence. Recently, minimally invasive procedures have become a trend. Endovascular embolization of the middle meningeal artery (MMA) is a relatively new and now in the world frequently used therapeutic modality. Methods: We present a series of patients treated with MMA embolization with or without trepanation. Results: Our cohort includes forty patients with CSDH –⁠ recurrent and primary. In 97.5% patients, we achieved complete resolution of CSDH after MMA embolization, one patient was re-hospitalized for another recurrence despite embolization. In three patients, MMA embolization was used as a primary and single treatment for CSDH. Conclusion: MMA embolization can be used as a single or additional treatment for CSDH recurrence. It can also be used in patients who are not suitable candidates for trepanation due to other comorbidities. MMA embolization appears to be a safe and relatively simple management of recurrences of CSDH, when the rules of endovascular treatment are followed.

Keywords:

embolization – chronic subdural hematoma – middle meningeal artery

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version.

 

Introduction

Chronic subdural hematoma (chSDH) is one of the most common neurosurgical diagnoses [1–3]. It is associated with significant morbidity and mortality, particularly in the elderly population, at 4% and 11%, respectively [4]. The incidence is reported as 14/100,000 [5], 17–20/100,000 [2], and in patients over 65 years of age, the incidence is up to 58.1/100,000 [6]. In the coming years, the incidence of chSDH is expected to double due to the aging population [1,4], and by 2030 it will likely be the most common neurosurgical diagnosis [7]. The higher incidence is also contributed to by the not always correctly indicated use of antiplatelet or anticoagulant therapy [1,8].

Given the increase in incidence and significant morbidity and mortality, the treatment of chSDH needs to be optimized. A quick and effective treatment method is trepanation –⁠ one or two burr holes under local anesthesia. Although this is the most commonly used method, in some cases it is not sufficient. During trepanation, we are usually unable to disrupt the neovascularized membranes responsible for chSDH recurrence, which occurs in 11.7–28% of cases [1], with some studies reporting up to 37% [9,10]. The aim of embolization of the middle meningeal artery (MMA) is to devascularize the small capillary networks responsible for the neovascularization of chSHD membranes, thereby preventing further recurrences [1,6].

In this paper, we present our experience with this method. A total of 40 patients underwent embolization –⁠ 37 patients had a recurrence of chSDH, and in three patients we used MMA embolization as the primary and only therapy.

 

Methods

We included all patients with recurrent chSDH from 2020 to 2024 in our cohort; three patients underwent embolization as part of primary chSDH therapy. All patients underwent MMA embolization, some of which was combined with additional drilling depending on the clinical condition and displacement of midline structures. In the case of surgical treatment, we mostly used the original trepanation, or performed additional trepanation if necessary. Patients who underwent a second trepanation and embolization had a native CT scan of the brain on the first day after the procedure; patients who underwent embolization only and were in good clinical condition did not undergo early imaging. We processed the following data for all patients: age, use of antiplatelet or anticoagulant therapy, periprocedural complications, and the resulting clinical condition and graphic findings.

As part of further follow-up, we invited all patients to our outpatient clinic for a clinical and imaging check-up 4 months after the procedure. This time interval proved to be optimal in view of the majority regression of findings and minimization of repeated exposure of patients to radiation.

 

MMA embolization

Embolization is most commonly performed via the common femoral artery in the groin using a 6F instrument. The MMA is a branch of the maxillary artery, which is a branch of the external carotid artery (ECA). The MMA enters the skull through the foramen spinosum, runs in the epidural space, and participates in supplying the dura mater and calvaria together with the significantly smaller anterior meningeal artery and posterior meningeal artery. The MMA branches intracranially into frontal and parietal branches. For safe embolization, it is important to visualize any collaterals and anastomoses of the MMA. Small branches originating in the vicinity of the spinosum f. may anastomose or directly supply the vasa nervorum for the V and VII cranial nerves. Therefore, during embolization, it is always necessary to insert the microcatheter distally behind the spinosum f. to avoid possible damage to these cranial nerves. Another important group are collaterals to the ophthalmic artery basin. In rare cases, the entire MMA or its branches may even branch off aberrantly from the ophthalmic artery. These variants then completely prevent or significantly limit MMA embolization. Due to the anastomoses and variants described above, it is always recommended to perform a comprehensive angiography of the internal carotid artery (ICA) and ACE basins before starting embolization [11]. A 6F guide catheter, e.g., Envoy 6F (Cerenovus, Irvine, CA, USA), is inserted beyond the ACE origin. The MMA is probed using microcatheters, e.g., Synchro, and microcatheters, e.g., Excelsior SL-10 (both Stryker Neurovascular, Portage, MI, USA). After penetration above the spinosum, DSA is performed, where a "capillary blush" –⁠ opacification of the membranes –⁠ is typically seen for chSDH [12,13]. No difference has been demonstrated between liquid embolization material and particles [8]. It follows that the choice of the optimal embolization material is therefore in the hands of the interventional radiologist, based on his or her experience. In their study, Kan et al. performed embolization in 154 patients, using particles in 70.2% and liquid agents in 25.3%, and found no statistically significant difference in the overall outcome [8]. Embolization of both branches of the MMA –⁠ anterior and posterior –⁠ is associated with a higher probability of hematoma regression than embolization of only one branch [14], 76% vs. 33% [15]. According to available sources, polyvinyl alcohol particles, e.g., Contour (Boston Scientific, Marlborough, MA, USA), were most commonly used for embolization. The most commonly used particle size is 150–250 microns. This size is assumed to provide optimal distal penetration, while at the same time preventing unwanted embolization of small collaterals, including vasa nervorum, which have a smaller diameter [8]. Another solid embolization material is Embosphere compressible particles (Merit Medical, South Jordan, UT, USA). When using the liquid embolization agent N-butyl 2-cyanoacrylate (NBCA, Histoacryl) (B. Braun, Melsungen, Germany), a dilution of 1 : 5 in combination with Lipiodol (Guerbet, Villepinte, France) is recommended. The use of non-adhesive embolization agents, such as Onyx 18 and 34 (Medtronic, Dublin, Ireland) and Squid (Balt, Montmorency, France), is very painful for the patient and therefore cannot be used without general anesthesia. Dimethyl sulfoxide-compatible microcatheters, such as Sonic (Balt, Montmorency, France), must be used for their application [16,17]. When using these agents, there is a risk that their excellent distal penetration will cause the closure of small, non-visualizable collaterals.

 

Results

A total of 40 patients were included in the study, 37 patients were rehospitalized for recurrence of chSDH, and in 3 patients we used MMA embolization as initial therapy for primary chSDH.

The average age was 58 years, and all patients had traumatic chSDH. Six patients (15%) had a history of antiplatelet therapy and 12 patients (30%) had a history of anticoagulant therapy.

Of the entire patient group, a total of 29 (72.5%) initially underwent trepanation, followed by rehospitalization for recurrence and further trepanation and embolization of the relevant MMA. Eight patients (20%) underwent primary trepanation and only embolization in case of recurrence. These patients had symptomatic recurrence with very minor imaging findings. Three patients (7.5%) underwent embolization only. These were two symptomatic patients with minor imaging findings and one patient for whom discontinuation of anticoagulant therapy for surgery was risky.

As part of further follow-up, a clinical and imaging check-up was performed after 4 months. Eight patients (20%) had minor, completely asymptomatic residuals up to a maximum width of 2 mm on CT imaging, and 28 patients (70%) had complete regression of the findings (complete resorption of SDH on native CT). Unfortunately, one patient died of pulmonary embolism during this period. The remaining two patients will be checked in the coming months. Despite repeated trepanation and embolization, one patient was rehospitalized for another, i.e., a second recurrence. Thus, in the entire cohort, MMA embolization failed to prevent further recurrence in one patient (2.5%).

In terms of clinical status, two patients (5%) continue to have stationary mild monoparesis, while the other patients have no apparent neurological deficit. Subjectively, almost half of the patients report headaches (42.5%), but these are not permanent and can be treated with common analgesics.

In terms of periprocedural complications, we observed transient contralateral limb paresis in three patients immediately after MMA embolization. All of these patients underwent a CT stroke protocol without evidence of ischemia and an EEG examination to rule out epileptic seizures. Two patients experienced complete recovery, while the third patient was diagnosed with possible status epilepticus and is now on chronic antiepileptic medication.

Figure 1 shows a native CT scan of the brain of a patient we hospitalized for recurrent chSDH. The patient underwent a second surgical evacuation and MMA embolization. Figure 2 shows the final condition during a follow-up scan after 4 months –⁠ complete resorption of the hematoma is evident.

Figure 3 illustrates a patient who had a small, almost asymptomatic (headache) finding of chSDH on the left side. The patient was treated only with MMA embolization; Fig. 4 shows the result after 4 months during a follow-up scan. Again, complete resorption of the hematoma is evident.

 

Discussion

The most common cause of chSDH is trauma, often in conjunction with antiplatelet or anticoagulant therapy. Initially, patients are usually asymptomatic, as the trauma is minor. However, there is injury to small cortical arterioles or bridging veins [3]. Over the next 3–4 weeks, fluid gradually accumulates in the subdural space. Due to increasing intracranial pressure, corresponding clinical symptoms such as confusion, speech disorders, limb paresis, or epileptic seizures begin to develop [18]. Non-specific symptoms, most commonly a decline in cognitive function, can be problematic, as they may be diagnosed as a new neurological deficit, especially in the elderly population. chSDH is a reversible cause of dementia if diagnosed and treated early and correctly [4].

At the molecular level, the formation of chSDH is even more interesting. The pathophysiological basis is the mutual interaction of cells of chronic inflammation, fibrinolysis, and angiogenesis, which potentiate each other. Initially, the hematoma in the subdural space undergoes fibrinolysis. The breakdown products of blood subsequently stimulate the activation of the inflammatory cascade, thickening of the inner dura mater, and angiogenesis. The newly formed capillaries, which are small branches of the MMA, do not have a sufficient vascular wall, resulting in repeated microhemorrhages. The entire cycle repeats several times. The result is fluid in the subdural space with numerous pseudomembranes, which are likely responsible for the recurrence of chSDH, as they exert positive feedback on the entire cycle [2,3,19]. Highly permeable gap junctions in the newly formed capillaries also contribute to the increase in fluid in the subdural space [9]. Although trepanation is a quick and effective method, it is not possible to completely remove these pseudomembranes [2]. Angiographic studies have shown that ipsilateral MMA has a much larger caliber than contralateral MMA due to chSDH [4].

A conservative approach may be chosen for the treatment of chSDH, usually in smaller and asymptomatic cases. This also includes surgical treatment and, more recently, endovascular treatment. However, there are no precise recommendations on how to proceed or which treatment method to choose for which patient [2].

Conservative treatment is intended for asymptomatic patients with minimal findings on CT examination. Although it spares patients from surgery, it can prolong hospitalization and bed rest. It also increases the need for further CT examinations, thus increasing the radiation exposure for the patient [2].

Surgical treatment of chSDH is indicated if the patient shows clinical symptoms, the size of the chSDH is greater than 10 mm, and the displacement of the midline structures is greater than 5 mm. In most cases, simple trepanation (one or two burr holes) under local anesthesia with or without the insertion of a subdural drain is recommended, depending on the practices of the facility. In some patients, a larger craniotomy under general anesthesia may be indicated [1–3]. In our series, all patients were treated with trepanation from one or two burr holes only; we use craniotomy under general anesthesia at our facility mainly for the treatment of acute subdural hematoma. The effect of the surgical procedure is usually immediate due to the alleviation of the mass effect and reduction of intracranial pressure [5]. However, the procedure is associated with common surgical complications and a relatively high recurrence rate of 10.5–18.5% [1], with some studies reporting a range of 2–37% [2].

The essence of MMA embolization is the devascularization of small arteries originating from the MMA, which are responsible for neovascularization in chSDH pseudomembranes and contribute to the recurrence of chSDH [1,3,10,18]. It was first described by Mandai et al. in 2000 [14]. The advantages of embolization include its minimally invasive nature, shorter hospital stay, and early rehabilitation of patients [3]. It is also possible to keep patients on established antiplatelet therapy, and some centers perform the procedure even if the patient is on anticoagulant therapy [20]. This significantly reduces the risk of ischemic complications in the post-procedural period [2]. At our facility, we routinely wait two days after discontinuing anticoagulant therapy before performing surgery, if the patient's clinical condition allows it. We perform surgery even if the patient is on antiplatelet therapy. We take a similar approach when preparing patients for embolization –⁠ we continue antiplatelet therapy but discontinue anticoagulant therapy for at least 48 hours.

The literature describes various protocols for the use of MMA embolization in the treatment of chSDH [4,15]. Some use embolization as the sole treatment or in combination with trepanation in patients with primary lesions or recurrences [1,3,18]. Larger studies comparing surgical treatment and MMA embolization clearly show that there are fewer cases of recurrence in the embolized group –⁠ 2.1% vs. 27.7% in the surgical group [5]. In general, the literature reports a 3–5% risk of recurrence after embolization [21]. In our cohort, only one patient was rehospitalized for another recurrence after embolization. We performed another evacuation through the original trepanation site. The next imaging examination showed favorable findings with no signs of residue.

Kan et al. used MMA embolization as the primary treatment for chSDH, and according to their results, a 50% reduction in hematoma was achieved in 70.8% of patients [8]. Shotar et al. presented a reduction in recurrence after MMA embolization from 14% to 4% in their study [4]. Court et al. showed regression of findings in 96.8% of their cohort of 190 patients without periprocedural complications [6]. A meta-analysis involving 902 patients demonstrated a reduction in recurrence rates with MMA embolization vs. conventional therapy of 5% vs. 22% [9]. In another study, Joyce et al. presented multicenter experience in 121 patients. The size of chSDH stabilized or decreased in 91% and 98% of patients, respectively [7]. Link et al. described a total of 49 patients in their cohort, 42 of whom were treated with MMA embolization as primary therapy. In 91.1% of patients, the size of the chSDH was stable or in regression, so patients did not need to undergo surgery [10]. Despite numerous studies in the literature, there is currently no therapeutic algorithm for the use of MMA embolization [9]. Its timing, the type of embolization agent, and whether to use it as a standalone therapy or in combination with surgical treatment have not been precisely determined [21].

Most studies report a very low incidence of complications –⁠ 3.6% [6]. These include new neurological deficits, MMA rupture during the procedure, or post-procedural epileptic seizures, as described by Kan et al. [8]. In our patients, we encountered three cases of contralateral paresis, which completely resolved in two patients. In one patient, the condition was diagnosed as status epilepticus and antiepileptic treatment was initiated. In this case, it was probably a combination of the underlying disease (the patient was being treated for advanced dementia) and the presence of chSDH. After initiation of antiepileptic treatment, the patient has been seizure-free.

As part of further patient follow-up, we used graphical and clinical checks after 4 months. This period proved to be the most productive, especially in terms of imaging methods, as earlier checks always showed residual effects. This reduced the need to repeat examinations and expose patients to further radiation.

 

Conclusion

MMA embolization has proven to be an effective and safe method for treating recurrent chSDH. Its advantages include its minimally invasive nature, which allows for early rehabilitation and discharge. In our cohort, patients with recurrent chSDH were indicated for embolization. In three patients, embolization was used as the primary and sole therapy.

 

Ethical aspects

The work was performed in accordance with the Helsinki Declaration of 1975 and its revisions in 2004 and 2008. The work was approved by the Ethics Committee of the České Budějovice Hospital on May 23, 2025 (approval number: 104/25).

 

Conflict of interest

The authors declare that they have no conflict of interest in relation to the subject of the study.