Contrast enhancement of chronic subdural hematomas after embolization of the middle meningeal artery

Abstract

Chronic subdural hematomas are a common neurosurgical presentation. They are difficult to treat, and current interventions – namely surgical evacuation – are not without complications or recurrences. Embolization of the middle meningeal artery is a promising new treatment option for this pathology. We have noted an interesting phenomenon in our patients following endovascular embolization, which is that the subdural hematoma is stained with contrast following the procedure. This ties into the basic physiology of chronic subdurals, which parasitize the middle meningeal artery during the process of membrane formation and neovascularization, which has previously been reported.

Introduction

Chronic subdural hematomas (CSDHs) are one of the most frequent radiographic presentations requiring neurosurgical consultation. They are challenging to treat, and have high recurrence rates with traditional management, namely surgical evacuation by way of burr holes or craniotomy.^1,2

Embolization of the middle meningeal artery (MMA) is growing in popularity as a management strategy for preventing the recurrence of CSDHs after evacuation.^2–4 This is based on the concept of vascular neoproliferation that occurs in the membranes seen in CSDHs, which parasitize vascular supply from the MMA through the outer membrane and dura.⁵ Recent case series have reported promising results, with a reported long-term success rate above 90% using this minimally invasive technique.^6,7 In our experience with endovascular embolization of the MMA, we have noted a pattern in contrast staining post-procedure that further supports this theory, as presented here.

Concept presentation

Hashimoto et al. reported on a ‘cotton wool-like staining’ seen on their angiographic evaluations of CSDHs, mimicking the abnormal vasculature of the membranous layers.⁸ This capillary pattern is often encountered during our angiograms as well, and supports the apparent neovascular proliferation seen in the outer membrane of these hematomas. We typically use Embozene particles from our procedures, mixed in a 1:1 ratio with contrast to allow for visualization during the procedure. During the embolization procedure, the continued penetrance of contrast mixed with particles given in the MMA stains the hematoma, resulting in a hyperintense character seen post-procedure.

Illustrative case 1

An 88-year-old man on clopidogrel for coronary stents presented to the emergency department with a scalp laceration and a mild headache after an unwitnessed fall. A computed tomography (CT) scan on admission revealed an acute subdural hematoma (Figure 1(a)). Surgical evacuation was not recommended because he had mild symptoms and no focal deficit. The patient was discharged to a rehab facility a few days later and quickly transitioned to an outpatient rehab program.

Figure 1.

(a) Initial computed tomography (CT) scan showing acute subdural hematoma; (b) Follow-up CT 2.5 months after the fall shows the collection is larger and causing more mass effect despite apparent liquefaction of the acute blood (more hypodense appearing); (c) Microcatheter run from the middle meningeal artery demonstrates a ‘cotton wool’ appearance; (d) DynaCT immediately after embolization shows contrast staining the subdural collection just below the dura; (e) he collection is significantly smaller on a follow-up CT scan performed 2 weeks after embolization; and (f) reabsorbed by 5 months.

Unfortunately, the patient did not improve significantly from a functional standpoint over the next 6 weeks, and his family reported on follow-up that his gait and cognition were slightly worse since discharge. Routine serial imaging showed that the collection had become hypodense, but also enlarged and causing more mass effect (Figure 1(b)). As the patient’s symptoms were still non-focal and he had an upcoming vacation with his family, we suggested embolization of the MMA to help reduce his risk of bleeding while traveling, and reserve surgery if his symptoms persisted.

MMA embolization was performed under conscious sedation. The left external carotid artery was accessed with a 4 French Fubuki (Asahi) angled guide sheath. The left MMA was accessed with a Headway 21 microcatheter (Microvention) over a Synchro2 microwire (Stryker). A microcatheter run demonstrated cotton-wool staining in the MMA territory (Figure 1(c)). The MMA was slowly embolized using 100 micron Embozene microspheres (Boston Scientific). A DynaCT performed immediately after the angiogram demonstrated contrast staining of the subdural collection (Figure 1(d)). The collection was significantly smaller in approximately 2 weeks (Figure 1(e)) and was fully resolved by 3 months.

Illustrative case 2

A 67-year-old woman on 81 mg of aspirin daily for general health presented to the emergency department after her family noticed mild expressive aphasia and difficulty ambulating for several days. She complained of a persistent headache and had mild confusion as well as a slight right upper extremity drift. A head CT revealed a septated left CSDH, with midline shift (Figure 2(a)). A subdural evacuating port system procedure was attempted by means of a bedside burr hole but was unsuccessful in completely evacuating the hematoma (Figure 2(b)). Discussion was held with the patient and her family and a decision was made to proceed with embolization of the MMA.

Figure 2.

(a) Initial computed tomography (CT) scan showing a large hypodense subdural collection; (b) A SEPS port (star) was inserted, but did not evacuate a significant amount of clot nor relieve the mass effect. Worse yet, there is now some acute blood mixed into the collection; (c) A microcatheter run shows robust filling of the middle meningeal artery (MMA). Note that the SEPS port (star) may have been inadvertently inserted through a branch of the MMA; (d) Post-embolization, there is enhancement of the subdural space on both the DynaCT imaging (e) and post-procedure CT (f) compared with the pre-procedure imaging.

The procedure was performed under conscious sedation. A 6 French short sheath was placed in the patient’s right femoral artery, and 6 French Envoy with Sim2 shape was used to select the left external carotid artery. A Headway 21 microcatheter over Synchro2 soft microwire was used to select the left MMA using roadmap guidance. A microcatheter digital subtraction run revealed a robust artery with frontal and parietal branches, supplying the neovasculature of the outer membrane of the CSDH (Figure 2(c)). Embolization was carried out by injecting 100 µm Embozene particles mixed in a 1:1 ratio with contrast, under live digital subtraction angiography until there was no contrast filling the MMA. A final microcatheter run confirmed full occlusion of the artery and no further filling of the capillaries of the CDSH membrane.

Post-procedure CT imaging was obtained, with contrast staining of the CSDH (Figure 2(d)–(f)). The patient improved over the course of several days, with improvement of her confusion and headaches. She was discharged to rehab on post-procedure day 3.

In addition to the two cases above, additional examples of this radiographic phenomenon from other representative cases can be seen in Figure 3.

Figure 3.

Additional illustrative cases. The first series is a 67-year-old man with a left chronic subdural hematoma (CSDH) shown both (a) pre and (b) one day post-middle meningeal artery embolization. The second series demonstrates a 77-year-old man (c) with a more septated left CSDH and smaller right-sided CSDH as well, and again (d) one day post-embolization. Both post-embolization images (b) and (d) show increased density (likely contrast enhancement) following the procedure.

Discussion

CSDHs continue to pose a challenge for the modern neurosurgeon. Based on data from multiple series, embolization of the MMA appears to be a promising adjunct in the armamentarium of those who are faced with this pathology daily. Not only does MMA embolization seem to prevent recurrence, especially in cases in which there is recurrence following surgical evacuation, it can generally be done under conscious sedation in a minimally invasive manner. Given the multiple comorbidities – including reliance on antiplatelet and/or anticoagulant drugs – and the advanced age of most patients with this presentation, embolization continues to grow in utility within our practice.

Several authors have reported on the histological patterns seen in CSDHs. Neovascular proliferation, associated with an increase in vascular endothelial growth factor signalling, is thought to be related to the unrelenting course of this disease process.⁹ During surgical exploration, there is a characteristic membranous coating lining the hematoma that surgeons can easily identify, which is shown to be histologically dissimilar to the dura itself.¹⁰ Capillary-like vessel growth in this outer membrane of the CSDH has been histologically confirmed, and these often derive arterial supply from the MMA.⁵ This vasculature penetrates the dura, anastomosing to the MMA, which is the distal continuation of the internal maxillary artery after its take-off from the external carotid artery.^2,9,11

While severe head trauma resulting in the tearing of bridging veins is the classically taught etiology of subdural hematomas, there is an increased recognition of CSDHs resulting from microtrauma in the setting of age-related cortical atrophy.¹² Thus it is posited that embolization of the MMA prevents the recurrent rupture of this fragile neovasculature, thereby preventing hematoma recurrence. Surgical evacuation is often incomplete, partly accounting for the high recurrence rate seen in this pathology.²

As MMA embolization grows in popularity, measuring the success of the embolization acutely becomes increasingly important. A study by Kim discussed statistically significant improved rates of brain re-expansion and less hematoma recurrence in patients who underwent embolization when comparing MMA embolization to conventional therapy.⁷ Link et al. recently reported a 60-patient case series with a 91% long-term success rate.⁶ The findings of Ban et al. mirrored the above, with similar complication rates and a positive therapeutic effect with MMA embolization.¹³ Although post-embolization digital subtraction angiography from the external carotid artery may reveal the disappearance of the MMA, it is often unclear how successful the embolization was in penetrating the capillaries within the subdural hematoma.

We propose that the post-procedure contrast staining seen in the CSDH suggests penetrance of particles – mixed with contrast – into the capillaries of the hematoma, which are the offending agents in the continued progression of these lesions. Similar radiographic findings have also recently been reported by other authors.⁴ This fits the proposed concept of ‘leaky capillaries’ that other authors have suggested as the cause of recurrent CSDHs despite appropriate healing time or surgical evacuation.

Conclusions

Embolization of the MMA may be a useful adjunct in the management of CSDHs, although further investigation is needed. While decompression of the mass effect by way of burr holes or craniotomy remains the standard of care for patients with midline shift or significant brain compression, minimally invasive angiographic embolization procedures may be an attractive option in patients who are poor candidates for more invasive surgery. Contrast staining of the hematoma following embolization may suggest sufficient penetration into the fragile neovasculature that accounts for the persistent nature of CSDHs. More cases and dedicated outcomes research is needed to evaluate better this radiographic feature post-embolization, and determine its utility in predicting outcomes following MMA embolization for CSDHs.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors received no financial support for the research, authorship and/or publication of this article.