Unexpected ocular morbidity after middle meningeal artery embolization: Lessons learned from a case of anastomotic-related diplopia

Abstract

Middle meningeal artery embolization (MMAE) has revolutionized chronic subdural hematoma management, yet procedural risks persist due to anatomical variability. We analyze a case report by Zhao et al describing transient diplopia caused by inadvertent embolization of the lacrimal artery via a dynamic middle meningeal–ophthalmic anastomosis. This correspondence advances three critical innovations in MMAE safety. First, intraoperative anastomotic unmasking—exposing occult middle meningeal-ophthalmic collaterals during particle injection—reveals dynamic vascular behavior missed by preoperative angiography, underscoring the need for adaptive imaging protocols. Second, hybrid embolization (liquid agents for proximal occlusion + particles for distal control) balances precision and safety, reducing reflux risks compared to monotherapy. Third, a 108-day follow-up establishes a benchmark for functional recovery, challenging assumptions about irreversible cranial nerve injuries and emphasizing structured postprocedural care. Collectively, these findings advocate for procedural agility, multimodal embolic strategies, and sustained rehabilitation to optimize MMAE outcomes while minimizing iatrogenic harm.

Key Words: Middle meningeal artery embolization; Chronic subdural hematoma; Lacrimal artery embolization; Hybrid embolization strategies; Functional recovery

Core Tip: Dynamic anastomotic unmasking during middle meningeal artery embolization mandates intraoperative angiographic vigilance. Hybrid embolization and tailored rehabilitation are critical for mitigating risks and improving outcomes.

TO THE EDITOR

We read with great interest the case report by Zhao et al[1]. Chronic subdural hematoma (CSDH) is a common neurosurgical condition, and middle meningeal artery embolization (MMAE) has emerged as a promising treatment option in recent years.

CSDH is characterized by headache and limb weakness due to hemorrhage accumulation beneath the dura mater, exerting pressure on brain tissue. Traditional surgical treatments have high recurrence rates, which has led to the exploration of alternative therapies like MMAE. MMAE targets the middle meningeal artery, which plays a crucial role in CSDH pathogenesis. The reported case of a 60-year-old man who developed diplopia after left MMAE for left-sided CSDH is significant as it provides real-world evidence of a rare but serious complication. Although previous studies have reported similar neurological deficits after MMAE, this case is unique in that it provides clear intraoperative imaging evidence of the anastomotic artery through which polyvinyl alcohol (PVA) particles flowed, leading to diplopia.

SIGNIFICANCE OF THE CASE REPORT

Zhao et al’s case report[1] represents a landmark contribution to the neurointerventional literature, addressing two critical gaps in MMAE safety. First, it documents dynamic anastomotic unmasking—a previously underrecognized phenomenon where catheter retraction during particle injection reveals occult anastomoses undetectable on preoperative angiography. This challenges the notion that superselective angiography at a single procedural stage ensures comprehensive vascular mapping. Second, the authors introduce a hybrid embolization paradigm combining liquid embolics (Onyx) with PVA to achieve distal penetration control while minimizing reflux risks. Prior studies have advocated for either particulate-Onyx or coil-Onyx strategies[2,3], but this hybrid approach leverages the strengths of both modalities: Onyx’s proximal anchoring capability and PVA’s distal occlusive efficiency[4].

Moreover, the 108-day follow-up confirms complete resolution of diplopia without permanent cranial nerve injury, contrasting with prior reports of irreversible palsies[4,5]. This extended observation period underscores the importance of structured postprocedural monitoring and rehabilitation, particularly for patients with partial abducens nerve palsies.

LIMITATIONS AND CRITIQUES

While the case provides critical insights, several limitations merit consideration. First, the reliance on retrospective angiographic interpretation risks misclassifying anastomotic dynamics. The exact hemodynamic forces unmasking the sphenoidal artery remain speculative, necessitating prospective hemodynamic studies. Second, the use of PVA particles (150-350 μm) raises questions about particle size thresholds for safe embolization. Prior studies suggest that smaller particles (< 150 μm) may reduce distal migration risks, though this case demonstrates that even intermediate-sized particles can traverse patent anastomoses under hemodynamic stress. Third, the absence of pre-procedural balloon test occlusion or multimodal imaging (e.g., cone-beam computed tomography) limits our ability to fully characterize the anatomic milieu. Future investigations incorporating four-dimensional angiography or computational fluid dynamics may better predict anastomotic behavior during MMAE.

CLINICAL INDICATIONS AND PREOPERATIVE EVALUATION FOR MMAE IN CSDH MANAGEMENT

The selection of CSDH candidates for MMAE remains a topic of active debate. While MMAE has shown promise in reducing recurrence rates compared to traditional surgical interventions—particularly in patients with coagulopathy, anticoagulant use, or multiple loculated hematomas—its optimal application requires careful patient stratification.

Indications for MMAE

Indications for minimally invasive MMAE include high-risk surgical candidates such as elderly patients, those with multiple comorbidities, or individuals with contraindications to general anesthesia; recurrent or refractory hematomas, particularly those that have undergone ≥ 2 prior surgical evacuations or continue to expand despite conservative treatment; and anatomical considerations where preoperative angiography identifies prominent middle meningeal artery branches supplying the hematoma capsule[6-8].

Limitations and alternatives

While MMAE is effective, it is not universally applicable. Nonsurgical management with corticosteroids or atorvastatin may suffice for asymptomatic, small-volume CSDHs. For symptomatic cases, twist-drill craniostomy or burr-hole drainage remains the first-line intervention. MMAE is best positioned as a bridging therapy for high-risk surgical patients or an adjunctive tool for complex hematomas[9-14].

Preoperative imaging imperatives

Preoperative imaging imperatives for procedures such as MMAE are crucial to mitigate risks of collateral damage, including ophthalmic artery embolization. Digital subtraction angiography is mandatory to identify dynamic anastomoses, such as middle meningeal-ophthalmic connections, which may not be evident on computed tomography angiography[15]. High-resolution magnetic resonance imaging with T2*-weighted sequences can detect hemosiderin deposits along potential collateral pathways, enhancing preoperative risk stratification[16]. Additionally, balloon test occlusion is reserved for cases with suspected complex vascular networks to assess hemodynamic tolerance[15,16].

Predictors of favorable outcomes after MMAE

Optimal outcomes depend on patient selection, procedural technique, and hematoma characteristics. Favorable factors include younger age, absence of anticoagulant use, homogeneous hematoma composition (high fluid-to-clot ratio), and absence of septations[17,18]. Hybrid embolization strategies (Onyx for proximal occlusion + PVA particles for distal penetration) improve hemostasis by addressing both proximal flow and distal collateral supply. Dynamic intraoperative angiography is critical to identify occult anastomoses (e.g., middle meningeal-ophthalmic connections) that may compromise safety.

Optimal timing of MMAE

Early intervention is indicated for acute neurological decline or unstable hematomas but carries risks of re-expansion edema if performed < 7 days[19]. Delayed intervention (1-3 months postoperatively) allows neomembrane maturation, enhancing embolic adhesion and reducing recurrence[20]. Controversy exists over combined MMAE + surgical evacuation, with some studies suggesting lower recurrence rates compared to surgery alone[21,22]. However, a staged approach—initial MMAE for stabilization followed by minimally invasive evacuation for persistent symptoms—may balance efficacy and invasiveness. Future randomized trials are needed to clarify optimal timing and treatment sequencing.

Intraoperative vigilance

Intraoperative vigilance is paramount during procedures like MMAE, as highlighted by the case reported by Zhao et al[1], where dynamic anastomotic unmasking during catheter manipulation emphasizes the necessity for sequential multi-angle contrast injections during catheter repositioning to thoroughly assess vascular connections, and the use of low-viscosity contrast agents to improve visualization of small-caliber vessels, thereby minimizing the risk of inadvertent embolization of collateral pathways.

By adopting a standardized preoperative evaluation protocol and embracing adaptive intraoperative imaging, clinicians can optimize MMAE safety profiles while expanding its therapeutic window.

FUTURE DIRECTIONS

This case reframes preoperative planning and intraoperative decision-making in MMAE. We propose the following actionable recommendations.

Adaptive intraoperative angiography

Sequential multi-angle injections should be performed during catheter repositioning to identify dynamic anastomoses. Institutional protocols should mandate dynamic imaging workflows to complement static preoperative studies.

Hybrid embolization protocols

The use of liquid embolics (e.g., Onyx) for proximal anchoring, followed by particulate agents for distal occlusion, should be standardized. This tiered approach balances proximal flow control with distal precision.

Postprocedural rehabilitation pathways

Structured ocular motor training programs should be implement for patients with transient cranial nerve palsies, incorporating visual field assessments and proprioceptive exercises.

Future research should focus on developing predictive models for anastomotic risk using machine learning algorithms trained on large angiographic datasets. Randomized controlled trials comparing hybrid embolization techniques with conventional approaches are urgently needed to establish evidence-based guidelines.

CONCLUSION

In conclusion, Zhao et al’s case[1] exemplifies the delicate interplay between technological innovation and anatomical complexity in neurointerventional procedures. By prioritizing adaptive strategies and embracing hybrid paradigms, clinicians can minimize iatrogenic morbidity while expanding the therapeutic frontier of MMAE.