Middle meningeal artery embolisation in chronic subdural hematoma: A double-edged sword

Abstract

Chronic subdural hematoma is essentially managed by surgical intervention. In recent times, middle meningeal artery embolisation has emerged as a less invasive procedure in such cases. The use of fine catheters to selectively embolise the specific involved branches of the middle meningeal artery using polyvinyl alcohol particles looks promising; however, the presence of anastomotic arteries can result in reflux and embolisation of these atypical branches, causing a myriad of complications. There is a need to identify these abnormal vessels in time to have a positive outcome with the least complications.

Key Words: Subdural hematoma; Middle meningeal artery; Polyvinyl alcohol; Diplopia; Embolization

Core Tip: Chronic subdural hematoma management involves middle meningeal artery embolisation in association with standard surgical procedures. The embolisation procedure selectively blocks the involved artery but may result in other local complications due to anastomotic arteries. Identifying these abnormal branches and adapting to alternate materials and interventional techniques is essential to prevent such issues.

TO THE EDITOR

We have written a letter to the editor on an in-press article in which chronic subdural hematoma is managed by middle meningeal artery embolisation.

I recently reviewed the manuscript by Zhao et al[1]. The authors have reported an interesting complication of diplopia due to impaired abduction of the eye post-MMA embolisation in a case of chronic subdural hematoma (SDH). This was attributed to an atypical anastomotic arterial communication, which was seen during the procedure. Despite taking the necessary precautions, reflux occurred secondary to microcatheter displacement, resulting in embolisation of neighbouring branches, and this led to the complication.

This procedure provides a target-specific treatment strategy wherein the branches of MMA that are involved in the pathogenesis of chronic SDH are targeted, thus avoiding potential systemic side effects and complications. The use of smaller polyvinyl alcohol (PVA) particles (150-350 microns), as in this case, has the advantage of selective embolization of the MMA branches. The use of this method, along with other surgical interventions, has proven to be beneficial in primary and recurrent cases of chronic SDH; however, the presence of bridging arteries in such cases poses a significant risk for inadvertent side effects, as seen in this case report. Usually, two types of abnormal pathways exist: The meningolacrimal and the sphenoidal artery. In this case, a type II vascular pattern, as suggested by Desir et al[2], was seen intraoperatively, which led to spillover of PVA particles and caused embolisation of the blood supply of the lateral rectus and the abducens nerve, causing diplopia. Other dreaded complications may also arise due to embolisation of the ophthalmic artery and the artery supplying the facial nerve, resulting in blindness and facial paralysis, but were not seen in this case[2,3]. Diplopia in this case recovered after starting oral methylcobalamine and ocular motility exercises nearly 1 month post-procedure. MMA embolization looks promising in cases of CSDH; however, due to the presence of anastomotic branches in such cases, it can undermine its impact, which warrants further multi-institutional studies to look into various anastomotic variations encountered in such cases and monitor the long-term neuro-ophthalmic complications across varied patient groups, as this study focuses only on a single complication, which is its inherent limitation. Although MMA embolisation has come up as a new strategy, which, when combined with standard treatment protocols, is useful in primary and recurrent cases of CSDH, it may also possess certain issues ranging from transient to vision-threatening complications. The selection of appropriately sized embolizing materials, such as PVA, is important so that they will enter only the targeted vessel and not leak or reflux into nearby abnormal bridging arteries, leading to complications. The use of alternative embolising agents should also be considered, which can help clinicians in targeted therapy[4]. Various embolising agents are useful in MMA embolisation, but most commonly, PVA is used due to its cost-effectiveness and track record. The benefit of using PVA is its proximal positioning and microcatheter readjustment; however, due to its lack of radiopacity, determining its distal penetration and proximal reflux becomes difficult. Also, there are increased rates of recanalisation due to PVS being reabsorbed and degrading over time. Liquid agents such as ethylene vinyl alcohol copolymer (Onyx) are useful due to their easy visualisation for better control and precision. Its non-adhesiveness, a property to be instilled in distal branches, and better durability due to lack of reabsorption are useful in MMA embolisation; however, cost, vasospasm, discomfort, and proximal stump embolisation are its limiting factors. N-butyl-2 cyanoacrylate (n-BCA) combined with ethiodized oil and tantalum powder improves visualisation and alters polymerization according to the surgeon's preference, thus improving durability and distal penetration. The risk of vessel rupture and higher cost are its limiting factors[5]. Neurological complications can occur with these agents, which can vary from 11.2% (PVA) to 3.2% (Onyx)[6]. Pre-procedure radiological investigations and getting them reviewed by an experienced clinician or several clinicians may help in identifying the anastomotic branches that are often missed in such cases. Super-selective angiography and embolisation of the MMA with much finer catheters and appropriate embolising agents can be useful to prevent reflux and further complications. The practice of segmental and slow catheter withdrawal procedures can help in identify atypical branches and prevent reflux. In cases where atypical bridging branches are identified, embolisation should be done distal to these sites. If all these fail, use of coils or termination of the procedure should be considered[7]. In cases where complications occur, prompt diagnosis and timely intervention are necessary. Patient counselling is of paramount importance, as nerve palsies, as encountered in such cases, usually take months to years to recover. Another aspect is to consider the broad range of management strategies in cases of chronic SDH, which is not limited to MMA embolisation as seen in this case. Mild cases (CSDH thickness < 10 mm with no mass effect) need only observation due to their spontaneous resolution. Pharmacological treatment in the form of anticoagulant/antiplatelet reversal, use of intravenous hypertonic saline, corticosteroids, and anticonvulsant therapy is also useful. Symptomatic patients with large bleeds > 1 cm or mass effect warrant surgical intervention[8].

CONCLUSION

In this case, diplopia post-chronic subdural hematoma was well managed by the middle meningeal artery embolisation. This is fast becoming a management choice in such complicated cases.