MMA Embolization - Chronic subdural hematoma - Ep.2/2

Middle Meningeal Artery (MMA) Embolization for Chronic Subdural Hematoma (CSDH)

Episode 2

Science Of MMA Embolization…. Liquids vs particles vs coils?! Which one is better?

Before answering, we need to have an overview about the anatomy and histology of dura, ….

Generally, most of the arteries are located inside the basal cell layer of the dura supplying the hematoma with a diameter of less than 50 um. There are vascular area (temporal) which includes a principal artery with a diameter of (534-2008um). While there is avascular area (parietal) which contains anastomotic arteries and satellite veins of smaller diameter of (291- 829 um). Additionally, arteries of meningeal area are less than 200 um. 

Thus, the important questions are (Do we need to embolize small arteries like this? Less than 200 um?! Do we need to embolize as distal as possible?! Maybe better results and less recurrence?! Several options were introduced into discussion….

Particles?! 

Could the use of 45 um -150 um help to embolize distally? The answer was no because still bigger particles will remain which blocks the primary arteries. In result, they will not embolize distal in comparative to liquids. However, they are easy to use, less painful and no need for GA and can be beneficial in some cases when the catheter cannot go further distally.  So, still has some chances regarding their comparative benefits.

EVOH Or NBCA?!

They have almost the same embolizing behavior in terms of the primary and smaller healthy arteries. Althoughr, it is possible that they don`t go distally to occlude smaller arteries.

Several physical theories were suggested; degree of distal embolization is directly proportional to degree of pressure applied (So apply higher pressure to go more distally while being as distal as possible). Being proximal will decrease pressure by having more reflux. Additionally, the larger the diameter, the higher is the distal penetration (As expected to be higher through AVMs Embolization as they have larger vascular diameters and expected to cover larger distances in the nidus). Finally, Lower viscosity can cause more distal embolization but according to the density as well. 

Regarding the Practice using Glue, it depends on position of microcatheter, and flow can be controlled by plug and push technique. 1:5 is the ratio suggested. Advantages: you stay anywhere and inject, and it will diffuse. Sometimes it is painful, for that reason, it could be preceded by 10-15 cc of lidocaine injection. In comparison to EVOH, it is faster and more convenient and does not have the problem of tantalum separation. 

It is worth mentioning the Results of Membrane trial on NBCA: significant efficacy for MMAE results regarding residual or reaccumulating hematoma of more than 10 mm and Re-surgical intervention or recurrence within 6 months. 

Proximal coiling only can be an option?... yes!!! 

Advantages can be used under conscious sedation and adapt to higher rate of cases with no need to GA as they are less painful. Furthermore, especially in cases where you cannot go distal by microcatheter so you can push the coil from your position. In addition, quick, can be in 30 minutes but can take longer if a GA or bilateral approach was required. Technique: Deploying the coil in the two branches of MMA very distal as possible making a V shaped. Type of coil used: Swift pack coil with 2d sinusoidal shape with longer 3-60 cm length. Initial experience about recurrence? Results are comparative to liquid embolic agents or other agents. 

In the end, as previously mentioned, the technique has proved its efficacy and safety outcomes. However, the same questions remained concerning the indications, Bilaterality, which agent to use for which case, and causes of recurrence. Accordingly. further studies are absolutely mandatory.

It is undoubtedly recommended to watch the two episodes for more fruitful information regarding various mentioned subheadings and exciting topics.