Q) What are the endovascular treatment options for distal Middle Cerebral Artery (dMCA) aneurysm?

A) The definition of dMCA aneurysm varies. Most refer to it as aneurysms that are located distal to MCA bifurcation (M2-M4 segments) or peripheral branches of MCA according to the Gibo et al classification.(1,2) They are very rare. The incidence ranges from 2-6% of all MCA aneurysms, and accounts for 2% of ruptured MCA aneurysms.(3) The probable causes of dMCA aneurysms include trauma, vasculitis, neoplastic emboli and endocarditis.(4)

Typically, dMCA is small in diameter, tortuous, and locates distally. Therefore, endovascular treatment options of dMCA aneurysms are very limited. Simple coil embolization of aneurysm sac might not be possible in fusiform-shaped aneurysms and has an inability to maintain optimal microcatheter position. Stent-assisted coil embolization in small vessels increases the risk of complications because the procedure requires 2 micro catheters.1 Parent Vessel Occlusion (PVO) ± aneurysm embolization using coil ± glue or Onyx have been successfully performed and seemed to be safe.(4-7)

 

Lv et al reported PVO ± aneurysm embolization using coil ± glue in 8 patients with dMCA aneurysms with great results and no recanalization of aneurysms after mean follow up of 14.6 months. All patients did well except for one who had mild right hemiparesis from hematoma evacuation. (5) Baltacioglu et al reported 11 dMCA aneurysm treatment with coil embolization in which 7 aneurysms were treated with PVO & aneurysm embolization with coils and none had complications. Only one patient who had selective aneurysm coil embolization had transient ischemic attack. At 6 months follow up, one patient had recurrent filling of aneurysm. Baltacioglu et al concluded that “When the parent artery cannot be preserved, leptomeningeal collaterals generally provide adequate blood supply to prevent consequent neurological deficits.” (4)

 

Current evidence shows the complete/near-complete occlusion of dMCA aneurysms from the Flow Diverter (FD) treatment is approximately 70-96%, however periprocedural complications were up to 20%. Pipeline FD was the most commonly used device followed by Silk FD. The example of reported complications includes in-stent thrombosis, slow filling of side branch, postoperative intracerebral hemorrhage, stent migration, and contrast extravasation. This is concerning and makes us think of the alternative options. (2,8,9,10)

 

The Silk Vista Baby (SVB), a flow diverter device, has the smallest FD profile using 0.017’ micro catheter system instead of 0.021/0.027’. It received CE mark approval for clinical use in Europe in 2018 but it is currently not available in the US. We don’t have a long-term efficacy and safety data yet. The first study is currently ongoing to check the safety and efficacy of the device in 5 years (2025).  The initial safety report (41 patients) showed 12% periprocedural complications which didn’t affect the outcome of patients. The smallest proximal vessel diameter that they placed SVB was 0.9 mm and smallest distal vessel diameter was 0.8 mm.10 Schob et al reported 0% periprocedural complication with SVB FD in peripheral cerebral arteries (25 patients). However, they had only 3 months follow up data which showed about 63% complete occlusion of aneurysm.(11) It would be interesting to see the results of the first study in the next 5 years. We might be able to treat dMCA more safely with FD.(12)

Reference

  1. Gibo H, Carver CC, Rhoton AL, et al. Microsurgical anatomy of the middle cerebral artery.    J Neurosurg 198; 54:151–69.

  2. Cimflova P, Özlük E, Korkmazer B, et al.  Long-term safety and efficacy of distal aneurysm treatment with flow diversion in the M2 segment of the middle cerebral artery and beyond. J Neurointerv Surg. 2020 Oct 20.

  3. Tsutsumi K, Horiuchi T, Nagm A, et al. Clinical characteristics of ruptured distal middle cerebral artery aneurysms: Review of the literature. J Clin Neurosci. 2017; 40:14-17. Baltacioğlu F, Cekirge S, Saatci I, et al. Distal middle cerebral artery aneurysms. Endovascular treatment results with literature review. Interv Neuroradiol. 2002;8(4):399-407.

  4. Lv N, Zhou Y, Yang P, et al. Endovascular treatment of distal middle cerebral artery aneurysms: Report of eight cases and literature review. Interv Neuroradiol. 2016;22(1):12-7.

  5. Douds GL, Kalapos P, Cockroft KM. Temporary test occlusion of distal middle cerebral artery using GDC coil. J Neuroimaging. 2010 ;20(2):183-6.

  6. Wang Q, Chen G, Gu Y, Song D. Provocative tests and parent artery occlusion in the endovascular treatment of distal middle cerebral artery pseudoaneurysms. J Clin Neurosci. 2011;18(12):1741-3

  7. Primiani CT, Ren Z, Kan P, et al. A2, M2, P2 aneurysms and beyond: results of treatment with pipeline embolization device in 65 patients. J Neurointerv Surg 2019; 11:903–7.

  8. Cagnazzo F, Perrini P, Dargazanli C, et al. Treatment of unruptured distal anterior circulation aneurysms with flow-diverter stents: a meta-analysis. AJNR Am J Neuroradiol 2019; 40:687–93.

  9. Cagnazzo F, Mantilla D, Lefevre PH, et al. Treatment of Middle Cerebral Artery Aneurysms with Flow-Diverter Stents: A Systematic Review and Meta-Analysis. AJNR Am J Neuroradiol. 2017;38(12):2289-2294.

  10. Martínez-Galdámez M, Biondi A, Kalousek V, et al. Periprocedural safety and technical outcomes of the new Silk Vista Baby flow diverter for the treatment of intracranial aneurysms: results from a multicenter experience. J Neurointerv Surg. 2019;11(7):723-727.