An “old” meta-analysis: coiling versus microsurgical clipping in the treatment of unruptured MCA aneurysms

Key point:

    • To compare endovascular coiling with microsurgical clipping among adults with unruptured middle cerebral artery aneurysms (MCAA) by conducting a meta-analysis.

The widespread use of neurovascular imaging has increased the amount of intracranial aneurysms eccidentally detected. Although the lifetime risk of aneurysmal rupture in many cases is relatively small (approximately 1% per year), rupture can results in permanent neurological deficits or death, the reason why often patients may desire the treatment of unruptured aneurysms to prevent later rupture. In the last 2 decades, incremental improvements of endovascular coiling techniques has led to significant controversy regarding the ideal management strategy for unruptured intracranial aneurysms of the cerebral vessels. In this paper, published online February, 2018, on Neurosurgery, Authors performed a meta-analysis of studies to compare endovascular coiling and microsurgical
clipping with regard to the safety and efficacy of the treatment of unruptured middle cerebral artery aneurysms
(MCAA), including 37 articles with 3352 aneurysms (2162 clipping, 1190 coiling). Results are reported in the following table.

Results

  Clipping group Coiling group
Analyzed articles 22 23
Number of patients 2162 1190
Aneurysmal occlusion rate
94.2% 53.2%
Neurological outcome 97.9% 95.1%

This meta-analysis showed the superiority of the surgical clipping vs. the endovascular coiling in terms of occlusion rate (clip occlusion rate = 94.2%, 95% CI, 87.6%-97.4% vs coil occlusion rate = 53.2%, 95% CI, 45.0%-61.1%) and no difference in terms of neurological outcome (clip favorable neurological outcome rate = 97.9%,95% CI, 96.8%-98.6% vs coil favorable neurological outcome rate = 95.1%, 95% CI, 93.1%-96.5%).

Our question is:

Is this study really actual? 
Analysis

As Alreshidi et al. said: “the technological and technical improvement of the endovascular treatment corresponds to an improvement of the clinical outcome”. But in this meta-analysis, Authors do not consider this technological and tecnical improvement. Historically, MCA aneurysm treatment strategies have favored microsurgical clipping due to the relative ease of dissection and due to the anatomical configuration of MCA aneurysms that generally makes tricky the endovascular coiling. The introduction of remodelling devices, such as stents and balloon microcatheters, flow disruption devices, such as the WEB device, or devices created to advance the waffle cone technique, that are self-expanding stents to position into the parent vessel with its distal tip implanted into the neck of the aneurysm in order to hold in place the coils, has broadened the scope of endovascular aneurysm treatment. These devices are now extensively used in daily practice. This is the reason why this meta-analysis is old.

It is like to ask to a neurosurgeon to treat all the MCA aneurysms with one type of clip, regardless the anatomy of the aneurysm.

Instead Authors excluded all studies that reported the use of assistive endovascular devices and demonstrated in this meta-analysis that aneurysmal obliteration rates in clipped cases were 44.7% higher than the coiled cases.

Just to demonstrate how this result is unuseful for the decision of the appropriate management of unruptured MCA aneurysms we report a study published on May, 2013, in Journal of Neurosurgery by Johnson et al.*; Authors presented a serie of 100 middle cerebral artery aneurysms treated with stent-assisted coiling with an intial obliteration rate of 95.2% and a 6 months follow-up obliteration rate of 90.7%; these results are completely different to those given in the meta-analysis.

Unassisted coiling occlusion rate
Stent-assisted coiling occlusion rate
53.2% 95.2%

What is sure is that at least 2 major decisions must be made when an unruptured intracranial aneurysm is identified:

  • Whether the "patient" (and not only the aneurysm) should be treated.
  • Whether it should be treated with "endovascular techniques" (and not only non assisted coiling) or with microsurgical clipping (possibly with a wide range of aneurysm clips available).

Reference

  • * Johnson AK, Heiferman DM, Lopes DK. Stent-assisted embolization of 100 middle cerebral artery aneurysms. J Neurosurg. 2013 May;118(5):950-5. doi: 10.3171/2013.1.JNS121298. Epub 2013 Feb 8.
  • Alreshidi M, Cote DJ, Dasenbrock HH, Acosta M, Can A, Doucette J, Simjian T, Hulou MM, Wheeler LA, Huang K, Zaidi HA, Du R, Aziz-Sultan MA, Mekary RA, Smith TR. Coiling Versus Microsurgical Clipping in the Treatment of Unruptured Middle Cerebral Artery Aneurysms: A Meta-Analysis. Neurosurgery. 2018 Feb 9. doi: 10.1093/neuros/nyx623. [Epub ahead of print]

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